A novel geometry for SPECT imaging associated with the EM-type blind deconvolution method

Image quality of single-photon emission computerized tomography (SPECT) is essentially determined by the count sensitivity of the detector and the geometry of the collimator. The authors introduce a novel geometry for a dual-head SPECT imaging system (Park Medical Systems Inc., Lachine, Quebec) to improve the count sensitivity. The imaging system is equipped with a coded aperture and a parallel hole collimators. The camera head equipped with the coded aperture collimator is used to acquire count-rich projection images, and the other head with the parallel hole collimator is used to acquire high resolution projection images. To further improve the image resolution of the projections, two expectation-maximization-type blind deconvolution (EMBD) algorithms were derived. The algorithms were evaluated using elliptical cylindrical rod phantom and human hand data. The coded aperture and parallel hole projections were acquired simultaneously using the dual-head SPECT imaging system. The acquired coded aperture projections were decoded using the standard uniformly redundant array (URA) decoding technique to yield decoded projections. The projections acquired from the parallel hole collimator head were incorporated into the decoded images in the EMBD restoration process. Using the coded aperture collimator, the count sensitivity was markedly increased, 8-fold for the phantom data and approximately 20-fold for the hand data, as compared to the parallel hole collimator. Also, image quality of the SPECT projections was significantly improved when the EMBD algorithms were implemented on the projections. Thus, the dual-head SPECT imaging system associated with the EM-type blind deconvolution algorithms may be a preferred system for low-count SPECT imaging.