Objective: Patients with cortical dysplasia (CD) are difficult to treat because the MRI abnormality may be undetectable. This study determined whether fluorodeoxyglucose (FDG)-PET/MRI coregistration enhanced the recognition of CD in epilepsy surgery patients. UCLA MRI identified CD in 78% of patients, and 37% of type I CD cases had normal UCLA scans. EEG and neuroimaging findings were concordant in 52% of type I CD patients, compared with 89% of type II CD patients. FDG-PET scans were positive in 71% of CD cases, and type I CD patients had less hypometabolism compared with type II CD patients. Postoperative seizure freedom occurred in 82% of patients, without differences between type I and type II CD cases. Cortical dysplasia (CD), first described in 1971, 1 is the most common malformation of cortical development identified in surgically treated patients with therapy-resistant epilepsy. Methods: Conclusions:2,3 The histopathology of CD is classified into mild Palmini type I and severe Palmini type II.4,5 Type I CD is characterized by cortical dyslamination and columnar disorganization often associated with excessive subcortical white matter neurons. Type II CD shows cortical disorganization plus abnormal dysmorphic or cytomegalic neurons with or without balloon cells. 6 In the past decade, improvements in MRI have increased awareness that CD is a frequent substrate causing epilepsy. This is especially true for patients with type II CD in whom structural MRI and functional neuroimaging often identify the lesion. 7-10 However, patients with type I CD are a challenge in that they often have negative MRI scans, making surgical treatment difficult without knowing the exact location and borders necessary for complete lesion removal.

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ObjectiveTo retrospectively determine the optimal b value of diffusion-weighted imaging (DWI) for predicting the presence of localized prostate cancer, and to evaluate the utility of DWI under different b values in differentiating between cancers and benign prostatic tissues.Materials and MethodsEighty patients with suspected prostate cancer underwent MRI including DWI at 3T, followed by radical prostatectomy. DWI was examined under different b values. Apparent diffusion coefficient (ADC) maps were generated by using b = 0, and other b values of 300, 700, 1000 or 2000 s/mm2. For predicting the presence of cancers, four different ADC maps were analyzed independently by two blinded readers. ADCs were measured in benign and malignant tissues.ResultsFor predicting the presence of 110 prostate cancers, the sensitivity and area under the curve (AUC) for an experienced reader was significantly greater at b = 1000 (85% and 0.91) than b = 300, 700 or 2000 s/mm2 (p < 0.01). For a less-experienced reader, the AUC was significantly greater at b = 700, 1000 or 2000 than b = 300 s/mm2 (p < 0.01). Mean ADCs of the cancers in sequence from b = 300 to 2000 s/mm2 were 1.33, 1.03, 0.88 and 0.68 × 10-3 mm2/s, which were significantly lower than those of benign tissues (p < 0.001).ConclusionThe optimal b value for 3T DWI for predicting the presence of prostate cancer may be 1000 s/mm2.

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