A new approach to simultaneous spatial resolution and attenuation correction in SPECT imaging is presented. Before these corrections, scatter is removed on the projections. This removal is performed by spectral constrained factor analysis. The innovation reported here is the use of the different impulse responses of the system, according to the source-detector distance, and their integration in a generalized version of the Chang attenuation correction method. This novel algorithm is evaluated on computed and physical phantoms. In the computer-simulated phantom, the count rates after full-processing are very close to the initial values. In the physical phantom, the contrast is increased by 1.8 after full processing. The activity profiles drawn both on raw projections and reconstructed slices demonstrate the effectiveness of the algorithm for the restoration of spatial resolution. Furthermore, the method improves the quality of the images greatly. A clinical study is also presented. When the whole procedure is applied, the resulting slice matches the corresponding computed tomographic scan very well, which is not the case with the usual back-projected images. The process is fully automatic and the computing time performance allows its daily use for single photon emission tomographic examinations.
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