In vivo dosimetry evaluation of semiconductor diodes and Thermoluminscence Detectors (TLDS) in advanced radiotherapy techniques

Abstract

Author(s): Areej Akram Al-Taee*, Wieeam Abdul-Fattah Saleh and Magdy M. Khalil

The performing of IVD for Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) is not well established and the studies and trails available are not sufficient to give us a clear view of the verified IVD methods in modulated radiotherapy. The objective of this study was to give validation of using diodes and TLDs for in vivo dosimetry in advanced radiotherapy techniques for early detection the uncertainties and significant errors of the dose delivery. Thirty nine patients (23 female and 16 male) with different clinical sites were selected for this study. The period of the study last for five months at Children's Cancer Hospital 57357 and we used paediatric anthropomorphic A 10-years-old phantom to measure doses in IMRT and VMAT by using Thermoluminescent Dosimeters (TLDs) and semiconductor diodes. Also, we utilized the Treatment Planning System (TPS) to calculate doses and compared it with detector readings. Diode is good to be used in IMRT but avoiding total blocked and partial blocked region of MLC that effective on measured diode ± 6 %. Diode is not valid to be used in VMAT cased orientate and dynamic MLC. Result of measurement with TLD in IMRT is less in accuracy than that for VMAT distribution at the edges. The penumbra edges have a percentage difference of ±10 % while it is very close to zero at the middle region. We have evaluated the use of diodes and TLD for application to IMRT and VMAT in vivo dosimetry. Phantom measurements in which diode and TLD used were compared, showing them to be in agreement to generally better than 90%. In comparison with plan prediction of TPS doses, average percent differences in the phantom measurements and patients also were mostly within 35%, with some discrepancies.

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