Distortion

Object thickness

The OID of a thick object changes measurably across the object -Due to the change of the OID the image of that structure is more distorted than an image of a thinner structure

Object position

Incorrect patient positioning

Shape distortion

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

Distortion

Misrepresentation of the size and shape of the structure being examined

Three conditions contribute to image distortion

(1) Object thickness (2) Object position (3) Spatial distortion

Size distortion (magnification) causes

(1) Source to image distance (2) Object to image distance

What are the two types of distortion?

-Size (magnification) -Shape (true) distortion.

Spatial distortion

-The misrepresentation in the image of the actual spatial relationship among objects. 1) Distortion is minimal for objects lying along the central ray 2) As the object's position is shifted laterally from the central ray, spatial distortion can become significant

***

1. Distortion exists even when it cannot be seen due to poor visibility when density and contrast are poor 2. Factors that control distortion are directly related to positioning

Distortion (Size)

1. Reduced magnification size distortion increases the resolution of recorded detail 2. Magnification size distortion is controlled by positioning the body part and x-ray tube to maximize SID while minimizing OID

Foreshortening

Projects the object so it appears shorter than it really is. -Occurs only when the part being examined is improperly aligned

Elongation

Projects the object so it appears to be longer than it is. -Occurs when the tube or IR are improperly aligned.