ch 13 ct safety Flashcards
skin dose in CT is (more/less) than in x-ray/fluoro
less
dose distribution in CT is (more/less) uniform
more
shielding in CT is no more effective than ___________
collimators
AEC for CT is _____________________
tube current modulation
tube current modulation uses ___________ to vary the mA during scan
scout image
tube current modulation is more effective than ______________
older bismuth shielding
with angular based modulation, anterior side mA will ______________; posterior side mA will __________
decrease, increase
iterative reconstruction is better than filtered back projection (could be done _____); iterative reconstruction can be done ________________
once, over and over
iterative reconstruction reduces radiation exposure ____% compared to filtered back projection
25-40%
increasing kVp in CT will (increase/decrease) patient dose
increase
reducing tube potential from 100 to 80 kVp will reduce patient dose ____
1.5x
CTDI is determined by _________________
an ionization chamber with a phantom
what does CTDI stand for?
Computed tomography dose index
CTDIW (weighted) is the __________________________
average of 2 measured CTDI volumes
CTDIVOL = _____________
CTDIW/Pitch
with CT effective dose, there is ________________ risk of cancer or early death _________ effective dose
no increased, <100 mSv
typical effective dose
Abdomen
Pelvis
Coronary angiography
Abdomen 5-8 mSv
Pelvis 3-6 mSv
Coronary angiography 1-18 mSv
typical effective dose
Head
Chest
Head 1-2 mSv
Chest 2-6 mSv
Effective mAs = mAs = _________
mAs/Pitch
_____________ is older than ___________ in CT cardiac imaging
Prospective gating, ECG gated imaging
