Development of a prototype stereotactic collimation assembly for Neptun 10 PC linac

Background: A set of hardware stereotactic radiosurgery is designed and constructed. The scope of this article is to describe how we have designed and developed stereotactic collimation assembly for a 9 MV Neptun 10 PC linac. Materials and methods: One collimator holder and six collimators were made, with their radiation field diameter between 12.5 mm to 25 mm at isocenter level. Beam data, such as depth dose percent, off axis ratio and output factor of the collimators were measured. Isocentric accuracy and dose delivery, accuracy tests were also performed using locally made isocentric alignment control device, target simulator and plexiglass phantom. Results: Average isocenter shifts resulting from gantry and couch motion were respectively 1.5 mm and 2 mm. Simulating a stereotactic radiosurgery with the help of a plexiglass phantom showed less than one percent radiation leakage to critical organs such as eyes and thyroid. Conclusion: Stereotactic collimation assembly in conjunction with the rest of constructed equipments can be employed to set up SRS treatment, provided safety and to compensate operations are taken into account. Iran. J. Radiat. Res., 2004; 2 (3): 135-140