Ch 13 Exposure Technique Selection

Primary Function of the AEC is to

• reduce patient dose

• control the amount of radiation reaching the IR

• help the technologist not to think too much

• all of the above

Answer explanation

AEC detectors DETECT radiation exposure . Once a preset radiation value is detected, it terminates the exposure. (controlling the seconds of exposure)

This is how it controls the amount of radiation reaching the IR, by not allowing too much radiation and not too little radiation.

Pt dose is affected by mAs

The first generation of AEC were known as

• IDK

• Photomultiplier Tube

• Phototimers

• Ionization Chamber

AEC controls radiation exposure reaching the IR by

• controlling exposure time

• controlling KVP and MAS

• controlling the mA

• all of the above

Answer explanation

mAs = milliamperage x seconds.

only the seconds are controlled by the AEC.

ma is controlled by the tech

AEC adjusts the seconds, which will affect the overall mAs

Ionization Chamber AEC are known as ___type devices

• Corridor

• In between

• Entrance Type

• Exit Type

Answer explanation

Ionization Chamber AEC are located before the Image Receptor, so the radiation ENTERS the AEC and then ENTERS the IR.

Phototimer AEC are EXIT type. Radiation EXITS the IR and then EXITS the AEC

Once X-rays reach the AEC device

they are converted into an ____

• Electric Charge/Signal

• Analog Signal

• Digital Signal

• Digital Image

Answer explanation

Xrays are ionizing radiation

Radiation interacts with the air in the ionization chamber

This creates electric charges /electric signal which travels to the meter

once the preset radiation level is reached, exposure is terminated

High KVP = ____contrast

• low

• high

• medium

• higher

Answer explanation

The higher the kVp, the more likely the x-ray beam will be able to penetrate through thicker or more dense material. tissues will not absorb as much of the xray beam

Low kVp photons are weak and easily absorbed by body tissues ...creating a higher contrast between adjacent tissues

High KVP ____ exposure time when using an AEC

Answer explanation

High KVP= more power/voltage in our xray beam. More xrays will reach the IR

If AEC detects more xrays, it will reach the preset radiation level faster, and terminate the exposure

High kvp = shorter exposure time (with AEC)

using high KVP with AEC, reduces exposure time, which _____patient dose

• does nothing

• no change

• reduces

• increases

Answer explanation

reducing exposure time, reduces overall mAs...

which reduces patient dose

minimum response time with the ionization chamber type AEC is

• 1.5 ms

• 1 min

• 1 ms

• 1 s

There are ___aec detectors in most radiographic equipment

• 1

• 3

• 5

• 2