Term
| Advantages of Digital Imaging |
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Definition
elimination of chemical processing
elimination of hazardous wastes
images can be electronically transferred to other health care providers without altering the image
receptors require less radiation than film - lowering pt. exposure |
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Term
| Disadvantages of Digital Imaging |
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Definition
Initial expense is high
digital systems have new or immature technologies and the systems could do out of business
intraoral systems are susceptible to rough handling and are expense to replace |
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Term
| What makes film x-rays competitive with digital? |
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Definition
| low cost and excellent image quality |
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Term
| What are the two ways in which digital imaging is numeric and discrete? |
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Definition
1. in terms of the spatial distribution of the pixels
2. in terms if the different shades of gray of each of the pixels. |
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Term
| What type of medium are film images considered to be in? |
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Definition
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Term
| What does it mean to be in an analog medium? |
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Definition
| differences in the size and distribution of black metallic silver results in a continuous density spectrum |
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Term
| What does ADC stand for? What does it consist of? |
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Definition
Analog-to-digital conversion
Two steps: sampling and quantitizing |
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Term
| Sampling and quantitized are steps of what process? |
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Definition
ADC (analog to digital conversion)
Sampling - small range of voltage values are grouped as a single value
Quantitized- every sample signal is assigned a value |
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Term
| What does the quantitized value represent? |
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Definition
| intensity of the image(grey level) |
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Term
| Two main technologies of digital image receptors are _______ and _________. |
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Definition
Solid- State technology
Photostimulate phosphor technology |
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Term
| The use of solid-state detectors is referred to as different things in medicine and dentistry. What are they? |
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Definition
In medicine they are referred to as digital radiography
In dentistry they are called sensors |
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Term
| What does Photostimulable phosphor consist of? |
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Definition
A phosphor coated on top of a plate in which an image is formed after x-ray exposure.
This technology is sometimes thought as storage phosphor bc the image is temporarily stored within the phosphor |
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Term
| What does Photostimulable phosphor consist of? |
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Definition
A phosphor coated on top of a plate in which an image is formed after x-ray exposure.
This technology is sometimes thought as storage phosphor bc the image is temporarily stored within the phosphor |
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Term
| Computed Radiology is another term for what? |
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Definition
| The use of PSP (photostimulable phosphor technology) plates in medical radiology |
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Term
| What are analog images composed of vs. digital images? |
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Definition
Analog are composed of a continuous gradient
Digital are composed of pixels of numerical info that are organized into a matrix. |
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Term
| T/F The intensity of the voltage (when a photon strikes the pixel area on the sensor) produces a gradient |
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Definition
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Term
| T/F The expense of the detector increases with decreasing number of pixels |
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Definition
FALSE. The expense increases with an increasing number of pixels (matrix size)
pixel size varies from 20 to 70 micrometers |
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Term
| How many solid-state sensors are commonly used? |
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Definition
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Term
| What are the three types of solid-state sensors? |
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Definition
Charge coupled device (ccd)
Complementary metal oxide semiconductors
Flat panel detectors |
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Term
| T/F The charge coupled device was the last type of digital receptor to be used in dentistry ( of the 3 types) |
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Definition
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Term
| Thin silicon wafer, pixels read in a continuous chain (bucket bridage style), more bulky than other receptor types - what type of sensor is described? |
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Definition
| Charge coupled device (CCD) |
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Term
| Describe Complementary metal Oxide Semiconductors (CMOS) |
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Definition
Use silicon detector with same mechanism as CCD
Pixels read ONE at a time, isolated from neighbors (unlike CCD) |
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Term
| What do both CCD and CMOS have in common? What is an advantage of CMOS? |
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Definition
Both generate electron-hole pairs within the pixel in proportion to the amount of x-ray energy that is absorbed.
CMOS are less expensive than CCDs |
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Term
| t/f CCD detectors are more sensitive to light than to x-rays |
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Definition
| True. Bc of this, manufacturers use a layer of scintillating material (cesium iodide or gadolinium oxybromide) coated on the CCD surface or coupled to the surface by fiberoptics - increasing the x-ray absorption efficiency of the detector |
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Term
| What are CCD, CMOS, and Flat Panel detectors each used for? |
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Definition
CCD- intraoral imaging
CMOS- video cameras
Flat panel - extraoral imaging |
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Term
| t/f flat panel detectors provide small matrix areas |
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Definition
| False - large matrix areas with pixel sizes less than 100 micrometers |
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Term
| What does the large matrix area in Flat panel detectors allow? |
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Definition
| Imaging of larger areas of the body - head |
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Term
| What are two approaches of Flat panel detectors? |
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Definition
Indirect and Direct
Indirect - sensitive to visible light, use an intensifying screen to convert x-ray energy into light (thicket screens use less radiation but yield lower quality images)
Direct - use photoconductor material selenium)which permits more efficient absorption of x-rays |
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Term
| Are Flat panel detectors afforable and used often? |
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Definition
| No, they are expensive and limited to specialized imaging such as cone beam imaging |
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Term
| Compare Indirect intensifying screens and Direct photoconductor material in Flat panel detectors |
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Definition
| Direct use selenium and provide higher resolution but lower efficiency compared to Indirect using intensifying screens with galdolinium or cesium. |
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