Mapping the Minimum Detectable Activities of Gamma-Ray Sources in a 3-D Scene

TL;DR

This paper introduces a real-time method for mapping the minimum detectable activities of gamma-ray sources in a 3D scene, enhancing radiological search efficiency and decision-making.

Contribution

It presents a novel near real-time MDA mapping approach for point source detection in 3D environments using spectral data and a constant background assumption.

Findings

MDA maps accurately identify source locations in real scenarios.

Method detects sources above thresholds with high reliability.

No false positives in background-only measurements.

Abstract

The ability to formulate maps of minimum detectable activities (MDAs) that describe the sensitivity of an ad hoc measurement that used one or more freely moving radiation detector systems would be significantly beneficial for the conduct and understanding of many radiological search activities. In a real-time scenario with a free-moving detector system, an MDA map can provide useful feedback to the operator about which areas have not been searched as thoroughly as others, thereby allowing the operator to prioritize future actions. Similarly, such a calculation could be used to inform subsequent navigation decisions of autonomous platforms. Here we describe a near real-time MDA mapping approach that can be applied when searching for point sources using detected events in a spectral region of interest while assuming a constant, unknown background rate. We show the application of this MDA mapping method to a real scenario, a survey of the interior of a small building using a handheld detector system. Repeated measurements with no sources and with Cs-137 sources of different strengths yield results consistent with the estimated thresholds and MDA values; namely, that for background-only measurements no sources are seen above threshold anywhere in the scene, while when sources are present they are detected above the thresholds calculated for their locations.