Which of the following factors is are important in determining thickness of protective barriers?

When performing a mobile radiographic examination, if the Protection factors of distance and shielding are equal, the radiographer should stand at a (blank) to the scattering object (the patient) line.

Diagnostic imaging personnel may receive an annual occupational effective dose of (blank) for whole body exposure during routine operations

At a 90-degree angle to the primary X-ray beam, at a distance of 1 m, the scattered radiation is what fraction of the intensity of the primary beam?

If a radiographer stands 6 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 12 m from the X-ray tube?

Which of the following are methods that can be used by a C-arm operator to reduce occupational exposure for himself or herself and other personnel?
1. Collimate the X-ray beam to include only the anatomy of interest
2. Use the foot pedal or the handheld exposure switch with their cables extended away from the machine as far as possible whenever making an exposure
3. Use magnification whenever possible to visualize body parts better

If the bucky slot shielding device and spot film device protective curtain, or sliding panel, were not in the correct position during a routine fluoroscopic examination, what would the fluoroscopist do?

Exceed an exposure rate dose of 1 mGya/hr at a distance of 0.6 m from the side of the X-ray table

Units of either mAs/wk or mA-min/wk are used to determine the (blank) for a specific X-ray room

A Bucky slot shielding device of at least (blank) must automatically cover the Bucky slot opening in the side of the X-ray table during a fluoro exam when the Bucky tray is positioned at the foot end of the table.

For mobile radiography units, which are not equipped with remote control exposure devices, the cord leading to the exposure switch must be long enough to permit the radiographer to stand at least (blank) from the patient, the X-ray tube, and the useful beam to reduce occupational exposure

Of the following factors, which is considered when determining thickness requirements for protective barriers?
1. Occupancy factor (T)
2. Workload (W)
3. Use factor (U)

The greatest occupational hazard in diagnostic radiology comes from:

The annual effective dose limit for individual members of the general population not occupationally exposed is (blank) for continuous or frequent exposures from artificial sources other than medical irradiation & natural background and (blank) for infrequent annual exposure

What adjustment in technical exposure factors decreases the production of scattered radiation?

Increase kVp and decrease mAs in compensation

For C-arm devices with similar fields of view, the dose rate to personnel located within a meter of the patient is:

Comparable to that of routine fluoroscopy

The maximum weekly permitted equivalent dose for a controlled area must not exceed:

Because occupational exposure of the radiographer can be kept as low as reasonably achievable (ALARA) through individual monitoring & other protective measures, and the use of protective devices and because exposure from radiation related jobs will not alter the (blank), radiation workers may receive a larger equivalent dose than members of the general population

Genetically significant dose (GSD)

If the intensity of the x-ray beam 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 the distance of a measurement point is tripled?

It decreases by a factor of 9 at the new distance

A spot film device protective curtain, or sliding panel, of a minimum thickness of 0.25 mm lead equivalent should normally be positioned between the fluoroscopist and the patient to intercept what type of radiation?

Scatter radiation above the tabletop

In terms of occupational risk, radiography may be compared with the occupational risk associated with:

Other industries considered reasonably safe, such as government and trade

Annual EfD limits for occupationally exposed personnel include:

When being used as shielding during a fluoroscopic exam, a protective lead apron must be the equivalent to at least what?

Whenever scattered radiation decreases, the radiographers exposure:

When the time is spent in a higher radiation area is reduced or limited, occupational exposure:

Calculation of the thickness of the Primary and the Secondary Protective Barrier for the necessary shielding of an X-ray equipment

Click here for the calculations

The calculations presented below follow the recommendations and tables from reference [1]. The code calculates the thickness of the shielding necessary to reduce the exposure at levels permitted by regulations, for an X-ray source that can generate up to 300 keV.
It is considered controlled areas with maximum annual exposure of 50 mSv or 20 mSv.
For uncontrolled areas, a maximum annual exposure of 5 mSv and 1 mSv is considered. The maximum annual exposure of 0.05 mSv is added for ALARA considerations.
The results are done for lead, concrete and drywall. The values for drywall are only approximated.

For the total thickness of the secondary barrier, the following criteria are used: if the difference between the leakage thickness and the scattered thickness is lower than the TVL, then the total thickness is equal to the bigger of both values plus a HVL. If the difference is bigger than a TVL, then the bigger thickness will suffice.

The distance d2 and d3 are used also to calculate the angle of scattering. This angle is approximated to 30, 45, 60, 90, 120 or 135 degrees in order to select the correction factor

Definitions:

Controlled area = A defined area in which the exposure of persons to radiation is under the supervision of a Radiation Protection Supervisor (the area requires control of access, occupancy and working conditions).

Uncontrolled area  = an area to be occupied by public.

Occupancy factor = Occupancy is the fraction, expressed as a percentage, of the time the area will be occupied while the source is on.

Protective barrier:

           a) Primary = barrier sufficient to attenuate the useful beam to the required degree.

b) Secondary = barrier sufficient to attenuate the stray radiation (leakage + scattered) to the required degree.

Usage factor = Fraction of the time during which the beam is directed to a particular barrier.

Scattering surface = area of the phantom, patient or sample (normalized to 400 cm2 in the calculations)

d1 = distance between the irradiation source and the point of interest after the primary protective barrier.

d2 = distance between the irradiation source and the point of interest after the secondary protective barrier.

d3 = distance between the irradiation source and the patient or sample.

Reference:

[1] NCRP Report No. 49 “Structural Shielding Design and Evaluation for Medical Use of X-ray and Gamma Rays of Energies up to 10 MeV”, Issued September 15, 1976.First Reprinting July 15, 1 99, Second Reprinting November 1, 1994, Third Reprinting July 1 5, 1998

Which of the following factors is are important in determining the thickness of protective barriers?

Which of the following materials is the most effective as a protective barrier?

What is protective barriers in radiology?

What is the thickness of lead barrier?