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orange final
Principles
| Question | Answer |
|---|---|
| At least a _____% change in mAs is necessary to produce a visible change in optical density. | 30 |
| 40 mAs is used with a 12:1 grid. What is the mAs needed if the grid is changed to a 6:1? | 24 |
| If a low kVp technique is used and a very light image results, what happened to the x-ray photons in that beam? | most were absorbed into the patient |
| The small focal spot will provide a _____. | finer detail of image |
| Both beam quality and beam quantity are increased by _____. | * increasing kVp * using 3-phase voltage |
| Which kVp setting should be used with a grid if imaging the abdomen? | 75 |
| All other factors remaining constant, an increase in kVp will have what effect on density? | increase |
| What happens to density as SID increases? | decreases |
| What are the four primary exposure factors? | kVp, mAs, time, and SID |
| If 15 mAs is used at a 40-inch SID, what mAs is needed at a 48-inch SID to maintain density? | 22 |
| Using a fixed kVp chart approach, adjust the following knee technique: 60 kVp @ 10 mAs, 8 cm thick to a knee measuring 12 cm. | 20 |
| Why does an increase in OID reduce the amount of scatter that exposes the image receptor? | Extra distance causes scatter to miss receptor. |
| What happens to density with increases in filtration? | decreases |
| Film should be stored at a temperature lower than_____, and with humidity no lower than _____. | 68°F 40% |
| What percentage of change in kVp is roughly equal to doubling the mAs? | 15% |
| With automatic exposure control the exposure is terminated when the optimum _____ is reached. | OD |
| A radiograph is taken using 75 kVp @ 20 mAs. Which change in technique would increase contrast but maintain the same density? | 65 kVp @ 40 mAs Reducing kVp by 15% and doubling the mAs will increase contrast but maintain the same optical density. |
| Collimation acts to reduce scatter and its resultant image fog primarily by which of the following? | Limiting area of exposure |
| If 20 mAs is used for a 14x17-inch field and it is collimated to 7x17 inches, what is the minimum suggested adjustment in mAs? | 30% |
| A _____% increase in kVp has the same effect on optical density as doubling the mAs. | 15 |
| Why does a grid remove more scatter photons than remnant photons from the beam? | Scatter travels in more divergent angles |
| In a variable kVp technique chart, the optimal mAs is set for each body part and there is a _____ kVp increase for each cm of thickness. | 2 |
| What happens to density when a grid is introduced into the system? | decreases |
| What is the problem with scatter in terms of scale of contrast? | Photons interact in wrong area of image |
| Why does density decrease with use of cones if mAs is not adjusted? | Photons are removed from the beam |
Created by:
zlangdon
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