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08. Optimization of medical exposure: Therapy (64 KB)






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    08. Optimization of medical exposure: Therapy (64 KB) 08. Optimization of medical exposure: Therapy (64 KB) Document Transcript

    • 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. 1
    • IAEA RADIATION PROTECTION IN NUCLEAR MEDICINE PART 8. OPTIMIZATION OF MEDICAL EXPOSURE. THERAPEUTIC PROCEDURES Following treatment with a therapeutic radionuclide female patient should be advised to avoid pregnancy for an appropriate period. 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, intra- arterial 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 2
    • IAEA RADIATION PROTECTION IN NUCLEAR MEDICINE PART 8. OPTIMIZATION OF MEDICAL EXPOSURE. THERAPEUTIC PROCEDURES 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 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 3
    • IAEA RADIATION PROTECTION IN NUCLEAR MEDICINE PART 8. OPTIMIZATION OF MEDICAL EXPOSURE. THERAPEUTIC PROCEDURES 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 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. 4
    • IAEA RADIATION PROTECTION IN NUCLEAR MEDICINE PART 8. OPTIMIZATION OF MEDICAL EXPOSURE. THERAPEUTIC PROCEDURES A Visitors Instruction Card containing these restrictions should be affixed to the outside of the entrance door. 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 5
    • IAEA RADIATION PROTECTION IN NUCLEAR MEDICINE PART 8. OPTIMIZATION OF MEDICAL EXPOSURE. THERAPEUTIC PROCEDURES 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 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 131 I therapy for thyrotoxicosis. Nuclear Medicine Communications 1993, 14: 160-168. 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