Design and experimental validation of a quantitative myocardial Tl-201 SPECT system

We have developed a quantitative SPECT system, and evaluated its potential for quantitative assessment of bio-physiological functions in the myocardiu m particularly with Tl-201. Our approach included development of a transmis sion system that provides accurate attenuation CL maps, and implementation of ordered-subset EM reconstruction with transmission data based attenuatio n correction in addition to scatter correction using the transmission-depen dent convolution subtraction (TDCS) technique. The transmission system was designed using Monte Carlo simulation to minimize the scatter in the transm ission projection data while keeping loss of sensitivity minimal, and was a ttached to an opposing 2-head gamma camera fitted with parallel beam collim ators. Observed CI values agreed with the theoretical expected values in bo th phantoms and human thorax. Phantom experiments with Tl-201 also demonstr ated that, with both corrections for attenuation and scatter, observed imag es were directly proportional to the actual radioactivity distribution for various phantom geometries. Attenuation correction without scatter correcti on improved images in deep structure, but resulted in significant artifacts in the chest phantom in addition to dependency of observed radioactivity c oncentrations on the diameter of cylindrical phantoms. Absolute quantitatio n of bio-physiological functions, which is well established in PET, is show n to be feasible using SPECT, if both quantitative attenuation and scatter corrections are employed.