Ch 8 Flashcards by Nathanael Cotton

1 - Why was automatic exposure control (AEC) developed?

a. To decrease the need for technique charts
b. To make the radiographer more of a “button pusher”
c. To determine the radiation exposure required to produce a quality image
d. To increase the productivity and the patient dose

SOLUTION: C
The purpose of AEC is to produce consistently quality images, requiring fewer repeats.

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

a. Photodiode
b. Ion chamber
c. Ionization chamber
d. mAs readout

ANS: D - mAs readout

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

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3 - Once a predetermined amount of radiation is transmitted through a patient to the AEC detector, which of the following occurs?

a. The x-ray exposure increases
b. The x-ray exposure decreases
c. The x-ray exposure terminates
d. A and B

ANS: C - The x-ray exposure terminates

Once a predetermined amount of radiation is transmitted through a patient to the AEC detector, the x-ray exposure terminates.

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

a. Phototimer
b. Diode sensor
c. Ionization chamber
d. Bucky proliferator

ANS: C - Ionization chamber

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

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

a. In front of the patient
b. Behind the Bucky tray
c. In front of the image receptor
d. On the tabletop

ANS: C - In front of the image receptor

The ionization chamber is an entrance-type device located immediately in front of the image receptor, measuring radiation after it has passed through the patient, tabletop, and grid.

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

a. Phototimer
b. Gas detector
c. Ionization chamber
d. Backup timer

ANS: A - Phototimer

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.

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

a. In front of the patient
b. Behind the image receptor
c. In front of the image receptor
d. On the tabletop

ANS: B - Behind the image receptor

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

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

a. kVp
b. Focal spot size
c. Seconds
d. mA

ANS: C - Seconds

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

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9 - What would the result be if a film-screen radiographic examination required an exposure time shorter than the minimum response time of the AEC sensors?

a. Image density would be optimal
b. Image density would be excessive
c. Response time has nothing to do with AEC
d. Image contrast would be high

ANS: B - Image density would be excessive

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

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

a. Backup time
b. Minimum response time
c. Master density time
d. A and B
e. A and C

ANS: B - Minimum response time

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

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11 - AEC eliminates the need for the radiographer to select the actual ____ the examination will require.

a. kVp
b. SID
c. Exposure time
d. Focal spot size

ANS: C - Exposure time

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

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

a. kVp
b. Detector selection
c. Exposure time
d. Focal spot size

ANS: A - kVp

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

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

a. kVp
b. Backup time
c. Focal spot size
d. Density control

ANS: D - Density control

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.

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14 - What is the appropriate setting for backup time/mAs?

a. 50% of the expected mAs
b. 100% of the expected mAs
c. 150% of the expected mAs
d. 400% of the expected mAs

ANS: C - 150% of the expected mAs

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

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

a. To prevent excessive exposure of the patient
b. To make certain the contrast is acceptable if the chosen kVp is too low
c. To make certain the density is acceptable if the patient moves
d. To prevent the selection of the wrong detector

ANS: A - To prevent excessive exposure of the patient

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.

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16 - Which of the following is a system that allows the radiographer to select a particular button on the control panel that represents an anatomic area and displays a preprogrammed set of exposure factors?

a. mAs readout
b. Anatomically programmed technique
c. Automatic exposure control
d. Phototiming

ANS: B - Anatomically programmed technique

Anatomically programmed technique is a system of preprogrammed technical factors that are displayed once a specific anatomic area and position (i.e., PA chest, oblique knee) is selected.

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17 - When doing a film-screen study using AEC, what will happen to the density in the area of interest when changing from 70 to 90 kVp?

a. Density will increase
b. Density will decrease
c. Density will not change

ANS: C - Density will not change

Adjusting the kVp will not have any effect on the image density, because the detectors have terminated the exposure based on the amount of radiation transmitted. However, increasing the kVp will lower the image contrast.

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18 - If the detector is directly exposed to the primary beam during a film-screen study, the area of interest will appear:

a. Overexposed
b. Underexposed
c. Correctly exposed
d. To have high contrast

ANS: B - Underexposed

When the detector is exposed directly to radiation, the exposure is terminated right away, and the anatomy of interest will be underexposed, or too light.

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19 - In order to become familiar with manual technical factors (i.e., setting mAs and kVp and not using AEC), it is very helpful to pay attention to the:

a. Exposure time
b. Heat units
c. Density control
d. mAs readout

ANS: D - mAs readout

The mAs readout will briefly show the exact amount of mAs used for the previous exposure. It is important for the radiographer to pay attention to this readout so that there’s a greater familiarity with the mAs needed to produce optimal images.

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20 - With modern x-ray equipment, the AEC system’s minimum response time is typically:

a. 1 ms
b. 10 ms
c. 50 ms
d. 100 ms

ANS: A - 1 ms

The minimum response time for most of today’s equipment is 1 ms.

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21 - The most common cause for repeating images done with film-screen and AEC is inaccurate:

a. kVp selection
b. Backup mAs selection
c. Centering
d. Alignment of the tube and image receptor

ANS: C - Centering

Inaccurate centering is the primary reason for images to be repeated when using AEC with film-screen. If the anatomy of interest is not directly over the detector, the image will probably be less than optimal.

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22 - The mAs readout:

a. Is of little value because it’s not necessary to know mAs when using AEC
b. Reports the actual mAs used for an exposure
c. Reports the patient dose for the entire imaging study
d. Allows the radiographer to better set the mAs for an AEC examination

ANS: B - Reports the actual mAs used for an exposure

The mAs readout shows the actual mAs used for the exposure just made. Awareness of this value helps in producing non-AEC images.

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23 - With a CR system, when using AEC to image a patient who is having difficulty holding still, increasing the mA (if the unit allows) will:

a. Be a bad idea because the patient will be overexposed
b. Be a bad idea because the patient will be underexposed
c. Be a good idea because the exposure time will increase
d. Be a good idea because the exposure time will decrease

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ANS: D - Be a good idea because the exposure time will decrease

Increasing the mA will result in a shorter exposure time, always helpful in reducing the impact of patient motion. The exposure to the patient and IR will remain the same.

24 - If the backup time/mAs is automatically set by the x-ray unit, the exposure should end when a maximum of has been reached.

a. 600 s
b. 600 kVp
c. 600 mA
d. 600 mAs

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ANS: D - 600 mAs

It is required that x-ray units with AEC have a preset backup time or mAs which is 600 mAs.

25 - When doing a tabletop forearm study with CR, you should: a. Use AEC b. Set manual technique c. A and B

ANS: B - Set manual technique AEC cannot be used when the IR is tabletop, so mAs and kVp must be set manually.

26 - When a digital IR is overexposed due to poor use of AEC: a. Image contrast will be increased b. Quantum noise may be highly visible c. Patient exposure is increased d. Patient exposure is unaffected

ANS: C - Patient exposure is increased Overexposing the digital IR means that the patient was overexposed as well, even if the image quality is satisfactory.

27 - Exposure time will _______ while using AEC when patient thickness decreases. a. Decrease b. Remain the same c. Increase d. Double

ANS: A - Decrease Whether digital or film-screen imaging is being done, it will require a shorter exposure time for sufficient radiation to exit a thinner patient.

28 - Where does a radiographer find the established guidelines for selecting exposure factors for a radiographic examination? a. Technique chart b. Generator control panel c. Examination requisition d. A or B e. B or C

ANS: A - Technique chart A technique chart will provide the radiographer with established guidelines for selecting exposure factors.

29 - What is the purpose of a technique chart? a. To decrease the patient exposure by always using the highest kVp required b. To ensure consistent image quality c. To reduce the repeat imaging due to technique error and, in turn, reduce the patient exposure d. A and B e. B and C

ANS: E - B and C Technique charts are useful in maintaining consistent image quality, reducing the number of repeat exposures, and reducing patient dose.

30 - A technique chart should be established for: a. Each radiographer b. Each radiographic tube c. Each radiologist d. A and B e. A and C

ANS: B - Each radiographic tube A technique chart should be developed for each tube, even when tubes are located in the same room or share a generator.

31 - Which of the following is/are true regarding the development of an effective technique chart? a. The radiographic equipment must be operating properly b. A good-quality control program is in place c. The equipment must be from the same manufacturer d. A and B e. A and C

ANS: D - A and B In order for a technique chart to be effective, image processing must be consistent and the equipment must be calibrated to ensure the accuracy of the tube output.

32 - What are calipers used for? a. To measure the mA b. To select the kVp c. To select focal spot size d. To measure the part

ANS: D - To measure the part Calipers are used to measure the thickness of the part being examined. The technique chart should indicate where the part thickness should be measured.

33 - Which of the following is not part of a standardized technique chart? a. SID b. OID c. mA d. kVp

ANS: B - OID Object-to-image receptor distance (OID) is not included in the technique chart information. Typically, OID should be as little as possible, but patient condition may affect the OID.

34 - What is the appropriate change in kVp when using a variable kVp-fixed mAs technique chart for a 1 cm change in tissue thickness? a. 2 kVp b. 4 kVp c. 6 kVp d. 10 kVp

ANS: A - 2 kVp A 1 cm change in tissue thickness calls for a 2 kVp change when using a variable kVp-fixed mAs technique chart.

35 - If a part measures 14 cm and requires the use of 75 kVp, how much kVp would a part measuring 18 cm require when using a variable kVp-fixed mAs technique chart? a. 67 kVp b. 77 kVp c. 83 kVp d. 91 kVp

ANS: C - 83 kVp Increasing part thickness by 4 cm requires an increase of 8 kVp (2 kVp per centimeter).

36 - What kind of chart uses a kVp value that is high enough to adequately penetrate the part but does not diminish radiographic contrast? a. A variable kVp technique chart b. A fixed kVp technique chart c. A fixed mAs technique chart d. A and B e. A and C

ANS: B - A fixed kVp technique chart A fixed kVp technique chart identifies an optimal kVp, one that is high enough to ensure penetration but not so high that the contrast will be diminished.

37 - When using a fixed kVp-variable mAs technique chart, if part thickness increases by 5 cm, what needs to happen to the mAs? a. It should be halved b. It should be doubled c. It should be quartered d. It should be tripled

ANS: B - It should be doubled Increasing part thickness by 4 to 5 cm requires a doubling of the mAs when using a fixed kVp-variable mAs technique chart.

38 - Departmental standards, such as the SID or whether an examination is done tabletop or Bucky, should be determined: a. Prior to the development of technique charts b. After the development of technique charts c. At the same time as the development of technique charts d. Whenever the department can come to an agreement

ANS: A - Prior to the development of technique charts Because a goal of a technique chart is to standardize exposure factors, it is essential that departmental standards be developed prior to creation of technique charts.

39 - Accurate patient measurement is most critical for the: a. Variable kVp-fixed mAs technique chart design b. Variable kVp-variable mAs technique chart design c. Fixed kVp-variable mAs technique chart design d. Fixed kVp-fixed mAs technique chart design

ANS: A - Variable kVp-fixed mAs technique chart design In that the exposure factors will change with every 1 cm change in part thickness, accurate patient measurement is most critical with the variable kVp-fixed mAs technique chart.

40 - Radiographic contrast would be standardized with the: a. Variable kVp-fixed mAs technique chart design b. Variable kVp-variable mAs technique chart design c. Fixed kVp-variable mAs technique chart design d. Fixed kVp-fixed mAs technique chart design

ANS: C - Fixed kVp-variable mAs technique chart design In that kVp controls the level of radiographic contrast, the fixed kVp-variable mAs technique chart will best standardize the radiographic contrast.

41 - Generally speaking, patient dose will be decreased with the: a. Variable kVp-fixed mAs technique chart design b. Variable kVp-variable mAs technique chart design c. Fixed kVp-variable mAs technique chart design d. Fixed kVp-fixed mAs technique chart design

ANS: C - Fixed kVp-variable mAs technique chart design Patient dose is typically lower with the fixed kVp-variable mAs technique chart because the optimal kVp is higher than that used with a variable kVp chart.

42 - A variable kVp-fixed mAs chart may be most effective with: a. Geriatric patients b. Trauma patients c. Patients imaged with mobile equipment d. Pediatric patients

ANS: D - Pediatric patients A variable kVp-fixed mAs technique chart may be more effective for pediatric patients or for small body parts, due to the lower kVp needed.

43 - A patient measuring 26 cm requires 20 mAs at 75 kVp based on a fixed kVp-variable mAs technique chart. What technique should be used for the next patient, who measures 34 cm? a. 40 mAs at 75 kVp b. 80 mAs at 75 kVp c. 20 mAs at 91 kVp d. 40 mAs at 91 kVp

ANS: B - 80 mAs at 75 kVp In that a fixed kVp-variable mAs technique chart is being used, the kVp must remain at 75. The patient measuring 34 cm (8 cm larger than the first) requires the mAs to be four times the original (twice the mAs for every increase of 4 to 5 cm).

44 - Using the concept of comparative anatomy, if a child’s elbow measures the same as an adult wrist and all other procedural variables are the same (i.e., SID, image receptor type, etc.), the child’s elbow will require in comparison to the adult wrist. a. Less mAs b. More mAs c. The same mAs d. Higher kVp

ANS: C - The same mAs If both parts measure the same thickness and all other factors are the same, there should be no change in the amount of mAs used.

45 - When using film-screen, what happens when an outside detector is selected for an AP thoracic spine? a. The spine will have insufficient contrast b. The spine will be too dark c. The spine will have excessive contrast d. The spine will have insufficient density

ANS: D - The spine will have insufficient density 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.

1 - A good time to use AEC is when the radiographer is unable to accurately center the x-ray beam. a. True b. False

ANS: False Because 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.

2 - When the radiographer is considering whether to repeat an image using AEC, it is important to determine the reason the first radiograph failed. a. True b. False

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

3 - A good reason to use AEC density control is to increase the exposure to the IR to compensate for improper centering. a. True b. False

ANS: False Inaccurate centering is never a reason to adjust the density control. Correction of the centering problem is what’s needed.

4 - With AEC it is easy to use multiple types of image receptors, because the detectors can sense image receptor type and make appropriate adjustments. a. True b. False

ANS: False AEC devices are unable to determine the type of the image receptor that’s being used. If the wrong IR type is used by mistake, the resulting image will have inappropriate exposure to the IR.

5 - AEC can be used with tabletop examinations. a. True b. False

ANS: False In order for AEC to be used, the radiation must pass through the detectors. Because the AEC detectors cannot typically be moved to the tabletop, the radiographer must set a manual technique for tabletop examinations.

6 - When exposure factors are selected using anatomically programmed technique, the variables should not be adjusted. a. True b. False

ANS: False The technical information displayed when using APR is a starting point. It is up to the radiographer to make adjustments based on his or her knowledge and experience.

7 - Newer x-ray units may keep you from making an exposure if you’ve selected the table Bucky on the control panel but there’s no IR in the table Bucky. a. True b. False

ANS: True In order to protect the patient from unnecessary exposure, newer x-ray units may sense that the IR is missing from the selected Bucky (wall/table) and not allow the exposure to be made.

8 - Technique charts are still needed when using AEC. a. True b. False

ANS: True Technique charts are still highly useful when using AEC, because many procedural factors (i.e., kVp, detectors, SID, focal spot size, etc.) need to be standardized.

9 - The technique chart will provide information as to how to recognize and compensate for additive pathology. a. True b. False

ANS: False The technique chart cannot provide information for all patient variables. It is up to the radiographer to use critical thinking skills to assess the patient and make adjustments.

10 - Two identical rooms having the same generator and tube and installed at the same time do not require development of separate technique charts. The chart for one room can accurately be used in the other. a. True b. False

ANS: False Even though the rooms seem identical, individual technique charts should be developed for each tube.

11 - Optimal kVp values for each anatomic area have been established by law. a. True b. False

ANS: False Optimal kVp levels have not been established. Each department needs to determine the optimal kVp for each anatomic area.

12 - If a technique chart is being used, and the IR is overexposed, the radiographer should assume the chart is inaccurate and come up with his or her own exposure factors. a. True b. False

ANS: False Radiographers need to problem-solve when an image is overexposed. There are many variables that contribute to image quality, and chart effectiveness is only one.

Ch 8 Flashcards

(57 cards)