Andrzej Król James E. Bowsher Stephen H. Manglos David H. Feiglin Martin P. Tornai F. Deaver Thomas An EM Algorithm for Estimating SPECT Emission and Transmission Parameters from Emission Data Only. 218-232 2001 20 IEEE Trans. Med. Imaging 3 db/journals/tmi/tmi20.html#KrolBMFTT01 http://dx.doi.org/10.1109/42.918472