Occupational Radiation Dose Management

Basis for Protection Requirements Limit stochastic and non-stochastic effects STOCHASTIC Probability of an effect occurring, rather than its severity Regarded as a function of radiation dose without a threshold NON-STOCHASTIC Severity is affected by dose A threshold dose may need to occur before effect is recognized

ALARA A L R s ow s easonably chievable

Operator Radiation Sources Sources of radiation for operator: Operators of fluoroscopes receive their exposures through three distinct mechanisms. Each will be described in detail in the following slides. Operators of fluoroscopes are required by regulation to wear a personnel dosimeter or radiation monitor. The most common type of dosimeter is the film badge. The darkness or density of the film in the badge indicates the amount of radiation detected by the film badge. Badges are distributed by companies who maintain high quality control for accurate radiation measurement. There are several important features one should know about personnel dosimeters: 1. The dosimeter's only function is to detect radiation. In no way does it directly protect the operator. 2.Dosimeters are mailed in groups along with control dosimeters so that radiation received in transit can be subtracted from actual personnel exposures. This only occurs if personnel dosimeters are returned with the control dosimeter. When a personnel dosimeter is turned in late, the dosimeter does not get mailed with the control dosimeter. 3. There is a right way and wrong way to wear dosimeters. In most cases it is recommended that the dosimeter be worn outside the lead apron on the collar. When film is used it must be worn properly installed in the badge holder with the film (name) side out. There are various filters in film badges which allow an approximate determination of beam energy. These filter patterns must be visible on the film to obtain a valid radiation measurement. Primary Scatter Leakage

Occupational Exposure: Scatter Isoexposure lines during fluoroscopy

Scatter Radiation Levels Effects of scatter radiation during mobile/portable fluoroscopy (C-arm procedures) and fluoroscopy exams. Scatter radiation during portable fluoroscopy is more intense with the x-ray tube over the patient

Operator Protection: Time Minimize “beam-on” time Your exposure is directly proportional to beam time Although we must always be concerned about patient exposures, our operators are present day in and day out in a radiation environment. The four cardinal principles of operator protection are time, distance, shielding, and collimation. Each is explained in the following slides. Beam time = Exposure

Operator Protection – Other Distance Stand as far away from table as possible Shielding Collimation Anything that reduces patient exposure Lead drapes (except on C-Arms) Bucky slot cover Intensifier is primary barrier Protective garments (aprons, thyroid)

Tenth Value Layer (TVL) Shielding Half Value Layer (HVL) Tenth Value Layer (TVL) Tube Potential Lead (mm) Concrete (in) 40 kVp 0.03 0.13 0.06 0.40 60 kVp 0.11 0.25 0.34 0.87 80 kVp 0.19 0.42 0.64 1.4 100 kVp 0.24 0.60 0.80 2.0 125 kVp 0.27 0.76 0.90 2.5 150 kVp 0.28 0.86 0.95 2.8

X-Ray Attenuation of Lead Aprons Equiv. Thickness (mm Lead) Weight 50 kVp 75 kVp 100 kVp 0.25 mm 3-10 lbs 97% 66% 51% 0.50 mm 6-15 lbs 99.9% 88% 75% 1.00 mm 12-25 lbs 99% 94%

Weighting Factors for Various Types of Radiation Type of Energy Range Radiation Weighting Factor (Wr) X- and gamma rays, electrons 1 Neutrons, energy < 10 keV 5 10 keV to 100 keV 10 >100 keV to 2 MeV 20 > 2 MeV to 20 MeV >20 MeV Protons 2 Alpha particles

Find the cardinal principals at work in this picture.

Occupational Radiation Monitoring Film Badges

Occupational Radiation Monitoring Thermoluminescent Dosimetry (TLD)

Occupational Radiation Monitoring Optically Stimulated Luminescent (OSL)Dosimeters www.osldosimetry.com www.osldosimetry.com

Legal Dose Limits in the United States Annual 50 mSv/yr (5000 mrem/yr) Lens of the eye 150 mSv/yr (15 rem/yr Other organs 500 mSv/yr (50 rem/yr) Cumulative whole body 10 mSv (1000 mrem)×age Pregnancy, entire 5 mSv (500 mrem) Pregnancy, monthly 0.5 mSv (50 mrem)

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