Session Item

Optical fiber-based scintillating dosimetry is the most recent promising technique due to the miniature size dosimeter and improve quality assurance in modern radiation therapy. Despite several advantages, the major issue of using scintillating dosimeters is the Cerenkov Effect and predominantly requires extra measurement correction factors. Therefore, this work highlighted a novel micro-dosimetry technique to ensure Cerenkov-free measurement and provide quality treatment.

A micro-dosimetry technique was proposed with the performance evaluation of a novel infrared inorganic scintillator detector (IR-ISD). The detector essentially consists of a micro-scintillating head with a sensitive volume of 1.5x10^-6 mm³. The proposed system was evaluated under the 6/15 MV LINAC beam as well as 320KV- ¹⁹²Ir Brachytherapy (BT) source used in the patient treatment system. Overall measurements were performed using IBA^TM water tank phantoms by following TRS-398 protocol for radiotherapy and TG43U1 recommendations for BT. Cerenkov measurements were performed for different small fields from 0.5x0.5 cm² to 10x10cm² under LINAC as well as till 0.25cm distance from the BT source. In addition, several dosimetric parameters such as PDD, beam profiling, dose linearity, dose rate linearity, repeatability, and scintillation stability were investigated to realize the device’s performance. Finally, a comparative study will be shown using Monte-Carlo (MC) simulation, and data from recent literature.

This study highlighted a complete removal of the Cerenkov Effect using a point-like miniature detector, especially for small field radiation beam treatment. Measurements demonstrated that IR-ISD has acceptable behavior with dose rate variability (maximum standard deviation ~ 0.15%) for the dose rate of 20 cGy/s to 1000 cGy/s. An entire linear response (R²=1) was obtained with the dose delivered in the range of 4cGy to 1000 cGy, independently of the field size selected from 4 x 4 cm² to 0.5 x 0.5 cm². Perfect repeatability (0.15 % variation from average) with day-to-day reproducibility (0.25% variation) was observed. PDD profiles obtained in the water tank present identical behavior to the reference dosimeter with a build-up maximum depth dose at 1.5 cm. The small field of 0.5 x 0.5 cm² profiles have been characterized to determine convolution and penumbra effect. Eventually, in BT, a comparison with MC simulations shows that measurement agrees within 0.65% till 0.25 cm source-to-detector distance.

Unlike recent advanced PSD systems (e.g., exradin W1/W2), the proposed micro-dosimetry system in this study requires no Cerenkov corrections and showed efficient performance for several dosimetric parameters. Therefore, it is expected that the IR-ISD system can be promoted to validate with direct clinical investigations, such as in the small-field dose verification, intra-beam characterizations, and BT treatment plan.