| Author/Editor | Casar, Božidar; Pregelj, Andrej; Sekereš, Bogdan; Verk, T... | |
| Title | Collimator system for sterotactic radiosurgery with linear accelerator | |
| Type | članek | |
| Vol. and No. | Letnik 48, št. suppl. 1 | |
| Publication year | 1998 | |
| ISSN | 0167-8140 - Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology | |
| Language | eng | |
| Abstract | Purpose: The goal of our research project was to design and build tertiary collimator system for stereotactic radiosurgery with linear accelerator and to measure all relevant physical parameters of narrow photon beams. Methods: Our collimator systems is constructed of an alluminium plate with precision mechanism in its centre and a steel holder of lead collimators. The position of the collimar holder is set by two micrometer regulators. After reaching the required position we can fix both axis with steel regulators to prevent any movement during gantry rotation. Altogether we constructed 10 different, 12 cm long cylindrical collimators with circular divergent openings. Optical field diameters at the isocentre ranged from 1.0 cm to 4.0 cm. For each collimator we measured PDDs, output factors and off-axis ratios (beam profiles-penumbra determination) in water phantom or in phantom made of white polystyrene , using Scanditronix p-type silicon diode, Kodak X-Omat V films, PTW Marcus ionisiation chamber and TLD rods. Results: The collimar system showed high degree of mechanical stability. Output and PDDs measurement results were as expected. Following the profile measurements performed by diodes of films at SAD=100 cm and depth 8 cm, the width of penumbra ranged from 2.6 mm to 3.2 mm at the respective collimator diameters of 1.0 cm 4.0 cm (diode measurements) and from 2.5 mm to 3.1 mm at the respective collimator diameters of 1.0 cm to 4.0 cm (film measurements). Conclusions: Easy handling mechanical stability and favourable dosimetry results are the advantages speaking in favour of our tertiary collimator system and its technical properties. In our study it is also shown, that diodes and films are appropriate choice for dosimetry of narrow photon beams. | |
| Keywords | koordinatni pomični sitemi svinčene zaslonke za curek X-žarkov lokalizacija obsevanega mesta na pacientu |