TY - JOUR T1 - Exact emission SPECT reconstruction with truncated transmission data JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1510 LP - 1510 VL - 50 IS - supplement 2 AU - Gengsheng Zeng AU - Grant Gullberg Y1 - 2009/05/01 UR - http://jnm.snmjournals.org/content/50/supplement_2/1510.abstract N2 - 1510 Objectives It is common, even with the new SPECT/CT systems, that the transmission data is truncated. This paper develops a method that obtains exact attenuation correction with truncated transmission data. Methods The emission object (e.g., the heart) is assumed to have a finite, convex support, whose emission projections are not truncated. The transmission measurements over the support are available, but may be truncated outside the support (within the torso). A novel emission data reconstruction technique combines emission projections from conjugate views; a modified version of the ML-EM algorithms is used to reconstruct emission data. The attenuation map outside the support is not needed during reconstruction. The transmission measurements through the support are used to pre-scale the emission data and to reconstruct the attenuation map within the support. The attenuation map reconstruction within the support is an internal problem in which only a biased solution can be obtained using an iterative algorithm. The bias is then corrected by identifying a soft-tissue region within the support and the known attenuation coefficient values of these pixels for the soft-tissue. Results Proof of convergence of the new algorithm is provided. Computer simulations verify the accuracy of the new method. Conclusions An exact attenuation map within the support can be obtained provided the attenuation coefficient is known at one pixel within the support. The method, which requires emission data over 360°, provides a means to perform attenuation correction in SPECT with truncated transmission data. ER -