A novel approach to multipinhole SPECT for myocardial perfusion imaging

Myocardial perfusion imaging with SPECT remains critically important for diagnosing, assessing, and evaluating treatment of coronary artery disease. However, conventional rotational SPECT suffers from prolonged study times because of relatively low detection efficiency. We therefore have investigated a multipinhole collimator that could improve the detection efficiency in cardiac SPECT by a factor 5, while providing image quality comparable to standard rotational SPECT techniques using parallel-hole collimation.

We have measured the spatial resolution and efficiency of a 9-pinhole and a parallel-hole collimator mounted to a standard nuclear medicine gamma-camera as a function of distance from the collimator with a point source array. The efficiency was derived by integrating the detected counts, and the spatial resolution was determined from the full width at half maximum of the detected point spread function. In addition, we generated and reconstructed projection data of a 9-pinhole collimator from a digital heart phantom with a basal lesion. We simulated 3 scenarios: single view from left anterior, 2 views from left anterior and left lateral; and 4 views that include the 2 previous views and left lateral and anterior views.

We found that the spatial resolution of the 9-pinhole collimator with 8-mm diameter pinholes was 30% poorer than that for the parallel-hole collimator, whereas the detection efficiency was increased by >10-fold. This predicts that a 9-pinhole collimator having the same spatial resolution as a parallel-hole collimator will have 5 times greater efficiency. Reconstructed data from 1 angular view of the 9-pinhole collimator showed the expected loss of spatial resolution in the longitudinal direction with reduced resolution of the basal lesion. In addition, the tomograms showed distortions in the apical region. In contrast, the reconstructed data from 2 and 4 views of the 9-pinhole collimator demonstrated good lesion definition and also produced images describing the shape and size of the heart more accurately.

Our results indicate that myocardial multipinhole tomography with 2 or more views offers an image quality and spatial resolution comparable with current rotational SPECT techniques, but with the advantage of a 5-fold increase in efficiency.