Primary Exposure Factors
This factor directly controls the quantity of photons produced and the number of electrons boiled off the filament
mA
Increasing kVp increases penetration but has what effect on subject contrast?
decreases contrast
Underexposed digital images will show this even after processing
quantum noise/mottle
Increasing SID increases sharpness and decreases this type of distortion
Magnification
Grids must be used for body parts measuring at least how many cm?
10 cm
if mA decreases by half, what must happen to exposure time to maintain the same mAs?
time must double
Brightness in digital imaging is controlled by
computer processing
What exposure problem can cause the EI value to fall below the acceptable range?
Underexposure
SID and intensity at the IR follow this Law
Inverse Square Law
Collimating tighter decreases scatter but requires possible increases in THIS exposure factor
mAs
This image problem occurs when too little mAs is used in digital imaging, even though brightness is auto-corrected
quantum noise
An abdomen x-ray uses 80 kVp. Applying the 15% rule, what’s the new kVp?
92 kVp
When imaging a part with varying thickness, what can be placed in the primary beam to produce a uniform exposure?
Compensating Filter
Increasing OID increases contrast because it reduces THIS reaching the IR
Scatter
This type of generator is the most efficient and requires the least mAs
High-frequency generator
What exposure factor must increase when patient body thickness increase?
To maintain exposure, decreasing kVp by 15% requires this change to mAs
Increase mAs by doubling it
An image is overexposed but looks acceptable. What is the main concern pertaining to the pt?
Unnecessary patient dose
A radiograph is taken at SID 72” with an OID of 4”. Calculate the SOD.
68 inches
what factor determines how much scatter a grid can clean up?
Grid ratio
A tech uses 300 mA at 0.02 s. To reduce motion, exposure time is cut to 0.005 s. What mA is needed to maintain exposure?
1200 mA
What image quality decreases when kVp is raised too high?
Subject contrast
This number on each digital image is used to evaluate whether the technique was appropriate
Exposure Index
Calculate the MF if the SOD is 68” and the SID is 72”.
1.06
What effect does collimating to a smaller field size have on contrast?
Increases contrast