Question 1

It is easy, with AEC, to use image receptors with different speeds because the detectors can sense image receptor speed.

Accepted Answer

AEC devices are unable to determine the speed of the image receptor that's being used. If the wrong speed system is used by mistake, the resulting image will have inappropriate density.

Question 2

What is the appropriate setting for backup time/mAs?

Accepted Answer

Backup time should be set at 150%-200% of the expected exposure time (or mAs).

Question 3

AEC eliminates the need for the radiographer to select the actual _____ the examination will require.

Accepted Answer

The role of AEC is to terminate the exposure at the right time. The technologist must still select the SID, kVp, and focal spot size appropriate to the exam.

Question 4

What is the purpose of setting a backup time/mAs?

Accepted Answer

The backup time or mAs is the maximum amount of time that the x-ray exposure will stay on while using AEC. This is a safety mechanism, to protect the patient from excessive exposure.

Question 5

Where is the sensor located in an automatic exposure device with a gas-filled chamber?

Accepted Answer

The ionization chamber is located immediately in front of the image receptor, measuring radiation after it has passed through the patient, table-top, and grid.

Question 6

Where is the sensor located in an automatic exposure device that converts light into an electrical signal?

Accepted Answer

The phototimer AEC detector is typically located behind the image receptor. It is considered an exit-type device.

Question 7

Which exposure variable is controlled by the automatic exposure control device?

Accepted Answer

AEC only controls the length of the exposure (seconds). The radiographer must select the appropriate focal spot size, kVp, and mA (some units).

Question 8

When using AEC, what should the radiographer adjust to manipulate the contrast of the image?

Accepted Answer

As with radiography in general, kVp is the controlling factor for image contrast.

Question 9

When using AEC with film-screen, what should the radiographer adjust to manipulate the overall density of the image?

Accepted Answer

In order to adjust the density of the film-screen image produced using AEC, the density control (i.e., +2, 0, -2) is the only variable to be adjusted.

Question 10

When using film-screen, what happens when an outside detector is selected for an AP thoracic spine?

Accepted Answer

If an outside detector is selected for an AP T-spine, the lungs will have appropriate density but the spine will be underexposed. This results in insufficient density.

Question 11

What would happen if a film-screen radiographic exam required an exposure time faster than the minimum response time of the AEC sensors?

Accepted Answer

If the minimum response time is longer than what is needed to produce optimal density, the image will be overexposed, or have excessive density.

Question 12

When the radiographer is considering whether to repeat a film using AEC, it is important to determine the reason why the first radiograph failed.

Accepted Answer

As with all unacceptable images, the technologist must problem-solve to determine the cause of the repeat, so the same mistake will not happen again.

Question 13

What does APR stand for?

Accepted Answer

APR, or anatomically programmed radiography, is a system of pre-programmed technical factors that are displayed once a specific anatomic area and position (i.e., PA chest, oblique knee) is selected.

Question 14

Which automatic exposure device works by using a gas-filled chamber?

Accepted Answer

The ionization chamber contains air and, when exposed to x-radiation, creates an electric charge due to ionization.

Question 15

A good reason to use density control is to make the film darker to compensate for improper centering.

Accepted Answer

Inaccurate centering is never a reason to adjust the density control. Correction of the centering problem is what's called for.

Question 16

Why was automatic exposure control (AEC) originally developed?

Accepted Answer

The purpose of Automatic Exposure Control is to produce consistently excellent quality images, thereby requiring fewer repeats.

Question 17

Which automatic exposure device works by converting x-ray photons first into light and then into an electronic signal?

Accepted Answer

The phototimer, using either a photodiode or photomultiplier tube, converts the absorbed radiation to light and then into an electrical signal that can be measured.

Question 18

Which of the following terms does not belong in the list?

Accepted Answer

The mAs readout, while a component of AEC, is not another term for an AEC detector.

Question 19

What describes the shortest exposure time required for the AEC device to operate?

Accepted Answer

Minimum response time is the minimum amount of time that it takes for the exposure to be terminated.

Question 20

A good time to use AEC is when the radiographer is not sure where the structure to be radiographed is located.

Accepted Answer

In that accurate centering is critical to effective use of AEC, it is not a good idea to use this technology when the location of the anatomy of interest is uncertain.

Quiz 11: Automatic Exposure Control