ASN Report 2017

275 ASN report on the state of nuclear safety and radiation protection in France in 2017 Chapter 09  - Medical uses of ionising radiation 3.3.2 Pulsed Dose-Rate (PDR) brachytherapy ཛྷ ཛྷ delivering dose-rates of between 2 and 12 Gy/h; ཛྷ ཛྷ using sources of iridium-192 displaying a maximum activity of 18.5 GBq and applied using a specific afterloader. This technique requires patient hospitalisation for several days in a room with radiological protection appropriate for the maximum activity of the radioactive source used. It is based on the use of a single radioactive source which moves in steps, and stops in predetermined positions for predetermined times. The doses are delivered in sequences of 5 to 20 minutes, sometimes even 50 minutes, every hour for the duration of the planned treatment, hence the name pulsed dose-rate brachytherapy. Pulsed dose-rate brachytherapy offers a number of radiation protection advantages: ཛྷ ཛྷ no handling of sources; ཛྷ ཛྷ no continuous irradiation, which enables the patient to receive medical care without irradiating the staff or having to interrupt the treatment. However, it is necessary to make provisions for accident situations related to the operation of the source afterloader and to the high dose-rate delivered by the sources used. 3.3.3 High Dose-Rate (HDR) brachytherapy ཛྷ ཛྷ delivering dose-rates in excess of 12 Gy/h; ཛྷ ཛྷ using sources of iridium-192 displaying a maximum activity of 370 GBq and implemented with a specific afterloader (some afterloaders use a high-activity cobalt-60 source [91 GBq]). This technique does not require the patient to be hospitalised in a room with radiological protection; it is performed on an out-patient basis in a room with a configuration comparable to that of an external-beam radiotherapy room. The treatment is performed with an afterloader containing the source and involves one or more sessions lasting a few minutes, spread over several days. High dose-rate brachytherapy is used mainly for gynaecological cancers. This technique can also be used to treat prostate cancers, and can be combined with an external beam radiotherapy treatment. 3.4. Technical rules applicable to facilities 3.4.1 Technical rules applicable to external-beam radiotherapy installations The devices must be installed in rooms specially designed to guarantee radiation protection of the staff, turning them into veritable bunkers (wall thickness can vary from 1 m to 2.5 m of ordinary concrete). A radiotherapy installation comprises a treatment room including a technical area containing the treatment device, a control station outside the room and, for some accelerators, auxiliary technical premises. The protection of the premises, in particular the treatment room, must be determined in order to respect the annual exposure limits for the workers and/or the public around the premises. A specific study must be carried out for each installation by the machine supplier, together with the medical physicist and the Radiation Protection Expert-Officer (RPE-O) 7 . This study defines the thicknesses and nature of the various protections required, which are determined according to the conditions of use of the device, the characteristics of the radiation beam and the use of the adjacent rooms, including those vertically above and below the treatment room. This study should be included in the file presented to support the application for a license to use a radiotherapy installation, examined by ASN. In addition, a set of safety systems informs the operator of the machine operating status (exposure in progress or not) and switches off the beam in an emergency or if the door to the irradiation room is opened. 3.4.2 Technical rules applicable to brachytherapy installations The rules for radioactive source management in brachytherapy are comparable to those defined for all sealed sources, regardless of their use. Low Dose-Rate brachytherapy In cases where permanent implant techniques are used (seeds of iodine-125 in particular for treating prostate cancer), the applications are carried out in the operating theatre with ultrasonography monitoring, and do not require hospitalisation in a room with radiation protection. Pulsed Dose-Rate brachytherapy This technique uses source afterloaders (generally 18.5 GBq of iridium-192). The treatment takes place in hospital rooms with radiological protection appropriate for the maximum activity of the radioactive source used. High Dose-Rate brachytherapy As the maximum activity used is high (370 GBq of iridium-192 or 91 GBq of cobalt-60), irradiation can only be carried out in a room with a configuration comparable to that of an external beam radiotherapy room. 7 . In France, the Radiation Protection Expert-Officer (RPE-O) [formerly referred to in ASN documents as the PCR (Person Competent in Radiation protection), reflecting the French term and acronym “ Personne compétente en radioprotection (PCR)” ], is appointed by the employer of persons exposed to ionising radiation in the course of their work. Under the responsibility of the employer, the RPE-O participates in preparing the notification or licensing file and assessing the nature and extent of the risks to which the workers are exposed and in organising radiation protection. The RPE-O carries out internal radiation protection controls and keeps track of third-party radiation protection controls carried out by approved organisations. The RPE-O monitors worker radiation protection. Lastly, the RPE-O is involved in defining and implementing worker safety training for aspects concerning radiation protection and participates in the management of cases where worker exposure limit values are exceeded. These duties correspond to those of both Radiation Protection Expert (RPE) and Radiation Protection Officer (RPO), hence the adoption of the umbrella term Radiation Protection Expert-Officer (RPE-O).

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