Comparison of three applications of ConTraSPECT

Today, the trend in SPECT attenuation correction is to acquire a transmissi on data set and reconstruct the corresponding attenuation map, for incorpor ating into the emission reconstruction. Recently, some techniques have been developed to determine the attenuation map directly from the emission data , by exploiting the fact that in the absence of noise only some specific tr ansmission data can be consistent with given emission data. However it is n ecessary to include some a priori information so that the consistency condi tions can be used in an efficient manner. In this paper, three types of pri ors are used: a uniform ellipse, a uniform spline curve, and a uniform spli ne curve knowing the untruncated part of the transmission sinogram. Once th e corresponding attenuation map has been computed, it is used to correct fo r attenuation in the emission image reconstruction process. The three metho ds have been tested on both simulations and experimentally acquired data. T he results show that the two first methods give equally acceptable results, while the third method provides reconstructions which are closer to recons tructions obtained when the attenuation map is computed from untruncated tr ansmission data.