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Showing 2 results for Beam Data
M.t. Bahreyni Toossi, A.r. Khoshbin Khoshnazar,
Volume 2, Issue 2 (9-2004)
Abstract
Background: Radiosurgery is a focal brain irradiation technique that delivers, usually in a single session, high dose of ionizing radiation. The presence of lateral electronic disequilibrium and steep dose gradients in small fields demands special attention to the selection of a suitable detector with respect to its size, composition and response. Materials and Methods : Small circular fields were produced by home-made collimators attached to a 9MV Neptun 10 PC linac ranging from 12.5mm to 25 mm at isocenter level in 2.5 mm
increment. Stereotactic beam data including percent depth dose, off axis ratio and output factor were measured using p-type silicon chip detector in a water phantom. Beam data were plotted for all available collimator sizes. Results: Percent depth dose values at depth of 100 cm show 10 percent increase with enlargement of the field sizes from 12.5 mm to 25mm. Small overestimation of output factor has been observed using diode detector. Conclusion: It is concluded for stereotactic radiosurgery with higher energy photon diode
detector could be a good and reasonable choice to measure percent depth dose and off axis ratio. Regarding the output factor, it is better to compare the results with those obtained by other
detectors. Iran . J. Radiat. Res., 2004 2 (2): 79-84
Ph.d., S. Khoudri, Z. Chaoui,
Volume 20, Issue 3 (7-2022)
Abstract
Background: For various practical reasons in radiotherapy practice, it is very advantageous to have linear accelerators dosimetrically matched. The present work assesses the extent of beam matching by investigating the similarity of dosimetric data from three Clinac-iX accelerators in photons (6, 18 MV) and electrons (6, 9, 12, 16 and 20 MeV) mode. Materials and Methods: The following study is based on detailed comparisons of measured and determined parameters such as percent depth doses (PDDs), cross-plane beam profiles, flatness, symmetry, penumbra and dosimetric leaf gap, MLCT interleaf transmission factor, quality index, Relative output factor, in addition of depth R50, therapeutic range R90 and particle range Rp of electron beam. Results: The current measured data, for both photons and electrons, exhibited satisfactory degree of agreement among the three Clinac-iX. For 6 MV and 18 MV photons energies the maximum deviation of percentage depth does not exceed 0.4 %. For electron depth dose measurements (dmax, R50, R90, Rp) the results revealed a maximum deviation of 0.54 mm for all electron energies and applicators. As a direct clinical application, a left breast and prostate cancer cases were planned on the three Clinac-iX machines and compared for their dose volume histograms. Conclusion: In clinical applications, the patient’s treatment can be shifted from one Clinac-iX to another without reducing the treatment quality in the case of periodic preventive maintenance or interruption of the functioning of the Clinacs; the treatment can be preserved without having to replan.
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