Gated cardiac SPECT in rodents using a dedicated SPECT system: X-SPECT

Cardiac function is an important physiological parameter in preclinical studies. Nuclear cardiac scans are a standard of care for patients with suspected coronary artery occlusions and can assess perfusion and other physiological functions via the injection of radiotracers. In addition, correlated acquisition of nuclear images with electrocardiogram (ECG) signals can provide myocardial dynamics, which can be used to assess the wall motion of the heart. We have implemented this nuclear cardiology technique into a microSPECT/CT system, which provides sub-millimeter resolution in SPECT and co-registered high resolution CT anatomical maps. Radionuclide detection is synchronized with the R-wave of the cardiac cycle and separated into 16 time bins using an ECG monitor and triggering device for gating. Images were acquired with a 12.5 x 12.5 cm2 small field of view pixilated NaI(Tl) detector, using a pinhole collimator. In this pilot study, rats (N = 5) were injected with 99mTc-Sestamibi, a tracer of myocardium, and anesthetized for imaging. Reconstructed 4-D images (3D plus timing) were computed using an Ordered Subset Expectation Maximization (OSEM) algorithm. The measured perfusion, wall motion, and ejection fractions for the rats matched well with results reported by other researchers using alternative methods. This capability will provide a new and powerful tool to preclinical researchers for assessing cardiac function.