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

results documented (38). For HDR and PDR units, these wipe tests are obviously performed on the afterloading drive assembly and not the high activity sources. The hot lab is of course a controlled area (24, 38). It should be locked at all times and a latch to automatically lock the door is recommended (36). An area radiation monitor should be visi- ble on entering the room, and while manipulating the sources radiation protection measures and their effectiveness should be periodically reevaluated and periodic area surveys should be performed around the room (12, 38). The hot lab, and treat- ment, treatment planning, operating and patient rooms must be located as close as possible to each other to reduce distances over which patients and sources have to be transported, particularly avoiding the use of elevators (12). Source transport should be made using a mobile, shielded con- tainer which reduces exposure to less than 2 mSvh -1 in contact and 1 mSvh -1 at 1 m (41) or as required by national regulations. The transport container should be clearly marked for its radio- active content, never left unattended, and surveyed both before and after brachytherapy procedures. The movement of sourc- es should be entered in a source movement log with a signed record of the date of removal from the safe, patient name and the return of the source (38). Besides access restriction, source registry and periodic inventories, additional measures for source control might be in order according to the specific applications. For example, HDR brachytherapy patients should be surveyed to ensure source return to its safe, all linen, dressing, clothing, equipment and refuse collectors should not be removed from the brachytherapy patient room until they are checked for stray sources and results are documented, and a filter should be used wherever there is a risk of loss of a source through a drain (i.e applicator cleaning, LDR seed dislodging from the prostate). Old sources (‘orphan’ sources), such as unused 125 I seeds or de- cayed 192 Ir wires, can be stored in the storage room before dispos- al according to national and international regulations. Among other aspects of setting up a brachytherapy program, a radiation protection program must be established to ensure compliance with regulations for radiation safety and protection produced by government agencies (9, 12). The radiation pro- tection program should be designed and developed to ensure the doses to medical staff and the general public are as low as is reasonably achievable (see Introduction). A qualified radia- tion safety officer, who is responsible for implementing the ra- diation protection program, should be identified and officially appointed. The radiation safety officer should be given sufficient administrative authority, in writing, to supervise the program. A radiation safety committee should also be established if the institution plans to start a brachytherapy program that involves multiple types of procedures and multiple types of radioactive sources. The committee should include an authorized user of each type of use permitted by the license, the radiation safety officer, a representative of the nursing service, and a representa- tive of management. The committee may include other members whom the licensee considers appropriate. 7. ORGANIZATIONAL ISSUES

Fig. 3.6 Example of the shielding on a preparation table in the storage room of a brachytherapy department. (Courtesy: J. Venselaar)

mum exposure rate of less than 1 μSvh -1 at 10 cm distance from the container surface and most commercially available equip- ment ensures a surface dose rate of about 25 μSvh -1 (41). Their functionality and their place in the room should ensure that oc- cupational doses are maintained as low as reasonably achievable. For example, a safe for a particular source type should be close to the area reserved for the manipulation of the sources for prepa- ration or quality control purposes, and a diagram on the source safe showing the exact location of each source within it helps to reduce the time to locate and identify a source (38). Source manipulation, for any purpose, should be made using forceps or tongs and never directly by hand (38). The use of lead gloves or other protective garments serves little to reduce expo- sure from high energy sources and might unnecessarily prolong the manipulation time (41). However, personnel shielding such as a lead “L-block” or a structure made from interlocking lead blocks must be provided, including a leaded window of sufficient thickness (36) or at least a mirror system. See the example in Fig. 3.6. A magnifying viewer might be required in the shielded preparation area since sources for manual brachytherapy must be inspected visually for damage after each use, especially if they are subject to possible damage from heat, abrasion, chemical attack and mechanical stress for cleaning and sterilization pur- poses (38). In general, sources should never be left on prepara- tion surfaces and the work surface should be easily cleaned and brightly lit to facilitate finding dropped sources (12, 38). Espe- cially for 192 Ir wires, equipment for cutting and handling should be properly decontaminated and any radioactive waste collected and stored (12, 38). Wipe tests for source leakage and prepara- tion area contamination need to be periodically performed and