Adding SISCOM to routine evaluation of brain SPECT studies for determining rCBF alterations after medication in schizophrenia

Abstract

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Objectives: In SISCOM (Subtraction Ictal SPECT Coregistred to MRI) method which has been developed for advanced evaluation of epileptic focus, interictal brain perfusion SPECT images are subtracted from ictal SPECT and the final solution is overlapped on MRI. The final image is used to optimally determine regions of altered activation during seizure. Altered rCBF in frontal cortex and basal ganglia in response to antipsychotic medication can differentiate the responders from nonresponder schizophrenic patients. Our aim was to test whether SISCOM can also be applied for the evaluation of rCBF changes due to medication in schizophrenia. Methods: 19 schizophrenic patients(9m,10f) were given clozapine treatment after one week drug free interval. Tc-99m HMPAO Brain SPECT was obtained both before(pre-SPECT) and 8 weeks after(post-SPECT) clozapine therapy. Each study was evaluated visually. Pre and post-SPECT data were subtracted from each other with SISCOM by using Analyze 6.0 workspace. SISCOM images and visual evaluation were compared with each other. Results: Final SISCOM images and visual evaluation of pre and post-SPECT studies were well concordant in 16 patients (84%) according to the basal ganglia and frontal lobe rCBF alterations. Discordance was observed in 3 patients (16%); in 1 patient alterations observed with SISCOM was confirmed as subtle changes in basal ganglia and frontal cortex on visual re-evaluation of images. In 2 patients, SISCOM did not confirm the changes observed by visual analysis. Additionally, SISCOM depicted the increased occipital rCBF better than visual evaluation in 4 patients who had visual activation during the injection of the radiopharmaceutical. Conclusions: Complementery use of SISCOM to visual evaluation in schizophrenic patients seems to be useful to assess the rCBF changes due to medication effect, provides addiditional information and makes the visual analysis easy.