Imaging 131 I in mouse phantoms and living mice with the MACACO III+ Compton camera

Abstract

Abstract Compton cameras (CCs) are a promising tool for imaging radioisotope distributions during radiopharmaceutical therapy (RPT) monitoring, dosimetry and preclinical development, in cases with high energy secondary emissions for which gamma cameras are not optimal. In the case of preclinical imaging using murine models, the reduced size of the subjects and low injected activities require the optimization of both efficiency and spatial resolution. The IRIS group (IFIC, Valencia) has developed a CC based on continuous lanthanum (III) bromide (LaBr3) crystals for this purpose. The latest prototype, MACACO III+, consists of two detector planes, the first one composed of a single detector with 25.8 × 25.8 × 5 mm3 crystal size and the second comprising four such detectors. MACACO III+ was tested for imaging the therapeutic radioisotope iodine-131 (131I) in a mouse phantom and in living mice at CIC biomaGUNE (San Sebastian). The images were qualitatively compared with those obtained using the γ-CUBE commercial preclinical single-photon emission computed tomography (SPECT) system from Molecubes. 2D images reconstructed from 30 and 45 minute CC acquisitions were similar to the equivalent slices from 3-hour tomographic scans using the γ-CUBE. This study presents the first images of 131I distributions in live mice obtained using a LaBr3-based CC, showing similar quality with shorter acquisition times compared to a commercial preclinical SPECT system. The results demonstrate the potential of using a LaBr3-based CC as a tool in the development of 131I therapies in mice and motivate the exploration of its use for preclinical imaging of other therapeutic radiopharmaceuticals, in particular alpha-emitters such as 225Ac.