RDSC 201 LAB - quiz 6 review (distortion)

__________: a misrepresentation of the true size and shape of an object demonstrated on a radiograph

distortion

list types of distortion

size and shape

T or F: it is impossible to have the image smaller than the object in mgnification

true

as OID increases, magnification ________

increases

as SID increases, magnification _________

decreases

you can reduce image magnification by:

- reducing ____

- increasing ____

OID and SID

image magnification can never be eliminated, only _______

reduced

the magnification factor will always be ______ than 1

greater

magnification factor

image width / object width

% of magnification equation

(image width - object width) / object width x 100

shape distortion is caused by misalignment of (list)

- central ray

- anatomical part

- film or image receptor

types of angles

town and water

direction of "town" angle

down (town)

direction of "water" angle

(keep your head) above (water)

shape distortion classifications (list)

foreshortening and elongation

________: central perpendicular to IR and object

foreshortening

_________: part parallel to IR, when tube is angled

elongation

shape distortion reduction

tube - part - IR alignment

can you have both magnification and shape distortion on the same radiograph?

yes

what are the types of shape distortion?

foreshortening and elongation

what causes magnification?

x-ray photons diverge as they exit the x-ray tube window. this divergence causes the object being radiographed to be magnified on the radiograph

how can you control magnification

reduce OID and increase SID

distortion is one of the geometric properties affecting _________

quality

_________: part appears to be shorter than it actually is; happens when the part isn't parallel w/ the IR

foreshortening

_________: part appears longer than it actually is; happens when the CR is not perpendicular to the IR

elongation

__________: the difference in the apparent position of an object as compared to its actual position

parallax error

parallax error is derived from the Greek word which means _________

alteration

bad tube part film / IR relationships

- object is not centered w/ CR; going to overlap the image

- CR is centered, but not the IR

- the object and IR are centered, but the CR is not aligned

what is the ideal tube part film / IR relationship?

tube part film alignment is hitting in the joint (where we want)

factors affecting distortion (list)

distance and tube part film / IR relationship