Distortion (Chapter 29)

Distortion

The misrepresentation of the size or shape of the structures being examined

2 types of distortion are?

1. Size distortion

2. Shape distortion

What is an example of size distortion?

Magnification

Magnification reduced _____

Recorded detail

What are factors affecting size distortion?

OID and SID

The greater the SID, the ____ the magnification

Less

The greater the OID, the _____ the magnification

More

Magnification or size distortion can be calculated by using the

Magnification Factor

Magnification Factor=

SID/ SOD

Object Size=

Image size/ magnification factor

% magnification of the object=

IS-OS/OS x 100

What is shape distortion?

An unequal magnification of the object

Two types of shape distortion?

Elongation and foreshortening

What affects shape distortion?

Tube/part/film alignment

What are the factors affecting shape distortion?

Angulation and alignment

Central ray: beam divergence is _____ at edges of beam due to angle of beam

Greater

Anatomical part: part aligned correctly to ______

Central ray

Image receptor: should lie flat, not _____ or ______ to beam

Angled to part, perpendicular

What is elongation caused by?

Misalignment of the CR and the IR

The greater the angle the ____ the elongation

Greater

Foreshortening is when?

Object appears to be shorter than it really is

Tube or IRS angle will cause elongation, never ______

Foreshortening

What are the ways to minimize distortion?

1. Use small OID

2. Use large SID

3. Insure proper tube/part/film alignment