Measurement of energy deposition of therapeutici on beams using a 100 μm thick pixelated semiconductor detector Timepix
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2018
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Abstract
Recently there has been an increasing interest in the implementation of different sources of radiation to treat challenging situations which include deep seated radioresistant tumors and pediatric patients. In this regard ion beam radiotherapy playsan important role, thanks to its characteristic confined dose deposition and low entrance and exit doses. For the prediction of its radiobiological effect, it becomes necessary to verify the energy deposition of single ions accurately. However, measuring devices for a realistic clinical application for a position-resolved assessment of the distributions are widely lacking. In this work, the capabilities of a Timepix pixelated semiconductor detector with a 100 μm thick silicon sensor to measure single-ion energy depositions were investigated. Energy loss spectra were analyzed with respect to the mean deposited energy and the width of the distributions. The results were compared to expected behaviors from Monte Carlo simulations. A good agreement between measurements and simulations was found in the range of 0.638 MeV/mm to 18.196 MeV/mm mean deposited energy in silicon, with deviations below 10%. The corresponding deviations in the width of the spectra were between 1.1% and 18.2%. However, significant differences with respect to simulations were observed in 12C and 16O energy loss spectra, reaching deviations up to 38.6% (mean deposited energy) and 303.6% (spectrum width). The detector’s performance was compared with that of a Timepix with a 300 μm thick sensor. Due to the reduced sensor thickness, leading to lower registered signals, the 100 μm detector measured the energy deposits in some cases more accurately. In particular, a significantly improved response to deposited energies above 2.81 MeV/mmby at least a factor of 2 was found. Below 0.89 MeV/mm the performance of the 100 μm sensor was limited by too low signals. The results of this thesis highlight the capabilities and limitations of thin Timepix detectors in measuring energy deposition in a wide range of types and energies of therapeutic ion beams.
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Tesis (Master in Clinical Medical Physics)--Pontificia Universidad Católica de Chile, 2018
Tesis (Master in Clinical Medical Physics)--Heidelberg University, 2018
Tesis (Master in Clinical Medical Physics)--Heidelberg University, 2018