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adv img CT 1
advanced imaging - CT set 1
| Question | Answer |
|---|---|
| Narrow window width produces what? | short scale |
| Wide window width produces what? | long scale |
| Window allows the viewer to alter what? | contrast |
| Window level controls what? | density |
| Window width controls what? | contrast |
| BUN number range for contrast: | 7-18 |
| Creatnine number range for contrast: | .6-1.5 |
| A “viscous” material is: | thick |
| CTDI | dose to pt within the primary beam |
| MSAD | average dose pt receives during an exam |
| Noise in CT is: | the variation in CT numbers above and below 0 |
| Linearity: | calibration of CT scanner so that water = 0 |
| Most important component of the CT QC program is: | spatial resolution test (bar or hole pattern) |
| Laser localizer for CT should be how accurate? | to within +/- 1mm |
| How does pt dose change with slice thickness? | thinner slices = more pt dose |
| Scintillation | detector made of crystal with 50% detector efficiency. Most common. |
| Pre-patient collimation controls: | pt dose |
| Postpatient (pre-detector) collimation controls: | slice thickness |
| How must the CT computer be stored? | in a cool dry place, under 68 degrees and 30% relative humidity |
| Formula for pixel size | FOV / matrix size |
| Formula for voxel | pixel size X slice thickness |
| CT numbers +1000 represent : | hard bone |
| CT numbers -1000 represent: | air |
| Ct numbers 0 represent : | water |
| CT number range for lung tissue: | -250 to -850 |
| CT number range for blood fluid: | +25 to +50 |