{Figure - 1: These are unregistered MR (left row) and SPECT (right row) images of the brain phantom. The anatomical limitation of the SPECT image is evident even with this very simple model of the brain.
Figure - 2: The translation errors are constant regardless of the radial boundary of the dispersion of the points sets used for the registration. They increase when homology error is increased and when fewer feature points are used. This plot is for a homology error of 10 mm FWHM (about the resolution of the SPECT system used).
Figure - 3: The rotation errors decrease as the radial boundary of the dispersion of the points sets is increased. Similar to the translation errors, they increase when the homology error is increased and when fewer feature points are used. This plot is for a homology error of 10 mm FWHM.
Figure - 4: These registered images which display the
three cardinal planes (transverse-top row, sagittal-middle row, coronal-bottom
row) from MR (left column) and SPECT (middle column) show the correspondence
of HMPAO uptake and rCBF in the preferrential uptake of gray to white matter.
The right column shows the SPECT images transparently overlayed on the registered
MR images to more clearly show the underlying neuroanatomy of the corresponding
SPECT. This patient had a mild right hippocampal atrophy (1 below the
mean) with seizure onset in the left hippocampus. Co-registered MR and interictal
SPECT shows hypopefusion in the left hippocampus. The patient had a left
selective amygdalo-hippocampectomy.
Figure - 5: These are registered MR/SPECT volumes similar to figure 4. For this patient, the semi-quantitative analysis of perfusion patterns in hippocampal VOI's indicated an interictal hypoperfusion in the right hippocampus. The asymmetry between right and left hippocampal VOI's was 22 %. The results from the registered SPECT were consistent with findings from EEG. This patient underwent a right temporal lobectomy.