Scatter Radiation

A change in direction of x-ray photon after interaction w/ atoms of patient

Scatter Radiation

Where does scatter radiation come from?

• A fraction of og. intensity of primary beam

• Patient and x-ray equipment

• Bounces off patients body isotropically and absorbed by patient

__ to __% of density is the result of scatter radiation

50-90%

As density on an image increases, contrast ____ and resolution _____

Decreases, Decreases

Radiation emitted from x-ray tube and travels in a straight line & diverges

Primary Radiation

Unabsorbed & scattered x-rays that interact with I/R, carrying the aerial image

Remnant (Exit) Radiation

Remnant radiation carries both _____ and _____ radiation

Scatter & primary radiation

What factors influence scatter radiation

• Field size

• Thickness of object

• Density (composition) of anatomy

• kV

Can field size and kV be controlled?

Yes

Advantages of beam limitation

• Increase image quality by reducing scatter to IR

• Increase detail

• Reduce patient exposure

What are beam limiting devices constructed of

Lead or lead lined because of its tendency to attenuate x-rays

Disadvantage of cylinder Conde

Unnecessary patient exposure

Field size definition

Area of x-ray beam

Main advantage of flared beam

Flare is larger than beam so edges are not cleaned out

Beam limiting device we use today

Variable Aperture (Collimator)

Purpose of Positive Beam Limiting Device

Assures the field does not exceed the size of IR

Two sets of horizontal lead shutters that allow infinity number of field size options

Automatic Collimator Housing

Upper shutters control ____ _____

Stem radiation (off focus)

Stem radiation (off focus, extra focus) refers to..

Photons that are not produced at the focal spot of anode

Poor field to light congruency causes

Anatomy to be cut off

As field size decrease, patient exposure ____

Decreases

The larger the field size, the more ___, greater ___, less ___

The larger the field size, more grays, higher fog (density), less detail

The smaller the field size, the more ___/___, less _____, and more ____

The smaller the field size, the more black/white, less fog, greater detail

lower shutters control ____

blur