SPECT is widely available in clinical institutions and has been contributing to provide valuable diagnostic and treatment response information. SPECT has also potential to support large-scale multicenter clinical trials. Existing SPECT systems have however been limited in providing consistent functional parametric images across the centers, largely attributed to lack of standardized procedures to correct for attenuation and scatter. Recently, a novel software package has been developed, to reconstruct quantitative SPECT images both for brain and thorax regions. This approach has been extensively investigated in our group, for 99mTc for brain and heart, and also in cardiac 201Tl studies. A recent study also demonstrated the accuracy of this approach in a combined CT/SPECT system for a thorax region. By incorporating a correction for collimator septal penetration by high-energy emissions, the technique is also applicable to 123I. Scatter and attenuation occur in the object and are thus object dependent, but are not dependent on the geometry of the imaging equipment. Thus, the program should be able to provide quantitative images that are intrinsically independent of the geometric design of SPECT cameras. This home page was aimed at sharing this software package for clinical research projects in different institutions. We would be most pleased to support academic projects conducted using QSPECT with a variety of SPECT devices and imaging protocols.