New Method for Quantification of the Left Ventricular Function from Low-dose Equilibrium Radionuclide Angiocardiography: Comparisons with Conventional Methods in Patients

Planar equilibrium radionuclide angiocardiography (ERNA) has been used as a gold standard for assessments of the left ventricular (LV) function with high precision for over 3 decades. However, this imaging modality has recently gained less favor due to the growing concerns of radiation exposure to patients. Although single photon emission computerized tomography (SPECT) cameras with high-sensitivity detectors and high-resolution collimators can acquire images with much-reduced radiation dose and/or acquisition time, calculations of LV end-diastolic volume (EDV), ejection fraction (EF) and peak filling rate (PFR) from gated blood pool SPECT require a reliable LV segmentation. Furthermore, the segmentation accuracy is affected by image noise and the segmentation algorithms used, inevitably resulting in less reproducibility in the LV function quantification. We propose a heuristic scheme to forward project (re-project) the short axis (SA) slices of gated blood pool SPECT to generate a quasi-2D stack of images to improve the signal-to-noise ratio and simplify the LV segmentation process. Fourteen patients were randomly selected for this study that had standard in vitro 99mTc labeling of red blood cells. Patients were first imaged following a low-dose (8 mCi) injection using a cardiac dedicated SPECT camera and were then imaged following a high-dose (25 mCi) injection using a conventional planar camera. Left anterior oblique (LAO) views were generated from 3-D SPECT using GE multi-gated software and SA reprojections were created via a new Yale method. Six different quantification methods were compared for quantitative accuracy of EDV, LVEF and PFR assessments. The new method that incorporated the SA reprojection scheme was most comparable to the results from gold standard high-dose ERNA method in terms of EDV quantification. The new method allows for a greater than 67% dose reduction from 25 mCi to 8 mCi without compromising the accuracy of EDV, LVEF and PFR quantification.