Geometrical Qualities
Spatial Resolution (sharpness)
Sharpness = SOD/OID
Penumbra = (FS x OID) / SOD
Radiographer's Job
*Digital equipment parameters
Increase SID
Reduce focal spot size
reduce OID
eliminate motion
Poor spatial resolution
caused by unacceptable levels of penumbra as compared to the umbra
Umbra
uniform darkness of the inner-most shadow
Penumbra
blurry, fading partial shadow projected at each edge
Higher spatial resolution
higher resolution means two objects can be demonstrated to be smaller or closer together
Sharpness of the structural edges recorded int he image
Magnification (size distortion)
Calculations
Image Size/Object Size = SID/SOD
Magnification = SID/SOD
the difference between the size of the real object and the size of its projected image
Shape Distortion
The difference between the shape of the real object and the shape of its projected image
