Designing for Radiation Protection

The protective housing surrounding the tube must reduce leakage radiation to less than ______ mGy per hour at 1 meter from the housing

1

X-ray beam on must be positively and clearly indicated to the radiologic technologist

True

A SID indicator must be accurate to within _____ percent of the indicated SID

2

The alignment of the x-ray beam must be within _____ degree of perpendicular to the image receptor

1

Positive Beam Limitation is a feature of radiographic collimators that automatically adjusts the radiation field to the size of the image receptor

True

The PBL must be accurate to within _____ % of the SID

2

The total filtration for x-ray equipment that operate above 70 kVp must be a minimum of:

2.5 mm aluminum

Primary Protective Barrier

Any wall to which the useful beam can be directed

Secondary Protective Barrier

Barrier designed to shield an area from scatter or leakage radiation

Reproducibility

At a given technique (with the exact same kVp, mAs, and time) the output radiation intensity should be constant from one exposure to another

Reciprocity

The output radiation should remain constant from one mA station to another if the mAs remains the same (mAs = mAs)

Controlled Area

Area where personnel occupancy and activity are subject to control and supervision for the purpose of radiation protection

Uncontrolled area

Area occupied by anyone; the maximum exposure rate allowed in this area is based on the recommended dose limit for the public

Work load (W)

Product of the maximum miliamperage (mA) and the number of x-ray examinations performed per week

Use Factor (U)

Proportional amount of time during which the x-ray beam is energized or directed towards a particular barrier

Primary Radiation

The useful beam

Secondary Radiation

Leakage and scatter radiation

Leakage radiation

Secondary radiation emitted through the tube housing

Scatter radiation

Secondary radiation that results when the useful beam intercepts any object, causing some x-rays to be scattered

The Bucky Slot Cover and the Protective Curtain are Fluoroscopic Protection features that offer at least _____ mm Pb equivalent

0.25

The Bucky Slot Cover is a fluoroscopic protection feature that is in place to protect the:

• radiologist

• x-ray technologist

The SSD (source-to-skin distance) in mobile fluoroscopy must be:

A minimum of 12 inches

Levels of occupancy of areas that may be adjacent to x-ray rooms (suggested by NCRP): Work areas

Full occupancy

Levels of occupancy of areas that may be adjacent to x-ray rooms (suggested by NCRP): waiting rooms

Occasional occupancy

Levels of occupancy of areas that may be adjacent to x-ray rooms (suggested by NCRP): corridors

Frequency occupancy

Levels of occupancy of areas that may be adjacent to x-ray rooms (suggested by NCRP): patient rooms

Frequency occupancy

Levels of occupancy of areas that may be adjacent to x-ray rooms (suggested by NCRP): closets

Occasional occupancy

Levels of occupancy of areas that may be adjacent to x-ray rooms (suggested by NCRP): children’s play areas

Full occupancy

Levels of occupancy of areas that may be adjacent to x-ray rooms (suggested by NCRP): living quarters

Full occupancy

Levels of occupancy of areas that may be adjacent to x-ray rooms (suggested by NCRP): restrooms

Frequent occupancy

Film's silver halide emulsion is ionized by x-ray photons

Film badge

Provides an immediate readout

Ionization chambers

Geiger-Muller detectors

Gas-filled detectors

Used in Nuclear Medicine Gamma Scanners

Scintillation detectors

Use of lithium fluoride and measures doses as low as 5 mrem

TLD’s

Can measure doses as low as 1 mrem

OSL’s

Leakage radiation

A secondary type of radiation that emerges from the leaded tube housing in direction other than that of the port

As an integral part of a QC program, which of the following tests must be within -/+ 2%

All of the above

True or false: Both perpendicularity and central ray congruency can be evaluated with a Beam Alignment Tool

True

True or false: Beam Alignment must be within +/- 1 degrees of perpendicular

True

True or false: Central Ray Congruency must be within +/- 1% of the SID

True

Based on NCRP Report #102, what is the minimal total filtration requirement for radiography units operating below 50 kVp?

0.5 mm aluminum

An increase in tube filtration results in: _____ patient dose (ESE)

Decrease

An increase in total tube filtration results in: _____ the overall average energy of the beam

Increase

An increase in total time filtration results in: ____ in mR tube output

Decrease

Do the following set of exposure factors listed below represent reproducibility or reciprocity? (75 kVp @ 100 mA and 0.10 seconds= 25 mR, and 75 kVp @ 100 mA and 0.10 seconds = 26.5 mR)

Reproducibility

True or false: According to the NCRP Report #102, the conventional pedal or positive pressure switch satisfied the requirement for stationary fluoroscopic unit being the '“dead man” type switch

True

Which of the following C-arm positions could potentially increase the dose to the operator’s eyes by up to 100x?

Tube on top (reversing the C-arm)

An increase in the source-to-skin distance (SSD) results in an _____ in entrance-skin exposure (ESE)

Decrease

Utilizing magnification mode during an analog fluoroscopic exam with an Image Intensifier (II) results in an increase in magnification, a _____ in the field-of-view (FOV) and a _____ in patient dose

Decrease, increase

As part of NCRP #102, 21 CFR, with the tower at the maximum SID and the shutters wide open: the intensity of the x-ray beam at the TT should not exceed _____ mGy/min/mA of operation at 80 kVP

21

As part of NCRP #102, 21 CFR, with the tower at the maximum SID and the shutters wide open: if no optional high-level control (normal mode), intensity is not to exceed _____ mGy/min

100

As part of NCRP #102, 21 CFR, with the tower at the maximum SID and the shutters wide open: with optional high-level control (boost mode), the maximum tabletop intensity allowed is ____ mGy/min

200

With a mobile fluoroscopic unit, the SSD must not be less than ____ cm

30

This type of radiation is most intense and therefore the most hazardous and the most difficult to shield

1 degree radiation

This type of radiation includes both scatter and leakage

2 degree radiation

Controlled area

This area is occupied by x-ray personnel trained in radiation safety and the barrier must reduce the exposure rate to an area to less than 50 mSv per year

Uncontrolled area

This area is occupied by non-radiation personnel or the general public and must reduce the exposure rate to 1 mSv/year or less

Workload

The number of exams performed each week (mAmin/week) or the total beam-on time for a radiography fluoroscopic room per week

Use Factor

The percentage of time during which the x-ray beam is on and directed toward a particular protective barrier

Primary radiation is also known as?

The useful beam

Why should the useful beam never be pointed or directed toward the operating console?

The operating console is a secondary protective barrier

Is this a primary or secondary barrier requirement: Consists of control booth barrier, x-ray tube housing, lead aprons, gloves, and portable barriers

Secondary

Is this a primary or secondary barrier requirement: Usually consists of 1.6 mm or 1/16th inch lead or lead equivalent

Primary

Is this a primary or secondary barrier requirement: Four inches of masonry would be an acceptable equivalent

Primary

Is this a primary or secondary barrier requirement: Four thickness of 5/8 inch gypsum board is adequate

Secondary

Is this a primary or secondary barrier requirement: Usually consists of only 0.8 mm or 1/32 inch of lead or lead equivalent

Secondary

Is this a primary or secondary barrier requirement: Consists of radiographic room walls, floor, and exposure room door

Primary

The controlled area barrier must reduce the exposure rate to less than ____ mSv/year

50 (5000 mrem/year)

The uncontrolled area barrier must reduce the exposure rate to less than ____ mSv/year

1(100 mrem/year)

The NCRP recommends that walls be assigned a use factor of ____ and the floor a use factor of ____

1/4, 1

The wall Bucky in a dedicated chest radiography room is considered a primary protective wall barrier and has a use factor of ____

1

All other walls in a dedicated chest radiography room (tube cannot be pointed towards these other walls) have a use factor of _____ for primary radiation

Zero

What is the single most important scattering object?

Patient