Ponente
Descripción
The main challenge in radiotherapy is to deposit a high enough (curative) dose in the tumor while risk organs remain at tolerable doses. Nevertheless, delivering higher doses are limited by radiation-induced toxicities in the healthy tissues surrounding tumor. A promising approach that is facing this issue is the FLASH therapy [2], which delivers ultra-high dose-rate (UHDR) (≥40Gy/s), i.e., several orders of magnitude faster than the applied dose in traditional RT (~0.05Gy/s) [1]. It points to reduce toxicities in the healthy tissue surrounding the tumor while facilitate a better tumor response, reducing the treatment time and therefore the organ motion-related issues. Thus, the FLASH effect substantially can widen the therapeutic window of radiotherapy and overcome the dose-limiting radiation toxicity, opening a new paradigm in RT treatments. However, enabling the clinical implementation of FLASH RT is very challenging and current dosimeter systems renders obsolete most of the available dosimetry equipment [2].
The implementation of FLASH therapy requires accurate real-time dosimetry. Novel Silicon carbide p-n diode dosimeters have been designed and fabricated at the IMB-CNM-CSIC, and characterized in an ultra-high pulse dose rate electron beam. They were fabricated in 3 μm epitaxial 4H-SiC. Their characterization was performed in PTB’s ultra-high pulse dose rate reference electron beam.
The linearity of the diode response was investigated up to doses per pulse (DPP) of 11 Gy and pulse durations ranging from 3 to 0.6 μs (Figure 1). The diode response was independent both of DPP and of pulse dose rate up to at least 11 Gy per pulse and 6 MGy/s, respectively, with tolerable deviation for relative dosimetry (<5%).
Percentage depth dose measurements were performed in ultra-high dose per pulse conditions. When measuring the percentage depth dose under UHDR conditions, with DPP values of 11.6 Gy per pulse for 2.9 μs at the maximum of the curve, the SiC diode performed comparably well to the reference flashDiamond (Figure 2).
The sensitivity reduction after 100 kGy accumulated dose was <2% of 20 MeV electrons. A diamond prototype detector (flashDiamond) and Alanine measurements were used for reference dosimetry.
The results of this study demonstrate for the first time the suitability of silicon carbide diodes for relative dosimetry in ultra-high dose rate pulsed electron beams up to a DPP of 11 Gy per pulse [3]. Currently we are developing 3D configurations for both FLASH therapy and advanced microdosimetry.
