IAEA
RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 4. SAFETY OF SOURCES. DESIGN OF FACILITIES
1.
BASIC CONCEPTS
Defence in depth is a well-established principle that is applied to safety. A single
equipment fault or a human mistake should not directly result in an accident. Defence
in depth is defined in the glossary of the BSS as “the application of more than a
single protective measure for a given safety objective such that the objective is
achieved even if one protective measure fails”. The BSS have established the
following requirement for defence in depth (para. 2.35):
“A multilayer (defence in depth) system of provisions for protection and safety
commensurate with the magnitude and likelihood of the potential exposures involved
shall be applied to sources such that a failure at one layer is compensated for or
corrected by subsequent layers, for the purposes of:
 preventing accidents that may cause exposure;
 mitigating the consequences of any such accident that does occur; and
 restoring sources to safe conditions after any such accident.”
In nuclear medicine these principles can be applied to the design of the facilities and
the security of sources. The general principle should be to keep the sources under
control and to minimize the consequences of any spread of contamination. The
licensee should also develop appropriate contingency plans for responding to events
that may occur, display plans prominently and periodically conduct practice drills.
The licensee should adhere to the following requirements regarding location
of sources:
“IV.13. Account shall be taken in choosing the location for any small source
within installations and facilities such as hospitals and manufacturing plants of:
a) Factors that could affect the safety and security of the source;
b) Factors that could affect occupational exposure and public exposure caused by
the source, including features such as ventilation, shielding and distance from
occupied areas; and
c) The feasibility in engineering design of taking into account the foregoing factors.”
2.
SOURCES
The sources used in nuclear medicine are mainly unsealed sources. Sealed sources
are used for calibration and QC of equipment.
Several types of unsealed sources (radiopharmaceuticals) are used in
different applications both in diagnosis and therapy.
Radionuclide
Pure -emitter
(e.g. Tc-99m, In-111, Ga-67, I-123)
Positron emitters (ß+)
(e.g. F-18)
, ß- emitters
(e.g. I-131)
Pure ß- emitters
(e.g. P-32, Sr-89, Y-90, Er-169)
-emitters
(e.g. At-211, Bi-213)
Diagnostics
X
Therapy
Ð-
X
Ð
X
-e
X
Ð
1
(-
Ð
-
X
-
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IAEA
RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 4. SAFETY OF SOURCES. DESIGN OF FACILITIES
The radiopharmaceuticals can be classified as follows:
• ready-to-use e.g. 131I- MIBG, 131I-iodide, 201Tl-chloride, 111In- DTPA
• instant kits for preparation of products e.g. 99mTc-MDP, 99mTc-MAA, 99mTcHIDA, 111In-Octreotide
• kits requiring heating e.g. 99mTc-MAG3, 99mTc-MIBI
• products requiring significant manipulation e.g. labelling of blood cells, synthesis
and labelling of radiopharmaceuticals produced in house
Radiopharmaceuticals shall be manufactured according to good manufacturing
practice and shall comply with the BSS (BSS II.13) and other relevant international
standards for:
Radionuclide purity;
Specific activity;
Radiochemical purity;
Chemical purity; and
Pharmaceutical aspects such as toxicity, sterility, pyrogenicity.
The licensee shall store, handle and use materials in accordance with manufacturer’s
instructions.
3.
BUILDING REQUIREMENTS
The facility should be designed in such a way that provisions for safety systems or
devices are inherent to the equipment or the room in order to lower the probability of
occurrence of undesirable radiation exposure.
For the use of low activity unsealed sources, e.g. for RIA tests, the Regulatory
Authority may specify minimal requirements regarding the design of the facility and
safety equipment.
The design of the facility should take into consideration the type of work to be
done and the radionuclides (and their activity) intended to be used. The ICRP’s
concept of categorization of hazard and safety assessment should be used in order
to determine the special needs concerning ventilation, plumbing, materials used in
walls, floors and work benches.
The general layout of the nuclear medicine department should take into
account a possible separation of the work areas and the patient areas. A sign such
as recommended by ISO shall be posted on doors as a warning of radiation hazard.
The sign shall be in accordance with the requirements of the Regulatory Authority.
The floors of controlled areas should be finished in an impermeable material
which is washable and resistant to chemical change.
Worktop surfaces must be finished in a smooth, washable and chemicalresistant surface with all joints sealed. Open shelving should be kept to a minimum
to prevent dust accumulation. Light fixtures should be easy to clean and of an
enclosed type in order to minimize dust accumulation.
Fume hoods shall be installed for use, as appropriate, for volatile radioactive
substances. The exhaust of the fume hood shall not become a source of radiation
exposure to the public.
A wash-up sink should be located in a low-traffic area adjacent to the work
area. Taps should be operable without direct hand contact and disposable towels or
hot air dryer should be available. An emergency eye-wash should be installed near
the hand-washing sink and there should be access to an emergency shower in or
near the laboratory.
A separate toilet room for the exclusive use of injected patients is
recommended. The facilities shall include a wash-up sink as a normal measure of
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RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 4. SAFETY OF SOURCES. DESIGN OF FACILITIES
hygiene. Washrooms designated for use by nuclear medicine patients should be
finished in materials that are easily decontaminated. Hospital staff should not use
the patient washing facilities as it is likely that the floor, toilet seat and sink faucet
handles will be contaminated frequently.
A source storage area and an area for temporary storage of radioactive waste
shall be provided with appropriate protection. When designing the facility, the
licensee should consider access control when determining source storage areas and
rooms for hospitalized patients undergoing radionuclide therapy.
4.
SAFETY EQUIPMENT
Suitable personal protective equipment must be provided and properly maintained for
the use of all persons employed at work. The safety equipment provided should
include protective clothes (lab coat, gloves, shoes, shoe covers etc.) adequate to
prevent any contamination of the bodies of the persons for whom it is provided.
Every person while engaged in work must wear the personal protective
equipment provided for his use in the course of that work. After such work personal
protective equipment used must be placed in the accommodation provided for it and
personnel must then wash their hands.
Safety glasses, goggles or face shields should be worn when handling 32P,
89
90
Sr, Y, 188Re or other high-energy beta emitting radionuclides. This will reduce the
external irradiation of the eye as well as prevent the high radiation doses to the eye
which accompany accidental contamination by splashing.
Shoes worn during work with radionuclides should cover the top of the foot to
minimize skin contamination from the splash that occurs if radioactive material is
spilled on the floor. Running shoes are quite adequate. Bare feet in sandals are
strongly discouraged.
Forceps or tongs should be available and used to reduce the radiation
exposure by increasing the distance between the source and the hands.
A portable contamination monitor must be readily available in the laboratory
to facilitate frequent monitoring, particularly of hands and sleeves. Care must be
taken to prevent accidental contamination of the detector disk source to ensure that
the response is constant.
Nuclear medicine and radiopharmacy staff must use syringe shields and vial
shields. Shielding is primarily used to protect against gamma radiation, but is also
necessary to protect individuals against some high-energy beta emitting
radionuclides such as 32P and 90Y.
It is usually much cheaper and more convenient to shield the source, where
possible, rather than the room or the person. The shielding material and thickness
depends on the type and amount of the radionuclides used. The most common
shielding material for gamma rays is lead, but high energy beta emitters such as 32P
require an inner shield of a low atomic number material, such as acrylic (e.g.
perspex), to prevent bremsstrahlung production.
In the nuclear medicine department, common examples of shielding
configurations include shielded work stations, syringe shields, shielded storage of
radionuclide source vials, shielded barriers between cameras, shielded receptacles
for radioactive waste, movable shields in therapy wards, etc. In addition to shielding
the individual sources, it may be necessary to incorporate some shielding into the
handling area walls, particularly if there is a high occupancy rate in adjacent
locations. Sometimes advantage can be taken of a fortuitous choice of building
material, such as concrete or brick, to provide shielding.
When considering the thickness of shielding required for particular
radionuclides, attention must be paid to the photon emissions of the highest energy
even if their abundance is low; the penetration of high-energy photons will be much
greater.
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RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 4. SAFETY OF SOURCES. DESIGN OF FACILITIES
5.
SECURITY OF SOURCES
The objective of source security is to ensure continuity in the control and
accountability of each source at all times.
The licensee shall maintain an inventory of sources received by the practice
and develop procedures to ensure the safe movement of radioactive sources within
the institution at all times from receipt to disposal.
The licensee shall establish security systems to prevent theft, loss,
unauthorized use, or damage to sources, or entrance of unauthorized personnel to
the controlled areas.
6.
REFERENCES
1. INTERNATIONAL ATOMIC ENERGY AGENCY. International Basic Safety
Standards for Protection Against Ionizing Radiation and for the Safety of
Radiation Sources. Safety Series No.115, IAEA, Vienna (1996).
2. INTERNATIONAL ATOMIC ENERGY AGENCY, Radiation Protection and the
Safety of Radiation Sources, Safety Series No. 120, IAEA, Vienna (1996).
3. INTERNATIONAL ATOMIC ENERGY AGENCY. Model Regulations on
Radiation Safety in Nuclear Medicine. (in preparation).
4. INTERNATIONAL ATOMIC ENERGY AGENCY, Building Competence in
Radiation Protection and Safe Use of Radiation Sources, Safety Standards
Series, IAEA, Vienna (in preparation)
5. WORLD HEALTH ORGANIZATION and INTERNATIONAL ATOMIC
ENERGY AGENCY. Manual on Radiation Protection in Hospital and General
Practice. Vol. 1. Basic requirements (in press)
6. WORLD HEALTH ORGANIZATION and INTERNATIONAL ATOMIC
ENERGY AGENCY. Manual on Radiation Protection in Hospital and General
Practice. Vol. 4. Nuclear medicine (in press)
7. WORLD HEALTH ORGANIZATION QA of pharmaceuticals: A compendium
of guidelines and related materials. Vol 2. Good manufacturing practice and
inspection (1999).
8. INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION
Protection of workers in medicine and denstistry, ICRP Publication 57.
Oxford, Pergamon Press, 1989 (Annals of the ICRP 20, 3).
9. EUROPEAN PHARMACOPOEIA, Third Edition, 1997, Council of Europe,
Strasbourg, 1996, as amended by the Supplement 2000, Council of Europe,
Strasbourg, (1999).
10. BRITISH PHARMACOPOEIA 2000, British Pharmacopoeia Commission, Her
Majesty's Stationery Office, London, (2000).
11. THE UNITED STATES PHARMACOPOEIA 2000, USP 24, The National
Formulary, NF 19, The United States Pharmacopoeial Convention Inc.,
Rockville MD, (1999).
12. ARCAL XV: Producción y Control de Radiofármacos. Manual de Protocolos
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RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 4. SAFETY OF SOURCES. DESIGN OF FACILITIES
de Calidad de Radiofármacos, ARCAL/OIEA, Vienna (1999).
13. SAHA GB, Fundamentals of Nuclear Pharmacy. 4th edition. Springer Verlag,
1998.
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