Rad103 shape distorotion

shape distortion

misrepresentation of the true shape of the image as compared to the object

types of shape distortion

foreshortening, elongation, spatial distortion

causes of shape distortion

x-ray beam, position of digital detector, position of part

ideal relationship

setup of IR, CR, and object that creates the least amount of shape distortion

center of beam

central ray (cr)

shape of beam

cone

in ideal relationship, how are the IR, CR, and object placed in relationship to each other

object parallel to IR, CR perpendicular to IR

foreshortening

when the object is angled but the CR remains perpendicular to the IR

how do foreshortened images appear

squashed, fatter

avoid foreshortening

CR perpendicular to object, even if that makes CR not perpendicular to the IR

what causes elongation

object is parallel to IR but the CR is angled or CR is perpendicular to the object but the object is not parallel to the IR

images with elongation appear

stretched out and thin

exams where you want elongation

clavicle, foot, sigmoid colon

minimizing elongation

place CR directly over structure of interest

why do all images have some elongation

the beam is cone shaped/diverges from the source

spatial distortion

the CR is at an angle but the object and the IR are parallel to each other

how does an image with spatial distortion look

stretched out and thinner, parts appear further away from each other

more OID=

more magnification