Abstracts

Cortical tubers (CT) are the most frequent epileptogenic lesions in tuberous sclerosis (TS). CT may go unrecognized by standard radiological analysis due to the lack of signal abnormalities on T2-weighted images, their subtlety and the complexity of brain folding patterns. We previously demonstrated that computational models based on texture analysis increases the sensitivity of conventional T1-weighted MRI for the detection of subtle dysplastic lesions by 30% (Bernasconi, 2001). Our objective here was to assess the performance of MRI texture analysis as diagnostic test in TS., We studied 5 TS patients (mean age: 27; two males). All had 3D T1-weighted (FFE sequence, 1mm3 isotropic voxels), proton-density (PD), T2-weighted, and FLAIR images (thickness 3-5mm). To model cortical thickness, blurring of the GM/WM transition and hyperintense signal, we used our previously developed method (Bernasconi, 2001) based on a set of voxel-wise operators applied to 3D T1-weighted MRI and resulting in a 3D map for each feature. To maximize visibility, the three maps were combined into a composite map. Conventional images and texture maps were co-registered in a common stereotaxic space. Conventional MRIs were presented in random order to two independent observers who labeled each CT. A CT was considered to have been detected only if found by both observers. Disagreement was resolved by consensus. A consensus label was created for each conventional MRI modality. A final consensus including all conventional modalities was created and presented concomitantly to the composite texture map., A total number of 32 CT were identified on T1-weighted MRI. The number of CT increased to 79 on T2-MRIs (T2, PD and FLAIR combined), yielding an increase of 146%. All but one CTs seen on T1-MRI were seen on FLAIR. By using the composite texture map concomitantly with the conventional MRIs, further 35 CT were seen, yielding an additional increase of 44%. All lesions seen on the texture maps were overlooked on the initial evaluation of FLAIR images most likely because of their small size. 25% of tubers were bilateral mirror lesions, i.e. located in the same gyrus in both hemispheres., MRI texture analysis of T1-weighetd MRI enhances the visibility of small cortical lesions in TS that may be overlooked by conventional MR imaging. This method is a useful adjunct to T2-weighted images, particularly FLAIR sequences.[table1], (Supported by Canadian Institutes for Health Research.)