Real-Time In Situ Radiation Detection for Mitigating Injury to the Gastrointestinal Tract.

Radiation therapy is a common cancer treatment method. However, injury to the gastrointestinal (GI) tract remains an unavoidable side effect, which reduces patient quality of life and increases healthcare costs. In vivo dosimetry is a treatment adaptation tool that helps reduce geometric setup uncertainties by providing real-time feedback on the patient’s absorbed dose in the local body area where the technology is positioned. Current in vivo dosimetry technology is limited to measurements in minimally invasive areas of the body. This work demonstrates the use of PIN diode-based capsule electronics placed internal to the GI tract for increased precision radiation monitoring. The diode was first characterized in vitro for response to gamma and X-ray radiation and to varying temperatures ranging from 20 °C to 40 °C. Various sources were employed for characterization, including Cesium, Cobalt, 320 kV X-ray irradiator, a thermal neutron beam sourced by a 5.7 MW nuclear reactor, and a therapeutic linear accelerator (LINAC) with 6, 10, and 18 MV beam qualities. The diode was then placed in a swine’s stomach to observe in vivo X-ray radiation detection. The diode showed repeatability within 3% during its detection of the tested range of gamma and X-ray intensities and energies. The LINAC characterization results show the diode to be energy-independent for absorbed doses below 3.0 Gy. As expected, radiation absorption by body tissue greatly influenced the differing results between the in vitro and in vivo studies. This study demonstrates successful, first-time in situ radiation detection directly from core body areas in a non-invasive manner. Clinical relevance— A real-time dosimeter, purposed for in vivo detection, has been characterized using pre-clinical and clinically used irradiators.