Tomographic Imaging by a Si/CdTe Compton Camera for In-111 and I-131 Radionuclides

TL;DR

This study demonstrates the potential of Si/CdTe Compton cameras for high-resolution tomographic imaging of radionuclides like In-111 and I-131 at close distances, improving spatial resolution with advanced reconstruction methods.

Contribution

First experimental demonstration of Si/CdTe Compton camera imaging for In-111 and I-131 radionuclides with improved resolution using LM-MLEM reconstruction.

Findings

Back-projection resolution: 11.5 mm for In-111, 9.0 mm for I-131

LM-MLEM method improves resolution to 4.0 mm and 2.7 mm

Successful resolution of tetrahedral source structure at 28 mm separation

Abstract

Tomographic imaging with radionuclides commonly used in nuclear medicine, such as $^{111}$In (171 and 245 keV) and $^{131}$I (364 keV), is in high demand for medical applications and small animal imaging. The Si/CdTe Compton camera with its high angular and high energy resolutions is an especially promising detector to extend the energy coverage for imaging to the range that covers gamma-ray emitted from these radionuclides. Here, we take the first steps towards short-distance imaging by conducting experiments using three-dimensional phantoms composed of multiple sphere-like solutions of $^{111}$In and $^{131}$I with a diameter of 2.7 mm, placed at a distance of 41 mm. Using simple back-projection methods, the positions of the sources are reproduced with a spatial resolution of 11.5 mm and 9.0 mm (FWHM) for $^{111}$In and $^{131}$I, respectively. We found that a LM-MLEM method gives a better resolution of 4.0 mm and 2.7 mm (FWHM). We resolve source positions of a tetrahedron structure with a source-to-source separation of 28 mm. These findings demonstrate that Compton Cameras have the potential of close-distance imaging of radioisotopes distributions in the energy range below 400 keV.