82Rb-PET is feasible in rodent AMI model after positron range correction
Authors: Madsen J , Bentsen S , Jensen M , Clemmensen A H , Ripa R S , Akjaer A 
Published: May 2024

Abstract

Funding Acknowledgements
Type of funding sources: Other. Main funding source(s): Prof. Andreas Kjær
Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Department of Biomedical Sciences, Rigshospitalet and University of Copenhagen, Copenhagen, Denmark

Background
Myocardial infarction (MI) remains a leading cause of morbidity and mortality worldwide, necessitating innovative approaches for accurate diagnosis and treatment. Positron emission tomography (PET) using 82-Rubidium (82Rb) is well-established as non-invasive myocardial perfusion imaging (MPI). However, the long position range of 82Rb disables MPI and analysis of MI through 82Rb-scans in rats. Exact assessment of myocardial infarction (MI) in small animal models is important for translational research.

Purpose
To investigates if positron range correction (PRC) of 82Rb PET can improve the quantification of infarct size in a rat model of MI.

Method
10 Sprague-Dawley rats were included. 8 rats with MI established through coronary artery ligation and 2 rats with sham operations, where the rats underwent the same open chest procedure as the MI-rats except for the ligation of the coronary artery. Rats were PET scanned with ~ 60 MBq 82Rb PET one week after MI induction/sham operation (acute scan) in a preclinical PET/CT scanner. At 30-days following MI induction/sham operation the rats were re-scanned with 82Rb PET and 18 flu-deoxy-glucose (18F-FDG) to assess final infarct size. 82Rb PET data were reconstructed both with and without positron range correction. All acquisitions were gated by pulse and respiratory frequency. The image analysis of the static reconstructions was conducted using Corridor4DM version 2023. Infarct size was quantified by summed rest score (SRS). Due to n=10 Spearman’s rank correlation was used.

Results
Acute 82Rb SRS without PRC showed no correlation to the SRS of 18F-FDG follow-up PET (r=0,015 and p=0,67). Nor was there a correlation between the acute 82Rb with PRC and 18F-FDG-scans (r=0,067, p= 0,85). (Figure1)
However, the follow up scan at 30 days post MI induction showed a significant correlation between infarct size of 82Rb with PRC and infarct size of the 18F-FDG scans (r=0,71 and p=0,02). No such correlation was found 82Rb results without PRC and the 18F-FDG results (r=0,51 and p=0,13) (Figure2). The 82Rb PRC scans revealed a significant correlation with 18F-FDG scans, indicating improved alignment between the two in assessing infarct size. This contrasted with the original 82Rb-images.

Conclusion
In this study we show the possibility of utilizing 82Rb-PET as a cardiac perfusion radioisotope in small animal research by applying positron range correction. 82Rb-PET with positron range correction provides a useful tool to delineate perfusion defects more accurately in a rodent MI-model and shows significant correlation to 18F-FDG results. Further research is warranted to validate the translational potential of these findings.Figure 1Figure 2