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 |