Clinical advantages of interictal SPECT coregistered to magnetic resonanceimaging in patients with epilepsy

Purpose: The aim of this study was to investigate the clinical value of cor egistration of interictal SPECT and magnetic resonance imaging (MRI) in pat ients with partial epilepsy. Materials and Methods: Seventeen patients with partial epilepsy were examin ed with I-123 IMP or Tc-99m ethyl cysteinate dimer SPECT during the interic tal phase. The SPECT images were automatically coregistered to axial T1 wei ghted MRIs, Asymmetry indexes (Als) were calculated in both nonregistered i mages and coregistered images, Results: SPECT images showed areas of decreased tracer uptake in 12 patient s, in two patients, the relation between the tumor and the extent of decrea sed uptake became more accurate in the coregistered images. In five cases, the coregistered images clearly showed that the decreased uptake was locate d in the sulcus, The AIs were significantly reduced from 14.29 +/- 7.23 to 5.86 +/- 3.48 (P < 0.001) after the images were coregistered in these cases , In five cases, the coregistered images indicated that the decreased areas were in agreement with the cortical findings. No significant differences i n the AIs were observed in these cases (16.50 <plus/minus> 6.19 versus 17.8 3 +/- 4.45). Thus, the coregistered images were useful not only to differen tiate actual hypoperfusion from artificial hypoperfusion resulting from par tial volume effects but also to improve the accuracy of Als. Conclusion: The coregistration of interictal perfusion SPECT and MRI is use ful not only to provide precise functional and anatomic mapping but also to improve the accuracy of calculations of the semiquantitative analysis of r egional cerebral blood flow parameters during the interictal state of epile psy.