Microstructure imaging in patients undergoing evaluation for epilepsy surgery or low-grade glioma: Clinical utility of a novel diffusion MRI method.

OBJECTIVE

To investigate a recently developed MRI technique for mapping the Mean Diffusivity of Tissue (MDT), which improves diffusion MRI imaging of the cerebral cortex by reducing partial volume effects from cerebrospinal fluid (CSF). As cortical lesions are common in patients with focal epilepsy, we explored the clinical value of MDT imaging in patients with drug resistant epilepsy and low-grade glioma.

METHOD: This is a prospective study in which 18 patients undergoing evaluation for epilepsy surgery and five patients undergoing evaluation for low-grade glioma were recruited. Patients underwent conventional MRI and MDT imaging. The images were analyzed by a neuroradiologist who visually assessed the images using a lesion visibility score.

RESULTS

Elevated MDT coincided with suspected FLAIR-positive FCD lesions in the majority of cases (5 out of 8 lesions). Ulegyria was also MDT-positive, but heterotopias were not. MDT did not detect abnormalities in epilepsy surgery cases previously deemed MRI-negative. In low-grade gliomas, MDT and FLAIR findings were co-localized; however, the MDT abnormalities were more conspicuous, and tumor-associated signals were more distinct relative to FLAIR. MDT was helpful in visual demarcation of ischemia and glioma tumor-associated signals in postoperative imaging.

SIGNIFICANCE: MDT frequently aligns with the FLAIR signal, but MDT is visually more prominent. In the presurgical evaluation of epilepsy patients, it contributes to supporting existing or ambiguous findings. The very pronounced MDT signal in low-grade gliomas might have the potential to be a visual aid in the diagnosis, treatment, and follow-up of low-grade gliomas.

PLAIN LANGUAGE SUMMARY: This is a pilot study that investigates a newly developed MRI technique called MDT imaging. The study shows that MDT helps identify brain lesions in patients with epilepsy. Finding brain lesions can improve the success of epilepsy surgery and help patients become seizure-free. MDT imaging also helps visualize tumors in low-grade glioma patients, which could improve surgical planning. These early findings suggest that MDT could be an additional useful tool for imaging in epilepsy surgery and low-grade glioma patients, but more research is required to confirm its benefits.