IAEA
RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 8. OPTIMIZATION OF MEDICAL EXPOSURE.
THERAPEUTIC PROCEDURES
1.
BASIC REQUIREMENTS
Radionuclide therapy is an important part of nuclear medicine. Like in all therapeutic
procedures there is always a risk to seriously harm the patient in case of a wrongly
performed treatment. It is, therefore, highly important that safety and quality is at the
highest level. A qualified staff that has the support from the hospital management
(the licensee) basically achieves this. All must know their responsibilities.
A decision on whether or not to administer radiation therapy must be taken by a
physician who has proper training and sufficient knowledge of radionuclide therapy
and of alternative therapeutic methods such as surgery, chemotherapy and hormonal
therapy. The physician should be aware of the relative risks and benefits of all
protocols and planned therapeutic methods.
The prescribed absorbed dose or the activity of the radiopharmaceutical should
be in accordance with recommendations from professional international or national
bodies.
A qualified medical physicist should be responsible for measurement of
radionuclide activity, identification of radionuclides and internal radiation dosimetry.
In addition to protection of the patient, there will also be considerations of radiation
protection of the staff, of the immediate family, of other patients and of members of
the public.
Optimization in general in radionuclide therapy should include issues such as:
 Safe handling of unsealed sources (ordering, receipt and unpacking, storage,
dispensing, internal transports, radioactive waste).
 Safe administration of therapy (patient identification, pregnancy, breastfeeding)
 Patient information
 Dose constraints to members of family and general public
 Care of the hospitalized patient (patient instructions, instructions to nursing staff
and visitors, discharge of patient, decommissioning of the ward)
 Emergency procedures
2.
ADMINISTRATION OF TREATMENT
Great care should always be taken to properly identify the patient prior to
administering any therapeutic amounts of radioactivity.
A checklist should be used for the verbal information given to the patient.
Important questions to female patients are about pregnancy and breastfeeding.
Other issues to discuss include incontinence, nausea, living conditions (small
children, pregnant partner etc), type of work and public transportation. The questions
should reveal any objections against the treatment and should also form the basis for
the restrictions in daily living when the patient is discharged from the hospital. Written
individual instructions should be given to the patient.
Certain radiopharmaceuticals can rapidly cross the placenta. It is therefore
necessary to exclude the possibility of pregnancy in a female patient before
therapeutic radionuclides are administered. As a rule a pregnant woman should not
be treated with a radioactive substance unless the therapy is life saving. In such an
event the potential absorbed dose to the foetus should be estimated (normally by the
radiation protection officer) and in serious cases (>100 mSv) consideration should be
given to terminating the pregnancy. In the rare event of administration to an
undeclared pregnancy similar steps would need to be taken.
Following treatment with a therapeutic radionuclide female patient should be
advised to avoid pregnancy for an appropriate period.
1
IAEA
RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 8. OPTIMIZATION OF MEDICAL EXPOSURE.
THERAPEUTIC PROCEDURES
The licensee shall ascertain whether the female patient is breast-feeding.
Cessation of breast-feeding is recommended after most types of radionuclide
therapy, especially thyroid treatments.
The activity to be administered shall be measured in a calibrated activity
meter. BSS states about calibration and clinical dosimetry the following:
The licensee shall ensure that (BSS II.19):
 the calibration of radionuclide activity calibrators and other equipment and
sources utilized for the practice of nuclear medicine is traceable to a standards
dosimetry laboratory;
 radionuclides for nuclear medicine procedures are calibrated in terms of activity
of the radiopharmaceutical to be administered;
 records of calibration measurements and associated calculations are maintained
in accordance with the requirements of the Regulatory Authority;
 the calibration of the instruments is maintained by a regular quality control
programme. The licensee should participate in a regular intercomparison
programme.
Licensees shall ensure that (BSS II.20):
 the activity to be administered is determined and recorded at the time of
administration;
 for diagnostic procedures, representative absorbed doses to the organs and the
effective dose to the patient are determined and documented for the amount of
activity normally administered according to their standard clinical protocol;
 for therapeutic procedures, absorbed doses to relevant organs are determined
and documented.
Be prepared for an emergency situation when the prescribed activity is
administered to the patient. This is most important in the case of iodine-131 for
thyroid treatments when the radiopharmaceutical is administered as a solution. In
this case the following rules can be applied:
 I-131 should be administered in a controlled area (hot lab or the patient’s hospital
bedroom).
 A plastic bag for contaminated items should be available as well as paper
tissues.
 The patient is asked to sit at a table covered with adsorbent pads and adsorbent
pads should also cover the floor beneath the patient.
 If the I-131 is administered in capsules they should be transferred to the patient
mouth by tipping from a small shielded (>1 cm Pb) container.
 I-131 administered in an oral solution (50 ml) should be sucked up through a
straw from the shielded vial by the patient. The vial should be flushed with water
several times. The patient should drink several glasses of water to clean the
mouth.
When administering the therapeutic radiopharmaceutical via intravenous, intraarterial or intra-articular routes, it is extremely important to confirm that the delivery
needle or catheter is properly placed in the patient prior to injecting the material.
.
3.
THE RADIOACTIVE PATIENT: DOSE CONSTRAINTS
After administration, the patient is a source of external exposure and contamination
and the question arises whether or not the patient can leave the hospital. If the
2
IAEA
RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 8. OPTIMIZATION OF MEDICAL EXPOSURE.
THERAPEUTIC PROCEDURES
patient is discharged from the hospital are there any restrictions regarding daily life
activities?
The BSS have given a guidance level of 1100 MBq iodine-131, meaning that
all patients who have received a higher activity shall be hospitalized.
The decision regarding restrictions should be based on the dose constraints
and dose limits given in the BSS:
Registrants and licensees shall constrain any dose to individuals incurred
knowingly while voluntarily helping (other than in their occupation) in the care,
support or comfort of patients undergoing medical diagnosis or treatment, and to
visitors to patients who have received therapeutic amounts of radionuclides or who
are being treated with brachytherapy sources, to a level not exceeding that specified
in Schedule II, para. II-9.
II-9.
The dose limits set out in this part shall not apply to comforters of patients,
i.e., to individuals knowingly exposed while voluntarily helping (other than in their
employment or occupation) in the care, support and comfort of patients undergoing
medical diagnosis or treatment, or to visitors of such patients. However, the dose of
any such comforter or visitor of patients shall be constrained so that it is unlikely that
his or her dose will exceed 5 mSv during the period of a patient's diagnostic
examination or treatment. The dose to children visiting patients who have ingested
radioactive materials should be similarly constrained to less than 1 mSv.
For members of the general public, which includes co-workers, the annual
dose limit is 1 mSv. This should be constrained to 0.3 mSv/procedure.
The risk posed to other people by discharging the patient from hospital will
depend on the personal circumstances of the patient as well as the type, quantity and
biokinetics of the radioactive substance administered. Together with proper
knowledge of the external radiation field and possible spread of contamination, the
dose to members of the family, co-workers and other members of the general public
can be estimated. Based on these estimations, the periods of restrictions, such as
close contact with members of the family, use of public transports etc, can be
established in order to control the external dose hazard in the majority of cases.
For a journey in private car (<6h, and with the patient sitting in rear of the
vehicle) and for public transportation (<1h) it is very unlikely that the driver and other
passengers receive doses that exceed 0.3 mSv.
Most patients leaving hospital after receiving treatment with radioactivity may
return to work the following day. Restrictions may be necessary if the patient is likely
to spend long periods of time less than 2 m from other workers, or their work involves
close contact with children and pregnant women.
Where it is necessary to restrict the extent of contact between the patient and
others, verbal and written instructions should be issued and explained to the patient.
It is a good practice to keep a patient at least 2h and preferably the whole day in
hospital after any radionuclide therapy.
4.
THE HOSPITALIZED PATIENT
Hospitalization of a patient receiving radionuclide therapy is generally only needed in
treatment of thyroid cancer with I-131. Occasionally other patients will stay in the
hospital due to medical reasons. In such cases the RPO should be consulted to give
advice regarding restrictions for visitors and instructions to the nursing staff.
A decision concerning the possible discharge of the patient should be based
on the results of a series of radiation surveys following the administration of the
therapy dose. This survey may be conducted by using a radiation survey meter to
measure the dose rate at 1 or 2 metres perpendicular to the patient's abdomen. The
dose rate observed immediately after the radiopharmaceutical is given represents
3
IAEA
RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 8. OPTIMIZATION OF MEDICAL EXPOSURE.
THERAPEUTIC PROCEDURES
100% of the activity. Subsequent measurements in the same geometry will give an
indication of the residual activity.
It is recommended that the hospital designate a particular ward and/or patient
bedroom(s) where the patient undergoing therapy with I-131will be housed. It will
then be much simpler to ensure that all special requirements, including staff training
and waste disposal are satisfactorily met. The patient should remain in the room
except for special medical or nursing purposes. Non-essential staff (e.g.
housekeeping, maintenance, and hospital volunteers) should be instructed not to
enter the room once therapy has begun.
It should be a private hospital room, with a private bathroom. Assigning two
131
I therapy patients together does not significantly alter the individual dose received
by the patient. However, when patients are together, the ambient dose rate in the
room is considerably higher, which poses problems for attendants trying to minimize
their exposure and may make it difficult for either patient to have visitors.
The room should be a controlled area and can be categorized as a high
hazard environment. It then should fulfil the general requirements regarding flooring,
surfaces etc. for such areas. All utensils in the room should be easy to
decontaminate. Containers for collection of radioactive waste should be available as
well as a movable lead shield and equipment for decontamination. A radiation
warning sign must be posted outside the patient's room together with any specific
restrictions relating to visitors and non-essential personnel.
Verbal and written information should be given to the patient. It should contain
instructions such as:







Stay in the room.
Drink as much as possible.
Eat lemon slices.
Use only the private toilet and flush 3 times. (Men should sit down to avoid
splashing.)
Wash hands well in soapy water after using toilet.
Wear footwear when leaving the bed.
In event of vomiting or incontinence notify the nurse immediately.
During the first 48 hours after administration of a therapeutic dose of a
radionuclide, nursing should be reduced to the basic minimum. The amount of time
spent by the nursing staff in the presence of the patient should be limited in such a
way as to minimize the irradiation to which they are subjected and to ensure that the
doses received remains within the dose limits. Protective clothing should be worn.
Local rules should be available. The nursing staff should also be trained to handle
emergency situations.
The following precautions are recommended for visits to hospitalized patients:
 visitors are discouraged, particularly within the first 48 hours after treatment;
 women who are pregnant and children under 18 years are not allowed to visit;
 visitors should limit themselves to less than 30 minutes per day and should stay
at least 2 metres from the patient;
 there should be no hugging or kissing between patients and visitors;
 visitors are not to eat, drink or smoke in the patient's room;
 visitors are not to use the patient's washroom.
A Visitors Instruction Card containing these restrictions should be affixed to the
outside of the entrance door.
4
IAEA
RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 8. OPTIMIZATION OF MEDICAL EXPOSURE.
THERAPEUTIC PROCEDURES
For iodine -131 patients, immediately after the radiopharmaceutical has been
administered, the following information should be recorded:
 activity (MBq) given;
 date administered;
 estimated date of discharge;
 results of radiation surveys;
 emergency telephone numbers including those of the attending physician, the
radiation protection officer and their respective designates.
Because of variable excretion rates, radiological surveys of in-patients should be
repeated daily after treatment and prior to patient discharge, until radiation levels are
deemed low enough by the RPO or designate for the patient to be released from
hospital. The RPO should also supervise the removal of contaminated waste, the
decontamination of the room and equipment and should make a final survey of the
room.
Monitoring and decontamination must be done prior to entry of nursing and
housekeeping staff to prepare the room for the next patient. When survey and
decontamination procedures are complete, the RPO will remove the radiation
warning sign and notify the nursing and housekeeping staff that the room is now
clear for general use.
5.
EMERGENCY PROCEDURES
Medical emergency
In the event of a medical emergency, medical personnel should proceed with
emergency care while attempting to take precautions against the spread of
contamination. Direct contact with the patient's mouth should be avoided. All
members of the emergency team should wear impermeable protective gloves.
Radiation protection considerations should not prevent or delay life-saving operations
in the event emergency surgery on the patient is required.
Individual radiation doses to surgical staff should be monitored by the RPO or
designate. At the end of the procedure appropriate contamination monitoring of
personnel, the operating theatre and instruments and materials (e.g. dressings,
drapes, apparatus, etc.) should be performed and these should be decontaminated
as required.
Death of a radionuclide therapy patient
Occasionally the condition of a patient treated with radionuclides may lead to death
while the body still contains substantial residual activity. The rules and regulations
governing the embalming, burial, or autopsy of cadavers containing substantial
residual activities vary from country to country since they take account of various
social, climatic, and religious factors.
The nuclear medicine department should be consulted immediately to the
amount of residual radioactivity in a cadaver. If there is still significant residual
radioactivity, the physician who declares the patient dead should attach a label to the
body indicating the presence and amount of radioactivity and the radionuclide. The
label should be readily recognizable, legible, and easy to understand. The
precautions to be taken in handling such cadavers depend on the nature and quantity
of the radionuclide present and on the type of handling intended (e.g., autopsy or
merely simple treatments prior to burial). As a general rule it can be said that no
appreciable hazard exists unless the body is opened, when the hands and face of the
5
IAEA
RADIATION PROTECTION IN NUCLEAR MEDICINE
PART 8. OPTIMIZATION OF MEDICAL EXPOSURE.
THERAPEUTIC PROCEDURES
pathologist could receive high radiation doses, depending on the duration of
exposure and the dose rate.
Storage of the cadaver is generally to be avoided for ethical and practical
reasons; however, it may be a useful technique to use if there is a significant amount
of activity in the cadaver, and if the radionuclide is of sufficiently short half-life that a
reasonable storage time would reduce the activity levels to below those specified by
the Regulatory Authority.
The autopsy of highly radioactive cadavers should be invariably restricted to
the absolute minimum. It is essential that the staff should wear disposable gloves,
and supplementary measures for radiation protection and decontamination should be
provided in consultation with the radiation protection officer.
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.
WORLD HEALTH ORGANIZATION and INTERNATIONAL ATOMIC
ENERGY AGENCY. Manual on Radiation Protection in Hospital and General
Practice. Vol. 4. Nuclear medicine (in press)
3.
EUROPEAN COMMISSION. Radiation protection following iodine-131
therapy (Exposure due to outpatients or discharged inpatients). Radiation
Protection 97, EC, Bruxelles (1998).
4.
U.K. DEPARTMENT OF HEALTH , London, 1994, Administration of
Radioactive Substances Advisory Committee Notes for Guidance (ARSAC).
5.
O'DOHERTY M.J. et al. Radiation dose rates from adult patients receiving 131I
therapy for thyrotoxicosis. Nuclear Medicine Communications 1993, 14: 160168.
6.
SHIELDS RA.for the Radiation Protection Committee of the British Institute of
Radiology. "The Guidance Notes Revisited: Advice to patients leaving
hospital after diagnostic nuclear medicine." (editorial). British Journal of
Radiology, 1991, 64: 567-568.
6