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VTI Rad1 CH 5
| Question | Answer |
|---|---|
| Non-image forming radiation that is scattered in all directions because of objects in the path of the xray beam | Scatter radiation |
| Where does scatter come from? | Patient/Table or Back Scatter |
| Radiation that is reflected from behind the image plane back to the image | Back Scatter |
| When will scatter be noticeable on film? | The film is darkened and the contrast is decreased. |
| The measurable difference between two adjacent densities | Contrast |
| Degree of blackness on film | Density |
| Density is influenced by ... | mAs and kVp |
| If the radiograph is too dark what do you change first? | mAs |
| Short Scale/ Black and White/ Bone/ Lower kVp | High Contrast |
| Long Scale/ Soft tissue/ Higher kVp | Low Contrast |
| If you need to increase your mAs, you would increase it by what % | 30-50% |
| If you are overexposed you will lower your mAs and kVp by what percent? | mAs is 30%to50% and kVp is by 10-15% |
| Underexposed? you will increase by what percent? | mAs is 30%to50% and kVp is by 10-15% |
| a device placed between patient and film to absorb scatter | grid |
| Main disadvantage of a grid... | absorb some of the primary beam |
| Grid Patterns | Linear and crossed |
| Grid Types | Focused grids, unfocused, and bucky |
| Two parallel or two focused grids that are set at right angles. | Crossed grid |
| A grid with a parallel center lead strip and inclined strips on either side of that radiate at progessively greater angles. | Focused grid |
| Variation in normal size and shape of anatomic structures due to their position in relation to the xray source and film | geometric distortion |