physics RSNA Flashcards
the probablity of both PE and CS increased w/
P ( physical density)
dose limit to the fetus for working tech
5 mSv
electronic mag results in
Dose are SP»_space; same
noise is increased
while mag»_space; reduce SR
SID in MG
50-70 cm
compression resluts in ?
decrease dose, mA and Kvp
decrease scatter»_space; decrease noise»_space; better Con
less motion
less mottle
absorption K-edge does not play role in non enhanced study T/F
true
T/F U C.S interaction varies little
true vs PE
reject rate investigation?
adult <5, > 10%
peds: <3, >7
what is mach band ?
The Mach band occurs because the more-attenuating (“whiter”) benign lesion is adjacent to less-attenuating (“darker”) adipose tissue in the breast, producing a contrast between lesion and breast. This contrast is interpreted as a dark Mach band by the eyes.
GRID
Magnification mode mammography typically relies on air gap instead of grids for scatter rejection. Typical Bucky factor is 3-8. Focused grids should be selected based on the SID. Digital Radiography typically uses stationary grids with high grid frequencies to reduce the visibility of grid lines. In addition, post processing is used to further suppress grid lines.
bit depth determines
possible pixel values
in DR: Post img processing can change CNR
False
only affects contrast
primary indicator of detector resol in DG?
MTF not detextor pixel size
MTF is a measure of ?
MTF is a measure of resolution. Noise is measured by the noise power spectrum (NPS). The SNR of an image is best described in terms of the detective quantum efficiency (DQE). Latitude can be graphically represented with a histogram which depicts frequencies at which particular exposure values, detector signals, or pixel values are represented in an image.
If all else is kept constant, reducing the Source to Image Distance (SID)?
Reducing the SID will not impact the patient dose assuming all the imaging techniques are kept constant, including the source to object distance (SOD)
