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MRO module 4
Question | Answer |
---|---|
Density | The overall amount of blackening on a radiograph; also called optical density or radiographic density |
Contrast | The differences in density on adjacent areas of the radiograph |
What determines the energy of the x-ray beam? | kVp |
mAs literally controls the current through the x-ray tube. T or F? | True |
In general, which kVp is appropriate for a very thick and dense anatomic area to ensure penetration? 40, 50, 60, 70 | 70kVp |
The level or degree of penetration of the x-ray beam is a primary factor in determining the scale of contrast. T or F? | True |
mAs should be used to control which of the following. 1)Contrast 2)Scatter 3)Density? | Density |
kVp affects which of the following. 1)Scatter 2)Patient dose 3)Density 4)All of the above? | All of the above |
Aluminum equivalent | A measurement of the filtering capacity of a filter comparing it to the filtration provided by aluminum |
Grid ratio | The ratio between the height of the lead strips in a grid and the width of the interspace material between them |
Intensifying screen | A device that converts x-ray photons to light photons to help create the latent image on the film, thereby reducing the x-ray exposure required |
What are the standard distances used in general radiography? | 40 and 72 |
What is the purpose of a grid? | Absorb scatter |
Convert 24 mAs used for slow-speed screens to a mAs appropriate for fast screens? | 6mAs. (x=24x1/4) (new mAs=old mAs x old speed factor/new speed factor) |
Increasing the speed screen allows for a reduction in the mAs needed for a given projection. T or F? | True |
If 20mAs is used as a non-grid technique, what mAs should be used with an 8:1 grid? | 80mAs. (x=20x4/1) (new mAs=old mAs x new bucky factor/old bucky factor) |
If 20mAs is used at a 40-inch SID, what mAs should be used at 72inches to maintain density? | 64.8mAs or round to 65mAs (new mas=(72/40)^2 x 20) (new mas=3.24x20) (64.8) |
If a 14x17 inch field is collimated to a 9x9 inch field with no other changes, what will happen to density? | Decrease |
Fixed kVp technique chart | A technique chart in which the kVp stays the same but different mAs selections are used for patients of different thickness |
Variable technique kVp chart | A technique chart in which the mAs stays the same but different kVp selections are used for patients of different thickness |
What increases voltage to kilovoltage in the x-ray circuit? | Step-up transformer |
All photons produced in an x-ray beam will have the same ability to penetrate. T or F? | False |
In the filament circuit, voltage is stepped down before passing to the filament. T or F? | True |
mAs controls density by controlling what? | Number of electrons boiled off of the filament. |
In general, we try to keep OID as large as possible. T or F? | False |
Grid ratio is the expression of the relationship between the lead strips and the interspace material. T or F? | True |
When compared to NOT using intensifying screens, use of a screen reduces patient dose. T or F? | True |
The use of precise collimation helps to reduce scatter reduction. T or F? | True |
The infant and elderly patient may require a decrease in technique from the average. T or F? | True |
The selection of kVp is based on the desired scale of contrast and penetration of the part. T or F? | True |