Cardiac Radionuclide Imaging in Rodents: A Review of Methods, Results, and Factors at Play.

The interest around small-animal cardiac radionuclide imaging is growing as rodent models can be manipulated to allow the simulation of human diseases. In addition to new radiopharmaceuticals testing, often researchers apply well-established probes to animal models, to follow the evolution of the target disease. This reverse translation of standard radiopharmaceuticals to rodent models is complicated by technical shortcomings and by obvious differences between human and rodent cardiac physiology. In addition, radionuclide studies involving small animals are affected by several extrinsic variables, such as the choice of anesthetic. In this paper, we review the major cardiac features that can be studied with classical single-photon and positron-emitting radiopharmaceuticals, namely, cardiac function, perfusion and metabolism, as well as the results and pitfalls of small-animal radionuclide imaging techniques. In addition, we provide a concise guide to the understanding of the most frequently used anesthetics such as ketamine/xylazine, isoflurane, and pentobarbital. We address in particular their mechanisms of action and the potential effects on radionuclide imaging. Indeed, cardiac function, perfusion, and metabolism can all be significantly affected by varying anesthetics and animal handling conditions

Comment on Hatzoglou et al: Dynamic contrast-enhanced MRI perfusion versus 18FDG PET/CT in differentiating brain tumor progression from radiation injury.

We read with great interest the paper by Hatzoglou et al, recently published in Neuro-Oncology,1 concerning the discrimination between progressive disease and radiotherapy-induced changes in brain tumors, which is a clinical challenge of paramount importance. To address this diagnostic problem, the authors compared dynamic contrast enhanced (DCE) MRI and fluorine-18-fluorodeoxyglucose (FDG) PET/CT in a total of 53 patients with primary brain tumors (n = 29) or brain metastases (n = 26). They found that the DCE MRI–derived plasma volume ratio (Vpratio) and transfer coefficient ratio (Ktransratio), as well as the FDG PET–derived standardized uptake value ratio (SUVratio) were useful in distinguishing between progression and radiation injury, both in the overall cohort and in the 2 main subgroups (primary and secondary brain tumors). They concluded, however, that DCE MRI–derived Vpratio was the “most robust” predictor of progression after showing a trend toward higher performances for Vpratio with respect to SUVratio (sensitivity and specificity = 92% and 77% vs 68% and 82%; AUC = 0.87 vs 0.75, P = .061, for Vpratio and SUVratio, respectively)