Rapid Review Flashcards
Average brems energy is what fraction of kvp?
1/3
Characteristic energy of Tungsten k shell
-69.5
Effect on quality & quantity: Increase voltage ripple?
Decreased BOTH quality & quantity
T or F: Compton scatter depends on density?
True
Compton scatter dominates ABOVE ___keV
30
PE effect dominates BELOW ___keV
30
DQE is proportional to ___.
MTF. Modulation Transfer Function
DQE is INVERSELY proportional to ___.
SNR
DQE is better at high or low spatial resolution?
low
Approx. DQE for DR & plain film?
DR: 0.45
Plain film: 0.25
MTF describes relationship between ___ & ____.
sharpness & resolution
kVp controls contrast. Low kVp = Low or High contrast?
Low kVp = HIGH contrast
For constant density: decrease mA by 50% requires ___% increase in kVp?
15%
4 cm tissue requires __ x’s the mA
2x mA for each 4 cm tissue
Standard of care for digital display size is ___.
3 mega pixels
Primary factor in FILM image contrast?
kVp
Primary factor in DIGITAL image contrast?
LUT (or as Onetian would say, SLUT). kVP still matters.
Major determinate of spatial resolution in digital?
Pixel size & pitch
Indirect digital systems use what material?
Thallium doped CsI (scintillator)
Direct digital systems use what material?
Amorphous selenium
Increased CR sampling frequency increases or decreases pixel pitch?
Decreases pixel pitch.
Improves spatial resolution.
Spatial resolution is better for DR or CR? Why?
DR. Because pixel detector is built into the DR flat panel.
What kVp energy is used for mammo? For general radiology?
Mammo: 25-35 kVp
General: 50-120 kVp
What tube current is used for mammo? For general radiology?
Mammo: 100 mA
General: 500 mA
Receptor Air Kerma for mammo? For general radiology?
Mammo: 100 uGy
General: 5 uGy
Grid ratio for mammo? For general radiology?
Mammo: 5-1 (lower)
General: 10-1 (higher)
View box cd/m^2 for mammo? General radiology?
Mammo: 3000
General: 1500
What does Nuclear Regulatory Commission (NRC) regulation 10 CFR Part 20 deal with?
Standards for protection against radiation
The threshold for permanent sterility in males is approximately __ Gy from an acute exposure.
6 Gy
