Cardiac Imaging Using a Four-Segment Slant-Hole Collimator

The main objective of this paper is to evaluate four-segment slant-hole (FSSH) SPECT for cardiac imaging. FSSH is a slant-hole collimator that is divided into four segments and arranged such that the photons from the volume of interest (VOI) are projected four times for every location of the detector. These multiple projections help to improve the sensitivity of the photons from the VOI by a factor 4cos³sigma, where sigma is the slant angle of the collimator. Another advantage of FSSH SPECT is a reduction in the total scan time, since a gantry rotation of pi-2sigma is sufficient to satisfy Orlov´s condition. That means, for a slant angle of 30deg, a gantry rotation of 120deg is sufficient to satisfy Orlov´s condition and obtain a complete dataset. In this paper, we evaluate and compare the reconstructed images obtained using an FSSH collimator, for a gantry rotation of 180deg and 120deg, with those obtained from a parallel-hole (PH) SPECT system using a 180deg acquisition. The reconstructed images from the three imaging geometries were compared in terms of average image noise, contrast, and percentage error, for seven different clinical count levels and for multiple noise realizations in each case. The increase in sensitivity of the FSSH system was found to translate into a proportional decrease in statistical noise for voxels in the VOI of the reconstructed images. Finally, a physical phantom study was performed using a prototype FSSH collimator. Our findings show that FSSH collimators have the potential of being the collimator of choice for cardiac SPECT imaging. Though we explore the potential of FSSH collimators for cardiac imaging in this paper, the concept can be extended for imaging other organs such as the breasts, kidney, and brain