The filtered backprojection images obtained from classical SPECT studies are not adequate for evaluation of volumes or parameters of clinical interest. Noise, scattering, boundary accuracy and attenuation are the main problems of SPECT quantification. It is the aim of the following study to overcome these difficulties. The first step of all correction algorithm is the contour detection of the attenuation medium. A new procedure, previously described by the authors, accurately and automatically found the boundaries of the surrounding body. The Compton scattering elimination is carried out by a modified version of Jaszczak's method. This alteration is essential to implement the iterative attenuation correction algorithm derived from Chang's method. Results obtained using computer simulation and real phantoms or clinical studies demonstrate the high improvement of contrast and count levels in the corrected slices. The process is fully automatic and the efficiency of the procedures allow fast processing of the daily SPECT examination.