Background photo of blue digital binary code or hexadecimal data stream. Learning Objectives * Understand differences between analogue and digital imaging * Know different types of imaging sensors * What are advantages & disadvantages of digital imaging?  - Understand differences between analogue and digital imaging - Know different types of imaging sensors - What are advantages & disadvantages of digital imaging? Iconic diagram showing a blue silhouette of a human head in profile with two white gears inside, symbolizing learning or cognitive processing. This visual supports the 'Learning Objectives' text. # 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 - 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 # Analogue vs Digital ## Film vs Digital Receptors ## Processing - Chemical vs Electronic, time, health & safety, … ## Storage & Transfer ## Image display ## Image resolution - Analogue = continuous density spectrum - Digital = numeric format of the image content and its discreteness - Pixels - At each pixel of an electronic detector, the absorption of x-rays generates a small voltage ## Dosage ## Others - Cost, image enhancement, etc. ### Film vs Digital Receptors ### Processing - Chemical vs Electronic, time, health & safety, … ### Storage & Transfer ### Image display ### Image resolution - Analogue = continuous density spectrum - Digital = numeric format of the image content and its discreteness - Pixels - At each pixel of an electronic detector, the absorption of x-rays generates a small voltage ### Dosage ### Others - Cost, image enhancement, etc. ## Pixels **FIG. 4.1** A digital image is made up of a large number of discrete picture elements (pixels). The pixels are so small that the image appears smooth at normal magnification. The location of each pixel is uniquely identified by row and column coordinates within the image matrix. The value assigned to a pixel represents the intensity (gray level) of the image at that location. <table> <thead> <tr> <th>pixel</th> <th>350</th> <th>351</th> <th>352</th> <th>353</th> <th>354</th> <th>355</th> <th>356</th> <th>357</th> </tr> </thead> <tbody> <tr> <td>261</td> <td>228</td> <td>222</td> <td>184</td> <td>107</td> <td>76</td> <td>92</td> <td>90</td> <td>98</td> </tr> <tr> <td>262</td> <td>227</td> <td>218</td> <td>186</td> <td>110</td> <td>90</td> <td>104</td> <td>103</td> <td>98</td> </tr> <tr> <td>263</td> <td>222</td> <td>219</td> <td>181</td> <td>107</td> <td>97</td> <td>107</td> <td>102</td> <td>104</td> </tr> <tr> <td>264</td> <td>225</td> <td>217</td> <td>176</td> <td>107</td> <td>98</td> <td>100</td> <td>100</td> <td>107</td> </tr> <tr> <td>265</td> <td>221</td> <td>204</td> <td>159</td> <td>107</td> <td>105</td> <td>101</td> <td>107</td> <td>102</td> </tr> <tr> <td>266</td> <td>217</td> <td>196</td> <td>157</td> <td>114</td> <td>105</td> <td>104</td> <td>106</td> <td>100</td> </tr> <tr> <td>267</td> <td>209</td> <td>190</td> <td>154</td> <td>114</td> <td>107</td> <td>103</td> <td>97</td> <td>100</td> </tr> <tr> <td>268</td> <td>202</td> <td>195</td> <td>166</td> <td>118</td> <td>102</td> <td>102</td> <td>92</td> <td>94</td> </tr> <tr> <td>269</td> <td>197</td> <td>196</td> <td>168</td> <td>122</td> <td>98</td> <td>102</td> <td>90</td> <td>94</td> </tr> <tr> <td>270</td> <td>195</td> <td>190</td> <td>166</td> <td>130</td> <td>104</td> <td>105</td> <td>92</td> <td>97</td> </tr> <tr> <td>271</td> <td>199</td> <td>190</td> <td>172</td> <td>144</td> <td>111</td> <td>107</td> <td>100</td> <td>106</td> </tr> <tr> <td>272</td> <td>201</td> <td>193</td> <td>177</td> <td>160</td> <td>120</td> <td>103</td> <td>112</td> <td>106</td> </tr> <tr> <td>273</td> <td>203</td> <td>195</td> <td>181</td> <td>166</td> <td>129</td> <td>102</td> <td>111</td> <td>106</td> </tr> <tr> <td>274</td> <td>201</td> <td>200</td> <td>186</td> <td>172</td> <td>133</td> <td>110</td> <td>112</td> <td>102</td> </tr> </tbody> </table>   **FIG. 4.1** A digital image is made up of a large number of discrete picture elements (pixels). The pixels are so small that the image appears smooth at normal magnification. The location of each pixel is uniquely identified by row and column coordinates within the image matrix. The value assigned to a pixel represents the intensity (gray level) of the image at that location. | pixel | 350 | 351 | 352 | 353 | 354 | 355 | 356 | 357 | |-------|-----|-----|-----|-----|-----|-----|-----|-----| | 261 | 228 | 222 | 184 | 107 | 76 | 92 | 90 | 98 | | 262 | 227 | 218 | 186 | 110 | 90 | 104 | 103 | 98 | | 263 | 222 | 219 | 181 | 107 | 97 | 107 | 102 | 104 | | 264 | 225 | 217 | 176 | 107 | 98 | 100 | 100 | 107 | | 265 | 221 | 204 | 159 | 107 | 105 | 101 | 107 | 102 | | 266 | 217 | 196 | 157 | 114 | 105 | 104 | 106 | 100 | | 267 | 209 | 190 | 154 | 114 | 107 | 103 | 97 | 100 | | 268 | 202 | 195 | 166 | 118 | 102 | 102 | 92 | 94 | | 269 | 197 | 196 | 168 | 122 | 98 | 102 | 90 | 94 | | 270 | 195 | 190 | 166 | 130 | 104 | 105 | 92 | 97 | | 271 | 199 | 190 | 172 | 144 | 111 | 107 | 100 | 106 | | 272 | 201 | 193 | 177 | 160 | 120 | 103 | 112 | 106 | | 273 | 203 | 195 | 181 | 166 | 129 | 102 | 111 | 106 | | 274 | 201 | 200 | 186 | 172 | 133 | 110 | 112 | 102 | A composite figure demonstrating the concept of pixels in digital imaging. It includes an X-ray radiograph of dental implants on the left, with a zoomed-in section showing pixelated detail. To the right of the zoomed-in area is a numerical table representing pixel intensity values for specific grid coordinates. On the far right is a diagram illustrating a 3D voxel representation of the jawbone, showing how a single slice corresponds to a 2D image plane. A data table displaying numerical values representing pixel intensities. The rows are indexed by 'pixel' numbers ranging from 261 to 274, and columns represent spatial coordinates labeled 350 through 357. The values range between 76 and 228. Analog-to-Digital Conversion (ADC) • Ie. From photons/voltages to digital Image • Involves TWO steps • 1. Sampling • A range of voltages are grouped together • 2. Quantisation • Each sampled range is assigned a grey value • Large sampling = ‘pixelated’ image ‘B’ • Narrow sampling = close to original signal ‘C’  #### Analog-to-Digital Conversion (ADC) - Ie. From photons/voltages to digital Image - Involves TWO steps 1. Sampling - A range of voltages are grouped together 2. Quantisation - Each sampled range is assigned a grey value - Large sampling = ‘pixelated’ image ‘B’ - Narrow sampling = close to original signal ‘C’ Labelled diagram illustrating Analog-to-Digital Conversion (ADC) via three vertically stacked graphs. Graph A shows a smooth analog waveform representing the original signal. Graph B displays a stepped, pixelated approximation of the signal, corresponding to the text 'Large sampling = 'pixelated' image 'B''. Graph C shows a more detailed stepped approximation closer to the original curve, corresponding to the text 'Narrow sampling = close to original signal 'C''. The diagrams visually demonstrate the concepts of Sampling and Quantisation. 1 2 3 4 5 6 7 8 8 pixel numbers 8 shades of grey 2 8 2 8 2 8 4 6 4 8 2 6 1 6 2 8 4 6 4 8 2 8 2 8 2 Each pixel allocated a number Each pixel allocated a shade of grey A B C D   ``` 1 2 3 4 5 6 7 8 8 pixel numbers 8 shades of grey 2 8 2 8 2 8 4 6 4 8 2 6 1 6 2 8 4 6 4 8 2 8 2 8 2 Each pixel allocated a number Each pixel allocated a shade of grey A B C D ``` Diagram illustrating the mapping of pixel numbers to shades of grey. The left panel shows a grid where each pixel is allocated a number (e.g., 2, 8, 4). An arrow points to the right panel showing the corresponding visual representation where those numbers are replaced by specific shades of grey. A radiographic image divided into four quadrants labeled A, B, C, and D. It displays anatomical structures, likely teeth and jawbone, with varying densities represented in grayscale. # Digital Image Receptors * **Two types** * Solid-state detectors / <u>sensors</u> * Charged-coupled device (CCD) * Complementary metal oxide semiconductors (CMOS) * Flat panel detectors $\rightarrow$ extra-oral use * Photostimulable phosphor (PSP) <u>plates</u> - **Two types** - Solid-state detectors / <u>sensors</u> - Charged-coupled device (CCD) - Complementary metal oxide semiconductors (CMOS) - Flat panel detectors → extra-oral use - Photostimulable phosphor (PSP) <u>plates</u> CCD • charge-coupled device • first digital image receptor to be adapted for intraoral imaging • thin wafer of silicon pixels consisting of n-type silicon and p-type silicon covered with a scintillation layer • Light and silicon interaction creates **charge packet** for each pixel (latent image) A B C Scintillation layer CCD pixels Scintillation layer P-type silicon N-type silicon Insulating layer Electrodes Photoelectric absorption in silicon Conduction band - Electron e⁻ Hole Valence band + e⁻    #### CCD - charge-coupled device - first digital image receptor to be adapted for intraoral imaging - thin wafer of silicon pixels consisting of n-type silicon and p-type silicon covered with a scintillation layer - Light and silicon interaction creates **charge packet** for each pixel (latent image) ``` A B C Scintillation layer CCD pixels Scintillation layer P-type silicon N-type silicon Insulating layer Electrodes ``` Photoelectric absorption in silicon: ``` Conduction band - Electron e⁻ Hole Valence band + e⁻ ``` Labelled diagram of a CCD sensor unit (A). Shows an outer plastic casing containing a grid-like CCD array, with a cable extending from the bottom. Labels include 'CCD array', 'Outer plastic casing', and 'Cable'. Cross-sectional diagrams illustrating CCD construction. Panel B shows a zoomed view of the top edge showing the Scintillation layer and CCD pixels. Panel C shows a vertical cross-section detailing the layers: Scintillation layer on top, followed by P-type silicon, N-type silicon, Insulating layer, and Electrodes at the base. Diagram titled 'Photoelectric absorption in silicon'. Illustrates electron excitation where light energy (wavy line) moves an electron from the Valence band to the Conduction band, creating an electron-hole pair. Labels include 'Electron', 'Hole', 'Conduction band', 'Valence band', and charge symbols (+/-). **CCD Image Read-out** • "bucket brigade" • As a charge reaches the end of its row, it is transferred to a readout amplifier and transmitted as a voltage to the ADC located within or connected to the computer  #### CCD Image Read-out - "bucket brigade" - As a charge reaches the end of its row, it is transferred to a readout amplifier and transmitted as a voltage to the ADC located within or connected to the computer Labelled diagram illustrating CCD Image Read-out. The visual shows three columns of photodiodes (grey squares) arranged in rows, with vertical shift registers (white rectangles) and transfer control elements (brown bars). Green arrows indicate the 'bucket brigade' charge transfer from photodiode to vertical register, then down the column. Blue arrows show charge movement within the vertical registers towards the bottom horizontal shift register (orange bar). Labels include 'vertical shift registers', 'transfer control', 'photodiodes', and 'horizontal shift register'. ### CMOS (Complementary Metal Oxide Semiconductor) X-ray Detector #### Explosion View of CMOS (Complementary Metal Oxide Semiconductor) Sensor **Components:** - **Back Housing + Cable** - **Electronic Substrate** - **CMOS Imaging Chip** - **Fiber-optic Face Plate** - **Scintillator Screen** - **Front Housing** **Direction of X-ray Beam:**  #### CMOS (Complementary Metal Oxide Semiconductor) X-ray Detector ##### Explosion View of CMOS Sensor **Components:** - Back Housing + Cable - Electronic Substrate - CMOS Imaging Chip - Fiber-optic Face Plate - Scintillator Screen - Front Housing **Direction of X-ray Beam:** Explosion view diagram of a CMOS X-ray detector. The image displays the internal layers of the device separated for clarity. Labels point to specific components: 'Back housing + cable' (top), 'Electronic substrate', 'CMOS imaging chip', 'Fiber-optic face plate', 'Scintillator screen', and 'Front housing'. An orange arrow at the bottom indicates the 'Direction of x-ray beam' pointing upwards through the layers. CMOS Image Read-out * **CCD** * **CMOS** * Photon to electron conversion * Conversion: Charge to electrical signal * Two different principles: CCD vs CMOS  #### CMOS Image Read-out - **CCD** - **CMOS** - Photon to electron conversion - Conversion: Charge to electrical signal - Two different principles: CCD vs CMOS Comparative diagram illustrating the structural differences between CCD and CMOS image sensor read-out mechanisms. The diagram is divided into three main sections labeled 'CCD', 'CMOS', and a central process description. On the left, the 'CCD' section shows a grid of pixels with arrows indicating charge transfer to a single output node at the bottom. In the center, text explains 'Photon to electron conversion' and 'Conversion: Charge to electrical signal'. On the right, the 'CMOS' section displays a grid where each pixel has its own associated transistor (red triangles), with an arrow pointing from a specific pixel to the output path. The caption below reads 'Two different principles: CCD vs CMOS'. PSP * Photostimulable Phosphor * Europium-doped barium fluorohalide * Image processing is NOT instant * Absorb and store **energy** from x-rays * $\rightarrow$ latent image * Release this **energy** as light (phosphorescence) when stimulated by another light of an appropriate **wavelength** (= scanner)  #### PSP - Photostimulable Phosphor - Europium-doped barium fluorohalide - Image processing is NOT instant - Absorb and store **energy** from x-rays → latent image - Release this **energy** as light (phosphorescence) when stimulated by another light of an appropriate **wavelength** (= scanner) Layered cross-section diagram of a Photostimulable Phosphor (PSP) plate. The diagram shows stacked layers from top to bottom: Protective layer, Phosphor layer (BaFX : Eu²⁺ containing irregular white shapes representing phosphor crystals), Reflective layer, Conductive layer, Support, Backing layer, and Bar code layer.   Clinical photo of a white and gray medical device with a black component on the front. Clinical photo of a cylindrical medical instrument with multiple components and a base. - Capacity for distinguishing fine detail in an image - Measured and reported in units of line pairs per millimeter - Eyes can detect 6 lp/mm. - Film > 20 lp/mm - SSD ~ 20 lp /mm - PSP ~ 10 lp/mm - The smaller the size of the pixel, the higher the maximally attainable resolution  - Capacity for distinguishing fine detail in an image - Measured and reported in units of line pairs per millimeter - Eyes can detect 6 lp/mm. - Film > 20 lp/mm - SSD ~ 20 lp/mm - PSP ~ 10 lp/mm - The smaller the size of the pixel, the higher the maximally attainable resolution A spatial resolution test pattern figure containing four distinct rows labeled A, B, C, and D on the left margin. Each row displays a series of black vertical bars with increasing density (line pairs per millimeter). Row A shows numbers 14-20 above dense patterns; Row B shows numbers 8-13; Row C shows numbers 5-10; and Row D shows high-density vertical lines at the bottom. This visual demonstrates the concept of distinguishing fine detail as described in the text. Image Resolution – Contrast Resolution • Ability to distinguish different densities in the radiographic image • Current digital detectors capture data at 8, 10, 12, or 16 bits. • Conventional computer monitors are capable of displaying a grey scale of only 8 bits ($2^8 = 256$ shades of grey) • The human eyes in darkroom / reporting room are capable of distinguishing 60 grey levels • Less than 30 grey levels in operatory dental clinics  - Ability to distinguish different densities in the radiographic image - Current digital detectors capture data at 8, 10, 12, or 16 bits. - Conventional computer monitors are capable of displaying a grey scale of only 8 bits (2^8 = 256 shades of grey) - The human eyes in darkroom / reporting room are capable of distinguishing 60 grey levels - Less than 30 grey levels in operatory dental clinics Visual demonstration of contrast resolution showing a grayscale gradient. The image consists of a rectangular grid of square blocks ranging from black on the left to white on the right. Vertical columns represent different shades of gray, while horizontal rows (labeled A, B, C, D) demonstrate variations in pixel size or blockiness, illustrating how different bit depths or resolutions affect the smoothness of the transition between densities. # Image Manipulation / Adjustment * Magnification * Brightness * Contrast * Inversion * Sharpening * Smoothing - Magnification - Brightness - Contrast - Inversion - Sharpening - Smoothing **5.**9 Examples of digital image enhancement. A Original image. B Inverted/reversed. C Altered contrast. D Embossed/pseudo 3-D. E Automated measurement. F Magnified. G and H Pseudocoloured.  5.9 Examples of digital image enhancement. - A Original image. - B Inverted/reversed. - C Altered contrast. - D Embossed/pseudo 3-D. - E Automated measurement. - F Magnified. - G and H Pseudocoloured. A composite figure demonstrating various digital image enhancements applied to dental radiographs (panoramic view). The figure is divided into eight panels labeled A through H. Panel A shows the original grayscale X-ray of two molar teeth with a large restoration on the right tooth. Panel B displays an inverted/reversed version where light areas are dark and vice versa. Panel C shows altered contrast for enhanced visibility. Panel D presents an embossed or pseudo-3D effect. Panel E illustrates automated measurement with a line drawn across the root canal space. Panel F provides a magnified view of the same area. Panels G and H display pseudocolored versions of the image using heat-map color gradients to highlight density variations. SSD vs PSP (clinical factors) * **SSD vs PSP (clinical factors)** * **Patient comfort** * Intraoral SSDs are bulky (5-7mm) & often corded * PSPs are similar to films – flexible and thin * **Intra-oral holders** * SSD holders are different * **Exposure** * Computer & software must be ready before exposure * **Processing** * SSDs are immediate * PSPs need a scanner * **Sterilisation**  - **SSD vs PSP (clinical factors)** - **Patient comfort** - Intraoral SSDs are bulky (5-7mm) & often corded - PSPs are similar to films – flexible and thin - **Intra-oral holders** - SSD holders are different - **Exposure** - Computer & software must be ready before exposure - **Processing** - SSDs are immediate - PSPs need a scanner - **Sterilisation** Clinical photo showing a comparison of two types of dental sensors. On the left are two dark grey rectangular intraoral sensors labeled 'PLANMECA dixi' with attached black cables (SSDs). On the right are two white, flexible, square-shaped plates (PSPs) without cords. The visual demonstrates the physical differences in size and flexibility between SSDs and PSPs mentioned in the text. END. END. [^1]: Original PDF page 1: [[L4 Digital Imaging.pdf#page=1|L4 Digital Imaging, p.1]] [^2]: Original PDF page 2: [[L4 Digital Imaging.pdf#page=2|L4 Digital Imaging, p.2]] [^3]: Original PDF page 3: [[L4 Digital Imaging.pdf#page=3|L4 Digital Imaging, p.3]] [^4]: Original PDF page 4: [[L4 Digital Imaging.pdf#page=4|L4 Digital Imaging, p.4]] [^5]: Original PDF page 5: [[L4 Digital Imaging.pdf#page=5|L4 Digital Imaging, p.5]] [^6]: Original PDF page 6: [[L4 Digital Imaging.pdf#page=6|L4 Digital Imaging, p.6]] [^7]: Original PDF page 7: [[L4 Digital Imaging.pdf#page=7|L4 Digital Imaging, p.7]] [^8]: Original PDF page 8: [[L4 Digital Imaging.pdf#page=8|L4 Digital Imaging, p.8]] [^9]: Original PDF page 9: [[L4 Digital Imaging.pdf#page=9|L4 Digital Imaging, p.9]] [^10]: Original PDF page 10: [[L4 Digital Imaging.pdf#page=10|L4 Digital Imaging, p.10]] [^11]: Original PDF page 11: [[L4 Digital Imaging.pdf#page=11|L4 Digital Imaging, p.11]] [^12]: Original PDF page 12: [[L4 Digital Imaging.pdf#page=12|L4 Digital Imaging, p.12]] [^13]: Original PDF page 13: [[L4 Digital Imaging.pdf#page=13|L4 Digital Imaging, p.13]] [^14]: Original PDF page 14: [[L4 Digital Imaging.pdf#page=14|L4 Digital Imaging, p.14]] [^15]: Original PDF page 15: [[L4 Digital Imaging.pdf#page=15|L4 Digital Imaging, p.15]] [^16]: Original PDF page 16: [[L4 Digital Imaging.pdf#page=16|L4 Digital Imaging, p.16]] [^17]: Original PDF page 17: [[L4 Digital Imaging.pdf#page=17|L4 Digital Imaging, p.17]] [^18]: Original PDF page 18: [[L4 Digital Imaging.pdf#page=18|L4 Digital Imaging, p.18]] [^19]: Original PDF page 19: [[L4 Digital Imaging.pdf#page=19|L4 Digital Imaging, p.19]] [^20]: Original PDF page 20: [[L4 Digital Imaging.pdf#page=20|L4 Digital Imaging, p.20]]