Rad Protection Unit 4

A young girl comes to the radiology department for scoliosis evaluation. To produce the highest degree of radiation protection for her developing breast tissue, which of the following projections should the technologist use?

posterioanterior (PA)

Which one of the following is not a beam limitation device?

compensating filter

Gonad shielding may reduce female gonad dose by up to ____ and male gonad dose up to ____.

50% - 95%

Which one of the following sets of exposure factors would produce the least patient exposure?

5 mAs at 90 kVp

When using an automatic exposure control (AEC), regulations state that generators must terminate the exposure at 600 mAs or ____ seconds for exposures above 50 kVp.

6

kVp relates to the _____ of the x-ray beam.

quality/energy

The radiographic beam should be collimated so that it is:

no larger than the image receptor

Which field size would lower the patient’s dose the most if all technical factors remained the same?

8 × 10-inch field size

Which one of the following is the MOST versatile type of x-ray beam limitation device?

collimator

When using AEC with digital imaging systems, assuming all other factors are correct, selecting the center chamber on a PA chest image results in:

increased exposure in the lung area

All of the following demonstrate adherence to the As Low As Reasonably Achievable (ALARA) principle for the patient EXCEPT:

wearing occupational dosimeters

Intensity relates to the _____ of the x-ray beam.

quantity

Modern automatic exposure control (AEC) sensors are of the ____ type.

Ionization chamber

All of the following EXCEPT _____ will result in an increase in AEC response/ exposure time.

a. decreasing the kVp

b. increasing the focal spot size

c. increasing the part thickness

d. decreasing the mAs

b. increasing the focal spot size

The rationale behind the development of automatic exposure control (AEC) is to:

Reduce repeats and improve image quality

A backup timer for the automatic exposure control (AEC) serves to:

terminate the exposure in the event of equipment or operator error

AEC devices work by measuring:

radiation that exits the patient

If mAs doubles, what happens to patient dose?

it doubles

400 mA at 0.03 seconds would be equal to ____ mAs.

12

Gonad shielding should be considered if the:

1. shielding does not interfere with the objectives of the study

2. person has reasonable reproductive potential

3. gonads lie wihtin or close to the exposure field

1, 2, and 3

The AEC controls which of the exposure variables?

seconds

The primary function of the filtration is to reduce:

patient skin dose

To reduce patient exposure during pulse mode fluoroscopy, _____ should be chosen.

smallest pulse width

Which one of the following would result in the highest patient dose?

conventional/ continuous fluoroscopy

Automatic brightness control (ABC) in fluoroscopy adjusts which two factors for various part/patient thickness to provide adequate brightness and contrast of the image?

kVp and mA

Which one of the following radiation situations is potentially the most harmful?

a large dose to the whole body all at one time

Which image would produce the highest patient dose?

image B (the one on the right

To radiograph an infant for suspected free air within the abdominal cavity, which of the following projections of the abdomen will demonstrate the condition with the least patient exposure?

left lateral decubitus with grid

The _____ is the primary protective barrier for the fluoroscopic imaging system.

image intensifier / Flat panel

Radiographic grids should be used only when the body part examined is greater than _____ cm. in thickness.

10

Which image would produce the highest patient dose?

image B

The kerma (kinetic energy released in matter) rate, measured in air at the position where the center of the useful beam enters the patient for both fixed and mobile fluoroscopy units should NOT exceed the following entrance skin exposure rates (ESE) is there if no optional high-level control.

100 mGya/min

With pulsed digital fluoroscopy, which pulse system would reduce the patient exposure the most?

3.0 pulses/second

What is the minimum aluminum equivalency of total filtration required for diagnostic radiographic x-ray tubes operating above 70 kVp?

2.5 mm aluminum

During a fluoroscopic examination, which of the following would reduce the patient exposure?

1. intermittent fluoroscopy

2. last image hold

3. use of a grid

4. collimation

1, 2, and 4

Automatic exposure rate control _____ the quantity of radiation for large patients compared to smaller patients

increases

The source-to-skin distance must be no less than ____ on moble fluoroscopic equipment.

30 cm (12 in)

The source-to-skin distance must be no less than ____ on starionary fluoroscopic equipment.

38 cm (15 in.)

increasing filtration will:

increase the average energy of the x-ray beam

Intensity means the same thing as:

quantity of radiation

When using an automatic exposure control (AEC), regulations state that generators must terminate the exposure at 600 mAs or ____ seconds for exposures above 50 kVp.

6

This factor mainly controls the quantity of radiation produced.

mA/mAs

If mAs is doubled, what happens to patient dose?

patient dose doubles

Kilovoltage (kVp) relates to the:

penetrating power/ energy of the x-ray beam

How many detectors are typically found in an AEC system?

3

Modern automatic exposure control (AEC) sensors function by using ____.

Ionization chambers

When performing a lateral knee examination and only the center chamber is activated, the image receptor (IR) would be _______________ if the center chamber was centered over the patella.

underexposed

AEC devices work by measuring:

radiation that exits the patient

Accurate operation of the AEC device depends on:

1. The thickness and density of the object

2. positioning of the object with respect to the photocell

3. bea, restriction (coning)

1, 2, and 3

The function/purpose of the backup timer when using an AEC is to:

1. protect the radioprapher from overexposure

2. protect the patient from overexposure

3. protect the x-ray tube

2 and 3

When using AEC, the radiographer ___ set the mAs.

does not

When using AEC with digital imaging systems, assuming all other factors are correct, selecting the center chamber on a PA chest image results in:

increased exposure in the lung area

If the center photocell was selected for a lateral projection of the lumbar spine, and it was positioned over the spinous processes (posterior) instead of the certebral bodies, the resulting effect would be:

the IR would be underexposed

All of the following EXCEPT _____ will result in an increase in AEC response time.

increasing the focal spot size

As kVp increases, patient dose:

decreases

Which one of the following sets of exposure factors would produce the least patient exposure?

10 mAs at 80 kVp

The AEC controls which of the follwoing exposure variables?

seconds/time

Total filtration is the sum of _____ filtration plus added filtration.

inherent

The radiographic beam should be collimated so that it is:

No larger than the image receptor

Filters used in radiographic x-ray tubes are generally composed of:

aluminum

Which one of the following is the most versatile type of x-ray beam limitation device?

collimator

Which one of the following is used to limit the area of the patient being irradiated?

collimator

If the filtration for a radiographic unit were inadvertently omitted for a series of chest exposures, the greatest increase in exposures would occur in the:

skin of the chest

Gonad shielding may reduce male gonad dose by up to:

95%

Which field size would lower the patient dose the most if all technical factors remained the same?

8 X 10

Which type of gonadal shield would NOT be suitable for use during a fluoroscopic examination?

shadow shield

Which of the following radiologic examinations would deliver the greatest entrance skin exposure (ESE)?

abdomen

Which one of the following types of gonadal shielding should be used for a patient having an examination requiring a sterile field?

shadow shield

Which one of the following is not a beam limitation device?

filter

What is the minimum aluminum equivalency of total filtration required for diagnostic x-ray tubes operating above 70 kVp?

2.5 mm

The function of a filter is to:

reduce patient skin dose

An x-ray beam is:

heterogeneous

_____ is defined as the thickness of an absorbing material which will reduce the intensity of the primary beam by half of its initial/original value.

half-value layer

What is the minimal HVL for three-phase equipment operating at 90 kVp?

3.1 mm Al

A filter is placed in the path of the x-ray beam to remove:

long-wavelength x-rays

A variable aperture is also known as a:

collimator

Collimators that automatically restrict the beam to the size of the cassette have a feature called automatic collimation or:

positive beam limitation

The most commonly used gonadal shield is the:

contact shield

A flat piece of lead with a circle or square opening in the middle that is used to restrict the x-ray beam is called a:

aperture diaphragm

Gonadal shielding is indicated if the:

1. shielding does not interfere with the objectives of the study

2. Person has a reasonable reproductive potential

3. Gonads lie within or close (5 cm) to the exposure field

1, 2, and 3

Increasing filtration will:

increase the average energy of the x-ray beam

The advantages of beam restriction include which of the following?

1. less scattered radiation is produced

2. less biologic tissue is rradiated

3. less total filtration will be necessary

1 and 2

_____ provides the technologist with an indication of the accuracy of the exposure settings for that given image.

S number or exposure indicator

The largest dose to the male gonads is most likely to result from which of the following exposures?

cross-table lateral hip

Which one of the follwoing grids would produce the least patient exposure?

5:1

12:1

8:1

16:1

5:1

Overall, children are up to ____ times more radiosensitive than adults.

10

Which of the following would help in reducing the radiation exposure to a child during a radiographic study?

1. the use of gonadal shielding

2. the use of high-speed imaging system

3. the use of a tightly collimated beam

1, 2, and 3

Issues to consider when imaging bariatric patients include diameter of fluoroscopic imaging equipment and:

table weight limit

Which one of the following is used as part of an effort to observe the ALARA concept?

Collimation

Which combination of exposure factors would best help eliminate motion for a child having a radiographic procedure?

400 mA, 0.0025 second (10 mAs)

A radiographic image was performed without a grid using 6 mAs. The radiologist wants the image repeated with an 8:1 grid due to excessive scattered radiation on the radiographic image. What new mAs should be used to maintain receptor exposure?

24 mAs

Which one of the following procedures would most likely contribute a higher gonadal dose to a female than a male?

AP abdomen

All of the following can be used to reduce the repeat rate for radiographic images except:

1. effective communication skills

2. careful selection of exposure factors

3. proper immobilization techniques

4. high ratio radiographic grids

high ratio radiographic grids

Which one of the following positions or projections would provide the greatest radiation protection to the lens of the patient’s eyes?

1. left lateral skull

2. right lateral skull

3. AP skull

4. PA skull

PA skull

Which of the following radiation situations is potentially the most harmful?

A large dose to the whole body all at one time

All of the following devices are generally used to help reduce patient dose, except:

1. grid

2. collimator

3. gonadal shield

1. grid

The magnification mode in fluoroscopy will produce:

1. Less patient dose

2. Higher/better contrast resolution

3. Higher/better spatial resolution

2 and 3

According to 21 CFR (Code of Federal Regulations Title 21), how often shall the air kerma rate (AKR) be displayed on fluoroscopic equipment?

once every second

Automatic brightness control during fluoroscopy adjusts which two factors for various part/patient thickness to provide adequate brightness and contrast of the image?

kVp and mA

To reduce patient exposure during pulse mode fluoroscopy, ______ should be chosen.

smallest pulse width