[Effect of scattering and spatial resolution on SPECT quantification values: experimental study using phantoms and clinical application].

The relative SPECT values are often inaccurate by the scattering and limited spatial resolution of single photon emission CT (SPECT). These effects were studied using phantoms and some attentions on clinical application were investigated. Using cylindrical phantom divided into six compartments filled with various radioactivities, the linear correlation between SPECT value and radioactivity, and also correlation with partial reduction of radioactivity were identified. But the SPECT value was relatively increased in proportion to the reduction of radioactivity due to the increase of scattering contribution. The SPECT value represented lower radioactivity when the cortical thickness was smaller than two times of FWHM and represented half radioactivity when the cortical thickness was equal to FWHM. Excellent correlation between SPECT value and radioactive partial volume averaging of brain with CSF was recognized using our hand made phantom simulating various degree of atrophic brain. It is very important to compare SPECT image with X-CT or MR image to avoid misreading taking the above mentioned effects due to scattering and limited spatial resolution.