1.7 Types of Beam Restrictors

What are the types of beam limiting devices?

Aperture diaphragms (cones, cylinders), Collimators, and Ancillary devices

How does the beam exit the tube?

The beam flares outward as it goes further away from its source

What does the x-ray tube use a combination of to project coverage of where the x-ray beam will end up essentially?

combination of a light source and mirrors

What does the mirror needs to be accurate within of the SID?

± 2%

What are Aperture Diaphragms?

Very simple, flat piece of lead that has a hole in it

Is Aperture Diaphragms on the inside or outside of the tube?

Outside- tapped directly to the tube housing

Is the field size fixed or adjustable when using an Aperture Diaphragm?

Fixed

What is Aperture Diaphragms dedicated to?

Chest or head/skull units, Trauma units, Dental equipment

What is the disadvantage of Aperture Diaphragms?

Penumbra and Off-focus

What is Penumbra?

unsharpness due to proximity of the tube port, Decreases the closer the beam restrictor is to the object being imaged

What is Off-focus?

Another name for penumbra, Due to distance from focal spot

Is a cone or cylinder the same size all the way down?

Cylinder

Is a cone or a cylinder flare out and allows divergence?

Cone

What is cones and cylinders used for?

Greater detail in a smaller area, reduction in scatter make images appear sharper

What is the best type of beam restricting device?

collimator

How many set of shutters does a collimator have?

2 sets

What does the first set of collimating shutters do?

help remove off-focus radiation leaving the anode

What does the second set of collimating shutters do?

the technologists adjusts

What are Ancillary Devices also known as?

Positive Beam liminations or PBL

What do lead blockers do?

helps absorb scatter before reaching the image receptor, after leaving the Patient

What produces more scatter, a larger or smaller patient?

larger patient