Magnetic resonance investigations were repeated on a 1.5-T scanner (Philips Gyroscan NT-Intera; Philips Medical Systems, Best, the Netherlands) after informed consent had been obtained. None of the 4 patients had a seizure on the day the MRI was performed. FLAIR scans were performed with a repetition time, echo time, and inversion time of 6000, 100, and 2000 ms, respectively; a section thickness of 4 mm; no intersection gap; a 230 × 230-mm field of view; 2 averages; a 256 × 256 matrix size; and a scan reduction of 85% (ie, 85% of the data points acquired). Corresponding DWI scans were performed with a fat-suppressed (spectral presaturation with inversion recovery), multishot, spin echo and echo planar imaging sequence with repetition and echo times of 5393 and 87 ms, respectively; a section thickness of 4 mm; no intersection gap; a 230 × 230-mm field of view; 1 average; a 256 × 256 matrix; a scan reduction of 75%; and 8 b-values: 0, 240, 480, 720, 960, 1200, 1400, and 1680 s/mm2. Apparent diffusion coefficient (ADC) maps of the trace of the diffusion tensor were calculated on the basis of the DWIs that were acquired at each b-value over the 3 principal axes (trace ADC = [x + y + z]/3), thus eliminating diffusion anisotropy effects. On the FLAIR images, tubers were segmented with the use of a previously published protocol.12 These FLAIR segmentations were registered manually on the matching slices of the trace DWI and ADC maps. The ADC measurements were performed in the epileptogenic and nonepileptogenic tubers and in the normal-appearing cortex on FLAIR images. Differences in ADC between the normal-appearing cortex, the nonepileptogenic tubers, and the epileptogenic tubers were calculated with analysis of variance and Scheffé post hoc tests. The ADC values are expressed as mean, SD, and range.