Simultaneous triple-registration of ictal SPECT, interictal SPECT and MR images for epilepsy studies: Method and validation

Subtraction of ictal and interictal SPECT images is known to be successful in localizing the seizure focus in presurgical evaluation of patients with partial epilepsy. Computer-aided method for producing subtraction ictal SPECT coregistered to MRI (SISCOM method) is commonly used. There are two registrations involved in SISCOM: between the ictal-interictal SPECT images, which was shown to be more critical, and between the ictal image and MRI. The aim of this paper is to improve registration accuracy of ictal-interictal registration in SISCOM by registering all three images (ictal, interictal SPECT, MRI) simultaneously. The results of the simulation study demonstrates that, in surface-based registration, triple-registration method results in smaller ictal-interictal SPECT registration error than the pairwise registration method (p<0.05) for a range of cost-function parameter values.