MacroRad Flashcards
what happens when objects are further away from IR
they magnify compared with those that are closer
x-ray beam is ___ shaped
pyramid
what does macrorad allow for
fine anatomical details at the expense of original & more accurate diagnosis
Magnification factor formula
M = SID (total distance) / SOD (distance from source to object)
OID = SOD (M - 1)
To get a magnification factor of 1.6, assuming SOD is 100 cm, what is the OID
OID = 100 (1.6 - 1) = 60 cm
to maintain dose to IR, what factor needs to be increased
mAs; patient dose also increases
In macrorad, if SID increases, mAs ___
increases
what is the main cause of scatter loss
inverse square law
what factors affect a magnified image of acceptable sharpness
movement & geometrical unsharpness
direct magnification by increased OID can only be done if ____
complete immobilization of patient
why is complete immobilization of patient important for preventing movement unsharpness
any movement will be magnified on radiograph due to increased OID
For any given focal spot size, can you continue to magnify image as much as you can?
cannot due to limit to image magnification beyond which significant details are lost
smaller the focal spot size, the ___ the possible magnification while retaining image quality
greater
geometrical unsharpness formula
Ug = f (M - 1)
if f = 0.1 & Ug = 0.3, what is the max magnification
Ug = f (M - 1)
0.3 = 0.1 (M - 1)
M = 4
