Ponente
Descripción
New detection systems for hadrontherapy and FLASH therapy have been designed and manufactured at the Centro Nacional de Microelectrónica (IMB-CNM, CSIC) in Barcelona, Spain.
Silicon microdosimeters that can reduce the radiobiological uncertainties in the normal tissue surrounding the target by allowing for further RBE calculations are based in silicon 3D-cylindrical microdetectors. They have a cylindrical shape with a size comparable to that of the nuclei of human cells (20 µm-thick, 25 µm-diameter). Using this unit cell, different arrays configurations were designed and fabricated to cover a wide range of resolutions. Each of these multi‒arrays is integrated in a customized electronic readout by using multichannel ASICs. This ASIC enables a beam trigger and an analogue output for 128 microdetectors. They are chained to others, which allows to increase the number of channels. The microsensor arrays have been successfully used at the Orsay Proton Therapy Center (France) for measuring 2-dimensional LET distributions, proving that they can contribute to the optimization of hadrontherapy treatments.
In addition, silicon carbide (SiC) diodes have been developed for dosimetry for ultra-high dose-per-pulse radiation at FLASH radiotherapy. The diodes have been characterized in an ultra-high pulse dose rate electron beam at National Metrology Institute (PTB, Germany). The linearity of the diode response was investigated and it 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%). When measuring the percentage depth dose under ultra-high dose per pulse conditions, the SiC diode performed comparably well to a reference diamond dosimeter. The sensitivity reduction after 100 kGy accumulated dose was <2%.
In a further radiation test, these detectors were tested at the CNA in Sevilla, studying their signal response, sensitivity and radiation hardness with 14 MeV proton beams up to a cumulative dose of 1.5 kGy. The diode response was stable with a +-4% deviation that could be attributed to beam drift during the irradiation. The diode dark current was not affected by the accumulated dose. The results of these studies demonstrate for the first time the suitability of radiation-hard silicon carbide diodes for relative dosimetry in ultra-high dose rate pulsed radiation beams.
