Chapter 15: Management of Imaging Personnel Radiation Dose During Diagnostic X-ray Procedures

The intensity of radiation is inversely proportional to the square of the distance from the source is in reference to:

the inverse square law.

Which type of barrier protects against leakage and scatter radiation?

Secondary barriers

The annual occupational effective dose in metric units for whole-body exposure during routine operations is:

50mSv

Restricts the dimensions of the radiographic beam so that its margins do not extend beyond the image receptor

Beam restrictors (Collimator)

Barrier that prevents direct, or unscattered, radiation from reaching personnel or members of the general public on the other side of the barrier

Primary barrier

Monthly allowable equivalent dose to the embryo-fetus in metric units from occupational exposure of a pregnant technologist

0.5mSv

The beam direction factor is also known as the:

Use factor (U)

Annual effective dose (EfD) limit set for individual members of the general public

1 mSv or 0.001 Sv

Specified either in units of mAs per week or milliampere-minutes (mA-min) per week

Workload (W)

During a standard fluoroscopic examination, when the Bucky tray is positioned at the foot end of the table, this device automatically covers the Bucky slot opening in the side of the x-ray table. It protects the radiologist and radiographer at the gonadal level

Bucky slot shielding device (Lead curtain)

Most common materials used for structural protective barriers

Lead and concrete

This is used to modify the shielding requirement for a particular barrier by taking into account the fraction of the work week during which the space beyond the barrier is occupied

Occupancy factor (T)

Permits the radiologist and assisting radiographer to remain outside the fluoroscopic room at a control console behind a protective barrier while the x-ray beam is on

Remote control fluoroscopic system

Mode of operation in which the exposure rate may significantly exceed the rate used in routine fluoroscopy

High-level control

During a fluoroscopic examination, this device should be positioned between the fluoroscopist and the patient to intercept scattered radiation above the tabletop

protective curtain

A permanent protective barrier for the radiographer that is located in an x-ray room housing stationary radiographic equipment

control booth barrier

A radiation worker’s whole-body lifetime effective dose in mSv should not exceed 10 times the person’s age in years. This is referred to as:

the cumulative effective dose limit (CumEfD limit)

All the radiation that arises from interactions of an x-ray beam with the atoms of an object in the path of the beam are called:

scatter radiation

Principle that holds that occupational exposure of the radiographer and other occupationally exposed persons should be kept as low as reasonably achievable

ALARA principle

The average annual gonadal equivalent dose to members of the population who are of childbearing age is the:

Genetic Significant Dose (GSD)

Consists of radiation that has been deflected from the primary beam. This radiation is made up of leakage radiation from the tube housing and scatter primarily from the patient

secondary radiation.

protective eyeglasses with optically clear lenses must contain a minimal lead equivalent protection level of:

0.35mm lead equivalent.

Should be used to immobilize patients during radiographic exposures, whenever possible, instead of people

mechanical restraining devices

Special garments (e.g., aprons, gloves, and thyroid shields) that conventionally are made of lead-impregnated vinyl and are worn during fluoroscopic and certain radiographic procedures are called:

radiation protective apparel.

A portable device for producing real-time (motion) images of a patient. This device holds an x-ray tube at one end and an image intensifier at the other end

C-arm fluoroscope.

Because the workforce in radiation-related jobs is small compared with the population as a whole, the amount of radiation received by this workforce can be larger than the amount received by the general public without altering the:

GSD

Which of the following is a tenet of the ALARA concept?

a. The radiographer’s occupational exposure should not exceed the annual EDL allowed for individual members of the general population.

b. The radiographer’s occupational exposure should be as high as necessary to allow for holding of patients during diagnostic x-ray procedures.

c. The radiographer’s occupational exposure for the whole body should limit that individual’s lifetime EfD to his or her age times 50 mSv.

d. The radiographer’s exposure should be kept as low as reasonably achievable.

d. The radiographer’s exposure should be kept as low as reasonably achievable.

A facility that employs a pregnant diagnostic imaging staff member should provide that individual with an additional monitor to be worn at waist level during all radiation procedures. The purpose of this additional monitor is to ensure that the monthly EqD to the embryo-fetus does not exceed _________ in metric units.

0.5 mSv per month

Which of the following are radiation sources that can be generated in a diagnostic x-ray room?

1. Primary radiation

2. Scatter radiation

3. Leakage radiation

All 3

During C-arm fluoroscopy, the exposure rate caused by scatter near the entrance surface of the patient (the x-ray tube side) ____________ the exposure rate caused by scatter near the exit surface of the patient (the image intensifier side).

exceeds

For high-level-control interventional procedures, the radiographer should verify that which of the following dose reduction features are available and in good working order?

1. High-quality, low-dose fluoroscopy mode and pulsed beam operation

2. Manual collimation, correct beam filtration, and removable grids

3. Roadmapping, time-interval differences, and last-image-hold mode

All 3

In diagnostic radiology, which radiation source poses the most significant occupational hazard for the radiographer?

scattered radiation

During a fluoroscopic examination, which of the following methods and devices reduce(s) the radiographer’s exposure?

1. Adequate x-ray beam collimation

2. Control of technical exposure factors

3. Use of a cumulative timing device

All 3

If the peak energy of the diagnostic x-ray beam is 120 kVp, the primary protective barrier in a typical installation consists of at least ____________ and extends _________ upward from the floor of the x-ray room, when the tube is 1.5 to 2.1 m from the wall in question.

1.6 mm lead; 2.1 m

Of the following radiation sources, which is the control booth barrier not intended to intercept in a diagnostic x-ray room?

1. Leakage radiation

2. Primary radiation

3. Scattered radiation

2 only

A radiographic x-ray suite is in operation 5 days/wk. The average number of patients per day is 25, and the average number of images per patient is 3. The average technical exposure factors are 70 kVp, 300 mA, and 0.2 s. Find the weekly workload.

375 mA-min/wk

Which of the following statements is true?

a. When wearing a protective apron, a radiographer may stand in the useful beam to restrain a patient during a difficult radiologic procedure.

b. When wearing protective aprons, nurses, orderlies, relatives, or friends may stand in the useful beam to restrain a patient during a difficult radiologic procedure.

c. When wearing protective aprons, pregnant radiographers or other nonoccupationally exposed pregnant women may stand in the useful beam to restrain a patient during a difficult radiologic procedure.

d. Radiographers and nonoccupationally exposed individuals should never stand in the useful beam to restrain a patient during a radiographic procedure.

d. Radiographers and nonoccupationally exposed individuals should never stand in the useful beam to restrain a patient during a radiographic procedure.

Of the devices listed here, which eliminates non-useful low-energy photons from the primary beam?

1. Collimator light source

2. Electronic sensors

3. Aluminum filtration

3 only

Which of the following is the most effective means of protection from ionizing radiation normally available to the radiographer?

a. Reducing the amount of time spent near a source of radiation

b. Placing as much distance as possible between oneself and the source of radiation

c. Remaining behind a mobile protective shield during an exposure

d. Using protective shielding garments

b. Placing as much distance as possible between oneself and the source of radiation

The lead glass window of the control booth barrier in a stationary (fixed) radiographic installation typically consists how much shielding?

1.5mm lead equivalent

If the intensity of the x-ray is inversely proportional to the square of the distance from the source, how does the intensity of the x-ray beam change when the distance from the source of radiation and a measurement point is quadrupled?

It decreases by a factor of 16

Leakage radiation and scatter radiation are forms of:

secondary radiation

Diagnostic x-ray installations must be equipped with:

radiation absorbent barriers

Which of the following principles can be used to minimize occupational radiation exposure?

1. Time

2. Distance

3. Shielding

All 3

Pregnant radiographers can wear an additional monitoring device at waist level to ensure that the monthly EqD does not exceed:

0.5 mSv

During fluoroscopy, which of the following will provide radiation protection for the radiographer and the radiologist?

1. Using appropriate source-to-skin distance

2. Having a diagnostic-type x-ray tube housing

3. Using a remote control fluoroscopic system

All 3

Floors of radiation rooms except dental installations, doors, walls, and ceilings of radiation rooms exposed routinely to the primary beam are given a use factor of:

1.0

If a radiographer stands 1 m away from an x-ray tube and receives an exposure rate dose of 4.0 mGya/hr, what will the exposure rate dose be if the same radiographer moves to stand at a position located 2 m from the x-ray tube?

1.0 mGya/hr

If a radiographer moves closer to a source of radiation, the radiation exposure to the radiographer:

increases significantly

True or False Compared with routine radiographic procedures, general fluoroscopic procedures increase the radiographer’s risk of exposure to ionizing radiation.

True

True or False A radiographer’s annual occupational EfD includes personal medical and natural background radiation exposure.

False; Personal medical and natural background radiation exposures are not included in a radiographer’s annual occupational EfD

True or False The ALARA concept takes economic and social factors into consideration

True

True or False Protective lead (Pb) aprons and shielded barriers function as gonadal shields for diagnostic imaging personnel.

True

True or False The intensity of radiation is directly proportional to the square of the distance from the source.

False; inversely proportional

True or False Radiographic and fluoroscopic exposures can be made when room doors are open.

False; exposures should not be made with doors open to ensure safety and reduce radiation exposure.

True or False If the peak energy of an x-ray beam is 100 kVp, a Pb apron must be equivalent to at least a 2.5-mm thickness of lead.

False; a Pb apron must be equivalent to at least a 0.25-mm thickness of lead for 100 kVp.

True or False During a routine fluoroscopic examination, if the radiographer’s immediate presence is not required near the x-ray table to assist the radiologist, the radiographer may either stand behind the radiologist, who is also wearing protective apparel, or stand behind the control-booth barrier until his or her services are required.

True

True or False The protective curtain on a fluoroscopic unit protects the radiologist and radiographer at the gonadal level.

False; the protective curtain provides limited protection mainly to the radiologist and may not effectively shield the gonadal level.

True or False For C-arm devices with similar fields of view, the dose rate for personnel located within a meter of the patient is comparable to that in routine fluoroscopy—approximately several milligray in air (mGya) per hour.

True

True or False The physical configuration of a C-arm fluoroscopic unit allows the operator many methods of achieving protection from scattered radiation.

False; it limits the methods

True or False From the perspective of increased radiation safety, it is best to reverse the C-arm to place the x-ray tube under the table and the image intensifier over the table.

True

True or False A radiographer may hold a patient during a radiographic exposure as long as the radiographer stands in the useful beam.

False; this practice increases radiation exposure.

True or False The primary radiation intensity for a selected kVp at the barrier location for an x-ray suite may be determined by making air kerma measurements on the suite’s x-ray unit at a reference distance (e.g., 100 cm) from the x-ray tube target with the aid of a calibrated ionization chamber.

True

True or False Because scatter and leakage radiation emerge in all directions in the x-ray room, every wall, door, viewing window, and other surface are always struck by some quantity of radiation.

True

True or False Filtration primarily benefits the radiographer.

False; it primarily benefits the patient by reducing radiation dose.

True or False During a diagnostic x-ray procedure, the patient becomes a source of scattered radiation as a consequence of the coherent scattering process.

False; During a diagnostic x-ray procedure, the patient becomes a source of scattered radiation as a consequence of the Compton scattering process

True or False At a 90-degree angle to the primary x-ray beam, at a distance of 1 m, the scattered x-ray intensity is generally approximately 1⁄1000 of the intensity of the primary x-ray beam.

True

True or False Methods and techniques that reduce patient exposure also reduce exposure for the radiographer.

True

True or False Pregnant diagnostic imaging department staff members must immediately stop performing their respective duties and discontinue employment as a consequence of pregnancy.

False; pregnant diagnostic imaging staff members may continue to work with appropriate precautions to limit radiation exposure.

True or False The amount of radiation a worker receives at a particular location is inversely proportional to the length of time the individual is exposed to ionizing radiation.

False; it is directly proportional to the length of time of exposure.

True or False If a declared pregnant radiographer is reassigned to a lower radiation exposure risk area, then the other remaining radiographers in the higher risk area, who must fill in, can be subject to increased risk. Therefore, the declared-pregnant radiographer does not necessarily need to be reassigned to a lower radiation exposure area as a direct consequence of the declared pregnancy.

True

True or False In accordance with ALARA guidelines, work schedules are designed to distribute radiation exposure risk evenly to all employees.

True

True or False In a typical x-ray room, a secondary barrier should overlap the primary barrier by about 1.27 cm.

True

True or False During a fluoroscopic examination, a radiographer need not wear a protective apron when he or she is in the x-ray room during a procedure

False. The radiographer must wear a protective apron to minimize radiation exposure during fluoroscopic procedures.

Although the radiographer and other diagnostic imaging personnel are allowed to absorb more radiation than the general public, the ____________ received must be minimized whenever possible.

equivalent dose

___________ radiation poses the most significant occupational hazard in diagnostic radiology.

scattered

Radiation warning signs are an important component of ________ in a radiology department.

safety

After receiving radiation safety counseling, a pregnant radiologic technologist must read and sign a form acknowledging that she has received counseling and understands the practices to be followed to ensure the _________ of the ___________.

safety; embryo-fetus

Primary radiation is also known as __________ radiation.

direct

___________ the length of time spent in a room where x-radiation is produced reduces occupational exposure.

shortening (reducing)

The most effective means of protection from ionizing radiation is ___________.

distance

Structural barriers such as walls and doors in an x-ray room provide protective ___________ for both imaging department personnel and the general public.

shielding

Accessory protective shielding includes __________, __________, and _________ made of lead-impregnated vinyl.

aprons, gloves, and thyroid shields

No one should touch the tube __________ or ___________ cables while a radiographic exposure is in progress.

housing; high-voltage

When high-speed image receptor systems are used, smaller radiographic exposure (less milliamperage) is required, which results in fewer x-ray photons being available to produce ____________. Because of this reduction in ____________, personnel exposure is decreased.

Compton scatter; Compton scatter

It is imperative that the EqD to the embryo-fetus from occupational exposure of the mother not exceed the National Council on Radiation Protection and Measurements (NCRP)–recommended monthly EDL of ________ or a limit of ________ during the entire pregnancy.

0.5 mSv; 5 mSv

Maternity protective aprons consist of _______ lead equivalent over their entire length and width and also have an extra _______ lead equivalent protective panel that runs transversely across the width of the apron to provide added safety for the embryo-fetus.

0.5mm; 1.0mm

Shortening the length of ________ spent in a room where x-radiation is produced, standing at the greatest ________ possible from an energized x-ray beam, and interposing a radiation-absorbent _________ material between the radiation worker and the source of radiation all reduce occupational exposure.

time; distance; shielding

When the distance from the x-ray target, a point source of radiation, is doubled, the radiation at the new location spans an area ________ times larger than the original area. However, because the same amount of radiation exists to cover this larger area, the intensity at the new distance decreases by a factor of ________.

four; four

Primary protective barriers are located _____________ to the undeflected line of travel of the x-ray beam.

perpendicular

If the peak energy of the x-ray beam is 120 kVp, the primary protective barrier in a typical installation consists of approximately _________ and extends __________ upward from the floor of the x-ray room when the x-ray tube is 1.5 to 2.1 m from the wall in question.

1.6 mm lead; 2.1 m

In a typical diagnostic x-ray installation, the secondary barrier consists of ___________.

0.8 mm lead

During general fluoroscopy and x-ray special procedures, a neck and thyroid shield can guard the thyroid area of occupationally exposed people. It should be __________ equivalent.

0.5 mm lead

To ensure protection from ___________ radiation emanating from the patient during a fluoroscopic examination, the radiographer should stand as far from the ___________ as is practical and should move closer to the patient only when ____________ is required.

scattered; patient, assistance

Protective lead gloves of at least ________ equivalent should be worn whenever the hands must be placed near the fluoroscopic field.

0.25 mm lead

For better visualization of small body parts, C-arm fluoroscopes have the capability to _______ the image.

magnify

During a fluoroscopic examination, a_____________ protective apron is recommended to protect personnel who must move around the x-ray room.

wraparound

The radiographer should attempt to stand at ___________ (_____ degrees) to the x-ray beam-scattering object (the patient) line; when the protective factors of distance and shielding have been accounted for, this is the place where the __________ amount of scattered radiation is received.

right angles; (90); least