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Equipment > 8. (AEC) Automatic Exposure Control > Flashcards

8. (AEC) Automatic Exposure Control Flashcards

1
Q

A radiographer uses AEC to radiograph an AP projection of a patient’s hip. The exposure indicator (EI) number displays an underexposure and a surgical prosthesis is visible in the image. For the repeat exposure the technologist could:

Raise the kVp for a correctly exposed image
Adjust the density control setting to -2
Lower the kVp for a correctly exposed image
Adjust the density control setting to +2

A

Adjust the density control setting to +2

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2
Q

While imaging a 100 year old, 80 pound patient for a lateral chest using AEC, two consecutive images are overexposed. The technologist decides the MRT is too slow and she can alleviate this issue on the next repeat image using AEC by

  1. Lowering the mA station
  2. Increasing kVp
  3. Decreasing kVp

2 and 3 only
1 and 3 only
1 and 2 only
1 only

A

1 and 3 only

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3
Q

While imaging a patient for a PA chest projection using AEC with a 3 detector configuration, a radiologic technologist selects the center cell instead of the two side cells. Describe the amount of exposure to the air filled lungs.

The radiation exposure will be optimal for the lungs
The radiation exposure will be appropriate for the lungs
The radiation exposure will be too low for the lungs
The radiation exposure will be too high for the lungs

A

The radiation exposure will be too high for the lungs

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4
Q

When using the automatic exposure control (AEC) to radiograph a patient, what factors below can the radiographer control on the operator’s console when technical adjustments are needed to improve the image?

  1. mA
  2. kVp
  3. exposure time

3 only
1 only
2 and 3
1 and 2

A

1 and 2

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5
Q

The AEC backup timer

Adjusts the kVp during an exposure

Is the quickest length of time necessary for the AEC to respond to the radiation and for the generator to terminate the exposure

Is the quickest exposure time that an x-ray generator will allow

Is a separate timer used as a safety measure to end the exposure if the AEC fails to do so

A

Is a separate timer used as a safety measure to end the exposure if the AEC fails to do so

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6
Q

The essential function of AEC is to:

Assist in technologist positioning

Terminate the x-ray exposure once the IR is exposed correctly

Provide a brighter fluoroscopic image

Automatically adjust collimation levels so that the IR is not overexposed

A

Terminate the x-ray exposure once the IR is exposed correctly

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7
Q

Using AEC, an optimal radiograph is acquired at a 72” SID with a image receptor exposure of 3.8 mGy. If the radiograph is repeated at a 40” SID, the image receptor exposure should be equal to about:

3.8 mGy
.95 mGy
10 mGy
7.6 mGy

A

3.8 mGy

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8
Q

A technologist using AEC equipment makes an image of a lateral lumbar spine with wide open collimation and no lead strip behind the patient’s back. The same technologist using the same AEC equipment makes the same lateral lumber spine image on the same patient but this time he collimates appropriately and uses a lead strip behind the patient’s back. How would the second image’s exposure time differ from the first image’s exposure time?

It would be longer
There would be no difference
It would be shorter

A

It would be longer

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8
Q

Attempting to collimate too tightly near an AEC’s activated ionization chamber (cell) location will result in:

  1. a shorter exposure time
  2. a longer exposure time
  3. an overexposed image
  4. an underexposed image

3 and 4
1 and 2
2 and 3
1 and 4

A

2 and 3

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9
Q

Which of the following affect AEC exposure termination?

  1. tissue thickness and density
  2. coverage of patient’s anotomy over the correct cell (ionization chamber)
  3. beam restriction (collimation)
  4. contrast agents (both negative and positive contrast)

3 and 4
1, 2, and 3
1 and 2
1, 2, 3, and 4

A

1, 2, 3, and 4

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10
Q

If while using AEC a radiographer wants to create a properly exposed image with a short exposure time, the technolgoist could:

decrease kVp
increase mA
increase the density control to +1
increase the back up timer

A

increase mA

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11
Q

According to US pulic law, this part of the AEC should be set at 150 % of the anticipated manual exposure mAs and should help to terminate an exposure at 600 mAs for exposures above 50 kVp.

density control
backup time
ionization chamber (cell)
minimum response time (minimum reaction time)

A

backup time

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12
Q

If while using AEC with a 3 detector configuration with the center cell activated, a lateral knee radiograph is exposed with the center cell receiving a larger than expected amount of primary radiation due to the anatomic part not being positioned properly over the center cell. What will be the result?

The knee will be off-center but correctly exposed
The knee will be overexposed
The knee will be underexposed

A

The knee will be underexposed

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13
Q

Using AEC, a radiograph of the abdomen is produced with low image receptor exposure, but the patient is properly positioned over the properly activated ionization chambers. Using AEC again on the repeat, what should be done to increase image receptor exposure?

decrease mA
increase mA
increase kVp
increase the density control setting

A

increase the density control setting

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14
Q

A device used to ensure reproducible radiographs by maintaining consistent IR exposure regardless of variations in patient tissue thickness and density is the:

Automatic exposure control (AEC)
Capacitor
Transformer
Rectifier

A

Automatic exposure control (AEC)

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15
Q

While imaging a patient using AEC, a portion of lead shielding accidentally was placed over a portion of an active ionization chamber. What will be the result?

The exposure time will be longer and the image will be overexposed

The exposure time will not be affected and the image will be properly exposed.

The exposure time will be shorter and the image will be underexposed

A

The exposure time will be longer and the image will be overexposed

16
Q

A parallel-plate ionization chamber receives a particular charge as x-ray photons travel through it and the exposure time is terminated. This is the operating principle of which of the following device?

Solid-state rectifiers
Image intensifier
Autotransformer
Automatic exposure control (AEC)

A

Automatic exposure control (AEC)

16
Q

The AEC minimum response time (MRT) may be defined as the quickest exposure time that an x-ray generator will allow. An AEC may need less exposure time than the MRT when:

  1. Using a high mA station
  2. Imaging small body parts
  3. Imaging large body parts
  4. Using a high-speed imaging system (high DQE)

1, 2, and 3
1 only
1,2 and 4
1 and 2

A

1,2 and 4

Equipment (9 decks)

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