**Radiation Physics** **and Safety** **Dr Dayea Oh** **Oral and Maxillofacial Radiologist** **UWA Dental School** **Radiation Physics** and **Safety** Dr Dayea Oh Oral and Maxillofacial Radiologist UWA Dental School Small blue radiation hazard symbol logo located on the left side of the slide. Large, faded light-blue radiation hazard symbol graphic positioned in the background on the right side of the slide. ## Recommended Textbooks **Essentials of dental radiography and radiology 5th edition** by Whaites, Eric; Drage, Nicholas Churchill Livingstone 2013 **Pocket atlas of dental radiology** by Pasler, Friedrich A; Visser, Heiko Flexibook, 2007 **Oral radiology: principles and interpretation 7th edition** by White, Stuart C; Pharoah, M. J Permalink 2014 - 8th edition available now Recommended Textbooks - **Essentials of dental radiography and radiology 5th edition** by Whaites, Eric; Drage, Nicholas Churchill Livingstone 2013 - **Pocket atlas of dental radiology** by Pasler, Friedrich A; Visser, Heiko Flexibook, 2007 - **Oral radiology: principles and interpretation 7th edition** by White, Stuart C; Pharoah, M. J Permalink 2014 - 8th edition available now 1. Radiation Physics How is x-ray generated? 1. Radiation Physics How is x-ray generated? # Contents * X-ray Use in Dentistry * What is X-ray? * Ionising radiation * How is X-ray generated? * Spectrum of X-ray Photons * Bremsstrahlung & Characteristic Radiations * Factors Controlling the X-ray Beam - X-ray Use in Dentistry - What is X-ray? - Ionising radiation - How is X-ray generated? - Spectrum of X-ray Photons - Bremsstrahlung & Characteristic Radiations - Factors Controlling the X-ray Beam <code> History of Dental X-ray ! Professor Wilhelm Conrad Roentgen discovered the X-ray in 1895 ! Otto Walkhoff took first dental X-rays on himself (took 25 minutes) ! "It was a real torture but I felt tremendously happy when I saw the results. It was when I weighed up the importance of Roentgen’s discovery for future dentistry." </code> _figures/img_7e75bf0dc4c0ebe4.webp) History of Dental X-ray Professor Wilhelm Conrad Roentgen discovered the X-ray in 1895 Otto Walkhoff took first dental X-rays on himself (took 25 minutes) "It was a real torture but I felt tremendously happy when I saw the results. It was when I weighed up the importance of Roentgen’s discovery for future dentistry." Historical dental radiograph showing the first dental X-ray taken by Otto Walkhoff on himself in 1896. The image displays a dark silhouette of teeth and jawbone structures against a lighter background, demonstrating early X-ray imaging capabilities. Indications for Dental X-rays * **Dental History** * Previous treatment * **Clinical Signs and Symptoms** * Dental Pain * Trauma * Caries * Periodontal Disease * Absence of teeth eg. delayed eruption * Impacted teeth * Implants, **etc...** _figures/img_1d4c7c47b014a92c.webp) Indications for Dental X-rays - **Dental History** - Previous treatment - **Clinical Signs and Symptoms** - Dental Pain - Trauma - Caries - Periodontal Disease - Absence of teeth eg. delayed eruption - Impacted teeth - Implants, **etc...** Clinical photo: An intraoral dental X-ray sensor (phosphor plate) positioned in the patient's mouth. The device is white with a purple band around the handle and is attached to a grey mounting arm. **Nature of Radiation** • Radiation is the **transmission of energy** through space and matter. • Occurs as particulate and electromagnetic radiation . **Two Basic Types of Radiation** **Particulate Radiation** • Alpha particles • Beta particles **Electromagnetic Radiation** • Radio waves • Microwaves • Infrared waves • Ultraviolet light • Gamma radiation • X-radiation _figures/img_7389b0e0296af9c5.webp) **Nature of Radiation** - Radiation is the **transmission of energy** through space and matter. - Occurs as particulate and electromagnetic radiation. **Two Basic Types of Radiation** **Particulate Radiation** - Alpha particles - Beta particles **Electromagnetic Radiation** - Radio waves - Microwaves - Infrared waves - Ultraviolet light - Gamma radiation - X-radiation A labeled chart illustrating the electromagnetic spectrum. It displays a horizontal bar showing the progression from Radio waves (longest wavelength) to Gamma Ray (shortest wavelength). The chart includes axes for 'Wavelength (meters)' and 'Frequency (Hz)', with corresponding values in scientific notation. A visual representation of wave amplitude decreases as frequency increases. Below the spectrum, icons represent objects relative to the wavelength size, ranging from Buildings and Humans on the left to Atomic Nuclei on the right. # Electromagnetic Radiation (EMR) **1. Quantum Theory:** - Considers electromagnetic radiation as small discrete particles of energy called **photons**. - Electron volt (**eV**) is the unit of energy - the amount of energy acquired by one electron accelerating through a potential difference of one volt. **2. Wave Theory:** - Movement of photon energy through space as a combination of electric and magnetic fields. - Fields oriented in planes at right angles to one another that oscillate perpendicular to the direction of motion. $γ$ rays, **x-rays**, UV rays, visible light, infrared radiation (heat), microwaves, and radio waves. All made up of photons. _figures/img_5d7dc7bc380a0b24.webp) **1. Quantum Theory:** - Considers electromagnetic radiation as small discrete particles of energy called **photons**. - Electron volt (**eV**) is the unit of energy - the amount of energy acquired by one electron accelerating through a potential difference of one volt. **2. Wave Theory:** - Movement of photon energy through space as a combination of electric and magnetic fields. - Fields oriented in planes at right angles to one another that oscillate perpendicular to the direction of motion. $γ$ rays, **x-rays**, UV rays, visible light, infrared radiation (heat), microwaves, and radio waves. All made up of photons. Labelled diagram of an Electromagnetic Wave. The image displays a transverse wave propagating horizontally to the right, depicted by two interlaced sinusoidal lines: one red and one blue. Vertical arrows are drawn perpendicular to the main axis, indicating field oscillations. A horizontal double-headed arrow spans the top of the first cycle with the label 'λ = Wavelength'. To the upper right, a legend defines the components: a vertical red arrow labeled 'Electric Field', a diagonal blue arrow labeled 'Magnetic Field', and a purple arrow pointing right labeled 'Direction'. **x-ray photons have high energy and short wavelengths** **FIG.** Electromagnetic spectrum showing the relationship between wavelength, photon energy, and physical properties of various portions of the spectrum. Note that the photons with shorter wavelengths have higher energy. Photons used in dental radiography have a wavelength of 0.1 to 0.001 nm. _figures/img_da097734714b990f.webp) **x-ray photons have high energy and short wavelengths** **FIG.** Electromagnetic spectrum showing the relationship between wavelength, photon energy, and physical properties of various portions of the spectrum. Note that the photons with shorter wavelengths have higher energy. Photons used in dental radiography have a wavelength of 0.1 to 0.001 nm. Labelled diagram: An electromagnetic spectrum chart displaying two axes. The top axis represents 'Wavelength' in nanometers (nm) ranging from 10^13 down to 10^-7. The bottom axis represents 'Photon energy' in electron volts (eV) ranging from 10^-10 up to 10^10. The spectrum is segmented into regions including Radio, TV, Microwave, Infrared, Visible, Ultraviolet, X-rays, Cosmic rays, and Gamma rays. A red box highlights the 'X-rays' region, which corresponds to wavelengths between approximately 0.1 and 0.001 nm. Arrows indicate the position of the visible light range. **THE ELECTROMAGNETIC SPECTRUM** **non-ionizing** **ionizing** wavelength f<sub>(frequency)</sub> = c<sub>(speed of light)</sub> / λ<sub>(wavelength)</sub> geomagnetic & sub ELF sources extremely low frequency very low frequency radio frequency spectrum microwaves infrared** visible** ultra violet x-rays gamma cosmic rays EMF Sources earth & subways AC power CRT monitors mobile AM/FM TV cell/PCS microwave & satellite sunlight **medical x-rays** **radioactive sources** gigahertz (GHz) 10<sup>-9</sup> terahertz (THz) 10<sup>-12</sup> petahertz (PHz) 10<sup>-15</sup> exahertz (EHz) 10<sup>-18</sup> zettahertz (ZHz) 10<sup>-21</sup> yottahertz (YHz) 10<sup>-24</sup> _figures/img_7e6dbb33d21360f9.webp) **THE ELECTROMAGNETIC SPECTRUM** **non-ionizing** **ionizing** wavelength f (frequency) = c (speed of light) / λ (wavelength) geomagnetic & sub ELF sources extremely low frequency very low frequency radio frequency spectrum microwaves infrared visible ultra violet x-rays gamma cosmic rays EMF Sources earth & subways AC power CRT monitors mobile AM/FM TV cell/PCS microwave & satellite sunlight **medical x-rays** **radioactive sources** gigahertz (GHz) 10^-9 terahertz (THz) 10^-12 petahertz (PHz) 10^-15 exahertz (EHz) 10^-18 zettahertz (ZHz) 10^-21 yottahertz (YHz) 10^-24 Labelled diagram of the electromagnetic spectrum showing the relationship between frequency and wavelength. The diagram features a central sinusoidal wave that transitions from long wavelengths on the left to short wavelengths on the right. It is divided into two main sections: 'non-ionizing' (red background) covering lower frequencies like geomagnetic, ELF, VLF, radio frequency, microwaves, infrared, and visible light; and 'ionizing' (blue background) covering higher frequencies like ultraviolet, x-rays, and gamma cosmic rays. Below the wave, there are icons representing EMF sources for each category, such as earth/subways, AC power, CRT monitors, mobile phones, sunlight, medical x-rays, and radioactive sources. Based on the image provided, here is the extracted text. Note that "ionising" is formatted as bold. # Properties of X-ray * Composed of photons (a quanta of energy) * They are invisible * They have high energy (short wavelengths & high frequencies) * They have no mass or charge * Travel at the speed of light * **Each** x-ray photon travels in a straight line * X-ray beam can be deflected and scattered * Cannot be focused from their point of origin; they diverge * Can penetrate or may be absorbed by matter (other factors also involved) * Cause some substances to fluoresce * Can affect photographic film * They are **ionising radiation** & can cause biological damage _figures/img_7852ddc9144b0b2f.webp) - Composed of photons (a quanta of energy) - They are invisible - They have high energy (short wavelengths & high frequencies) - They have no mass or charge - Travel at the speed of light - **Each** x-ray photon travels in a straight line - X-ray beam can be deflected and scattered - Cannot be focused from their point of origin; they diverge - Can penetrate or may be absorbed by matter (other factors also involved) - Cause some substances to fluoresce - Can affect photographic film - They are **ionising radiation** & can cause biological damage A stylized graphic symbol representing an X-ray or radiation. The image depicts a purple lightning bolt shape pointing downwards and to the right, visually reinforcing the theme of high-energy ionizing radiation discussed in the text. _figures/img_0fa790475f712475.webp) _figures/img_dbdc78a13b1f3315.webp) _figures/img_62e8be93f032db35.webp) Labelled diagram of an atom showing the nucleus at the center containing protons (+) and neutrons. Two concentric circular orbits are shown around the nucleus with orbital electrons (-) positioned on them. Labelled diagram of an atom showing a central nucleus with protons (red) and neutrons (blue). Several elliptical orbits surround the nucleus with blue dots representing electrons at various positions along the paths. Chart illustrating electron shell capacity. It shows five concentric arcs labeled K, L, M, N, O from inner to outer shell. Below each arc is the maximum number of electrons it can hold: 2, 8, 18, 32, and 50 respectively. The chart includes a small illustration of a nucleus at the bottom center. Ionising Radiation • Ionisation is a process when an atom **loses an electron** and becomes a positive ion. • To ionise an atom, sufficient **energy** is required to overcome the electrostatic force (binding energy of the electrons to the nucleus). • The binding energy of an electron is related to the atomic number of the atom and the orbital type. * Large atomic number = large no. of protons in the nucleus → High bind energy of electrons electrons → **High energy is required to IONIZE atoms** • For molecules, exposure to ionizing radiation may also break chemical bonds, fragmenting the molecule → biological change! Ionising Radiation - Ionisation is a process when an atom **loses an electron** and becomes a positive ion. - To ionise an atom, sufficient **energy** is required to overcome the electrostatic force (binding energy of the electrons to the nucleus). - The binding energy of an electron is related to the atomic number of the atom and the orbital type. - Large atomic number = large no. of protons in the nucleus → High bind energy of electrons → **High energy is required to IONIZE atoms** - For molecules, exposure to ionizing radiation may also break chemical bonds, fragmenting the molecule → biological change! Purple lightning bolt icon symbolizing ionising radiation. X-ray Photon Production The production of x-ray photons requires 3 important processes: 1. **Production of electrons** 2. **Acceleration** of these electrons such that they have high kinetic energy 3. **Impact** of these electrons into other atoms _figures/img_efbc060c2ac22c7e.webp) X-ray Photon Production The production of x-ray photons requires 3 important processes: 1. **Production of electrons** 2. **Acceleration** of these electrons such that they have high kinetic energy 3. **Impact** of these electrons into other atoms Labelled diagram illustrating the three stages of X-ray photon production. The diagram is divided into three numbered panels (1, 2, 3) showing a schematic cross-section of an X-ray tube with a cathode (left), anode target (right), and electron beam path (red arrow). Panel 1 shows initial electron production from the cathode filament. Panel 2 depicts the acceleration of these electrons across the vacuum gap towards the anode. Panel 3 illustrates the impact of high-energy electrons striking the anode, resulting in the emission of X-rays (shown as red rays). **Dental X-ray Tubehead** * Primary components of a tube head include: > X-ray tube and power supply * Other components: * An electrical insulating material, usually oil, surrounds the x-ray tube (conducts heat away from the x-ray tube). * **Lead Casing/Glass**: Removes scattered x-rays. * **Aluminium Filter**: removes soft (low energy) x-rays from the primary beam. * **PID** (position indicating device; 200mm in length) $\rightarrow$ provides optimum distance (least divergence & unclearness) * **Collimator** (opening) $\rightarrow$ restricts beam to usable size * Entire tube head is supported by **an arm** that is mounted on a wall. * **Control panel** available for adjusting: duration of exposure, and energy and exposure rate of the x-ray beam. _figures/img_d036650efb6b442b.webp) **Dental X-ray Tubehead** - Primary components of a tube head include: - X-ray tube and power supply - Other components: - An electrical insulating material, usually oil, surrounds the x-ray tube (conducts heat away from the x-ray tube). - **Lead Casing/Glass**: Removes scattered x-rays. - **Aluminium Filter**: removes soft (low energy) x-rays from the primary beam. - **PID** (position indicating device; 200mm in length) → provides optimum distance (least divergence & unclearness) - **Collimator** (opening) → restricts beam to usable size - Entire tube head is supported by **an arm** that is mounted on a wall. - **Control panel** available for adjusting: duration of exposure, and energy and exposure rate of the x-ray beam. Labelled schematic diagram of a Dental X-ray Tubehead. The image displays the internal cross-section of the tube head with callouts identifying components: 'Leaded Glass Tube', 'Metal Housing', 'Oil' (filling the space), 'Cathode', 'Filament', 'Anode (Tungsten Target)', 'Lead Diaphragm', 'Electrons' path, and 'Aluminum Filter'. On the right side, it labels external attachments including the 'Cone', 'Tube', and 'Position Indicating Device (PID)'. X-ray Tube • Composed of a **cathode** (-ve) and an **anode** (+ve) within an **evacuated glass/tube**. Power Supply kVp & mA Typically, kvP of an intraoral x-ray machine is 70kvp _figures/img_8dbafe0730fd2555.webp) X-ray Tube - Composed of a **cathode** (-ve) and an **anode** (+ve) within an **evacuated glass/tube**. Power Supply kVp & mA Typically, kVp of an intraoral x-ray machine is 70 kVp. Labelled diagram of an X-ray tube. The visual depicts a 'cathode' on the left (containing a 'heated filament') and an 'anode' on the right (with a 'metal target (tungsten)' and 'anode mounting (copper)'). An 'electron beam' is shown traveling from the cathode to the anode. Upon impact, 'X-rays' are emitted through a 'window'. Labels indicate an 'evacuated chamber', 'coolant circulates here', and connections to a 'Power Supply kVp & mA'. A note states: 'Typically, kvP of an intraoral x-ray machine is 70kvp'. Cathode Tungsten filament Molybdenum cup Anode Electron stream Tungsten target Copper stem Unleaded glass window X-ray beam Vacuum Leaded-glass housing _figures/img_d1d9807cac154d7f.webp) Cathode Tungsten filament Molybdenum cup Anode Electron stream Tungsten target Copper stem Unleaded glass window X-ray beam Vacuum Leaded-glass housing Labelled diagram of an X-ray tube showing internal components and operational flow. Labels include: Cathode (with Tungsten filament inside Molybdenum cup), Anode (with Tungsten target on Copper stem), Electron stream (arrow from cathode to anode), X-ray beam (wavy red lines exiting through Unleaded glass window), Vacuum (inside Leaded-glass housing). The diagram illustrates the path of electrons accelerating from the negative cathode to the positive anode target within a vacuum environment. Cathode (-) - The cathode (-ve) consists of a **tungsten filament** and a **molybdenum focusing cup**. The *filament* is the source of *electrons* within the x-ray tube. - The filament is heated by the flow of current from the low-voltage source (~ 10 volts) and emits electrons at a rate proportional to the temperature of the filament. - **Focusing cup** is also negatively charged. - Concave shape and charge serve to focus the electrons into a beam that is aimed at the **focal spot** on the anode. (electron clouds) - Electrons are then accelerated (gaining kinetic energy) by the second high-voltage source (60-100 kilovolts) and move / are attracted to the positively charged anode (focal spot). - Diagram showing internal x-ray tube: *Focusing cup* (concave component left), *Filament* (small rod tip), *High voltage circuit* (top right electrical lead), and *Filament circuit* (bottom right electrical lead). _figures/img_a3f8cd8f4bad5c22.webp) ##### Cathode (-) - The cathode (-ve) consists of a **tungsten filament** and a **molybdenum focusing cup**. The *filament* is the source of *electrons* within the x-ray tube. - The filament is heated by the flow of current from the low-voltage source (~ 10 volts) and emits electrons at a rate proportional to the temperature of the filament. - **Focusing cup** is also negatively charged. - Concave shape and charge serve to focus the electrons into a beam that is aimed at the **focal spot** on the anode. (electron clouds) - Electrons are then accelerated (gaining kinetic energy) by the second high-voltage source (60-100 kilovolts) and move / are attracted to the positively charged anode (focal spot). - Diagram showing internal x-ray tube: *Focusing cup* (concave component left), *Filament* (small rod tip), *High voltage circuit* (top right electrical lead), and *Filament circuit* (bottom right electrical lead). Labelled diagram of an x-ray tube cathode assembly. The illustration shows a cutaway view of the internal components. Labels point to specific parts: 'Focusing cup' indicates the concave metallic structure on the left; 'Filament' points to the small rod-like element inside the cup; 'High voltage circuit' identifies the electrical lead at the top right; and 'Filament circuit' points to the lead at the bottom right. # Tungsten Atom (Z = 74) * Electron volt binding energy decreases as the shell to nucleus distance increases. * Tungsten has an K shell electron binding energy is approximately 70keV. * It has a high atomic number (74), a high melting point, **high thermal conductivity**, and low vapor pressure at the working temperatures of an x-ray tube. * Tungsten has **high thermal conductivity**, thus readily dissipating its heat into the copper stem. _figures/img_a28b6c4fb9022f5a.webp) ##### Tungsten Atom (Z = 74) - Electron volt binding energy decreases as the shell to nucleus distance increases. - Tungsten has an K shell electron binding energy is approximately 70 keV. - It has a high atomic number (74), a high melting point, **high thermal conductivity**, and low vapor pressure at the working temperatures of an x-ray tube. - Tungsten has **high thermal conductivity**, thus readily dissipating its heat into the copper stem. Bohr model diagram of a Tungsten atom (Z = 74). The central nucleus is labeled 'W' in a pink circle. Surrounding the nucleus are six concentric rings representing electron shells, with dots indicating electrons at specific orbital positions. Text above the diagram specifies '74: Tungsten' and provides the electron shell configuration as '2,8,18,32,12,2', corresponding to the number of electrons on each ring. Anode (+) • Consists of a **tungsten target** in a **copper stem**. • Typically, the target is placed at an angle (inclined about 20 degrees) to the electron beam • to generate a much smaller (outgoing) beam → the more ‘focused’ the beam, the sharper the radiographic image at the expense of generating more heat • Target converts the kinetic energy of the colliding electrons into **x-ray photons**. • Conversion of the kinetic energy of the electrons into x-ray photons is an inefficient process as 99% of the electron kinetic energy converted to heat. • A target made of a **high atomic number material** is **most efficient in producing x rays**. • Copper stem removes heat from the tungsten, reducing the risk of the target melting. • Additionally, the insulating oil carries heat away from the copper stem. _figures/img_9ef477c7aab2c29a.webp) _figures/img_7b2963f4f23f44b7.webp) ##### Anode (+) - Consists of a **tungsten target** in a **copper stem**. - Typically, the target is placed at an angle (inclined about 20 degrees) to the electron beam - to generate a much smaller (outgoing) beam → the more ‘focused’ the beam, the sharper the radiographic image at the expense of generating more heat - Target converts the kinetic energy of the colliding electrons into **x-ray photons**. - Conversion of the kinetic energy of the electrons into x-ray photons is an inefficient process as 99% of the electron kinetic energy converted to heat. - A target made of a **high atomic number material** is **most efficient in producing x rays**. - Copper stem removes heat from the tungsten, reducing the risk of the target melting. - Additionally, the insulating oil carries heat away from the copper stem. Diagram illustrating the concept of focal spots on an anode. It shows a cross-section of an angled target emitting X-rays. Dashed lines project from the actual point of electron impact (labeled 'ACTUAL FOCAL SPOT') to form a larger projected area (labeled 'EFFECTIVE FOCAL SPOT'), demonstrating how the angle affects the apparent size of the beam source. Enlarged schematic diagram of the anode target. It depicts incoming electrons striking a tungsten block embedded in a copper block. Arrows indicate the conversion process: most kinetic energy is converted to Heat (absorbed by the copper), while a smaller portion becomes X-ray photons that exit through a window in the lead casing as the X-ray beam. Heat Production in Tungsten Target (on Anode) - Most high-speed electrons interacting with the tungsten target release their energy as heat (99%) ☹ - Heat is produced the following ways: 1. The incoming electron is **deflected** by the cloud of outer-shell target electrons with a small loss of energy in the form of heat 2. The incoming electron **collides with** an outer shell target electron displacing the target electron to a more peripheral shell (excitation) or displacing the target electron from the atom (ionisation) with a small loss of energy in the form of heat _figures/img_e32b2341d3daa7fd.webp) _figures/img_8178bcc7bce3d665.webp) Heat Production in Tungsten Target (on Anode) - Most high-speed electrons interacting with the tungsten target release their energy as heat (99%) ☹ - Heat is produced the following ways: 1. The incoming electron is **deflected** by the cloud of outer-shell target electrons with a small loss of energy in the form of heat 2. The incoming electron **collides with** an outer shell target electron displacing the target electron to a more peripheral shell (excitation) or displacing the target electron from the atom (ionisation) with a small loss of energy in the form of heat Diagram illustrating heat production via electron deflection. Shows a cross-section of an atom with concentric electron shells and a central nucleus. An incoming electron path is shown being deflected by the outer-shell cloud, with a callout arrow labeled 'Heat' indicating energy loss. Diagram illustrating heat production via electron collision (excitation/ionization). Shows a similar atomic model. An incoming electron collides with an outer-shell target electron, which is displaced to a more peripheral shell or ejected. A callout arrow labeled 'Heat' indicates the small loss of energy from this interaction. **Bremsstrahlung radiation and characteristic radiation.** _figures/img_17b1a9902d3aeeb4.webp) **Bremsstrahlung radiation and characteristic radiation.** Labeled diagram illustrating X-ray production in a Tungsten target. It depicts two scenarios side-by-side: on the left, a 'Primary Electron Beam' interacts with atomic shells to produce 'Continuous X-rays' and a 'Scattered Electron'; on the right, the beam causes 'Characteristic X-ray Emission' and produces 'Scattered Electrons'. A URL source is visible at the bottom. # Bremsstrahlung Radiation **Bremsstrahlung = “Braking” in German** - More than **70%** of dental x-rays - Electrons’ sudden stopping or decrease in speed by tungsten nuclei causes the electrons to lose kinetic energy → producing bremsstrahlung photons - The closer the electron approaches the nuclei, the greater the braking effect, and the greater the energy of the resulting bremsstrahlung photons. - High Z (atomic number) metals (more protons) are more effective in deflecting the path of the incident electrons. - Large deflections produce high-energy photons - Small deflections produce low-energy photons _figures/img_30a4480d10b04598.webp) ##### Bremsstrahlung Radiation **Bremsstrahlung = “Braking” in German** - More than **70%** of dental x-rays - Electrons’ sudden stopping or decrease in speed by tungsten nuclei causes the electrons to lose kinetic energy → producing bremsstrahlung photons - The closer the electron approaches the nuclei, the greater the braking effect, and the greater the energy of the resulting bremsstrahlung photons. - High Z (atomic number) metals (more protons) are more effective in deflecting the path of the incident electrons. - Large deflections produce high-energy photons - Small deflections produce low-energy photons Labelled diagram illustrating Bremsstrahlung Radiation. The image depicts a Tungsten atom nucleus (labeled '74 p+ 110 n-') surrounded by electron shells. Two incident electrons approach the nucleus from different angles. One electron undergoes a large deflection close to the nucleus, emitting a 'High Energy Bremsstrahlung X-Ray Photon'. The other electron experiences a smaller deflection further from the nucleus, emitting a 'Low Energy Bremsstrahlung X-Ray Photon'. Bremsstrahlung Radiation cont’d. • Reality $\rightarrow$ more low energy • Resultant spectrum shows a large number of small energy photons and a small number of high energy photons, with a continuous spectrum in between • Note: Low energy photons have little penetrating power and do not contribute to a useful x-ray beam and a removed by filtration. _figures/img_ed9350cc200db918.webp) Bremsstrahlung Radiation cont’d. - Reality → more low energy - Resultant spectrum shows a large number of small energy photons and a small number of high energy photons, with a continuous spectrum in between - Note: Low energy photons have little penetrating power and do not contribute to a useful x-ray beam and are removed by filtration. Line chart showing the Bremsstrahlung radiation spectrum. The y-axis represents 'Number of photons (intensity)' and the x-axis represents 'Photon energy (keV)'. A diagonal line slopes downwards from high intensity at low energy to zero intensity at a point labeled 'Maximum energy (E max) of any photon' (at 100 keV). The area under the curve is shaded gray. Characteristic Radiation • Only a **small** fraction of dental x-rays • Occurs when an incident electron (from the incoming beam) ejects an inner orbit electron from the tungsten target. • The electron vacancy is filled by an electron from an outer orbit. • A photon is emitted with energy equal to the difference in energy between the two orbits. • The energies of characteristic photons are **discrete** because they represent the difference of the energy levels of electron orbital levels and hence are characteristic of the target atom. _figures/img_933b4ed3af6ac9c1.webp) ##### Characteristic Radiation - Only a **small** fraction of dental x-rays - Occurs when an incident electron (from the incoming beam) ejects an inner orbit electron from the tungsten target. - The electron vacancy is filled by an electron from an outer orbit. - A photon is emitted with energy equal to the difference in energy between the two orbits. - The energies of characteristic photons are **discrete** because they represent the difference of the energy levels of electron orbital levels and hence are characteristic of the target atom. A four-panel labelled diagram illustrating the process of characteristic radiation. The panels are numbered 1 through 4 and depict atomic models with K, L, and M electron shells. Panel 1 shows an 'Incident Cathode Electron' striking a target atom, causing the ejection of a K shell electron (indicated by an explosion graphic). Panel 2 depicts the result: an 'Ejected K Shell Electron' leaving the atom and a 'Deflected Cathode Electron' moving away. A label points to the empty space in the innermost shell as a 'K Shell Vacancy'. Panel 3 illustrates an outer orbit electron moving down to fill the vacancy in the K shell. Panel 4 shows the emission of an "L" Characteristic Radiation photon (represented by a wavy arrow) as the transition occurs. Another label indicates that this process can also produce "K" Characteristic Radiation. Characteristic Radiation cont’d. • Discrete, specific energies (**characteristic**) ie. no continuous spectrum _figures/img_52cc0aab8eecfd2f.webp) _figures/img_c3d0a131c270bb96.webp) Characteristic Radiation cont’d. - Discrete, specific energies (**characteristic**) ie. no continuous spectrum Energy level diagram showing the Binding Energy of tungsten. The y-axis lists electron shells (P, O, N, M, L, K) with corresponding binding energies: 0.02 keV, 0.07 keV, 0.6 keV, 2 keV, 11 keV, and 70 keV respectively. Red arrows labeled kα and kβ indicate transitions from the M shell to the K shell. Blue arrows labeled Lα and Lβ indicate transitions from the L shell to the K shell. Bar chart titled 'Characteristic Radiation Spectra (Tungsten Atom)'. The x-axis represents Photon energy (keV) ranging from 0 to over 100. The y-axis represents Number of photons (intensity). Two groups of vertical bars are visible: a cluster on the left at low energy labeled 'L lines', and a taller cluster around 60 keV labeled 'K lines'. # Spectrum of X-ray Photons (at 70 kVp & 100 kVp, Tungsten Target) ### [Left Graph] **Y-axis:** Relative number of photons **X-axis:** Photon energy (keV) [Scale: 10, 20, 30, 40, 50, 60, 70] **Main Curve:** Bremsstrahlung radiation **Spikes:** Characteristic radiation ### [Right Graph] **Title:** Direct Tungsten (W) Spectrum at 100 kVp **Y-axis:** Counts **X-axis:** Energy (keV) [Scale: 0 to 106] **Labeled Peaks (Discrete values):** * 59.3 keV * 67.2 keV **Labeled End Point:** * End Point Energy (kVp) at 100 keV _figures/img_32e00699e83aa8bf.webp) _figures/img_2d92ba12e6d4a070.webp) ##### Spectrum of X-ray Photons (at 70 kVp & 100 kVp, Tungsten Target) **Left Graph** - Y-axis: Relative number of photons - X-axis: Photon energy (keV) [Scale: 10, 20, 30, 40, 50, 60, 70] - Main Curve: Bremsstrahlung radiation - Spikes: Characteristic radiation **Right Graph** - Title: Direct Tungsten (W) Spectrum at 100 kVp - Y-axis: Counts - X-axis: Energy (keV) [Scale: 0 to 106] - Labeled Peaks (Discrete values): - 59.3 keV - 67.2 keV - Labeled End Point: - End Point Energy (kVp) at 100 keV Line chart showing the spectrum of X-ray photons at 70 kVp. The Y-axis represents the 'Relative number of photons' and the X-axis shows 'Photon energy (keV)' with a scale from 10 to 70. A broad curve labeled 'Bremsstrahlung radiation' dominates the graph, peaking around 20-25 keV. At higher energies (near 60 keV), sharp vertical spikes are labeled as 'Characteristic radiation'. Detailed histogram titled 'Direct Tungsten (W) Spectrum at 100 kVp'. The Y-axis is 'Counts' and the X-axis is 'Energy (keV)' ranging from 0 to 106. The purple distribution shows a continuous background with distinct peaks labeled 'Discrete values' at 59.3 keV and 67.2 keV. An arrow points to the cutoff on the right, labeled 'End Point Energy (kVp) at 100 keV'. # Factors Controlling the X-ray Beam 1. Tube Voltage (kVp) 2. Filtration 3. Tube Current (mA) 4. Duration (time in seconds) 5. Collimation 6. Target-Patient Distance • Inverse-square law ##### Factors Controlling the X-ray Beam 1. Tube Voltage (kVp) 2. Filtration 3. Tube Current (mA) 4. Duration (time in seconds) 5. Collimation 6. Target-Patient Distance - Inverse-square law A stylized purple lightning bolt icon located in the top right corner of the slide. X-ray Altered by: Tube Voltage (kVp) - Spectrum of photon energies showing that as the kVp increases (mA constant) there is a corresponding increase in: 1. the mean energy of the beam, 2. the total number of photons emitted, and 3. the maximum energy of the photons. _figures/img_1d29643361381e12.webp) ##### X-ray Altered by: Tube Voltage (kVp) - Spectrum of photon energies showing that as the kVp increases (mA constant) there is a corresponding increase in: 1. the mean energy of the beam, 2. the total number of photons emitted, and 3. the maximum energy of the photons. Line chart showing the spectrum of photon energies. The x-axis represents Photon energy (keV) from 0 to 100, and the y-axis represents Relative number of photons from 0 to 100. Three curves are plotted corresponding to different tube voltages: 80 kVP, 90 kVP, and 100 kVP. As kVP increases, the peak of the curve shifts to higher energy values and the total area under the curve increases. # X-ray Altered by: Filtration of Beam • Filtration of an x-ray beam with aluminium results in the preferential **removal of low-energy photons**, reducing the intensity of the beam but increasing its mean energy. (also decrease in no. of photons) *(Note: The graph has "Relative number of photons" on the y-axis and "Photon energy (keV)" on the x-axis. It displays two curves: "Nonfiltered beam" (peaking around 90-100) and "Filtered beam (Al filter)" (peaking around 55-60).)* 30 _figures/img_4d2a196d5d52d8c2.webp) ##### X-ray Altered by: Filtration of Beam - Filtration of an x-ray beam with aluminium results in the preferential **removal of low-energy photons**, reducing the intensity of the beam but increasing its mean energy. (also decrease in no. of photons) *(Note: The graph has "Relative number of photons" on the y-axis and "Photon energy (keV)" on the x-axis. It displays two curves: "Nonfiltered beam" (peaking around 90-100) and "Filtered beam (Al filter)" (peaking around 55-60).)* Chart showing the effect of aluminium filtration on an x-ray beam. The vertical axis represents the 'Relative number of photons' (0 to 100) and the horizontal axis shows 'Photon energy (keV)' (0 to 70). Two curves are plotted: the upper curve is labeled 'Nonfiltered beam' which peaks at a relative value of approximately 95 around 30 keV; the lower curve is labeled 'Filtered beam (Al filter)' which has a reduced peak height of about 55-60 at roughly 30 keV. This visual demonstrates that filtering removes low-energy photons, decreasing total intensity while shifting the spectral distribution. _figures/img_6c45260a7e4c45dc.webp) Chart showing the spectrum of photon energies resulting from increasing tube current (mA) while maintaining tube voltage (kVp). The x-axis represents Photon energy (keV) ranging from 0 to 70. The y-axis represents Relative number of photons ranging from 0 to 100. Two curves are shown: one for 20 mA and another for 10 mA. The curve for 20 mA is higher than the curve for 10 mA, indicating that increasing the tube current increases the relative number of photons. X-ray Altered by: Duration / Exposure Time - As the exposure time increases the total number of photons increases, but the mean energy and maximum energy of the beams are unchanged. _figures/img_515b8e14c71cca4f.webp) ##### X-ray Altered by: Duration / Exposure Time - As the exposure time increases the total number of photons increases, but the mean energy and maximum energy of the beams are unchanged. Line chart showing the relationship between photon energy and relative number of photons for two different exposure durations. The x-axis represents Photon energy (keV) ranging from 0 to 70. The y-axis represents Relative number of photons ranging from 0 to 100. Two curves are plotted: one labeled '2-second exposure' peaking near 100 at approximately 25-30 keV, and another labeled '1-second exposure' peaking near 50 at the same energy range. The visual demonstrates that increasing exposure time increases total photon count without altering the energy distribution shape. **X-ray Altered by: Collimation (shape of the beam)** * A collimator is a metallic barrier with an aperture in the middle used to reduce the size of the x-ray beam * Dental x-ray beams are usually collimated to a circle (7 cm in diameter) * Less frequently, there are rectangular collimators in dentistry * Typically, round collimators are built into open-ended aiming cylinders. * Rectangular collimators further limit the size of the beam to just larger than the x-ray film (intraoral x-ray films are rectangular), thereby further reducing patient exposure. A | B _figures/img_e216b84c279dbc8c.webp) _figures/img_d0c9e87f2aa4a08e.webp) ##### X-ray Altered by: Collimation (shape of the beam) - A collimator is a metallic barrier with an aperture in the middle used to reduce the size of the x-ray beam - Dental x-ray beams are usually collimated to a circle (7 cm in diameter) - Less frequently, there are rectangular collimators in dentistry - Typically, round collimators are built into open-ended aiming cylinders. - Rectangular collimators further limit the size of the beam to just larger than the x-ray film (intraoral x-ray films are rectangular), thereby further reducing patient exposure. A | B Diagram of an X-ray machine head with a circular collimator attached to the end of the aiming cylinder. The diagram shows the internal components and the path of the X-ray beam through the circular aperture. Three diagrams showing different types of collimators (A: round, B: rectangular) attached to X-ray machine heads and their alignment with a patient's mouth. The diagrams illustrate how the collimator shapes the X-ray beam to match the size of the intraoral film or sensor. **X-ray Altered by: Intensity / Distance** * **Inverse Square Law** = For a given beam, the intensity is inversely proportional to the square of the distance from the source * The intensity of an x-ray beam (the number of photons per cross-sectional area per unit of exposure time) depends on the distance of the measuring device from the focal spot. 2x distance = ¼ x Radiation **Visual Description:** The page contains two diagrams illustrating the Inverse Square Law. The top diagram shows an X-ray tube on the left emitting diverging dashed lines onto a grid of squares at two different distances (nearer and farther) to demonstrate beam divergence. The bottom diagram shows a source point emitting rays outward through three cross-sections marked A, $2r$, and $3r$, with labels for sphere area ($4\pi r^2$) and intensity ($I$), along with fractions representing intensity ($\frac{1}{4}$, $\frac{1}{9}$). _figures/img_766ff5240d095ae0.webp) _figures/img_a75ebc6f8d7e450a.webp) ##### X-ray Altered by: Intensity / Distance - **Inverse Square Law** = For a given beam, the intensity is inversely proportional to the square of the distance from the source - The intensity of an x-ray beam (the number of photons per cross-sectional area per unit of exposure time) depends on the distance of the measuring device from the focal spot. 2x distance = ¼ x Radiation **Visual Description:** The page contains two diagrams illustrating the Inverse Square Law. The top diagram shows an X-ray tube on the left emitting diverging dashed lines onto a grid of squares at two different distances (nearer and farther) to demonstrate beam divergence. The bottom diagram shows a source point emitting rays outward through three cross-sections marked A, $2r$, and $3r$, with labels for sphere area ($4\pi r^2$) and intensity ($I$), along with fractions representing intensity ($\frac{1}{4}$, $\frac{1}{9}$). Diagram showing an X-ray tube emitting diverging dashed lines onto a grid of squares at two different distances (nearer and farther) to demonstrate beam divergence. Diagram illustrating the Inverse Square Law with a source point emitting rays outward through three cross-sections marked A, 2r, and 3r. Includes labels for sphere area (4πr²), intensity (I), fractions representing intensity (1/4, 1/9), and text explaining that energy twice as far from the source is spread over four times the area, hence one-fourth the intensity. 2. Radiation Safety How to minimise radiation for patient and staff? How to minimise radiation for patient and staff? # Contents * X-ray & Tissue (eg. Patient) Interaction * Direct and Indirect Damage * Biological Effects of X-rays (& all other ionising radiation) * Dosimetry * Other Sources of Ionising Radiation (Patient Education) * How to minimise radiation in clinic? - X-ray & Tissue (eg. Patient) Interaction - Direct and Indirect Damage - Biological Effects of X-rays (& all other ionising radiation) - Dosimetry - Other Sources of Ionising Radiation (Patient Education) - How to minimise radiation in clinic? Patient Interactions with X-ray Photon 3 possible outcomes: 1. X-ray photons **pass through** patient without any interaction 2. X-ray photons are **completely absorbed** by patient 3. X-ray photons are **scattered** (coherent and incoherent) _figures/img_1bd8a5f8a6f76dd2.webp) #### Patient Interactions with X-ray Photon 3 possible outcomes: 1. X-ray photons **pass through** patient without any interaction 2. X-ray photons are **completely absorbed** by patient 3. X-ray photons are **scattered** (coherent and incoherent) Diagram illustrating the three possible outcomes of X-ray photon interactions with a patient. The visual shows an 'X-ray tubehead' at the top emitting rays toward a 'Patient's head'. Three numbered paths demonstrate the interaction types: Path 1 (labeled 'pass through') shows photons exiting the side of the head; Path 2 (labeled 'absorbed') shows photons stopping within the head; Path 3 (labeled 'scattered') shows photons deflecting in a different direction. A 'Film' detector is positioned below to capture the resulting image. No Interaction with Tissues (Atoms) - X-ray photon passes through atom unchanged - These photons contact the film emulsion or receptor to produce an area of darker density - ~9% of the primary photons _figures/img_9e9f6ea3c0e0546b.webp) #### No Interaction with Tissues (Atoms) - X-ray photon passes through atom unchanged - These photons contact the film emulsion or receptor to produce an area of darker density - ~9% of the primary photons Labeled diagram illustrating an X-ray photon passing through an atom. The diagram features a central nucleus surrounded by concentric dashed lines representing electron shells with small circles indicating electrons. An arrow labeled 'X-ray photon' points diagonally upwards and to the right, labeled 'Passes through atom', demonstrating no interaction. **X-ray Absorption & Scattering** • As the x-ray beam passes through tissues, photons get <br>absorbed or scattered by the tissues, resulting in <br>decreased energy of the beam • **Beam attenuation**: reduction of the x-ray beam intensity <br>as it passes through tissues. • In a dental x-ray beam, there are three means of beam <br>attenuation: <br>• 1) Photoelectric absorption (~27%) <br>• 2) Thompson/Coherent scattering (~7%) <br>• 3) Compton/Incoherent scattering (~57% of the primary <br>beam) _figures/img_6d3416dbbbd19e2a.webp) #### X-ray Absorption & Scattering - As the x-ray beam passes through tissues, photons get absorbed or scattered by the tissues, resulting in decreased energy of the beam - **Beam attenuation**: reduction of the x-ray beam intensity as it passes through tissues. - In a dental x-ray beam, there are three means of beam attenuation: - 1) Photoelectric absorption (~27%) - 2) Thompson/Coherent scattering (~7%) - 3) Compton/Incoherent scattering (~57% of the primary beam) Anatomical diagram illustrating X-ray beam attenuation through a human head. The image shows arrows representing the x-ray beam entering from the left and exiting to the right. Four distinct interaction pathways are labeled with percentages: 'No interaction 9%' (beam passes straight through), 'Coherent scattering 7%' (beam scatters slightly off-center), 'Photoelectric absorption 27%' (beam absorbed at the nose area), and 'Compton scattering 57%' (beam scattered significantly off-axis). Yellow starburst icons highlight the points of interaction within the facial anatomy. Photoelectric Absorption Incident photon interacts with an inner orbital electron of an atom in the patient. Incident photon gives up all of its energy and ceases to exist. Incident photon **ejects the electron** from its inner orbital, and it becomes a recoil electron (photoelectron). An atom that has participated in a photoelectric interaction is **ionized** as result of the loss of an electron. Electron deficiency is instantly filled, releasing **characteristic radiation** The characteristic photons generated are of such **low energy** that they are **absorbed within the patient** and do not fog the film. Primary contributor to diagnostic imaging. _figures/img_95ba2fbe27d3fced.webp) Incident photon interacts with an inner orbital electron of an atom in the patient. Incident photon gives up all of its energy and ceases to exist. Incident photon **ejects the electron** from its inner orbital, and it becomes a recoil electron (photoelectron). An atom that has participated in a photoelectric interaction is **ionized** as result of the loss of an electron. Electron deficiency is instantly filled, releasing **characteristic radiation**. The characteristic photons generated are of such **low energy** that they are **absorbed within the patient** and do not fog the film. Primary contributor to diagnostic imaging. Labelled diagram illustrating the Photoelectric effect. The image shows an atom with concentric electron shells and a central nucleus. An incoming 'X-ray photon' is depicted as a straight line striking an inner orbital electron. This interaction results in the ejection of the electron, labeled as a 'Photoelectron', which travels away from the atom. A wavy line labeled 'Characteristic radiation' emanates from the atom to represent the energy released when the electron vacancy is filled. Coherent Scattering / Thompson Scattering • Occurs minimally (7%) • **Low-energy incident photon** (<10 keV) interacts with a whole atom (*patient's*) • Atom becomes momentarily **excited** and incident photon ceases to exist. • Excited atom returns to the ground state and generates another x-ray photon with the same frequency (**energy**) as the incident photon, *however* this secondary photon is emitted in a different direction than the path of the incident photon (scattered). Coherent scattering contributes little to film fog (reduced image contrast) * Too low energy _figures/img_c1bf158fe43f802c.webp) ##### Coherent Scattering / Thompson Scattering - Occurs minimally (7%) - **Low-energy incident photon** (<10 keV) interacts with a whole atom (*patient's*) - Atom becomes momentarily **excited** and incident photon ceases to exist. - Excited atom returns to the ground state and generates another x-ray photon with the same frequency (**energy**) as the incident photon, *however* this secondary photon is emitted in a different direction than the path of the incident photon (scattered). Coherent scattering contributes little to film fog (reduced image contrast) - Too low energy Labelled diagram illustrating Coherent Scattering. The image shows an incident x-ray photon (labeled '1') approaching a whole atom model on the right side. The atom consists of concentric electron shells and a nucleus. The interaction causes the atom to momentarily excite, represented by label '2' pointing to the atom. A secondary scattered photon (labeled '3') is shown being emitted from the atom at a different angle than the incident path. The caption reads 'Coherent scattering (Thompson scattering)'. Compton Scattering - About 57% of interactions in a dental x-ray beam exposure involve Compton scattering. - Occurs when a photon interacts with an *outer orbital* electron. - **Recoil electron**: collided electron receives kinetic energy and recoils from the point of impact. - **Scattered photon**: the path of the incident photon is deflected by this interaction and is scattered in a new direction. - As with photoelectric absorption, Compton scattering results in the *loss of an electron* and *ionization* of the absorbing atom. - Scattered photons travel in all directions, carry no useful information and degrade the image by reducing contrast. (film fog) 😐 _figures/img_b433cdb0ac62276d.webp) ##### Compton Scattering - About 57% of interactions in a dental x-ray beam exposure involve Compton scattering. - Occurs when a photon interacts with an *outer orbital* electron. - **Recoil electron**: collided electron receives kinetic energy and recoils from the point of impact. - **Scattered photon**: the path of the incident photon is deflected by this interaction and is scattered in a new direction. - As with photoelectric absorption, Compton scattering results in the *loss of an electron* and *ionization* of the absorbing atom. - Scattered photons travel in all directions, carry no useful information and degrade the image by reducing contrast (film fog). Diagram illustrating Compton scattering. Shows an incident photon (labeled '1') interacting with an atom's outer orbital electron, resulting in a scattered photon (labeled '3') and a recoiling electron (labeled '2'). The diagram includes the atomic nucleus and electron shells. Sources of Ionizing Radiation • Natural Source • Background radiation (**cosmic, terrestrial, etc.**) • Approx. each person receives **2 mSv** per year • 1 day of background radiation = ~0.005 mSv • Artificial Source • Medical & Dental • Consumed products (potassium) • Occupational • Nuclear • Natural >>> Artificial per year *solar radiation* —— o ——— 14C cosmogenic radionuclides 3H 7Be 40K internal radionuclides 222Rn inhaled radionuclides 226Rn 232Th 238U 235U terrestrial radionuclides *Be - Beryllium* *C - Carbon* *H - Hydrogen* *K - Potassium* *Rn - Radon* *Th - Thorium* *U - Uranium* _figures/img_abbbf7212bc418c4.webp) _figures/img_ad014ae4fbbfa434.webp) #### Natural Source - Background radiation (**cosmic, terrestrial, etc.**) - Approx. each person receives **2 mSv** per year - 1 day of background radiation = ~0.005 mSv #### Artificial Source - Medical & Dental - Consumed products (potassium) - Occupational - Nuclear Natural >>> Artificial per year *solar radiation* —— o ——— 14C cosmogenic radionuclides 3H 7Be 40K internal radionuclides 222Rn inhaled radionuclides 226Rn 232Th 238U 235U terrestrial radionuclides *Be - Beryllium* *C - Carbon* *H - Hydrogen* *K - Potassium* *Rn - Radon* *Th - Thorium* *U - Uranium* Educational diagram illustrating the natural sources of ionizing radiation. The image depicts a central human figure standing in an environment divided into layers representing different radiation sources. The top layer is blue (sky), labeled with 'cosmic radiation' waves coming from space and specific isotopes like 14C, 3H, and 7Be ('cosmogenic radionuclides'). A sun icon on the left emits 'solar radiation'. The middle section contains the person, pointing to '40K internal radionuclides' inside their body. To the right of the person are rising bubbles labeled '222Rn inhaled radionuclides'. The bottom layer is orange (ground), showing various terrestrial elements including Be, C, H, K, Rn, Th, and U, with labels for 'terrestrial radionuclides', '226Rn', '232Th', '238U', and '235U'. A legend at the bottom left defines these chemical symbols. A photograph of a bunch of yellow bananas. Each banana has a black trefoil radiation hazard symbol overlaid on it. This visual serves as an illustrative example of 'consumed products' containing potassium-40, a source of artificial or internal radiation mentioned in the text. -In the US study (2006) _figures/img_5426ab28751d42f0.webp) In the US study (2006) Pie chart titled 'In the US study (2006)' showing percent contributions of various sources of exposure. Largest slice is red, labeled 'Radon & thoron (background) (37%)'. Second largest is blue, labeled 'Computed tomography (medical) (24%)'. Other slices include grey 'Nuclear medicine (medical) (12%)', brown 'Interventional fluoroscopy (medical) (7%)', olive green 'Conventional radiography/fluoroscopy (medical) (5%)', dark green 'Consumer (2%)', small grey 'Occupational (<0.1%)', light grey 'Industrial (<0.1%)', dark blue 'Terrestrial (background) (3%)', yellow 'Internal (background) (5%)', and green 'Space (background) (5%)'. A callout arrow points from text 'Dentistry contributes only 2.5% of this 5% from conventional radiography/fluoroscopy category.' (S. White, ADJ 2012) to the 'Conventional radiography/fluoroscopy' slice. _figures/img_780e671a18f4ad08.webp) Table titled 'Units for measuring quantities of radiation' with columns: QUANTITY, SI UNIT, TRADITIONAL UNIT, and CONVERSION. Rows list Exposure (Coulomb/kilogram, Roentgen), Absorbed dose (Gray, rad), Equivalent dose (Sievert, rem), Effective dose (Sievert, —), and Radioactivity (Becquerel, Curie). Includes conversion formulas in the rightmost column. # Radiation Dose Quantities and Units * **Absorbed dose:** radiation (in Joules) received by patient (in kg) * **Equivalent dose:** radiation absorbed by an organ * It is used to compare biologic effects of radiation on different types of tissue or organ * Unit is the Sievert (Sv) * **Effective dose:** radiation absorbed by an organ, affecting the *entire body*. * Effective dose = equivalent dose x tissue weighting factors (WT) according to ICRP 2007 * Tissues are grouped into: * high risk (WT = 0.12), * moderate risk (WT = 0.4-0.8) & * low risk (WT = 0.01) * Example) 100mSv to skin (=low risk tissue, WT = 0.01) = 1mSv to body * It is used to estimate the risk in humans. * Unit is the Sievert (Sv) _figures/img_e9aea702a936ae92.webp) - **Absorbed dose:** radiation (in Joules) received by patient (in kg) - **Equivalent dose:** radiation absorbed by an organ - It is used to compare biologic effects of radiation on different types of tissue or organ - Unit is the Sievert (Sv) - **Effective dose:** radiation absorbed by an organ, affecting the *entire body*. - Effective dose = equivalent dose x tissue weighting factors (WT) according to ICRP 2007 - Tissues are grouped into: - high risk (WT = 0.12), - moderate risk (WT = 0.4-0.8) & - low risk (WT = 0.01) - Example) 100mSv to skin (=low risk tissue, WT = 0.01) = 1mSv to body - It is used to estimate the risk in humans. - Unit is the Sievert (Sv) A structured table titled 'Radiation Dose Quantities and Units' presenting definitions for Absorbed dose, Equivalent dose, and Effective dose. It includes sub-points detailing units (Joules/kg, Sievert), risk categorizations (high, moderate, low with specific WT values), and an example calculation for effective dose. ### Title Tissue Weighting Factors & Radiosensitivity ### Table Data (ICRP 2007 Tissue Weighting Factors) <table> <thead> <tr> <th>Organs/tissue</th> <th>2007 WT</th> </tr> </thead> <tbody> <tr> <td>Gonads</td> <td>0.08</td> </tr> <tr> <td>Bone marrow (red)</td> <td>0.12</td> </tr> <tr> <td>Colon</td> <td>0.12</td> </tr> <tr> <td>Lung</td> <td>0.12</td> </tr> <tr> <td>Stomach</td> <td>0.12</td> </tr> <tr> <td>Bladder</td> <td>0.04</td> </tr> <tr> <td>Breast</td> <td>0.12</td> </tr> <tr> <td>Liver</td> <td>0.04</td> </tr> <tr> <td>Oesophagus</td> <td>0.04</td> </tr> <tr> <td>Thyroid</td> <td>0.04</td> </tr> <tr> <td>Skin</td> <td>0.01</td> </tr> <tr> <td>Bone surface</td> <td>0.01</td> </tr> <tr> <td>Brain</td> <td>0.01</td> </tr> <tr> <td>Salivary glands</td> <td>0.01</td> </tr> <tr> <td>Remainder</td> <td>0.12*</td> </tr> </tbody> </table> ### Radiosensitivity List (Figure) <table> <thead> <tr> <th>Cells/Tissue</th> </tr> </thead> <tbody> <tr> <td>BLOOD CELLS</td> </tr> <tr> <td>REPRODUCTIVE CELLS</td> </tr> <tr> <td>YOUNG BONE</td> </tr> <tr> <td>SKIN</td> </tr> <tr> <td>GLANDS</td> </tr> <tr> <td>MUSCLE</td> </tr> <tr> <td>NERVE</td> </tr> <tr> <td>MATURE BONE</td> </tr> </tbody> </table> #### Caption List of types of cells in order of sensitivity to x rays. ### Sensitive Cells Description Sensitive cells are more susceptible to damage: * Cells with a high mitotic activity * Cells with a high metabolic activity * Pluripotent (primitive) cells * Eg. Children _figures/img_e63b169448d53778.webp) _figures/img_9a1721572d450a45.webp) #### Tissue Weighting Factors & Radiosensitivity ##### ICRP 2007 Tissue Weighting Factors | Organs/tissue | 2007 WT | | :--- | :--- | | Gonads | 0.08 | | Bone marrow (red) | 0.12 | | Colon | 0.12 | | Lung | 0.12 | | Stomach | 0.12 | | Bladder | 0.04 | | Breast | 0.12 | | Liver | 0.04 | | Oesophagus | 0.04 | | Thyroid | 0.04 | | Skin | 0.01 | | Bone surface | 0.01 | | Brain | 0.01 | | Salivary glands | 0.01 | | Remainder | 0.12* | ##### Radiosensitivity List - BLOOD CELLS - REPRODUCTIVE CELLS - YOUNG BONE - SKIN - GLANDS - MUSCLE - NERVE - MATURE BONE *List of types of cells in order of sensitivity to x rays.* ##### Sensitive Cells Description Sensitive cells are more susceptible to damage: - Cells with a high mitotic activity - Cells with a high metabolic activity - Pluripotent (primitive) cells - Eg. Children Table titled 'Organs/tissue' with column '2007 WT'. Lists organs such as Gonads (0.08), Bone marrow (red) (0.12), Colon (0.12), Lung (0.12), Stomach (0.12), Bladder (0.04), Breast (0.12), Liver (0.04), Oesophagus (0.04), Thyroid (0.04), Skin (0.01), Bone surface (0.01), Brain (0.01), Salivary glands (0.01), and Remainder (0.12*). Caption below table: 'ICRP 2007 Tissue Weighting Factors'. Diagram labeled 'Figure' showing a list of cell types categorized by radiosensitivity. Left side lists: BLOOD CELLS, REPRODUCTIVE CELLS, YOUNG BONE grouped under 'RADIOSENSITIVE'; SKIN, GLANDS grouped under 'RADIORESPONSIVE'; MUSCLE, NERVE, MATURE BONE grouped under 'RADIORESISTANT'. Caption below: 'List of types of cells in order of sensitivity to x rays.' | TABLE | Effective dose from diagnostic x-ray examinations (mSv) | | :--- | :--- | | Barium enema\* | 4.06 | | Upper gastrointestinal tract\* | 2.44 | | **Computer tomography\*** | | | > Head and body | 1.11 | | Abdomen\* | 0.56 | | Skull\* | 0.22 | | Chest\* | 0.08 | | Full-mouth survey† | | | > 20 films, round collimation | 0.084 | | > 20 films, rectangular collimation | 0.033 | | Interproximal survey† | | | > 4 films, round collimation | 0.017 | | Panoramic tomography† | 0.007 | | Interproximal survey | | | > 4 films, rectangular collimation | 0.007 | | *From National Council on Radiation Protection and Measurements: *NCRP Reports* 100, Bethesda, MD, 1989. | | †From White SC: *Dentomaxillofac Radiol* 21:118-126, 1992. | | **Dose Thresholds (from top graphic)** | | :--- | | 10 mSv | | 100 mSv | | 1000 mSv | Intra-oral x-ray (bitewing / PA) = ~4μSv (0.004mSv) → Comparable to daily Australian background radiation (4- 5μSv at sea level) OPG ~ 10μSv Ceph view ~5μSv CBCT varies from 5 to 1073 μSv (depends on many factors) _figures/img_1730f962991619b1.webp) _figures/img_d00a94eb52406755.webp) | Effective dose from diagnostic x-ray examinations (mSv) | | | :--- | :--- | | Barium enema* | 4.06 | | Upper gastrointestinal tract* | 2.44 | | **Computer tomography*** | | | Head and body | 1.11 | | Abdomen* | 0.56 | | Skull* | 0.22 | | Chest* | 0.08 | | Full-mouth survey† | | | 20 films, round collimation | 0.084 | | 20 films, rectangular collimation | 0.033 | | Interproximal survey† | | | 4 films, round collimation | 0.017 | | Panoramic tomography† | 0.007 | | Interproximal survey | | | 4 films, rectangular collimation | 0.007 | *From National Council on Radiation Protection and Measurements: NCRP Reports 100, Bethesda, MD, 1989.* †From White SC: Dentomaxillofac Radiol 21:118-126, 1992. **Dose Thresholds (from top graphic)** - 10 mSv - 100 mSv - 1000 mSv Intra-oral x-ray (bitewing / PA) = ~4μSv (0.004mSv) → Comparable to daily Australian background radiation (4-5μSv at sea level) OPG ~ 10μSv Ceph view ~5μSv CBCT varies from 5 to 1073 μSv (depends on many factors) A table titled 'Effective dose from diagnostic x-ray examinations (mSv)'. It lists various procedures including Barium enema (4.06 mSv), Upper gastrointestinal tract (2.44 mSv), Computer tomography Head and body (1.11 mSv), Abdomen (0.56 mSv), Skull (0.22 mSv), Chest (0.08 mSv), Full-mouth survey with round collimation (0.084 mSv), rectangular collimation (0.033 mSv), Interproximal survey with round collimation (0.017 mSv), Panoramic tomography (0.007 mSv), and Interproximal survey with rectangular collimation (0.007 mSv). Footnotes cite NCRP Reports 100 and White SC: Dentomaxillofac Radiol. A diagram illustrating radiation risk thresholds on a horizontal scale marked at 10 mSv, 100 mSv, and 1000 mSv. The scale is divided into three zones indicated by arrows: 'Effects not well known (high uncertainty)' (left of 10 mSv), 'Cancer and hereditary effects (risk increases linearly with dose)' (between 10 and 1000 mSv), and 'Harmful tissue reactions' (right of 1000 mSv). - Annual Dose Limits (ARPANSA, 2020) - Allowable annual dose limits in Dentistry (effective dosage) - Public: 1mSv / year (averaged over 5 years) - Special clause: Can exceed in special circumstances (eg. Radiotherapy) as long as it is 1mSv averaged over 5 years - Dental workers: 20mSv / year (averaged over 5 years) - Underlined **No more than 50mSv in any one year** - *Italics: If under 18 but over 16, limit is 6 mSv per year* _figures/img_85c18f51cc416e0f.webp) ##### Annual Dose Limits (ARPANSA, 2020) - Allowable annual dose limits in Dentistry (effective dosage) - **Public:** 1mSv / year (averaged over 5 years) - Special clause: Can exceed in special circumstances (eg. Radiotherapy) as long as it is 1mSv averaged over 5 years - **Dental workers:** 20mSv / year (averaged over 5 years) - No more than 50mSv in any one year - If under 18 but over 16, limit is 6 mSv per year A text-based table summarizing Annual Dose Limits (ARPANSA, 2020) for Dentistry. The table is structured with bullet points and sub-bullets detailing effective dosage limits for the Public (1mSv/year averaged over 5 years) and Dental workers (20mSv/year averaged over 5 years). It includes specific clauses such as a special exception for Radiotherapy, a cap of 50mSv in any single year for dental workers, and a reduced limit of 6 mSv per year for those under 18 but over 16. # Ionising Radiation & Cell Damage 1. It may pass directly through the cell *without* causing any damage 2. It may interact with cells and cause **DAMAGE** Cells can either: a) Repair itself b) Mutate, or c) Die #### Ionising Radiation & Cell Damage 1. It may pass directly through the cell *without* causing any damage 2. It may interact with cells and cause **DAMAGE** Cells can either: - Repair itself - Mutate, or - Die # Ionising Radiation & Cell Damage * Damage to cell walls, mitochondria, mRNA, nuclear membrane, **DNA**, etc. * **DIRECT** damage: * 25%-30% of total damage * Direct damage to atoms / molecules eg. **DNA** * **INDIRECT** damage: * 70%-75% of total damage * Radiolysis of water (in cells) $\rightarrow$ release of toxic **free radicals** * **Changes to DNA result in:** * Changes in genetically sensitive information * Changes in structural protein synthesis * Changes in enzyme structure and function and enzyme substrate _figures/img_1f24e98a8166a781.webp) - Damage to cell walls, mitochondria, mRNA, nuclear membrane, **DNA**, etc. - **DIRECT** damage: - 25%-30% of total damage - Direct damage to atoms / molecules eg. **DNA** - **INDIRECT** damage: - 70%-75% of total damage - Radiolysis of water (in cells) → release of toxic **free radicals** - **Changes to DNA result in:** - Changes in genetically sensitive information - Changes in structural protein synthesis - Changes in enzyme structure and function and enzyme substrate Labeled diagram illustrating two mechanisms of ionising radiation damage to DNA. Panel A shows 'Direct action or damage' where an X-ray photon strikes the DNA helix directly. Panel B shows 'Indirect action or damage' where an X-ray photon interacts with H2O (water) to release free radicals, which then combine and cause damage to the DNA. **DNA Damage** • When only one strand is damaged (single strand defects/breaks), the other strand can be used as a template to guide the correction of the damaged strand. $ \Rightarrow $ repair • **Double strand breaks** are hard to repair and often result in cell death. ![Diagram illustrating single-strand vs. double-strand DNA damage and repair: Image A shows repair facilitated by DNA synthesis and X-ray exposure, while Image B shows cell death following double-strand breaks., Avoid] _figures/img_4a4146c2786c0350.webp) **DNA Damage** - When only one strand is damaged (single strand defects/breaks), the other strand can be used as a template to guide the correction of the damaged strand. → repair - **Double strand breaks** are hard to repair and often result in cell death. Scientific diagram illustrating the difference between single-strand and double-strand DNA damage. The image is split into two rows: Row A depicts a chromosome with a single break (orange spot) that undergoes repair via DNA synthesis and X-ray exposure, resulting in a corrected chromosome. Row B shows a chromosome with a double-strand break (blue spot) which leads to fragmentation and cell death. # Direct Damage ### **Flowchart** | Input | Processes | Result | Outcome | | :--- | :--- | :--- | :--- | | X-ray photon<br>interacts with* tissue<br> | Ionization<br>Excitation<br>Break bonds | Chemical changes | **Biologic** changes | ### **Molecule Comparison** **FREE RADICAL** AND **NORMAL MOLECULE** **STABLE MOLECULE** **FREE RADICAL** MISSING **ELECTRON** --- * **When an atom becomes ionized, it become unstable = free radicals, which are highly** **reactive and short-lived** * **Free radicals then quickly stabilize by dissociation (breaking apart) or cross-linking** **Structurally and functionally different molecules and a consequent biologic change.** _figures/img_7d25aebd5fc5a24d.webp) _figures/img_0e241d9a614a55bb.webp) ##### Direct Damage **Flowchart** | Input | Processes | Result | Outcome | | :--- | :--- | :--- | :--- | | X-ray photon interacts with tissue | Ionization, Excitation, Break bonds | Chemical changes | **Biologic** changes | **Molecule Comparison** FREE RADICAL AND NORMAL MOLECULE STABLE MOLECULE FREE RADICAL MISSING ELECTRON --- - When an atom becomes ionized, it become unstable = free radicals, which are highly reactive and short-lived - Free radicals then quickly stabilize by dissociation (breaking apart) or cross-linking - Structurally and functionally different molecules and a consequent biologic change. Flowchart diagram illustrating the mechanism of Direct Damage. It begins with 'X-ray photon interacts with tissue', which leads to three parallel processes: 'Ionization', 'Excitation', and 'Break bonds'. These converge into a single arrow pointing to 'Chemical changes', which then points downwards to 'Biologic changes'. Comparison diagram showing a 'STABLE MOLECULE' (left) versus a 'FREE RADICAL MISSING ELECTRON' (right). The stable molecule is depicted as an atom with a nucleus and full electron shells. The free radical is shown with a red 'X' indicating a missing electron in its outer shell, demonstrating structural instability. <div> Dissociation & Cross-linking Molecule (RH) becomes Free Radical R* Free radical production: RH + x-radiation → R* + H+ + e− Free radical fates: Dissociation: Breaking apart R* → X + Y* Cross-linking: R* + S* → RS Formation of structurally and functionally different molecules Joining of two molecules **Formation of structurally and functionally different molecules** </div> _figures/img_de5bf6b5ca27b650.webp) ##### Dissociation and Cross-linking Molecule (RH) becomes Free Radical R* Free radical production: RH + x-radiation → R* + H+ + e− Free radical fates: Dissociation: Breaking apart R* → X + Y* Cross-linking: R* + S* → RS Formation of structurally and functionally different molecules Joining of two molecules Diagram illustrating the processes of Dissociation and Cross-linking. The diagram begins with 'Free radical production' showing the reaction RH + x-radiation → R* + H+ + e−. Below this, it details 'Free radical fates': 'Dissociation' is shown as R* → X + Y*, labeled 'Breaking apart'. 'Cross-linking' is shown as R* + S* → RS, labeled 'Joining of two molecules'. Two arrows point from these reactions to a text box on the right stating 'Formation of structurally and functionally different molecules'. Indirect Damage X-ray photons interact with water in cells **ionization occurs** resulting in free radical formation X-ray photons H2O H2O H2O IONIZATION H+ OH- O- H+ OH- H+ OH- OH- Oxidative damage to cells _figures/img_324afab4ecb080f6.webp) _figures/img_5f109cba70e1757c.webp) ##### Indirect Damage X-ray photons interact with water in cells **ionization occurs** resulting in free radical formation X-ray photons H2O H2O H2O IONIZATION H+ OH- O- H+ OH- H+ OH- OH- Oxidative damage to cells Labelled diagram illustrating the process of indirect damage. The top section shows a flowchart: 'X-ray photons interact with water in cells' leads to 'ionization occurs', which results in 'free radical formation'. Below this text, a detailed schematic depicts three wavy arrows labeled 'X-ray photons' pointing down to three H2O molecules. A large arrow labeled 'IONIZATION' points from these molecules to a cluster of ions (H+, OH-, O-). A purple lightning bolt icon points to the upper right corner of this panel. Diagram showing the combination of free radicals into toxins. It displays a sequence starting with 'combine to form', leading via an arrow to 'toxins such as H2O2 (hydrogen peroxide)'. Below this, a second sequence shows a shaded arrow labeled 'COMBINE' pointing towards a list of chemical species: H2O2, H+, H+, and H2O. A purple lightning bolt icon points to the upper right corner of this panel. # Biological Effects of Ionizing Radiation ## Stochastic and Non-stochastic Effects 1. Stochastic effects on somatic tissues 2. Stochastic effects on genetic tissues 3. Non-stochastic effects / Deterministic effects (always on somatic tissues) ##### Stochastic and Non-stochastic Effects 1. Stochastic effects on somatic tissues 2. Stochastic effects on genetic tissues 3. Non-stochastic effects / Deterministic effects (always on somatic tissues) 1. Somatic Stochastic Effect * 'Somatic' = body cells * Probability of the change occurring (not severity) of which, is greater for a higher radiation dose * **No safe dose (= no threshold)** * Therefore, every exposure has the possibility of producing a stochastic effect * **Cancer** ##### Somatic Stochastic Effect - 'Somatic' = body cells - Probability of the change occurring (not severity) of which, is greater for a higher radiation dose - **No safe dose (= no threshold)** - Therefore, every exposure has the possibility of producing a stochastic effect - **Cancer** **2. Genetic Stochastic Effect** • **Reproductive organs** • Damage to gonad / reproductive cells can result in congenital abnormality of the offspring • **No safe threshold** • Risk of inducing a heritable mutation is estimated to be about 2 in 100,000 per mSv _figures/img_1b4ef9180f191139.webp) ##### Genetic Stochastic Effect - **Reproductive organs** - Damage to gonad / reproductive cells can result in congenital abnormality of the offspring - **No safe threshold** - Risk of inducing a heritable mutation is estimated to be about 2 in 100,000 per mSv A schematic diagram illustrating the 'Genetic Stochastic Effect' on reproduction. It depicts a flow of radiation (wavy arrows) impacting a parent dog, which branches into two outcomes: 'Genetic mutation' and 'Somatic mutation'. These lead to offspring in 'Future generations', showing how heritable mutations can be passed down versus somatic changes. 3. Non-stochastic / Deterministic Effect • Somatic tissues • **Severity** of the change is **proportional to dose** • There is a **threshold dose** below which no effect is seen • Biological Changes: loss of somatic function (> 1Gy → not seen in dental) • Xerostomia, loss of taste, skin reddening, hair loss, cataract formation • Severe = death ##### Non-stochastic / Deterministic Effect - Somatic tissues - **Severity** of the change is **proportional to dose** - There is a **threshold dose** below which no effect is seen - Biological Changes: loss of somatic function (> 1Gy → not seen in dental) - Xerostomia, loss of taste, skin reddening, hair loss, cataract formation - Severe = death The image displays three images: an eye with a cloudy lens, a face with red skin, and a top of a head with thinning hair. There is no text on or related to this image that can be extracted. _figures/img_0f8492eb1d7242ab.webp) _figures/img_bee9684614b955c2.webp) _figures/img_37b90a67338fbb2b.webp) The image displays three images: an eye with a cloudy lens, a face with red skin, and a top of a head with thinning hair. There is no text on or related to this image that can be extracted. Clinical photo of a human eye showing significant opacification of the lens, consistent with cataract formation. The pupil area is diffusely white and cloudy rather than black. Clinical photo of a patient's face in profile view showing diffuse erythema (redness) across the cheeks, nose, and chin. A black bar has been placed over the eyes to obscure identity. Clinical photo of the top of a head viewed from above, demonstrating thinning hair and widening of the part line, indicative of androgenetic alopecia or other forms of hair loss. _figures/img_6c76891390331b20.webp) A comparative figure displaying two graphs labeled (a) and (b). Graph (a), titled 'Non-stochastic', plots 'Severity of effect' against 'Absorbed dose, Gy'. It features a sigmoid curve starting at zero until a 'threshold dose' is reached, after which the severity increases. Graph (b), titled 'Stochastic (linear type)', plots 'Probability of effect' against 'Dose equivalent, Sv'. It shows a dashed line indicating that the likelihood of effect is random but increases linearly with increasing dose. **TABLE 2.1** Comparison of Stochastic and Deterministic Effects of Radiation | | Stochastic Effects | Deterministic Effects | | :--- | :--- | :--- | | **Caused by** | Sublethal DNA damage | Cell killing | | **Threshold dose** | No<br>There is no minimum threshold dose. Effect can be caused by any dose of radiation | Yes<br>Effect occurs only when the threshold dose is exceeded | | **Severity of clinical effects and dose** | Severity of clinical effects is independent of dose; all-or-none response—an individual either manifests effect or does not | Severity of clinical effects is proportional to dose; the higher the dose, the more severe the effect | | **Relationship between dose and effect** | Frequency of effect proportional to dose; the higher the dose, the higher the risk of manifesting the effect | Probability of effect independent of dose; most individuals manifest effect when threshold dose is exceeded | | **Caused by doses used in diagnostic radiology** | Yes | No | | **Examples** | Radiation-induced cancer<br>Heritable effects<br>Radiation-induced skin cancer | Osteoradionecrosis<br>Radiation-induced cataract formation<br>Radiation-induced skin burns | _figures/img_74f478bfd0fd4cd9.webp) **TABLE 2.1** Comparison of Stochastic and Deterministic Effects of Radiation | | Stochastic Effects | Deterministic Effects | | :--- | :--- | :--- | | **Caused by** | Sublethal DNA damage | Cell killing | | **Threshold dose** | No<br>There is no minimum threshold dose. Effect can be caused by any dose of radiation | Yes<br>Effect occurs only when the threshold dose is exceeded | | **Severity of clinical effects and dose** | Severity of clinical effects is independent of dose; all-or-none response—an individual either manifests effect or does not | Severity of clinical effects is proportional to dose; the higher the dose, the more severe the effect | | **Relationship between dose and effect** | Frequency of effect proportional to dose; the higher the dose, the higher the risk of manifesting the effect | Probability of effect independent of dose; most individuals manifest effect when threshold dose is exceeded | | **Caused by doses used in diagnostic radiology** | Yes | No | | **Examples** | Radiation-induced cancer<br>Heritable effects<br>Radiation-induced skin cancer | Osteoradionecrosis<br>Radiation-induced cataract formation<br>Radiation-induced skin burns | A structured table comparing 'Stochastic Effects' and 'Deterministic Effects' of radiation across multiple criteria including causes, threshold dose, severity, relationship to dose, presence in diagnostic radiology, and specific examples like cancer versus burns. _figures/img_1ee0d5eae0a60c7e.webp) A scientific diagram illustrating various models of health risk versus exposed dose. The graph features a vertical 'Health risk' axis and a horizontal 'Exposed dose' axis. The plot area is divided into two colored zones: a light green 'Uncertain effects range' on the left and a darker green 'Detrimental effects range' on the right. Five distinct curves are plotted with arrows pointing to their respective labels: a solid green line for the 'Linear-no-threshold model', a dashed blue curve for the 'Linear-quadratic model', a dashed black curve for the 'Supra-linear model', a dotted red curve dipping below the axis for the 'Hormesis model', and a solid black line starting at an intercept labeled 'Threshold dose' for the 'Linear threshold' model. **HBO ORIGINAL CHERNOBYL** **Fig 2.** The linear non-threshold hypothesis posits that the risk of exposure to radiation, cancer, is linearly related to exposure dose, even to the smallest exposures above background levels. The solid dots on the upper right side of the schematic graph indicate that at higher doses, above those used in diagnostic imaging, there is a known linear relationship between excess cancer rates and dose. **3 accidents (>100mSv)** 1. Fukushima Daiichi nuclear accident 2. Chernobyl -> On-site workers received ~6 Sv (= 6000mSv), died in a month 3. Three Mile Island (TMI) nuclear power plant accident _figures/img_b046d7a015f5f2df.webp) _figures/img_a21910d2716f523c.webp) **HBO ORIGINAL CHERNOBYL** **Fig 2.** The linear non-threshold hypothesis posits that the risk of exposure to radiation, cancer, is linearly related to exposure dose, even to the smallest exposures above background levels. The solid dots on the upper right side of the schematic graph indicate that at higher doses, above those used in diagnostic imaging, there is a known linear relationship between excess cancer rates and dose. **3 accidents (>100mSv)** 1. Fukushima Daiichi nuclear accident 2. Chernobyl → On-site workers received ~6 Sv (= 6000mSv), died in a month 3. Three Mile Island (TMI) nuclear power plant accident Labeled diagram: A schematic graph plotting 'Probability of Cancer' on the y-axis against 'Dose' on the x-axis. It illustrates the 'Linear non-threshold' hypothesis with a diagonal line starting from 'Background Incidence' at 'Background dose'. Purple arrows point to the graph from the text listing nuclear accidents. Photo: Promotional still from HBO Original 'Chernobyl' showing a worker in protective gear spraying a misty street, with the show's title overlaid. **Cumulative Effect of X-ray** There is evidence that dose accumulated over a long period carries less risk than the same dose received over a short period. <img>X-ray damage and repair diagram illustrating cumulative effects<br>**Repeated exposures of ionising radiation**<br>**Fast (Reaction)**<br>**X-RAY DOSE**<br>**X-RAY DOSE**<br>**Failure**<br>**X-RAY DOSE**<br>**X-RAY DOSE**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**TIME**<br>**Slower effective rate**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br>**Failure**<br>**Failure**<br>**DAMAGE**<br>**DAMAGE**<br>**Damage accumulation**<br><br>FIGURE<br>**Diagrammatic representation of cumulative effect of**<br>**x-radiation**<br><br>This applies to **radiotherapy**.<br>Typically, 2 Gy is delivered daily for a weekly exposure of 10 Gy. The radiotherapy course continues for 6 to 7 weeks until a total of 60 to 70 Gy is administered. Damaging effect of radiation at different doses. The descending curve shows that survival decreases as the dose increases. The rising curve shows that survival increases as time elapsed after exposure increases. This indicates that cells have time to repair themselves if given enough time. The diagram illustrates that the effect of radiation on a cell is not immediate but depends on both the size of the dose and the time interval between doses. This suggests that repeated exposures may be less harmful than a single large exposure because cells have time to repair themselves. The graph shows that if you split the total dose into smaller fractions given at intervals long enough for repair mechanisms to act, then the overall damage will be less than if all the dose were received at once. Hence the concept of the 'cellular survival curve'. This approach forms the basis of fractionated radiotherapy where full therapeutic effect is achieved using multiple daily treatments of small doses rather than one large dose of the same total amount. It is based upon the principle that biologically effective dose decreases with increasing separation of treatment sessions within the cellular recovery period of the organism (usually around 24 hours). _figures/img_4c79e58600b2b24c.webp) ##### Cumulative Effect of X-ray There is evidence that dose accumulated over a long period carries less risk than the same dose received over a short period. **Diagrammatic representation of cumulative effect of x-radiation** - Repeated exposures of ionising radiation - Fast (Reaction) - X-RAY DOSE - Failure - DAMAGE - TIME - Slower effective rate - Damage accumulation This applies to **radiotherapy**. Typically, 2 Gy is delivered daily for a weekly exposure of 10 Gy. The radiotherapy course continues for 6 to 7 weeks until a total of 60 to 70 Gy is administered. Damaging effect of radiation at different doses. The descending curve shows that survival decreases as the dose increases. The rising curve shows that survival increases as time elapsed after exposure increases. This indicates that cells have time to repair themselves if given enough time. The diagram illustrates that the effect of radiation on a cell is not immediate but depends on both the size of the dose and the time interval between doses. This suggests that repeated exposures may be less harmful than a single large exposure because cells have time to repair themselves. The graph shows that if you split the total dose into smaller fractions given at intervals long enough for repair mechanisms to act, then the overall damage will be less than if all the dose were received at once. Hence the concept of the 'cellular survival curve'. This approach forms the basis of fractionated radiotherapy where full therapeutic effect is achieved using multiple daily treatments of small doses rather than one large dose of the same total amount. It is based upon the principle that biologically effective dose decreases with increasing separation of treatment sessions within the cellular recovery period of the organism (usually around 24 hours). Labelled diagram showing the cumulative effect of X-ray radiation over time. The graph has 'DAMAGE' on the vertical axis and 'TIME' on the horizontal axis. It depicts two cycles of repeated ionising radiation exposure. Each cycle shows a spike in damage (labeled 'REACTION') immediately following an 'X-RAY DOSE', followed by a decline as the body undergoes 'REPAIR'. This process results in a lower overall 'RESULT' than if the dose were delivered all at once. A red box highlights the 'REPAIR' phase. ALARA / ALARP / ALADA • As • Low • As • Reasonably • Achievable ALWAYS! Principle of radioprotection stating that whenever ionizing radiation has to be applied to humans, animals or materials exposure should be as **low** as **reasonably** or **diagnostically** **achievable** / **practicable** / **acceptable**. It is fundamental to the **principles** of radiation protection. ##### ALARA / ALARP / ALADA - As - Low - As - Reasonably - Achievable ALWAYS! Principle of radioprotection stating that whenever ionizing radiation has to be applied to humans, animals or materials exposure should be as **low** as **reasonably** or **diagnostically** **achievable** / **practicable** / **acceptable**. It is fundamental to the **principles** of radiation protection. Minimising Exposure for Patient • Only take radiographs when necessary • Adequate filtration • Adequate collimation • Constant potential rectification • Lead apron and thyroid shield * • Fastest film or intensifying screens (in Analogue system) • Use digital imaging • Minimize technical errors • Well-maintained equipment ##### Minimising Exposure for Patient - Only take radiographs when necessary - Adequate filtration - Adequate collimation - Constant potential rectification - Lead apron and thyroid shield * - Fastest film or intensifying screens (in Analogue system) - Use digital imaging - Minimize technical errors - Well-maintained equipment # Minimising Exposure for Dental Staff - Avoid the primary beam - **Increase Distance (inverse square law)**, at least 2m - Shielding - Position - Most of the measures already mentioned to protect the patient ##### Minimising Exposure for Dental Staff - Avoid the primary beam - **Increase Distance (inverse square law)**, at least 2m - Shielding - Position - Most of the measures already mentioned to protect the patient Inverse square law source strength S sphere area 4\pi r^2 intensity at surface of sphere \frac{S}{4\pi r^2} = I I r **The energy twice as far from** **the source is spread over four** **times the area, hence** **one-fourth the intensity.** 2r I/4 3r I/9 A A A A A A A A A A A A A A A A A the intensity of an X-ray beam at a given point is inversely proportional to the square of the distance from the source of **radiation**. _figures/img_c9d8d575c4b4f2eb.webp) ##### Inverse Square Law source strength S sphere area 4πr² intensity at surface of sphere S / (4πr²) = I **The energy twice as far from the source is spread over four times the area, hence one-fourth the intensity.** 2r → I/4 3r → I/9 the intensity of an X-ray beam at a given point is inversely proportional to the square of the distance from the source of **radiation**. Diagram illustrating the inverse square law. It depicts a point source (S) emitting radiation that spreads outwards to form spherical shells at distances r, 2r, and 3r. The diagram visually compares the surface area of these spheres, showing that at distance 2r the area covers four 'A' units while at 3r it covers nine 'A' units. Corresponding intensity values are labeled above each shell: I, I/4, and I/9. A formula S/(4πr²) = I is shown near the source. Dentist’s Responsibilities - Patient Care - Determination of the clinical **NEED** to take X-ray - **Radiography** and dose determination - Processing technique (analogue films) - Maintenance of radiographic records - Maintenance of radiographic equipment - **Interpretation & Diagnosis** (*get help from DMF Radiologist*) - __All__ **3D** imaging legally requires radiologist’s report in WA ##### Dentist’s Responsibilities - Patient Care - Determination of the clinical **NEED** to take X-ray - **Radiography** and dose determination - Processing technique (analogue films) - Maintenance of radiographic records - Maintenance of radiographic equipment - **Interpretation & Diagnosis** (*get help from DMF Radiologist*) - **All** **3D** imaging legally requires radiologist’s report in WA <!-- The slide discusses comparing the probability of a child's death from diagnostic X-rays versus maternal smoking --> # Irradiating Pregnant Women ## Probability of Child’s Death from Diagnostic X-ray (dental or medical) VS. Probability of Child’s Death from Maternal Smoking → 10 x annual patient radiation dose <<<< 1 cig/day maternal smoking **Comparative risks during pregnancy*** Irradiation during gestation | Dose | Outcome | Probability | | :--- | :--- | :--- | | 10 mSv | Death from childhood leukemia | 1 in 3333 | | 10 mSv | Death from other childhood cancer | 1 in 3571 | Maternal smoking | Dose | Outcome | Probability | | :--- | :--- | :--- | | 1 pack or more/day | Infant death | 1 in 3 | Maternal alcohol consumption | Dose | Outcome | Probability | | :--- | :--- | :--- | | 2 to 4 drinks/day | Signs of fetal alcohol syndrome | 1 in 10 | | | Major malformation at delivery | 2.75% | _figures/img_7533e0b620c06df6.webp) ##### Irradiating Pregnant Women **Probability of Child’s Death from Diagnostic X-ray (dental or medical) VS. Probability of Child’s Death from Maternal Smoking** → 10 x annual patient radiation dose <<<< 1 cig/day maternal smoking **Comparative risks during pregnancy*** Irradiation during gestation | Dose | Outcome | Probability | | :--- | :--- | :--- | | 10 mSv | Death from childhood leukemia | 1 in 3333 | | 10 mSv | Death from other childhood cancer | 1 in 3571 | Maternal smoking | Dose | Outcome | Probability | | :--- | :--- | :--- | | 1 pack or more/day | Infant death | 1 in 3 | Maternal alcohol consumption | Dose | Outcome | Probability | | :--- | :--- | :--- | | 2 to 4 drinks/day | Signs of fetal alcohol syndrome | 1 in 10 | | | Major malformation at delivery | 2.75% | Table titled 'Comparative risks during pregnancy*' listing radiation doses and maternal habits alongside their associated health outcomes and probabilities. It includes: Irradiation during gestation (10 mSv causing childhood leukemia death at 1 in 3333 or other childhood cancer death at 1 in 3571), Maternal smoking (1 pack or more/day causing infant death at 1 in 3), and Maternal alcohol consumption (2 to 4 drinks/day causing signs of fetal alcohol syndrome at 1 in 10 and major malformation at delivery at 2.75%). This X-ray won't have to much radiation, will it? I don't want to get cancer. **10 mSv** **MDCT, chest** **1 year** **MDCT, head** **6 months** **Mammogram** **1 month** **CBCT, full FOV** **CBCT, medium FOV** **Full-mouth radiographs (CCD, round collimation)** **100 µSv** **Chest radiograph** **1 week** **CBCT, small FOV** **5-Hour airline flight** **Panoramic** **10 µSv** **1 day** **Four bite-wings** **Cephalometric** **Effective dose** **Background radiation** _figures/img_f594845019bff47b.webp) _figures/img_baccebf4e935d1ba.webp) "This X-ray won't have to much radiation, will it?" "I don't want to get cancer." - **10 mSv**: MDCT, chest, 1 year - MDCT, head, 6 months - Mammogram, 1 month - CBCT, full FOV; CBCT, medium FOV; Full-mouth radiographs (CCD, round collimation) - **100 µSv**: Chest radiograph, 1 week; CBCT, small FOV; 5-Hour airline flight; Panoramic - **10 µSv**: 1 day; Four bite-wings; Cephalometric Effective dose Background radiation A photo of a skeleton smoking. The image is overlaid with white text: 'THIS X-RAY WON'T HAVE TO MUCH RADIATION, WILL IT?' at the top and 'I DON'T WANT TO GET CANCER.' at the bottom. A comparison chart illustrating radiation doses from various medical procedures versus background radiation. The chart uses a central vertical axis representing time (from 1 year down to 1 day) and effective dose (10 mSv down to 10 µSv). A yellow triangular area highlights the range of common diagnostic exposures. Labels include 'MDCT, chest', 'MDCT, head', 'Mammogram', 'Chest radiograph', '5-Hour airline flight', 'CBCT' variants, 'Panoramic', 'Four bite-wings', and 'Cephalometric'. 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