Imaging of Spatially Extended Hot Spots with Coded Apertures for Intra-operative Nuclear Medicine Applications

TL;DR

This paper demonstrates that coded aperture gamma imaging can effectively detect and localize extended radioactive hot spots in intra-operative settings, offering high accuracy and rapid detection for medical applications.

Contribution

The study introduces a novel coded aperture imaging setup for intra-operative nuclear medicine, capable of resolving extended hot spots with high accuracy and speed, validated through experiments and simulations.

Findings

Extended sources with diameters of 11 and 24 mm are localized within 5% accuracy.

Neighboring sources with low radioactivity levels are distinguishable within 3 seconds.

The method is suitable for real-time intra-operative imaging of sentinel nodes and thyroid remnants.

Abstract

Coded aperture imaging transcends planar imaging with conventional collimators in efficiency and Field of View (FoV). We present experimental results for the detection of 141keV and 122keV {\gamma}-photons emitted by uniformly extended 99mTc and 57Co hot-spots along with simulations of uniformly and normally extended 99mTc hot-spots. These results prove that the method can be used for intra-operative imaging of radio-traced sentinel nodes and thyroid remnants. The study is performed using a setup of two gamma cameras, each consisting of a coded-aperture (or mask) of Modified Uniformly Redundant Array (MURA) of rank 19 positioned on top of a CdTe detector. The detector pixel pitch is 350 {\mu}m and its active area is 4.4x4.4 cm2, while the mask element size is 1.7mm. The detectable photon energy ranges from 15 keV up to 200 keV with an energy resolution of 3-4 keV FWHM. Triangulation is exploited to estimate the 3D spatial coordinates of the radioactive spots within the system FoV. Two extended sources, with uniform distributed activity (11 and 24 mm in diameter, respectively), positioned at 16cm from the system and with 3cm distance between their centers, can be resolved and localized with accuracy better than 5%. The results indicate that the estimated positions of spatially extended sources lay within their volume size and that neighboring sources, even with a low level of radioactivity, such as 30 MBq, can be clearly distinguished with counting time about 3 seconds