Phantom study and preliminary clinical evaluation of position-dependent Compton-scatter correction system

To achieve quantitative SPECT (single photon emission computed tomography) measurement, it is important that the Comptom-scatter and absorption correction technique handles SPECT values as primary activity over a large variety of geometries. The authors chose a liver study and expected a sufficient photon count in the SPECT scan because liver uptake of Tc-99m-labeled pharmaceuticals is high. However, the scatter and absorption volume was so large and so many scattered photons were contained in the projection data that, until now, quantitative SPECT measurements could not be done using only attenuation correction. In the present work, the practical application of the scatter compensation method modified from Ogawa´s method for clinical use was investigated. For reconstruction and attenuation correction, the authors used Inoue´s method and modified the table thickness parameters to make the attenuation coefficient of the tabletop equal to that of the human body. The results obtained indicate that image quality and quantity are improved by the compensation procedure. The proposed scatter compensation method can be applied to routine liver SPECT studies