Determination of the energy response of closely tissue-equivalent diamond dosimeters for radiotherapy dosimetry.

A monoenergetic X-ray syncrotron source was used to determine the energy response of a diamond detector in the range 5-25 keV, clarifying the elemental composition of the detector. The response is shown to be influenced by the detector housing and electrical contacts. A model for the energy response of the detector is determined that is valid in the 5 keV-15 MeV with an accuracy of 5% and therefore can be used to correct the dosimeter response to low-energy and scattered radiation.

X-ray synchrotron microdosimetry: experimental benchmark of a general-purpose Monte Carlo code.

Microdosimetry is useful in mixed-field radiation treatment strategies but relies on an understanding of electron physics at sub-micron dimensions. Monochromatic synchrotron light will be valuable in the development of Monte Carlo models of radiation transport at this length scale. In addition, synchrotron light offers new treatment strategies benefiting from high degrees of brightness and coherence including binary therapies such as photoactivation therapy (PAT) utilising photoelectric enhancement occurring in the kilovoltage range. Microdosimetric spectra for monoenergetic beams have been obtained in the range 15-33 keV with a tissue-equivalent proportional counter (TEPC) and have been compared to Monte Carlo calculations based on atomic models initially. Transport of electrons in molecular systems can also be considered where fundamental interaction data are also obtainable in synchrotron beams via photon scattering experiments utilising the optical model. In the absence of data from liquid water systems, MOSFET and silica-based optical fibre TLD are emerging contenders for experimental verification of microdosimetric spectra in the solid-state and glassy-state phases, respectively.