Modeling dose response to synchrotron X-rays in solid-state and biological systems

Abstract

The Monte-Carlo method is used to model perturbation to the dose response of solid-state detectors and biological systems in the vicinity of the K-edge of constituent elements. Diamond detectors are examined where silver-based (Ag) solders are used to form electrical contact with the diamond crystal. Perturbation from photoelectric interactions with Ag lead to a dose response that increases gradually above the K-edge of Ag (25.5 keV) reaching a maximum around 45 keV. Dose enhancements associated with synchrotron-based photon activation therapy (PAT) with platinum (Pt) are also examined. Perturbation from photoelectric interactions with Pt leads to a dose response that may increase to a maximum at the K-edge of Pt but falls dramatically above edge. For large volumes of irradiation, such as is typical for radiation therapy of the brain, self-absorption leads to a decrease in dose response above edge indicating that a high degree of localization of activating material is required for the treatment approach to be successful.

Dosimetry of Microdistributed Dose-Enhancing Agents in X-ray Synchrotron Binary Therapy

“…Calculations of dose enhancement due to binary agents can range in needed level of complexity from a KERMA model, to detailed Monte Carlo models of the radiation interaction with the agent. Fluctuations in concentration may occur at very small length scales, so it is often necessary to model electron processes [1][2][3][4] and self-absorption 5…”