RAD 172 Final- Distortion

Distortion

geometric property that affects the quality of the image.

Misrepresentation of the size/shape of the structures being examined.

Shape distortion

misrepresentation by unequal magnification of the actual shape of the structure being examined.

Size Distortion

can only be magnification in x-ray

what is size distortion controlled by?

OID and SID

Controlled by positioning the body part and the tube to maximize SID and minimize OID

Reduced magnification size distortion __________ spatial resolution

increases

SID =

SOD + OID

What kinda relationship does SID and magnification have?

inverse relationship

What kinda relationship does OID and magnification have?

direct

As OID __________, magnification _____________

increases, increases

Ways to decrease size distortion

increase SID

decrease OID

decrease patient thickness

ways to increase size distortion

decrease SID

increase OID

increase patient thickness

shape distortion increases when

Improper CR alignment

Improper anatomical part alignment

Improper receptor alignment

Improper direction of CR angle

Improper degree of CR angle

What is elongation?

It projects the object so it appears to be longer than it really is.

When does elongation occur?

When the TUBE or CR is at an angle.

What is foreshortening?

Foreshortening projects the object so it appears shorter than it really is.

When does foreshortening occur?

Foreshortening occurs when the object is at an angle and the CR is perpendicular to the IR.

Magnification factor =

SID / SOD

Object Size

Image size / magnification factor

Shape distortion can be caused or avoided by:

Careful alignment of the CR with the anatomical part and the IR

Part and IR must be parallel

Whenever the CR is not perpendicular, some degree of shape distortion will occur.

Spatial Distortion happens when

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

Angulation

refers to the direction and degree the tube is moved from its normal position perpendicular to the IR

most common tube angle

longitudinal

direction of tube angle must be __________ when patient position is reversed

reversed