SPECT transmission scans using multiple collimated line sources

Accurate attenuation correction, considered essential for quantitation in SPECT images, must be based on measured attenuation maps in order to properly account for the nonuniform distribution of the attenuating medium. These maps are also necessary for density dependent estimation of scatter distribution. A simple configuration for a transmission source is proposed, which utilizes a series of parallel collimated line sources. The source system is mounted opposite to a detector equipped with a standard parallel hole collimator and rotates together with it. In this paper we present the results of simulation tests using systems of line sources varying from 10 to 30 tubes. Attenuation maps were generated using filtered backprojection and iterative ART methods for uniform cylinders and chest phantoms. Although some artifacts can be seen, this method has a clear potential. By using exact fan beam geometry and an iterative reconstruction algorithm an improvement over filtered backprojection in a quantitative accuracy of the attenuation map can be achieved.