Real-Time Radiation Detection within the Gastrointestinal Tract

Abstract

The risk of a radiation emergency is becoming more prevalent as the misuse of nuclear facilities or technologies by terrorists or rogue nation-states continues to increase. A radiation emergency could cause instantaneous and sustained large releases of penetrating radiation, which would result in exposed individuals to suffer from acute radiation syndrome (ARS). FDA-approved medical countermeasures to combat ARS are most effective when administered as soon as possible to the point of exposure. Current methods to prevent morbidity and mortality require access to medical support and the proper use of radiation dosimetry. This work describes radiation monitoring internal to the gastrointestinal tract, which could provide a means of alerting the individual to their surroundings or trigger a drug delivery response.

Internal radiation monitoring also has benefits in radiation therapy applications where injury to the gastrointestinal (GI) tract remains an unavoidable side effect due to its extension over a large surface area. Current in vivo dosimetry technology is only positioned in minimally invasive areas to monitor radiation, which increases the likelihood of delivered dose discrepancies in or near the treatment area. This work overcomes this limitation by demonstrating the use of PIN diode-based ingestible electronics to monitor radiation as required throughout the gastrointestinal tract.

The diode was first characterized in vitro for response to X-ray and gamma radiation while in temperature environments of 20°C to 40°C. Various sources were employed for characterization, including 2525 Curie Cesium, 2100 Curie Cobalt, 320 kV X-ray irradiator, linear accelerator (LINAC) with 6, 10, and 18 MV beam qualities, and a neutron beam sourced by a 5.7 MW nuclear reactor. An in vivo study was then performed in which the encapsulated diode was placed in a swine’s stomach, and 110 kVp X-ray images were captured of the swine’s abdominal region.

The diode displayed repeatability within 3\% in its detection of the tested gamma and X-ray sources. The diode also proved to be energy independent for absorbed doses less than 3.5 Gy, evidenced by the LINAC characterization. Radiation absorption in body tissue had a dominating effect on the diode output signal, as shown by comparing the in vitro to in vivo results.

This study demonstrates successful, first-time in situ radiation detection directly from core body areas in a non-invasive manner. Real-time feedback on the received radiation dose to the GI tract allows for active monitoring of GI doses.