5.14.
A typical radiation therapy facility consists of six main functional areas: reception area, clinical consulting areas, and areas for external beam radiation therapy, brachytherapy, imaging and treatment planning. Within these areas there are several types of room and, depending on the treatment modalities being provided, the facility may include rooms or areas for patient imaging, treatment simulation, treatment planning, treatment control, treatment delivery, mould preparation and patient examination, as well as patient changing cubicles, public waiting rooms, operating theatres, and source storage and preparation rooms. Provision for the incorporation of radiation protection and safety features into these areas and rooms should be made at the facility design stage. Because the structural shielding of radiotherapy facilities is very heavy, care should be taken that the weight of the shielding can be supported by the building structure, especially in cases when machines are replaced by higher energy ones, such as is the case of a 60Co unit being replaced by a linac. The layout should take into account workload and staff and patient flow, both within the radiation therapy facility and, in cases where the radiation therapy facility is part of a larger hospital or medical centre, within other departments of the facility. Wherever possible, treatment rooms should be surrounded with rooms that have low or controlled occupancy. Physical signage should give information on where different areas are located and should designate hazardous areas; such signs should be preferably in both word and picture format. Colour coding of different areas is also very helpful. General guidance on the design of a radiation therapy facility is given in Refs [281–284].
5.15.
The three factors relevant to dose reduction for workers and the public (time, distance and shielding) should be combined in the design to optimize occupational exposure and public exposure.
5.16.
Access to the radiation therapy facility and its treatment, imaging, consultation and patient preparation rooms should be considered. This includes provision for the delivery of equipment and for ease of access for patients undergoing clinical assessment and daily treatment. Patients may arrive in wheelchairs or on trolleys or beds.
5.17.
As a general rule, the design of the radiation therapy facility should make provision for safety systems or devices associated with the equipment and rooms. This includes ventilation systems, electrical wiring relating to emergency off switches, and standby lighting, safety interlocks and warning signs and signals.
5.18.
A reliable and stable power supply should be available for all modern equipment and IT systems. An emergency diesel power generator alone is generally not sufficiently stable to power a linac or orthovoltage unit and should not be used in this way. An uninterruptible power supply or battery backup systems should be installed to capture the active information at the time of the outage and to shut down all software in a controlled manner. Servers should be programmed to shut down automatically when the power supply is interrupted. Diesel power generators could be used to run systems that are controlled only by timers, such as in the case of 60Co teletherapy units.
5.19.
The design of the facility should include an air conditioning system sufficient to maintain the temperature and humidity in the treatment room within the parameters defined by the equipment manufacturers. In addition, a ventilation system with four to six air changes per hour is recommended to remove any ozone generated [285].
5.20.
For external beam radiation therapy, lights in the treatment room should be dimmable so that the alignment lasers and the field defining lights can be seen easily to facilitate patient set-up. It is useful to be able to control the treatment and imaging room lights and lasers from the control pendant in the respective room. When the field light is switched on, the room lights should dim to a pre-set (but adjustable) level, and the alignment lasers should also be switched on. Since fluorescent lights do not dim very satisfactorily, it is recommended that incandescent lights are used for the dim level. Four alignment lasers are recommended. Three lasers projecting across: two aligned with the gantry positions of 90° and 270°, and one mounted in the ceiling directly above the isocentre. A fourth laser should project a sagittal line along the gantry axis. This laser is usually mounted on an angled bracket on the wall opposite the gantry. The laser switching should be controlled from the hand pendant, but it is also useful to be able to switch the lasers off independently for quality control tests.
5.21.
In addition to interlocks, as described in para. 5.31, signs and warning lights should be placed at the entrances of controlled areas to prevent inadvertent entry (see also paras 5.290 and 5.291 on control of access). For controlled areas, para. 3.90(c) of GSR Part 3 [3] requires the use of the basic ionizing radiation symbol recommended by ISO [56]. An illuminated warning sign should be displayed at the entrance to the maze or treatment room, and several signs should be displayed inside the treatment room. It should be possible to see a warning sign from any position within the treatment room. These signs should be interlocked with the treatment unit control. The illuminated signs may have two or three stages. For a two stage sign, the first stage will be illuminated when there is power to the treatment unit, and the second stage will illuminate when the beam or the source is on. For a three stage sign, stage one will be illuminated when there is power to the treatment unit, stage two will light when the treatment unit is programmed to deliver a radiation beam and stage three will illuminate when the beam or the source is on. Another possibility is that the warning lights flash when the beam is on. Other rooms that are also controlled areas, such as imaging, simulator and source storage rooms, should also have appropriate signs and warning lights.
5.22.
Radiation therapy facilities that use radioactive sources should implement technical measures so that unauthorized access to sources can be detected in a timely fashion, including after working hours. These technical measures should be independent of any interlocks that terminate the radiation beam during normal operation. Such measures could include a video camera that provides continuous remote surveillance of the device, a photoelectric beam or motion detector system installed in the entrance maze (see para. 5.30) and/or the treatment room, or a door interlock. If these devices indicate the possible presence of an unauthorized person, an alarm should indicate this locally and remotely so that personnel can respond in a timely fashion. Further guidance on security provisions for teletherapy sources and HDR, PDR, MDR and LDR brachytherapy sources is given in Ref. [282] (see also para. 5.88).
5.23.
Firefighting equipment should be available in all areas. For example, in brachytherapy this is in order to preserve the integrity of radioactive sources in the event of a fire. Further guidance is given in Ref. [283].