# **Imaging of Hard** # **and Soft Tissues** **Dr Dayea Oh** **Oral and Maxillofacial Radiologist** Lecture contents provided through the courtesy of Dr Tom Huang   #### Presentation Details - **Presenter:** Dr. Dayea Oh, Oral and Maxillofacial Radiologist - **Acknowledgement:** Lecture contents provided through the courtesy of Dr. Tom Huang A white horizontal line logo on a black background, located in the top right corner of the slide. A white plus sign logo on a black background, located in the bottom right corner of the slide. # **Imaging Modalities** - Intraoral radiographs - Extraoral radiographs - Computed tomography - Cone beam computed tomography - Magnetic resonance imaging - Ultrasound - Nuclear medicine #### Common Diagnostic Techniques Various imaging modalities are utilized to evaluate hard and soft tissues, ranging from traditional radiographic techniques to advanced cross-sectional and functional imaging: - **Radiographic Imaging** - Intraoral radiographs - Extraoral radiographs - **Advanced Tomography** - Computed tomography (CT) - Cone beam computed tomography (CBCT) - **Specialized Modalities** - Magnetic resonance imaging (MRI) - Ultrasound - Nuclear medicine  Radiographs are essential diagnostic tools in clinical practice, providing a non-invasive means to visualize internal structures of the body. In dentistry and orthopedics, they are primarily used to assess the integrity of hard tissues and identify underlying pathologies that are not visible during a clinical examination. #### Fundamental Principles of Radiography - **X-ray Generation**: Produced when high-energy electrons collide with a metal target within an X-ray tube. - **Differential Absorption**: Dense tissues (like bone and enamel) absorb more radiation and appear radiopaque (white/light gray), while less dense tissues (like pulp or gingiva) allow more radiation to pass through and appear radiolucent (dark gray/black). - **Image Capture**: Can be recorded on traditional film or digital sensors (CCD, CMOS, or PSP plates). black and white panoramic x-ray image of a human jaw, showing teeth and surrounding bone structure, with an 'R' marker indicating the right side.  #### Intraoral Radiographic Techniques 1. **Periapical Radiographs**: Focus on the entire tooth, from the crown to the apex of the root and the surrounding bone. These are critical for detecting apical periodontitis and assessing root morphology. 2. **Bitewing Radiographs**: Primarily used to detect interproximal caries and evaluate the height of the alveolar bone crest relative to the cemento-enamel junction (CEJ). 3. **Occlusal Radiographs**: Larger films used to view extensive areas of the maxilla or mandible, useful for locating impacted teeth, foreign bodies, or fractures. black and white dental X-ray image showing the jaw and teeth, with visible dental implants and surrounding bone structure. the image captures both upper and lower teeth, with some teeth appearing to have restorations or crowns. the overall quality suggests it is a diagnostic radiograph used for assessing dental health and implant placement.  #### Extraoral Radiographic Modalities - **Panoramic Radiographs (Orthopantomograms)**: Provide a broad overview of the entire dentition, mandible, maxilla, and temporomandibular joints (TMJ). While excellent for screening, they lack the fine detail of intraoral films. - **Cephalometric Radiographs**: Standardized lateral or posteroanterior views used primarily in orthodontics to measure craniofacial growth and skeletal relationships. - **Cone Beam Computed Tomography (CBCT)**: Provides three-dimensional reconstructions of hard tissues, offering superior visualization for implant planning and complex endodontic cases. A black and white dental X-ray image showing a panoramic view of the jaw, including teeth, roots, and surrounding bone structure. The image highlights the alignment of the teeth and the presence of dental structures such as molars and incisors.  #### Diagnostic Applications in Hard Tissue - **Caries Detection**: Identification of demineralized areas in enamel and dentin. - **Periodontal Assessment**: Evaluation of horizontal and vertical bone loss, furcation involvement, and calculus deposits. - **Endodontic Evaluation**: Determination of root canal length, curvature, and the presence of periapical lesions. - **Trauma Management**: Detection of jaw fractures, tooth luxation, or root fractures. a black and white dental X-ray image showing a section of the jaw with teeth, including a visible dental implant or prosthetic device in the lower arch. the surrounding bone structure is also visible, indicating the presence of dental work or restoration.   #### Limitations of Conventional Radiography - **Two-Dimensional Representation**: Superimposition of structures can mask pathology or create artifacts. - **Geometric Distortion**: Foreshortening or elongation can occur if the X-ray beam is not perpendicular to the object and sensor. - **Sensitivity vs. Specificity**: Radiographs may not show early-stage demineralization until a significant percentage of mineral content is lost (approximately 30-40%). black and white medical imaging scan showing a cross-sectional view of a dental structure with a visible implant or prosthetic component, likely a dental implant, embedded in the jawbone. black and white medical imaging scan displaying a detailed view of a dental implant with surrounding bone structure, highlighting the integration of the implant into the jawbone. <img src="dental_xray_image.jpg" alt="Dental X-ray showing the upper jaw with visible teeth and restorations.">  #### Clinical Radiographic Interpretation Visual analysis of the upper jaw (maxilla) reveals several key features: - **Dental Restorations**: Radiopaque materials indicating previous operative treatments. - **Alveolar Bone Levels**: Assessment of the supporting structures surrounding the teeth. - **Anatomical Landmarks**: Visualization of the maxillary sinus floor and its proximity to the root apices. Dental X-ray showing the upper jaw with visible teeth and restorations, including a prominent white restoration on the lower left molar area.   #### Radiation Safety and Protection - **ALARA Principle**: "As Low As Reasonably Achievable." Clinicians must minimize exposure to patients and staff. - **Protective Measures**: - Use of lead aprons and thyroid collars. - High-speed film or digital sensors to reduce exposure time. - Rectangular collimation to limit the X-ray beam size. - Proper distance and shielding for the operator. A black and white medical imaging scan showing a cross-sectional view of a dental structure, likely a CT scan of a tooth and surrounding bone tissue. A black and white medical imaging scan displaying a detailed view of dental roots and adjacent structures, possibly from a dental CT scan, with a cursor indicating a specific area of interest.  #### Digital Imaging Advantages - **Instant Image Acquisition**: Eliminates the need for chemical processing and reduces wait times. - **Image Enhancement**: Ability to adjust contrast, brightness, and zoom to improve diagnostic yield. - **Storage and Sharing**: Facilitates easy integration into Electronic Health Records (EHR) and simplifies referrals to specialists. - **Environmental Impact**: Removes the need for toxic processing chemicals and lead foil disposal. black and white dental X-ray showing a panoramic view of the teeth and jaw, with a visible dental implant or prosthesis in the lower anterior region.   #### Soft Tissue Visualization on Radiographs While radiographs are optimized for hard tissues, certain soft tissue features can be discerned: - **Soft Tissue Outlines**: The silhouette of the nose or lips may be visible on extraoral views. - **Pathological Calcifications**: Sialoliths (salivary stones), calcified lymph nodes, or tonsilloliths can appear as radiopaque entities within soft tissue regions. - **Air Spaces**: Radiolucent areas representing the nasopharynx or oropharynx. black and white medical imaging scan showing a cross-sectional view of a dental structure with a prominent tooth implant or restoration, surrounded by bone tissue. black and white medical imaging scan displaying a detailed view of multiple teeth, including a dental implant or crown, with surrounding bone and soft tissue structures.   #### Quality Assurance in Radiography To ensure diagnostic accuracy, images must meet specific criteria: - **Proper Positioning**: The area of interest must be centered with minimal overlap of adjacent structures. - **Optimal Density and Contrast**: The image must have a balanced range of grays to distinguish between different tissue types. - **Artifact Reduction**: Prevention of errors such as cone cuts, double exposures, or motion blur. A detailed diagram of a CT scanner showing the X-ray tube, X-ray beam, detectors, and CT table. The diagram illustrates how the tube/detector assembly rotates around the patient while the patient table moves into the gantry, highlighting the components involved in computed tomography imaging. A schematic diagram illustrating the movement of the patient table into the gantry and the rotation of the tube/detector assembly around the patient. It shows multiple rows of detectors and the X-ray tube, explaining the mechanics of multislice CT scanning.   #### Future Trends in Imaging - **Artificial Intelligence (AI)**: Automated detection of caries and bone loss through machine learning algorithms. - **Low-Dose CBCT**: Advancements in sensor technology allowing for 3D imaging with radiation doses comparable to traditional 2D views. - **Integration with CAD/CAM**: Combining radiographic data with digital impressions for guided surgery and prosthetic design. A high-resolution photo of a Siemens Somatom Force CT scanner, showcasing its modern design with a large circular gantry and an integrated patient table. The machine features a sleek white and silver exterior with blue lighting accents around the aperture. A diagram illustrating the operation of a CT scanner, showing a patient lying on a table being scanned by an X-ray source and detectors arranged in a circular configuration. The X-rays pass through the body, and the detectors capture the attenuated rays to create cross-sectional images. # **Hounsfield unit (HU)** - The **Hounsfield unit (HU)** is a quantity commonly used in CT scanning to express CT numbers in a standardised and convenient form. - Hounsfield units, created by and named after Sir Godfrey Hounsfield, are obtained from a linear transformation of the measured attenuation coefficient. - This transformation is based on the arbitrary definitions of air and water. Computed Tomography (CT) scanning utilizes standardized units to represent tissue density and attenuation. The Hounsfield unit (HU) is a quantity commonly used in CT scanning to express CT numbers in a standardized and convenient form. - Hounsfield units, created by and named after Sir Godfrey Hounsfield, are obtained from a linear transformation of the measured attenuation coefficient. - This transformation is based on the arbitrary definitions of air and water. # **MSCT Take Home** - 3D Imaging & Dimensionally accurate - Multiplanar reformatting - **Bony pathology** - **Shows soft tissue but not as well as MRI** - Contrast use - Superior Speed - Supine position - Hounsfield Units $\rightarrow$ Tissue density - Air: -1000, Water: 0 #### Density Reference Scales Hounsfield Units correlate directly to tissue density: - **Air:** -1000 - **Water:** 0 #### Core Capabilities of MSCT - 3D Imaging and dimensional accuracy - Multiplanar reformatting - Excellent visualization of bony pathology - Soft tissue visualization (though not as detailed as MRI) - Use of contrast agents - Superior scanning speed - Patient positioning: Supine   CT scan image showing a sagittal view of the head and neck, with visible bone structures including the skull, teeth, and cervical spine. The image is labeled with anatomical markers such as 'R' for right and 'P' for posterior, and includes a scale bar indicating 10.00mm/div. CT scan image showing an axial view of the head and neck, with visible bone structures including the mandible, teeth, and cervical spine. The image is labeled with anatomical markers such as 'R' for right and 'P' for posterior, and includes a scale bar indicating 10.00mm/div. MSCT Take Home * 3D Imaging & Dimensionally accurate * Multiplanar reformatting * **Bony pathology** * **Shows soft tissue but not as well as MRI** * Contrast use * Superior Speed * Supine position * Hounsfield Units $\rightarrow$ Tissue density * Air: -1000, Water: 0 #### Key Clinical Considerations - 3D Imaging & Dimensionally accurate - Multiplanar reformatting - **Bony pathology** - **Shows soft tissue but not as well as MRI** - Contrast use - Superior Speed - Supine position - Hounsfield Units $\rightarrow$ Tissue density - Air: -1000 - Water: 0  Two axial CT scan images of the head and neck region, labeled A and B, showing cross-sectional views with visible anatomical structures such as the skull, teeth, and soft tissues. The images include orientation markers (R for right, L for left) and scale bars indicating 10.00 mm/div. # **MSCT Take Home** * 3D Imaging & Dimensionally accurate * Multiplanar reformatting * **Bony pathology** * **Shows soft tissue but not as well as MRI** * Contrast use * Superior Speed * Supine position * Hounsfield Units $\rightarrow$ Tissue density * Air: -1000, Water: 0 <img src="image.png" alt="Figure with a large light grey rectangle on the right and some black markings.">  #### Summary of MSCT Features - 3D Imaging & Dimensionally accurate - Multiplanar reformatting - **Bony pathology** - **Shows soft tissue but not as well as MRI** - Contrast use - Superior Speed - Supine position - Hounsfield Units $\rightarrow$ Tissue density - Air: -1000 - Water: 0 A large light grey rectangle on the right side of the page with some black markings, likely representing a placeholder or an image related to MSCT imaging. The figure is positioned adjacent to a list of bullet points describing MSCT features, including 3D imaging, bony pathology, and Hounsfield units.  Two CT scan images side by side showing cross-sectional views of a bone structure, likely a dental or maxillofacial region, with visible teeth and surrounding tissue. The images are labeled with 'H' at the top and have scale markers indicating 10.00mm/div.  Two axial CT scan images of the head and neck, labeled A, showing cross-sectional views with anatomical structures. The images display soft tissue, bone, and air spaces, with labels indicating right (R) and left (L) sides, and a scale bar of 10.00mm/div.  The image displays two side-by-side CT scan images showing cross-sectional views of a bone structure, likely a dental or maxillofacial region. Both images are labeled with 'H' at the top and have a scale bar indicating '10.00mm/div' at the bottom. The scans reveal a curved, dense structure resembling a tooth or dental implant, with surrounding soft tissue and bone. The right image appears to show a slightly different angle or phase compared to the left, possibly indicating a comparison between two conditions or time points. # Radiation Dose Levels <table> <thead> <tr> <th>Type of Examination</th> <th>Effective Dose (ICRP 2007) MICROSIEVERTS</th> </tr> </thead> <tbody> <tr> <td>Bitewing (E)</td> <td>5-9</td> </tr> <tr> <td>OPG</td> <td>4.7-54</td> </tr> <tr> <td>CBCT</td> <td>27-1073</td> </tr> <tr> <td><span style="background-color: yellow;">CT</span></td> <td><span style="background-color: yellow;">180-1160</span></td> </tr> </tbody> </table> Ludlow et al. 2008, Ludlow et al. 2008, Ngan et al. 2003, Loubele et al. 2009, Gavala et all. 2008, Gihbell et al. 2005, Visser et al. 2000, Loubele 2005, Wuomalainen et al. 2009, Okano et al. 2009, Roberts et al. 2009, Kumar et al. 2007, Schultze et al. 2004.  #### Comparative Effective Doses The following table outlines the effective dose in microsieverts (µSv) based on ICRP 2007 standards for various dental and maxillofacial examinations: | Type of Examination | Effective Dose (µSv) | | :--- | :--- | | Bitewing (E) | 5 - 9 | | OPG | 4.7 - 54 | | CBCT | 27 - 1073 | | **CT** | **180 - 1160** | *Data compiled from Ludlow et al. 2008, Ngan et al. 2003, Loubele et al. 2009, Gavala et al. 2008, Gihbell et al. 2005, Visser et al. 2000, Wuomalainen et al. 2009, Okano et al. 2009, Roberts et al. 2009, Kumar et al. 2007, and Schultze et al. 2004.* A table titled 'Radiation Dose Levels' comparing the effective dose in microsieverts for different types of dental examinations, including Bitewing (E), OPG, CBCT, and CT. The table highlights that CT has the highest dose range of 180-1160 microsieverts, with the value highlighted in yellow. The data is sourced from multiple studies listed at the bottom of the table. Understanding MRI Signals T1 weighted sequence | (black) | low SI | intermediate SI | high SI | |---|---|---|---| | $\text{}$ | $\text{}$ | $\text{}$ | $\text{}$ | | air, calcium, cortical bone, rapidly flowing blood | fluid, ligaments/ muscles/tendons, abdominal organs, cartilage | high-protein tissue (abscess, complex cysts, synovial fluid) | **fat, blood, gadolinium (= contrast), melanin, protein** | T2 weighted image | (black) | low SI | intermediate SI | high SI | |---|---|---|---| | $\text{}$ | $\text{}$ | $\text{}$ | $\text{}$ | | air, calcium, cortical bone, rapidly flowing blood | ligaments, tendons, liver, pancreas, adrenals, cartilage | fat, liver, pancreas, adrenals, muscles, cartilage | fluid, CSF, bladder, bile/gallbladder, kidneys |   #### T1 Weighted Sequence Signal Intensity (SI) - **Low SI (Black):** Air, calcium, cortical bone, rapidly flowing blood. - **Intermediate SI:** Fluid, ligaments, muscles, tendons, abdominal organs, cartilage. - **High SI (Bright):** Fat, blood, gadolinium (contrast), melanin, protein, high-protein tissue (abscess, complex cysts, synovial fluid). #### T2 Weighted Sequence Signal Intensity (SI) - **Low SI (Black):** Air, calcium, cortical bone, rapidly flowing blood. - **Intermediate SI (Low):** Ligaments, tendons, liver, pancreas, adrenals, cartilage. - **Intermediate SI (High):** Fat, liver, pancreas, adrenals, muscles, cartilage. - **High SI (Bright):** Fluid, cerebrospinal fluid (CSF), bladder, bile/gallbladder, kidneys. Two MRI brain scans labeled T1 and T2, showing different signal intensities. The T1 image displays a lesion with high signal intensity, while the T2 image shows the same lesion with increased brightness, indicating fluid content. The surrounding brain tissue appears in varying shades of gray, illustrating differences in tissue composition and water content. A table comparing T1 and T2 weighted MRI sequences, detailing signal intensity (SI) levels for various tissues. It includes color-coded circles representing low, intermediate, and high SI, with corresponding tissue types such as air, calcium, fat, fluid, and contrast agents. The table explains how different tissues appear in T1 and T2 weighted images based on their signal intensity. # **MRI Applications in DMFR** - **TMJ disorders** - **Tumours and cysts in the head and neck** - Jaw lesions - Salivary gland lesions - Paranasal sinus lesions - **Assessment of IDN** - **Infection / inflammation eg. osteomyelitis** - **Vascular lesions** <br> | Mouth Closed | Mouth Open | | :---: | :---: | | <img>| <img>| | Glenoid fossa | Articular eminence | | Disc | Disc | | Condyle | | | Bilaminar zone | | | EAC | EAC | | <img>| <img>| | Disc $\rightarrow$ C | Disc $\rightarrow$ C | | | EAC | | | $\textcopyright$ Behrang Amini, MD/PhD |  #### Clinical Indications - **TMJ disorders** - **Tumours and cysts in the head and neck** - Jaw lesions - Salivary gland lesions - Paranasal sinus lesions - **Assessment of Inferior Dental Nerve (IDN)** - **Infection / inflammation** (e.g., osteomyelitis) - **Vascular lesions** #### TMJ Anatomical Landmarks in MRI - **Mouth Closed View:** - Glenoid fossa - Articular disc - Condyle - Bilaminar zone - External Auditory Canal (EAC) - **Mouth Open View:** - Articular eminence - Articular disc - Condyle - External Auditory Canal (EAC) A comparative diagram showing the temporomandibular joint (TMJ) in two states: 'Mouth Closed' and 'Mouth Open'. The top row illustrates anatomical structures like the glenoid fossa, disc, condyle, and articular eminence in schematic form, while the bottom row displays corresponding MRI images with labels for the disc and condyle. This diagram is used to demonstrate TMJ disorders and is related to the topic of MRI applications in DMFR. **T1WI** <img> [Axial T1-weighted MRI scan showing bright signal in subcutaneous fat of the right temporal region, indicated by a yellow arrow] Fat is bright <img> [Axial T2-weighted MRI scan showing bright signal in a fluid-filled structure within the cerebellum, indicated by a yellow arrow] Fluid is bright   #### Visual Identification of Sequences - **T1-Weighted Imaging (T1WI):** Fat appears bright (high signal). This is often observed in subcutaneous fat layers. - **T2-Weighted Imaging (T2WI):** Fluid appears bright (high signal). This is useful for identifying fluid-filled structures or edema. Axial T1-weighted MRI scan showing bright signal in subcutaneous fat of the right temporal region, indicated by a yellow arrow. The image is labeled 'T1WI' and includes the text 'Fat is bright' below it. Axial T2-weighted MRI scan showing bright signal in a fluid-filled structure within the cerebellum, indicated by a yellow arrow. The image is labeled 'Fluid is bright' below it. <br> CLOSED $\qquad$ OPEN  #### Comparative TMJ Imaging - Functional assessment of the Temporomandibular Joint is performed by comparing the relationship of the condyle and disc in both the **Closed** and **Open** mouth positions. Two MRI images labeled 'CLOSED' and 'OPEN' showing a disc in the hip joint, with arrows pointing to the disc in both images. The images compare the state of the disc in two different conditions, likely illustrating a medical condition or treatment outcome.  A black and white medical imaging scan, likely an MRI or CT, showing a cross-sectional view of a human head. The image includes anatomical labels [AL] and [PR], indicating anterior-posterior and left-right orientations, with technical parameters like 'T1 ms' visible in the top right corner.    black and white medical imaging scan showing a cross-sectional view of the left shoulder, with text indicating "LEFT MEDIAL CLOSED" and visible anatomical structures such as the humeral head and surrounding soft tissues. black and white medical imaging scan of the left shoulder, showing detailed soft tissue and bone structures, including the glenoid cavity and rotator cuff, with text indicating "LEFT MEDIAL CLOSED". black and white medical imaging scan of the left shoulder, highlighting the humeral head and surrounding soft tissue, with visible anatomical features such as the acromion and subacromial space.   two black and white medical images, likely MRI scans, showing cross-sectional views of anatomical structures with a bright area indicating a potential lesion or abnormality. a black and white medical image, likely an MRI scan, displaying a cross-sectional view of anatomical structures with a bright area indicating a potential lesion or abnormality.   axial MRI scan showing a cross-sectional view of the head and neck region, with a prominent lesion in the parotid gland characterized by multiple cystic components. sagittal MRI scan displaying a longitudinal view of the head and neck, highlighting a large cystic mass in the parotid gland region, with surrounding anatomical structures visible.  Two axial CT scan images of the skull, showing cross-sectional views of the head with detailed bone structures, including the nasal cavity, maxillary sinuses, and temporal bones. The images are presented side-by-side for comparison, with the left image showing a normal anatomy and the right image possibly indicating a pathological condition or post-surgical changes. # MRI Take Home ### Features * **No ionising radiation** and no known biological side effects * Superior soft tissue contrast – **soft tissue lesions, articular disc of TMJ** * Various sequences can be utilised to visualise different tissues * IV paramagnetic contrast agents eg. Gadolinium * Certain anatomical and pathological structures with greater vascularity and permeability can be enhanced. ### Weaknesses * Claustrophobia – “non-claustrophobic” MRI * Long imaging times * Ferromagnetic metals contraindicated eg cardiac pacemakers, cerebral aneurysmal clips * **May not detect osseous changes visualised in CT** * Calcific deposits may be undetected * Can over estimate extent of tumours due to response of adjacent tissues * **Gadolinium-based contrast media must be used with caution in those with renal impairment - has been associated with nephrogenic systemic fibrosis** * **Gadolinium deposition with regions of the brain has recently been discovered and is currently being investigated.** <img src="figure.png" alt="figure"> #### Key Features - **No ionising radiation** and no known biological side effects. - **Superior soft tissue contrast:** Excellent for soft tissue lesions and the articular disc of the TMJ. - **Versatile sequences:** Various sequences can be utilised to visualise different tissue types. - **Contrast enhancement:** IV paramagnetic contrast agents (e.g., Gadolinium) can enhance anatomical and pathological structures with high vascularity and permeability. #### Limitations and Contraindications - **Patient Factors:** Claustrophobia (though "non-claustrophobic" MRI units exist) and long imaging times. - **Safety Contraindications:** Ferromagnetic metals are contraindicated (e.g., cardiac pacemakers, cerebral aneurysmal clips). - **Diagnostic Limitations:** - May not detect osseous changes as clearly as CT. - Calcific deposits may go undetected. - Can overestimate the extent of tumours due to the inflammatory response of adjacent tissues. - **Gadolinium Risks:** - Must be used with caution in patients with renal impairment; associated with nephrogenic systemic fibrosis. - Recent discovery of gadolinium deposition within regions of the brain is currently under investigation. # Applications * Soft tissue lumps and swellings * Soft tissue pain/discomfort * Salivary glands * Lymph nodes * Guided FNA and core biopsies   Ultrasound is utilized for the diagnostic evaluation and procedural guidance of various head and neck conditions, including: - **Soft Tissue Assessment** - Evaluation of lumps and swellings - Investigation of localized pain or discomfort - **Glandular and Lymphatic Evaluation** - Examination of salivary glands - Assessment of lymph nodes - **Interventional Guidance** - Guided Fine Needle Aspiration (FNA) - Guided core biopsies A photo showing a hand holding an ultrasound probe labeled 'L8-18i' being used on another person's hand, illustrating an application for soft tissue imaging. The probe is part of a set of similar medical devices shown in the upper image. A photo displaying a collection of ultrasound probes with different models labeled, such as 'ML6-15' and 'M5S', arranged in a row. These are medical devices used for various diagnostic applications, including guided biopsies.   B-mode ultrasound image showing a grayscale cross-sectional view of tissue with a dotted line indicating a measurement between two points labeled '1' and '2'. The image includes a scale on the right side and a small anatomical outline at the bottom right. Color Doppler ultrasound image displaying a cross-sectional view of tissue with a highlighted region of blood flow indicated by a color overlay ranging from blue to red, suggesting varying velocities. The image includes a scale on the right side and a small anatomical outline at the bottom right. # Nuclear Medicine - Functional imaging $\rightarrow$ detects abnormal metabolic processes - Rather than anatomical/morphological changes - May not be discernible in the early stages of some diseases. - Radionuclide imaging: - Radionuclides which emit gamma rays (e.g. Technetium 99m) - combined with a pharmaceutical to form a radiotracer which is distributed to various parts of the body based on their chemical properties. - A gamma camera captures the emitted photons - $\text{**Single photon emission computed tomography (SPECT):**}$ - Acquires tomographic slices - gamma camera rotates around the patient detected emitted gamma rays. - similar to multislice CT Nuclear medicine focuses on functional imaging to detect abnormal metabolic processes rather than anatomical or morphological changes. These metabolic shifts may not be discernible in the early stages of some diseases through traditional imaging. #### Principles of Radionuclide Imaging - **Radiotracers:** Radionuclides that emit gamma rays (e.g., Technetium 99m) are combined with a pharmaceutical to form a radiotracer. This tracer is distributed to various parts of the body based on specific chemical properties. - **Detection:** A gamma camera captures the emitted photons to create an image. #### Single Photon Emission Computed Tomography (SPECT) SPECT acquires tomographic slices by rotating a gamma camera around the patient to detect emitted gamma rays. This process is similar in concept to multislice CT but focuses on emitted radiation from within the patient. <table> <thead> <tr> <th>View</th> <th>Label</th> </tr> </thead> <tbody> <tr> <td>Top Left Scan</td> <td>RT ANTERIOR LT</td> </tr> <tr> <td>Top Right Scan</td> <td>LT POSTERIOR RT</td> </tr> <tr> <td>Bottom Left Scan</td> <td>LT LATERAL</td> </tr> <tr> <td>Bottom Right Scan</td> <td>RT LATERAL</td> </tr> </tbody> </table>   #### Standard Scan Views and Labeling - **Anterior View:** Right (RT) Anterior Left (LT) - **Posterior View:** Left (LT) Posterior Right (RT) - **Lateral Views:** - Left (LT) Lateral - Right (RT) Lateral A panoramic dental X-ray showing the upper and lower teeth, jawbone, and surrounding structures. The image includes labels for the right (R) and left (L) sides, with visible dental restorations and a missing tooth on the lower right side. A set of four nuclear medicine bone scan images displaying anterior, posterior, left lateral, and right lateral views of the head and neck. The scans show radiotracer uptake in the skull and cervical spine, with labels indicating the view and side (e.g., RT ANTERIOR, LT POSTERIOR).    CT scan image showing a cross-sectional view of a head, with anatomical structures visible in grayscale. The image is labeled 'CT' and includes a scale bar for reference. SPECT/CT fusion image displaying a cross-sectional view of a head with areas of high metabolic activity highlighted in yellow and orange, overlaid on a blue anatomical background. The image is labeled 'SPECT / CT' and includes red crosshairs for orientation. SPECT scan image showing a cross-sectional view of a head with dark regions indicating areas of lower radiotracer uptake. The image is labeled 'SPECT' and includes red crosshairs for orientation. # Nuclear Medicine: Positron emission tomography (PET): * Positron emitting radionucildes - usually combined with pharmaceuticals such as glucose or amino acids, to assess metabolic processes in the body. * After a set period of time, positron emission decay occurs, and two photons are produced which travel in opposite directions * A PET camera has a ring of detectors which can map the photons that arrive at the same time - produce a functional image of organs and tissues. * Hybrid imaging systems where the nuclear medicine images are co-registered with a CT or MRI images ( ie PET/CT and PET/MRI) allowing for combined morphological and functional imaging. * Very high spatial resolution - detect very small lesions * **Examples of use** * **Cancers** * **Identify viable heart muscle with previous myocardial infarcts** * **Brain – identify epileptic foci, diagnosis of dementia** #### Mechanism of PET Imaging - **Radionuclides:** Positron-emitting radionuclides are typically combined with pharmaceuticals, such as glucose or amino acids, to assess metabolic processes. - **Decay Process:** After a set period, positron emission decay occurs, producing two photons that travel in opposite directions. - **Detection:** A PET camera utilizes a ring of detectors to map photons that arrive simultaneously, producing a functional image of organs and tissues. #### Hybrid Imaging Systems Nuclear medicine images can be co-registered with CT or MRI images (e.g., PET/CT and PET/MRI). This allows for combined morphological and functional imaging with very high spatial resolution, capable of detecting very small lesions. #### Clinical Applications - **Oncology:** Detection and staging of cancers. - **Cardiology:** Identification of viable heart muscle following myocardial infarcts. - **Neurology:** Identification of epileptic foci and the diagnosis of dementia.   A grayscale CT scan image showing a cross-sectional view of the head and neck, highlighting anatomical structures such as the skull, teeth, and cervical spine. A PET-CT fusion image displaying a cross-sectional view of the head and neck with a bright yellow and white area indicating a region of high metabolic activity, likely a tumor, overlaid on a grayscale anatomical background. # **Nuclear Medicine: Positron emission tomography (PET):** * Positron emitting radionuclides - usually combined with pharmaceuticals such as glucose or amino acids, to assess metabolic processes in the body. * After a set period of time, positron emission decay occurs, and two photons are produced which travel in opposite directions * A PET camera has a ring of detectors which can map the photons that arrive at the same time - produce a functional image of organs and tissues. * Hybrid imaging systems where the nuclear medicine images are co-registered with a CT or MRI images (ie PET/CT and PET/MRI) allowing for combined morphological and functional imaging. * Very high spatial resolution - detect very small lesions * **Examples of use** * **Cancers** * **Identify viable heart muscle with previous myocardial infarcts** * **Brain – identify epileptic foci, diagnosis of dementia** #### Mechanism of PET Imaging - **Radionuclides:** Positron-emitting radionuclides are typically combined with pharmaceuticals (e.g., glucose or amino acids) to assess metabolic processes. - **Decay Process:** Following a specific timeframe, positron emission decay occurs, resulting in two photons traveling in opposite directions. - **Detection:** A PET camera features a ring of detectors that maps photons arriving at the same time to produce functional images of tissues and organs. #### Hybrid Imaging Systems Nuclear medicine images are often co-registered with CT or MRI (PET/CT and PET/MRI) to provide combined morphological and functional data. These systems offer high spatial resolution for the detection of small lesions. #### Clinical Applications - **Cancers:** Detection and monitoring. - **Cardiology:** Identifying viable heart muscle after previous myocardial infarcts. - **Neurology:** Identifying epileptic foci and diagnosing dementia.   A grayscale CT scan image showing a cross-sectional view of the head and neck, highlighting anatomical structures such as the skull, teeth, and cervical spine. A PET-CT fusion image displaying a cross-sectional view of the head and neck with a bright yellow and red area indicating metabolic activity, likely representing a tumor or lesion.   A grayscale medical imaging scan showing a sagittal view of the jaw and teeth, highlighting the dental structures and surrounding bone tissue. A colored medical imaging scan displaying a cross-sectional view of the skull with highlighted areas in purple and green, indicating regions of interest or activity.   3D rendered image of a human skull, showing detailed bone structure with a metallic texture and visible teeth, set against a black background. Medical imaging scan of a pelvic region, highlighting the hip joints with purple and green areas indicating specific regions of interest, likely from a PET or CT scan. # Conclusion – **Assessment of hard tissue:** Intraoral Radiographs, Extraoral Radiographs, CBCT, MSCT – **Assessment of soft tissues:** MSCT, MRI, Ultrasound – **Functional Imaging Techniques:** SPECT, PET   #### Imaging Modalities for Tissue Assessment - **Assessment of hard tissue:** - Intraoral Radiographs - Extraoral Radiographs - CBCT (Cone Beam Computed Tomography) - MSCT (Multislice Computed Tomography) - **Assessment of soft tissues:** - MSCT (Multislice Computed Tomography) - MRI (Magnetic Resonance Imaging) - Ultrasound #### Functional Imaging Techniques - SPECT (Single-Photon Emission Computed Tomography) - PET (Positron Emission Tomography) A dark, low-resolution medical imaging scan showing a cross-sectional view of a body part, likely from a CT or MRI scan, with visible anatomical structures and a small highlighted area. A detailed medical imaging scan of a human head and neck region, displaying soft tissue and bone structures in a 3D reconstruction, likely from a CT or similar imaging modality. 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