The effect of scatter correction on 123I-IMP brain perfusion SPET with the triple energy window method in normal...

Scatter correction (SC) using the triple energy window method (TEW) has recently been applied for brain perfusion single-photon emission tomography (SPET). The aim of this study was to investigate the effect of scatter correction using TEW on N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) SPET in normal subjects. The study population consisted of 15 right-handed normal subjects. SPET data were acquired from 20 min to 40 min after the injection of 167 MBq of IMP, using a triple-head gamma camera. Images were reconstructed with and without SC. 3D T1-weighted magnetic resonance (MR) images were also obtained with a 1.5-Tesla scanner. First, IMP images with and without SC were co-registered to the 3D MRI. Second, the two co-registered IMP images were normalised using SPM96. A t statistic image for the contrast condition effect was constructed. We investigated areas using a voxel-level threshold of 0.001, with a corrected threshold of 0.05. Compared with results obtained without SC, the IMP distribution with SC was significantly decreased in the peripheral areas of the cerebellum, the cortex and the ventricle, and also in the lateral occipital cortex and the base of the temporal lobe. On the other hand, the IMP distribution with SC was significantly increased in the anterior and posterior cingulate cortex, the insular cortex and the medial part of the thalamus. It is concluded that differences in the IMP distribution with and without SC exist not only in the peripheral areas of the cerebellum, the cortex and the ventricle but also in the occipital lobe, the base of the temporal lobe, the insular cortex, the medial part of the thalamus, and the anterior and posterior cingulate cortex. This needs to be recognised for adequate interpretation of IMP brain perfusion SPET after scatter correction.