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RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 5. OCCUPATIONAL PROTECTION
1.
RESPONSIBILITIES AND CONDITIONS OF SERVICE
The optimization of staff protection requires commitment by the management of the
nuclear medicine facility. The protection of occupationally exposed individuals
working in hospitals requires a rigorous organizational framework and a structured
approach. This should be reflected in the Local Rules for each workplace, which
must define safe systems of work.
A structured approach requires a prior evaluation of all aspects of a practice
with implications for radiation protection. This is in turn used to form the basis of an
operational radiological protection programme. Successful implementation requires
management commitment with a clear identification of responsibilities to establish
objectives, authority to utilize resources and accountability of performance.
Responsibility in radiation protection affects all members of the administrative system
from the employing authority to the individual carrying out a nuclear medicine
procedure.
According to the Standards:
“The occupational exposure of any worker shall be so controlled that the following
limits are not exceeded:
(a) an effective dose of 20 mSv per year averaged over five consecutive years;
(b) an effective dose of 50 mSv in any single year;
( c) an effective dose to the lens of the eye of 150 mSv in a year; and
(d) an equivalent dose to the extremities (hands and feet) or the skin of 500 mSv in a
year.”
According to the Basic Safety Standards: “A female worker should, on
becoming aware that she is pregnant, notify the employer in order that her working
conditions may be modified if necessary. The notification of pregnancy shall not be
considered a reason to exclude a female worker from work; however, the employer
of a female worker who has been notified of the pregnancy shall adapt the working
conditions in respect of occupational exposure so as to ensure that the embryo or
foetus is afforded the same broad level of protection as required for members of the
public.” This means that the dose to the embryo or foetus should not normally
exceed 1mSv.
The possibility of a dose approaching 1 mSv to the embryo or foetus should
be assessed once pregnancy has been declared. The departmental manager, in
conjunction with the radiation protection officer, should also decide whether it is
appropriate to reallocate staff duties, or to apply extra protective measures.
As radiation dose levels to staff are low, it is not usually necessary to apply
extra protective measures (though the latter may be desirable for various
psychological reasons). Nevertheless many departmental managers would accept
requests from women to be reassigned to other duties for medico-legal reasons.
However, pregnant women should be removed from nursing teams
responsible for patients who have been treated with radionuclides and from the
laboratories where large quantities of nuclides are prepared and administered. These
staff members could receive a dose to the embryo or foetus comparable with the
dose limit over the period of the pregnancy.
According to the Basic Safety Standards : “No person under the age of 16
years shall be subjected to occupational exposure”, and “No person under the age of
18 years shall be allowed to work in a controlled area unless supervised and then
only for the purposes of training”.
Furthermore according to the Standards: “For apprentices of 16 to 18 years of
age who are training for employment involving exposure to radiation and for students
of age 16 to 18 who are required to use sources in the course of their studies, the
occupational exposure shall be controlled so that the following limits are not
exceeded:
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PART 5. OCCUPATIONAL PROTECTION
(a) an effective dose of 6 mSv in a year;
(b) an equivalent dose to the lens of the eye of 50 mSv in a year; and
(c) an equivalent dose to the extremities or the skin of 150 mSv in a year.”
When working in a nuclear medicine facility students and trainees should
always be accompanied by an authorized teacher.
2.
CLASSIFICATION OF AREAS
Areas in a nuclear medicine department are generally classified as controlled or
supervised (BSS I.21–25). The rooms for preparation, storage and injection of the
radiopharmaceuticals shall be controlled areas. Due to the potential risk of
contamination, the imaging rooms and waiting areas should also be controlled areas.
The area housing a patient to whom therapeutic amounts of activity have
been given shall also be a controlled area. In the case of pure beta emitters such as
Y-90, Sr-89 or P-32, which are not excreted from the body, the area may not need to
be classified as a controlled area.
The room for temporary storage of radioactive waste shall be a controlled
area.
It might be convenient to classify the whole nuclear department as a
supervised area mainly due to the risk of contamination.
Each room of the facility should only be used for its specified work.
On the basis of a safety assessment including the planned use of each area,
an evaluation of shielding and the potential for contamination, the licensee should
determine whether an area where unsealed sources are handled or stored will be
maintained as a controlled, supervised or uncontrolled area. The licensee should
also assess which other areas (e.g. other patient rooms, stairwells, nursing stations,
waiting areas, toilets) should be controlled, supervised or uncontrolled areas. The
radiation dose-rate levels associated with these areas must be in compliance with the
dose limits established by the Regulatory Authority.
3.
SOURCES OF EXPOSURE
Exposure of the worker may arise from unsealed sources either through external
irradiation of the body or through entry of radioactive substances into the body. The
main precautions required in dealing with external irradiation depend on the physical
characteristics of the emitted radiation, the activity and the half-life of the
radionuclide. When a radionuclide enters the body, the internal exposure will depend
on factors such as the physical and chemical properties of the radionuclide, the
activity and the biokinetics.
Every type of work performed in a nuclear medicine department will make a
contribution to the external exposure of the worker: unpacking radioactive material,
activity measurements, storage of sources, preparation of radiopharmaceuticals,
administration of radiopharmaceuticals, patient examination, care of the radioactive
patient and handling of radioactive waste. The highest doses will generally be
received during the patient examination.
Higher risk of internal exposure due to contamination is associated with
radioactive spills, animal experiments, emergency surgery of a therapy patient, and
autopsy of a therapy patient.
4.
PERSONAL PROTECTIVE EQUIPMENT AND SAFE HANDLING OF
SOURCES
Protective clothing should always be used in working areas where there is a
likelihood of contamination. It may include laboratory coats or protective gowns;
waterproof gloves of high quality; overshoes and, if required by the National
Authorities, special clothing for aseptic work.
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Laboratories used for work with unsealed sources should be provided with
equipment to minimize the external exposure of the worker and to deal with
radioactive spill. This equipment may need to include:
 Tools for remote handling of sources (forceps, tongs)
 Shielded containers for the radionuclides in use
 Syringe shields
 Lead barrier with lead glass window
 Area monitor with alarm
 Contamination monitor
 Carrying containers for moving radionuclides
 Equipment and materials to deal with spills (emergency kit)
Movable shields or the use of a lead apron should be considered during
patient examinations and in the care of patients undergoing therapy with unsealed
sources.
Working procedures should be designed to prevent contamination and spread
of contamination from the working areas. This will normally be achieved by a proper
use of the personal protective equipment, by adopting clean operating conditions and
good laboratory practice.
The worker should be trained to deal with radioactive spills and
decontamination procedures (surfaces, equipment, persons).
5.
MONITORING
Individual dose monitoring shall be undertaken for workers who are normally
exposed to radiation in controlled areas (BSS I.32–36).
These workers include nuclear medicine physicians, nuclear medicine
physicists, nuclear medicine technologists, nuclear medicine nurses and
radiopharmacists. Other users of radioisotope sources, such as clinical specialists,
research staff and ancillary workers who frequently work in controlled areas, should
also be individually monitored.
Individual external doses shall be determined by using individual monitoring
devices approved by the Regulatory Authority, such as thermoluminescent
dosimeters, film badges or other devices.
The individual monitoring device should be typically worn on the front of the
upper torso because, in nuclear medicine, the whole body is assumed to be fairly
uniformly exposed. When there is a possibility of high exposure to the hands, such
as in the preparation and administration of radiopharmaceuticals, extremity
dosimeters should be worn (if compatible with good clinical practice). The exchange
of dosimeters and receipt of the dose reports shall be for the period specified by the
Regulatory Authority.
Because evaluation of dosage is an essential part of the radiation protection
programme, it is important that workers return dosimeters on time for processing.
Delays in the evaluation of a dosimeter can result in the loss of the stored
information. Licensees should make every effort to recover any missing dosimeters.
If an individual’s dosimeter is lost, the RPO should perform and document an
evaluation of the dose the individual received and add it to the worker’s dose record.
This can be done using the workers recent dose-history, doses of co-worker or the
results of workplace monitoring.
In nuclear medicine, the exposure due to internal contamination shall be
monitored. It should be done by external monitoring of the thyroid for individuals
handling large activities of radioiodine. Note that a gamma camera with no collimator
mounted can be used as a whole body counter.
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A female worker should notify the licensee if she is pregnant as soon as she
knows of her condition, and also if she is breast feeding a baby, so that radiation
protection requirements for the foetus and baby can be met.
Licensees shall also develop programmes for monitoring the workplace
including both contamination monitoring and dose rate monitoring. Proper equipment
shall be available and calibrated. The calibration shall be traceable to a standards
dosimetry laboratory. Periodic monitoring shall be conducted for controlled and
supervised areas. Continuous monitoring with an area monitor should be considered
for source storage and handling areas.
Investigation levels shall be used and a formal investigation shall be
conducted whenever a worker receives an effective dose that exceeds any of the
levels. A report shall be submitted to the Regulatory Authority and other concerned
bodies as required, as soon as possible after the investigation
6.
EMERGENCY PROCEDURES
On the basis of events identified by a safety assessment, the licensee shall prepare
emergency procedures (BSS V.2–6). Such events include loss of shipment of
sources, damage to sources (e.g. Tc-generator), radioactive spills and medical
emergencies.
The procedures should be clear, concise and unambiguous and shall be
posted visibly in places where their need is anticipated. An emergency plan shall, as
a minimum, list/describe:
 predictable incidents and accidents and measures to deal with them;
 the persons responsible for taking actions, with full contact details;
 the responsibilities of individual personnel in emergency procedures (nuclear
medicine physicians, medical physicists, nuclear medicine technologists,
etc.);
 equipment and tools necessary to carry out the emergency procedures;
 training and periodic rehearsal;
 recording and reporting system;
 immediate measures to avoid unnecessary radiation doses to patients, staff
and public;
 measures to prevent access of persons to the affected area; and
 measures to prevent spread of contamination.
7.
LOCAL RULES AND SUPERVISION
Employers, registrants and licensees shall, in consultation with workers, through their
representatives, if appropriate (BSS I.26):
 establish written local rules and procedures necessary to ensure adequate
levels of protection and safety for workers and other persons;
 include in the local rules and procedures the values of any relevant
investigation level or authorized level, and the procedure to be followed in the
event that any such value is exceeded;
 make the local rules and procedures, the protective measures and safety
provisions known to those workers to whom they apply and to other persons
who may be affected by them
 ensure that any work involving occupational exposure be adequately
supervised and take all reasonable steps to ensure that the rules, procedures,
protective measures and safety provisions be observed.
These local rules should include: procedures for wearing, handling, and storing
personal dosimeters; actions to minimize radiation exposure during unusual events
(e.g. accidental contamination); means and methods for decontamination of persons,
equipment and surfaces; limitations on activities that are permitted in source storage
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PART 5. OCCUPATIONAL PROTECTION
and handling areas (e.g. no eating, drinking, or smoking); and procedures for the
control of sources (e.g. prompt removal of sources from transport containers),
checking the integrity of containers, checking the correctness of labels and checking
for contamination.
The work should be planned and performed in a way that minimizes the
spread of contamination in air and on surfaces. Work with unsealed sources should
be restricted to a minimum number of locations.
8.
HEALTH SURVEILLANCE
The licensee shall make arrangements to provide medical surveillance (medical
examinations) to workers as specified by the Regulatory Authority or other local
requirements. The primary purpose of medical surveillance is to assess the initial
and continuing fitness of employees for their intended tasks. Counselling should be
provided for women who are or may be pregnant (BSS I.41).
The routine medical supervision of the worker should be similar to that in
good industrial medicine. The medical examination should include the normal
examinations and tests to ascertain the health status of the individual. The skin
(particularly of the hands) must be examined for conditions such as eczema and
wounds, which may temporarily contraindicate work with unsealed sources, since a
person with such lesions could not be easily decontaminated. The hands are
especially vulnerable in this respect.
9.
RECORDS
The licensee shall maintain exposure and medical surveillance records for each
worker and the records shall be kept according to the requirements of the Regulatory
Authority.
Other records to kept and connected to occupational exposure include:
 Results of area surveys;
 Inventory of unsealed and sealed sources;
 Incident and accident investigation reports;
 Audits and reviews of the radiation safety programme;
 Installation, maintenance and repair work;
 Facility modification;
 Waste disposal;
 Training provided (initial and continuing), including the following information:
Name of the person(s) who delivered the instruction or training;
Name of the person(s) who received the instruction or training;
Date and duration of the instruction or training;
List of the topics addressed; and
Copy of the certificates of training.
10.
REFERENCES
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INTERNATIONAL ATOMIC ENERGY AGENCY. Occupational Radiation
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PART 5. OCCUPATIONAL PROTECTION
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COMMISSION
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RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 5. OCCUPATIONAL PROTECTION
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