3 Radiation Protection in Brachytherapy

Radiation Protection in Brachytherapy

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THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part I: The basics of Brachytherapy Version 1 - 01/12/2014

6. SOURCE STORAGE AND TRANSPORTATION

going brachytherapy treatment and labels with radiation signs should be attached to the patient. Radiation emergency equip- ment should be placed in the room in case of unexpected events. After the completion of treatment, additional radiation surveys should be conducted for patient, equipment, and room. Related radiation signs should be then removed from the room and pa- tient. For temporary implants, the removed sources should be counted, logged, and returned to storage in the hot lab. For per- manent implants, patients should be surveyed before release to ensure the implanted radioactive sources do not pose potential radiation risks to the general public. The criteria for the patient release are that -based on the patient radiation survey- the expo- sure to the public from the implanted radioactive source should not exceed the corresponding annual limit. Radiation safety instructions should be provided to the patients, including spe- cial instructions to protect pregnant women and children from being exposed to excessive radiation levels. The patients should be advised to minimize contacts with pregnant women and chil- dren. The patients should also be provided contact information so that radiation related questions can be answered after their discharge from hospital. These may concern, for example, fur- ther post-implantation surgery (TURP), autopsy or cremation. More information can be found in ICRP and NCRP documents (23, 36). Some practical data on radiation exposures to family and household members after prostate brachytherapy can be found in Michalski et al . (28) who used radiation monitors to measure dose values with mean lifetime doses to a spouse from her husband of 0.1 mSv for 29 125 I patients and 0.02 mSv for 15 103 Pd patients. Cattani et al . (2) recorded a mean dose rate after implants of 6.4 µSv/h at 0.5m distance for 200 125 I cases and 1.7 µSv/h for 16 103 Pd cases. From such data it can be estimated that the realistic lifetime exposures are well below the limits. 5.2 HDR brachytherapy The HDR, and similarly the PDR, source is periodically replaced. The frequency of replacement is based on the source half-life. For an HDR 192 Ir source type with a half-life of 74 days the inter- val between source changes is usually 3 or 4 months. Wipe tests should be performed for both new and old sources during the re- placement. Source strength should be independently measured during the source replacement and periodically thereafter. Since most HDR procedures are delivered with computerized systems, accuracy of source strength decay should be manually checked and confirmed before each treatment. Emergency procedure instructions should be posted in the con- trol area. Radiation monitors and safety interlocks and interrup- tion buttons should be checked before each treatment. Patients should be surveyed prior to treatment to establish a radiation baseline. Radiation emergency safety equipment should be read- ily available before the start of treatment and throughout the treatment procedure. The patient and the treatment procedure should be closely and continuously monitored via video mon- itors and audio communication devices. After the treatment is completed, patient and equipment should be surveyed to ensure that the HDR radioactive source has returned to the HDR unit safe. More information can be found in IAEA publications (9, 12).

Sources are delivered to the brachytherapy department in spe- cially designed containers that are clearly marked (isotope, activ- ity, transport index) and accompanied by appropriate shipping documents, all subject to international regulations for their safe transport (13). Beginning with the acceptance of the sources by authorized personnel, specific measures must be taken to ensure both optimal radiation protection and source security. For ra- diation protection, these measures consist of facility design el- ements, the configuration of specific procedures, and the use of appropriate instrumentation, all based on the three basic rules for radiation protection in practice (exposure time reduction, in- crease of distance from a source, use of shielding). Source securi- ty is ensured by exercising continuous accountability and control of the sources through appropriate procedures for the safe ex- change and movement of radioactive sources within the institu- tion and controls to prevent theft, loss, unauthorized withdrawal or damage of sources, or entrance of unauthorized personnel to controlled areas (38). Source exchange should be performed by well trained staff only, often by the service engineer of the com- pany and a radiation safety officer of the hospital. Written proce- dures should be available. HDR brachytherapy procedures using remote afterloaders do not require source preparation. The source is safely stored in the afterloader when not used for treatment since most afterloaders are certified as transportable radioactive containers (9). In terms of source security, the afterloader is usually kept in the treatment room which is a controlled area and consequently access is re- stricted. See also the last paragraph of section 7. A cutting device, a set of long forceps or tongs, and an emergen- cy source container (sufficiently large to accept the entire appli- cator assembly containing the source) must be available in the treatment room in case of source retraction failure during use. A dedicated storage room might still be required if unused sources are temporarily kept in the department to decay to safe levels. This room is also a controlled area subject to all requirements for appropriate labeling, access restriction, radiological surveil- lance and the establishment of written procedures and working instructions (24, 38). A dedicated source preparation and storage room (commonly called a “hot” lab) is an essential prerequisite for LDR and man- ual brachytherapy. The hot lab must include: an area where all LDR sealed sources can be safely stored in an orderly fashion, space and facilities for receiving and returning sources, source inventory, source calibration and quality control, space and equipment for source preparation for treatments, adequate space for QA and treatment aids and, if necessary, for storage of short- lived sources or temporary storage of unused long-lived sources (36). A work area should also be available, in or near the hot lab, where records can be prepared and stored without danger of radioactive contamination (36). Following their acceptance, sources and source containers should be marked using a unique identification scheme, entered in the department’s source register (listing the id, location, activity of all sources, as well as dates and results of checks and periodic inven- tories) and put in a storage safe (38). Different safes are used for different source types. These must be fire resistant, equipped with a lock and shielded. Regulations will generally require a maxi-