Dose Verification with diode versus TLD as in-vivo dosimeters for external radiotherapy

Yassin, Adel Elsayed; El Shahat, Khaled; Attalla, Ehab Marouf; Khaled, Hassn

doi:10.21608/ejbbe.2020.22441.1029

Dose Verification with diode versus TLD as in-vivo dosimeters for external radiotherapy

Document Type : Original Article

Authors

¹ Oncology Department Faculty of Medicine Al-azhar university Cairo Egypt

² Radiation Oncology Department, Faculty of medicine, Al-Azhar University

³ Radiotherapy &amp; Nuclear Medicine Dep.; National Cancer Institute ; Cairo university

10.21608/ejbbe.2020.22441.1029

Abstract

Background: Conformal radiotherapy was the first step toward patient-specific treatment, this is, in turn, arise the need to perform quality dose verification (DV) with in-vivo (IV) dosimetry. Aim: two common IV dosimeters were compared separately, diode and thermoluminescent dosimeters (TLD), the dose was compared with calculated dose and the isocenter dose measured with ion chamber (IC). Materials and Methods: First The absolute dose was measured in PTW Farmer IC (0.6 cc) on Varian machine model Unique for twenty cancer patients planned in 3D conformal radiotherapy, they were randomly selected to cover different clinical sites, the dose was calculated in Eclipse treatment planning system (TPS). Then in the treatment position, the in-vivo DV dosimetry was performed using: Sun nuclear Semiconductor diode and TLD. Results: the dose measured with Diode had less variance (-1.94±2.05) with TPS than dose measured with TLD/TPS (4.08 ±6.51), when comparing the dose measures with IC this discrepancy is not the case with IC/TPS as they were measured in the isocentre point and compared with prescribed doses Conclusion: patient specific DV performed with IC is the most accurate as a double check with prescribed dose. For IV dosimetry diode was closer to calculated dose, however, both diode and TLD characterized by uniform difference versus calculated dose within different clinical sites which keep each of them an accepted device especially when seeking their additive values either of small field dosimetry with TLD or skin dose measurement with diode. Those outcomes highlight the limitation of each device for IV dosimetry.

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