Purpose: To compare the performance of MR, cerebral flow SPECT and perfusion MRI (PWI) in NPSLE patients by using image co-registration.
Materials and methods: 20 SLE patients underwent MR (T2-weighted FLAIR), perfusion and diffusion MR, and SPECT (after ( 99m)Tc-HMPAO intravenous injection). Two experienced operators analysed the images both independently and jointly after multi-modal volumetric co-registration ("Statistical Parametric Mapping" software, based on the Maximization of mutual information method).
Results: The FLAIR examination depicted 82 small lesions in 11/20 patients. Perfusion SPECT showed 43 hypoperfused areas in 17/20 patients. PWI showed 13 hypoperfused areas in 10/20 patients. After co-registration of images, anatomical agreement between SPECT and PWI was found in 10 hypoperfused areas (8 patients). Co-registration with FLAIR showed some false positives, more frequent in SPECT (9/43 areas) than in PWI (2/13 areas).
Discussion and conclusions: The FLAIR examination confirmed its high sensitivity in detecting lesions. Perfusion SPECT confirmed high sensitivity for the detection of hypoperfused cerebral areas. PWI showed fewer areas of cerebral hypoperfusion than did SPECT. The disagreement between SPECT and PWI may be related to the different modalities for disease detection. The anatomical agreement of hypoperfused areas between SPECT and PWI, assessed after co-registration, can suggest the prognostic hypothesis of delayed appearance of permanent parenchymal lesions. Co-registration modality, being able to show some false positives, seems to be a valid support for the interpretation of SPECT and PWI findings; the joint analysis of SPECT and PWI highlighted the capability of PWI for the interpretation of uncertain cases.