Ponente
Descripción
The central challenge in radiotherapy (RT) is to deliver a sufficiently high dose to achieve tumour control while sparing healthy tissues. FLASH RT, which delivers radiation at ultra-high dose rates (≥40 Gy/s) compared with conventional RT (≈0.05 Gy/s), has emerged as a promising approach. Preclinical studies have shown that FLASH reduces toxicity in normal tissues while preserving or even improving tumour control. It also shortens treatment times, reducing the impact of patient and organ motion. However, the clinical translation of FLASH RT requires new dosimetry solutions, since conventional detectors saturate, lose linearity, or degrade rapidly under ultra-high dose rate conditions.
Silicon carbide (SiC) is a promising semiconductor material to address these needs. Compared to silicon, SiC has a wide bandgap that reduces leakage current and noise, a higher displacement energy threshold that increases radiation hardness, and lower signal yield per unit dose, which prevents saturation at very high instantaneous dose rates. Nowadays, SiC technology is mature, with reproducible wafer-scale fabrication.
At IMB-CNM (CSIC), 4H-SiC PiN diodes have been designed and fabricated specifically for FLASH RT applications. Their performance has been validated in different facilities and radiation conditions. At PTB (Germany), the devices showed linearity up to 11 Gy per pulse (≈4 MGy/s) with 20 MeV electron beams and a performance comparable to PTW’s flashDiamond. At CMAM (Spain), the diodes showed reproducible, linear response to 7 MeV protons up to 26 Gy per pulse. In addition, radiation hardness experiments at CNA (Spain) demonstrated that, after an initial sensitivity loss of ~1.3%/kGy, stability was reached near 1 MGy of 2 MeV protons, with linear response preserved up to cumulative doses of at least 4 MGy. All measurements were performed without external bias, like conventional silicon diodes are used in clinical settings, meaning no adaptation of existing workflows would be required.
In parallel, pixelated SiC arrays have been produced for spatially resolved dosimetry. A 12-pixel array was fabricated and tested with 7 MeV electrons at the Institut Curie (France). The array produced accurate 2D dose maps at 10 Gy per pulse, demonstrating the feasibility of SiC arrays for real-time QA under FLASH conditions. Efforts are currently underway to scale up the pixellated system to a larger array of 400 channels with a custom readout electronics for broader clinical and preclinical applications.
