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The electron therapy combined with surgery is now more often used in radiotherapy. The mobile accelerator is used during surgery in the standard operating room (often without additional radiation shielding). Therefore, it is extremely important to ensure proper radiological protection of the patient and staff.

The aim of the study was a detailed analysis of the air kerma value around the new mobile linear accelerator for IOERT (AQURE from National Centre for Nuclear Research) and on its basis issuing recommendations for its safe use in an operating room not equipped with additional radiological protection. 

The radiation study to determine the leakage and scatter of photons consisted of measurements of the air kerma at points shown in Figure 1 at 3 heights from the ground: 0, 102, and 150cm.  Additionally, the kerma was measured above the accelerator head in the beam axis (260 cm from the ground) and centrally in the beam axis at the floor level.

Measurements were made using a 30ccm cylindrical ion chamber (PTW Freiburg) with a 6cm plaster cylinder-shaped cover (density 2,3 g/ccm). The reference dose given at the maximum dose point in the beam axis in the water for each point was 10 Gy (1000 MU). Measurements were made on the AQURE (NCNR, Poland) accelerator for 9 MeV energy electron beam.

Then, based on the results obtained, it will be possible to estimate the exposure time  (minutes per year) for the staff (behind the 6 cm plaster wall) outside the operating room. These staff were divided into three groups: general population (limit dose of 1 mSv per year), category B workers - 6 mSv, and category A workers - 20 mSv.

The results of the equivalent dose calculation on the basis of the measurements are presented in Table 1.

At a distance of 3m from the axis of the radiation beam and at a 6cm plaster wall, a general population may spend 262 minutes per year. For one treatment, which takes about 1 minute, we have 262 operations per year. For B-category, this number is 1576, and for A-category-5253. For rooms located above the operating room, a person from the general population may stay in the area of ​​the beam axis for more than 410 minutes, category B-2462 minutes, and for category A-8207 minutes.

The analysis of air kerma measurements confirmed the assumptions that the AQURE mobile intraoperative accelerator is a safe device and can be used without additional covers during surgery in ordinary operating rooms. However, the placement of the device in the operating room must be taken into account when planning accelerator procedures. Following a risk analysis, recommendations were proposed for users and staff responsible for radiological safety in the operating room using the AQURE mobile intraoperative accelerator. These recommendations are indicative only and should be updated following environmental research at the target facility where the AQURE mobile intraoperative accelerator will be used.