Occupational ExposureProtection of the Worker

Lab # 4

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• The use of radiations and radiolabeled products for any purpose is governed by regulatory agencies in different countries all over the world.

• The use of radiopharmaceuticals in humans was almost unregulated until the late 1950s.

• Until 1963, all reactor-derived radiopharmaceuticals were under the control of the Atomic Energy Commission– (AEC, now the Nuclear Regulatory

Commission, (NRC)) only for their radiation hazards.

• The therapeutic or diagnostic efficacy and the pharmaceutical quality of radiopharmaceuticals were not regulated by the AEC or by the U.S. Food and Drug Administration (FDA) until the early 1960s.

• In 1963 the FDA introduced rules stating that the clinical efficacy of all radiopharmaceuticals.

Radiation Protection• Because radiation can cause damage in

living systems, international and national

organizations have been established to

set guidelines for the safe handling of

radioactive materials.• The International Committee on Radio

logical Protection (ICRP) • The National Council on Radiation

Protection and Measurement (NCRP)• They set guidelines for all radiation

workers to follow in handling radiations

Occupational Exposure Protection of the Worker

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Licensees shall ensure for all workers that:

1. Occupational exposure be limited

2. Suitable and adequate facilities, equipment and

services for protection be provided3. Appropriate protective devices and monitoring

equipment be provided and properly used4. Appropriate training be provided as well as periodic

retraining and updating

RESPONSIBILITIES

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Caution Signs and Labels • The NRC requires that specific signs, symbols, and labels

be used to warn people of possible danger from the presence of radiations

• These signs use purple, and black colors on a yellow background

• Some typical signs are shown in the figures

• Caution: Radiation Area: This sign must be posted in radiation areas.

• Caution: High Radiation Area or Danger: High Radiation Area: This sign must be posted in high radiation areas.

• Caution: Radioactive Material or Danger: Radioactive Material: This sign is posted in areas or rooms in which 10 times the quantity or more of any licensed material specified in Appendix C of 10CFR20 are used or stored.

• All containers with quantities of licensed materials exceeding those specified in Appendix C of 10CFR20 should be labeled with this sign.

Sources of exposure

Occupational Exposure Protection of the Worker

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EXPOSURES IN NUCLEAR MEDICINE

InternalIngested and/or inhaledradionuclides

ExternalVials, syringes, patients.

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• Unpacking radioactive material• Activity measurements• Storage of sources• Internal transports of sources• Preparation of radiopharmaceuticals• Administration• Examination of the patient• Care of the radioactive patient• Handling of radioactive waste• Accidents

Exposure of the workerExternal Exposure

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• spills• improper administration• experimental work with animals• emergency surgery of a therapy patient

Contamination of the worker

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0

0,5

1

1,5

2

2,5

Dispensing Injection Examination

Do

se (

uS

v)

Dose to worker

Measurements of this kind can show different results in different hospitals

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Radiation Protection Measures

Depend on:1. Activities used2. Type of radionuclide and its

chemical properties3. Time4. Distance5. Shielding6. Type of procedure

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TimeDose is proportional to

the time exposed

it is wise to spend no more timethan necessary near radiation sources

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Consequence

• Reduce time in contact with radiation sources as much as compatible with the task

• Training of a particular task using non-radioactive dummy sources helps

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Distance

• It is recommended that an individual remains as far away as possible from the radiation source.

• Procedures and radiation areas should be designed such that only minimum exposure takes place to individuals doing the procedures or staying in or near the radiation areas.

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Patient with iodine-131

1000 MBqI-131

0 0.5 1 2 m

0.5 0.1 0.06 0.03

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Consequence

• Distance is very efficient for radiation protection as the dose falls off in square

• Examples:– long tweezers for handling of sources– big rooms for imaging equipment

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Shielding• Various high atomic number (Z) materials that absorb

radiations can be used to provide radiation protection

• The ranges of alpha and b particles are short in matter the containers themselves act as shields for these radiations– Alpha can be stopped by a piece of paper– Beta low molecular weight element Al or glass can stop its effect.

(Whay don’t we use lead for shielding of beta radiation?)

• Gama radiations are highly penetrating absorbing material must be used for shielding of g-emitting sources– Lead is most commonly used for this purpose.

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Shielding

incident radiation transmitted

radiation

Barrier thickness

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Shielding

Bench top shieldVial shieldsSyringe shields

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SHIELDING OF SOURCES

Factors affecting the design:

• radionuclide• activity• shielding material

• Devices to measure personnel radiation exposure. • The film badge is most popular and cost-effective for

personnel monitoring and gives reasonably accurate readings of exposures from b, g, and x radiations.

• A: Pocket dosimeter. B: Film badge holder. • C: Film badge. D: Thermoluminescent chip in finger

badge

Dos and Don’ts in Radiation Protection Practice

• Do post radiation signs in radiation areas.• Do wear laboratory coats and gloves when working with

radioactive• materials.• Do work in a ventilated fumehood when working with

radioactive gases.• Do cover the trays and workbench with absorbent paper.• Do store and transport radioactive material in lead

containers.• Do wear a film badge while working in the radiation

laboratory.• Do identify all radionuclides and dates of assay on the

containers.

• Do survey work areas for any contamination as frequently as possible.

• Do clean up spills promptly, and survey the area after cleaning.

• Do not eat, drink, or smoke in the radiation laboratory.• Do not pipette any radioactive material by mouth.• Do monitor hands and feet after the day’s work.• Do notify the RSO in case of any major spill or other

emergencies related to radiation.

Dos and Don’ts in Radiation Protection Practice

Radiopharmaceuticals• A radiopharmaceutical is a radioactive

compound used for the diagnosis and therapeutic treatment of human diseases.

• In nuclear medicine nearly 95% of the radiopharmaceuticals are used for diagnostic purposes while the rest are used for therapeutic treatment.

• Radiopharmaceuticals usually have minimal pharmacologic effect – In most cases they are used in tracer

quantities.

Ideal Radiopharmaceutical• Radiopharmaceuticals should possess

some important characteristics

1. Easy availability

2. Short effective half life

3. Particle Emission

4. Decay by Electron Capture or Isomeric Transition

5. High Target-to-Nontarget Activity Ratio

1. Easy Availability

• Should be easily produced• Inexpensive• Readily available in any nuclear medicine facility. • Complicated methods of production of

radionuclides or labeled compounds increase the cost of the radiopharmaceutical.

• The geographic distance between the user and the supplier also limits the availability of short-lived radiopharmaceuticals.

2. Short Effective Half-Life

• A radionuclide decays with a definite half-life which is called the physical half-life Tp (or t1/2)

• The physical half-life is independent of any physicochemical condition

• Radiopharmaceuticals administered to humans disappear from the biological system through fecal or urinary excretion, perspiration, or other mechanisms

2. Short Effective Half-Life

• This biologic disappearance of a radiopharmaceutical follows an exponential law similar to that of radionuclide decay

• Every radiopharmaceutical has a biologic half-life (Tb)• The net or effective rate (λe) of the loss of radioactivity is

then related to the physical decay constant λp and the biologic decay constant λb. – λ e = λp + λb

• Te =Tp X Tb

Tp+Tb

• The physical half-life of 111In is 67 hr and the biologic half-life of 111In-DTPA used for measurement of the glomerular filtration rate is 1.5 hr. What is the effective half-life of 111In-DTPA?

• 1.47 hr• Radiopharmaceuticals should have a relatively

short effective half-life which should not be longer than the time necessary to complete the study in question

2. Short Effective Half-Life

3. Particle Emission

• Radionuclides decaying by a- or b-particle emission should not be used as the label in diagnostic radiopharmaceuticals

• Many b-emitting radionuclides such as 131I-iodinated compounds are often used for clinical studies

4. Decay by Electron Capture or Isomeric Transition

• Radionuclides emitting particles are less desirable

• The diagnostic radionuclides used should decay by electron capture or isomeric transition without any internal conversion.

• For diagnostic studies the radionuclide must emit a g radiation with an energy preferably between 30 and 300 keV.

5. High Target-to-Nontarget Activity Ratio

• For any diagnostic study it is desirable that the radiopharmaceutical be localized preferentially in the organ under study – Activity from nontarget areas can obscure the

structural details of the picture of the target organ.

– Target-to-nontarget activity ratio should be large.

Thank You