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Jen Test 6
Bushong Chapter 15
Question | Answer |
---|---|
The range of exposure over which a film produces an image if the definition for? | Exposure latitude |
Doubling the mAs on an inversely proportional system will result in: 1. Half the brightness level 2. Double the exposure index 3. A decrease in the exposure index | 2. Double the exposure index |
Which radiographic image capture method uses chemical development to produce the manifest image? | Film/screen radiography |
The exposure latitude of digital projection radiography responds in a _______ manner | Linear, non-threshold |
T/F: If grid lines are present and run parallel to the scanning laser, the image will not have the moire pattern present. | False |
T/F: Digital systems are less sensitive to scatter radiation than film/screen systems? | False |
The arrangement of pixels in rows and columns is known as? | A matrix |
T/F: Aliasing occurs when the sampling frequency is not greater than twice the frequency of the input signal? | True |
The active layer in a PSP plate is usually made of phosphors from what family group? | Barium fluorohalide |
Which layer of the PSP plate sends light in a more forward direction when released in the reader? | Reflective |
The laser excites the electrons trapped in the phosphor centers so that they energy may be released in the form of _______ | Light |
What device in the reader detects the light being released from the PSP plate during reading? | Photodetector |
3 ways the PSP plate is erased. | 1. After every PSP plate is read. 2. By flooding it with a bright light. 3. Manually by selecting the proper eraser method. |
T/F: Too much mAs will cause quantum mottle | False |
Exposure latitude with digital imaging is more _____ when compared with analog imaging. | Wide |
In digital imaging, the term _____ replaces density as applied in analog based imaging. | Brightness |
A ____ SNR is desired for best image density. | High |
Another term for imaging noise is? | Mottle |
T/F: The greater the exposure to the plate, the greater the intensity of the light is emitted from the plate during the reading. | True |
T/F: Fifty percent of the IP must be exposed to produce a correct reading of the image. | False |
The instantaneous production of light resulting from the interaction between a compound and a form of energy is known as ________ | Fluorescence |
Which of the following are advantages of digital systems over film-screen systems? 1. Increased dynamic range 2. Higher spatial resolution 3. More contrast resolution | 1. Increased dynamic dynamic range 3. More contrast resolution |
Each cell of an image matrix is called? | A pixel |
What is spatial resolution in digital imaging is determined by? | Matrix size and the size of the field of view |
Quantum mottle on an image is also referred to as? | Signal loss |
How would dirt on the light guide of a CR reader appear on a digital image? | White lines |
A quality assurance test for digital imaging receptors is to check for dark noise. What is the purpose of this test? | To assess the level of detector noise in the system. |
The latent image can remain "stored" in the PSP plate for ____ hours before information is lost. | 8 |
The active portion of a CR imaging plate is? | Barium fluorohalide phosphors |
When was CR invented? | In the 1970's |
When was CR introduced to the medical field? | 1981 |
T/F: CR is the most widely used from of digital radiography. | True |
What does PSP stand for? | Photostimulable phosphor |
What does SPS stand for? | Storage phosphor screen |
When is it called PSP and when is is called SPS? | PSP: before its exposed. SPS: after its exposed |
How many layers are in the PSP plate? | 5 |
What are the 5 layers of the PSP plate? | 1. Protective layer 2. Photostimulable phosphor layer 3. Reflective layer 4. Base 5. Backing |
What is the purpose of the protective layer? | To provide protection to the active layer. |
Whats is the purpose of the photostimulable phosphor layer? | It is the active layer where the latent image is formed. |
What is the purpose of the reflective layer? | To increase efficiency. |
What is the purpose of the base layer? | To provide support. |
What is the purpose of the back layer? | To absorb scatter. |
What is the back layer made of? | Lead (Pb) |
What 2 things are the photostimulable phosphors comprised of? | Barium fluorohalide and europium. |
What are the chemical symbols for barium fluorohalide with europium? | BaFBr:Eu or BaFI:Eu |
What is the role of the europium? | It acts as the activator. Plays the greatest role in the formation of the latent image. (It is similar to the sensitivity speck in the emulsion of the film) |
Photostimulable phosphors emit light when they are stimulated by?? | Xrays or by different light sources. |
Why are phosphors linear versus "block shape"? | To enhance absorption of the xrays and limit the divergence of light emission. |
What is the first step in the process of latent image formation? | Xrays interact with the outershell e- of photostimulable phosphor via compton (scatter) and photoelectric (absorption) interactions causing excitation of the outer shell e- |
What is the second step in the process of latent image formation? | Outer shell e- becomes excited, leaves it orbit while simultaneously producing light. |
What is the third step in the process of latent image formation? | The excited e- hovers just above its orbit causing a void and resulting in an unstable atom. |
What is the fourth step in the process of latent image formation? | When the e- return to its orbit light is emitted again. |
When can electrons return to their orbits? | On their own over time or when stimulated by an infrared laser. |
How many electrons lose energy and drop back into their shell? | 50% |