chapter 29: distortion

what kind of property is distortion?

it is a geometric property

what is distortion?

it is the misrepresentation of the size or shape of the structure being examined

what is size distortion ?

magnification

what is shape distortion known as? what controls is ?

true distortion.

alignment and angulation

what are factors that affect distortion ?

shape and size

how does SID effect distortion ?

the greater the SID, the less magnification there will be

how does OID effect distortion ?

the greater the OID, the more magnification there will be

how to figure up the magnification factor ?

M(magnification factor )= SID/OID

How to find SID?

sid= sod +oid

how to find SOD ?

sid-OID=SOD

how to find object size?

Object size = Image /Magnification factor

must know you magnification factor

what do you do to find the % of magnification ?

X 100

what is shape distortion ? what controls it?

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

Alignment and angulation

elongation? when does it occur?

object is longer than it really is

occurs what tube or IR is improperly aligned

foreshortening ? what does it occur ?

shorter than is really is

occurs only when part is improperly aligned

how do you want the part of interest to the IR and CR?

you want it parallel to the IR and you want your CR perpendicular

what is shape distortion controlled by?

beam, part, IR

any structure not at the CR will be distorted because of what?

the divergence of the beam

the farther away form the CR

the greater the distortion will be

how are long bone studies done?

3 exposures are made at the joints to ensure proper measurement

useful distortion?

when you angle to to uncover superimposed parts

example: axial clavical, tangebtial calcaneus, ap skull .

what happens when the long axis is not parallel to the IR and perpendicular to the CR?

distortion occurs

how does a part look what is it forshortned ?

usually one end of a long bone will be more magnified because the the increased OID

what does MA effect?

it effects density, it is a direct relationship. it does not effect contrast, detail, distortion.

what does time effect?

density, has a direct relationship

what does mas effect?

desnity, it has a direct relationship

what does kvp effect?

contrast, it has a inverse relationship. The more KVP, the less contrast it effects density also, has a direct relationship.

what does SID effect?

it effects density, has an inverse relationship. recorded detail, has a direct relationship. it effects distortion, has an indirect relationship.

what does OID effect?

it has a inverse relationship with density and recorded detail. it has an direct relationship with contrast and distortion

focal spot size, what does it effect?

recorded detial, it has an inverse relationship.

grid ration, what does it effect?

density, has an inverse relationship , and has an direct relationship with contrast.

filtration, what does it effect?

no properties effected

screen speed, what does it effect?

desnity, has a direct relationship amd recorded detail, it has an inverse relationship.

size distortion occurs when?

image is larger than the object

what is a major factor controlling size distortion?

OID