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Image aquisition
| Question | Answer |
|---|---|
| What are the two modes of electronic imaging? | (CR) computed radiography, (DR) digital radiography p.305 |
| What is another word for screen/film imaging? | Projection imaging 305 |
| What is the law the proclaims that any combination of mA and exposure time that will produce a particular mAs, will produce identical receptor exposure. | Reciprocity Law 306 |
| What law states that the exposure rate is inversely proportional to the square of the distance | inverse square law 306 |
| in what formula is the inverse square law used when making a repeat exposure at a different SID? | Exposure maintenance formula |
| Three ways that x-rays interact with tissue? | Penetrate the part, scatter within the part, be absorbed by the part 310 |
| Where would a moving grid be located? | inside Bucky 312 |
| Where would you find a focused grid? | as an attachment on the image receptor 312 |
| what happens where the CR angle is angled against the length of the lead strips inside a focused grid? | Grid cut-off 313 |
| characterized by a loss of exposure at the periphery of an IR, happens when SID is too low or too high from an IR with a grid? | Off-Focus error, grid cutoff occurs at periphery of images, out of focal range for a particular grid 313 |
| What does the grid ratio of an image receptor represent? | The height of the lead strips inside the grid compared with the distance between them 314 |
| what is the grid frequency? | The number of lead strips per inch 314 |
| What is the grid factor? | ratio of total amount of radiation incident upon the surface of the grid compared with amount of radiation transmitted through the grid. ( G= incident total/ transmitted total) 314 |
| most important way to reduce scatter | collimation 316 |
| scatter radiation increases with what factors | increases of field size, kV, thickness of tissue, volume of tissue 316 |
| what is the minimum requirement of total filtration for radiographic tubes that operate above 70kv | 2.5 mm Al equivalent 317 |
| Glass tube and collimators are considered what type of filtration? | Inherent 317 |
| type of filter that is added to tube to remove diagnostically useless x-rays? | Added filtration 317 |
| Examples of additive pathological conditions that reduce exposure to the IR? | Ascites, Rheumatoid arthritis, Paget's disease, pneumonia, atelectasis, CHF, edema 318 |
| Examples of destructive pathological conditions that have an undesirable increase in exposure to the IR? | Osteoporosis, Osteomalacia, Pneumoperitoneum,emphysema, 318 |
| What is directly proportional to patient dose and image density? | mAs 321 |
| How much of an increase or decrease in mAs is needed to correct an underexposed or overexposed image? | 30% 321 |
| density can be doubled or halved by increasing or decreasing the kV by what? | 15% 324 |
| used to provide a more uniform radiographic density with structures that have widely different attenuation coefficients? | Compensating filters 326 |
| how much ripple does a single phase generator produce? | 100% ripple 329 |
| how much ripple does a 3 phase 6 pulse generator produce? | 13% ripple 329 |
| how much ripple does a 3 phase 12 pulse produce? | 4% ripple 329 |
| how much ripple does a high frequency generator produce? | <1% ripple 329 |
| number of bits per pixel that determines greyscale? | Bit depth 334 |
| what kind of scale is high contrast? | Short grey scale 338 |
| what kind of scale is low contrast? | Long grey scale 338 |
| smaller pixel size does what to resolution? | Improves it 357 |
| Larger image matrix does what to resolution? | Improves it 357 |
Created by:
saluke
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