An insight on using in-vivo diode dosimetry to verify the delivered ‎doses during radiotherapy

In-vivo dosimetry (IVD) is one of the most accurate ways for determining the dosage provided to the patient during treatment . The aim of this work is to verify whether patients were receiving the accurate prescribed dose. Which occurs by assessing the dose delivery errors, caused by human or equipment malfunctioning, using in-vivo diode dosimetry (IVDD). In total, 302 fields were performed for 80 cases, including pelvis, abdomen, thorax, and head and neck (H & N) patients. Prior to the clinical application, Alderson Rando phantom was used to evaluate the diodes' dependability as a complement to the validation process. The results revealed that the measured dose of the phantom was within ±5% of the planned dose. Additionally, patients' doses achieved 91.4% of the measured dose were within ±5% of the planned dose. Of the other 8.6%, about 5.6 % of the measured doses were more than 5% and less than 10% and only 3% were larger than 10% of the planned dose. The outlying values that were more than 5% were repeated as in-vitro measurements on a phantom and the deviations were within ±5%. This study demonstrated that diode measurements provide an immediate readout during the treatment process and it is reliable as quality assurance for linear accelerator. Moreover, IVDD is capable of detecting major and common treatment errors such as patient setup errors and incorrect source surface distance.