Radiology: 7T MRI propels epilepsy diagnosis, treatment
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| Manual segmentation of two subregions of body of hippocampus on T2-weighted 7T MRI images in a 24-year-old man. Most posterior coronal section in body of hippocampus, as the image on the left of these pairs. Red cross marks the same point on the paired coronal and sagittal images, and on sagittal section indicates level of coronal section. Image Source: Radiology |
Current options for the one million patients with epilepsy whose disease cannot be controlled by medication are somewhat limited. “Current clinical imaging, 1.5T and 3T MRI, is pretty good at finding the most common pathology for temporal lobe epilepsy in a general way, but not at showing the exact extent of pathology,” Thomas R. Henry, MD, a neurologist at University of Minnesota, Minneapolis, told Health Imaging.
Specifically, 1.5T and 3T systems do not produce reliable images of the major hippocampal structures because of submillimetric dimensions and limited MR contrast. Meanwhile, surgical treatment for temporal lobe epilepsy, caused by scarring inside the hippocampus, requires precise localization of the lesion to determine whether or not critical functions such as memory, language or motor skills would be affected.
"We believe that by using 7T machines, we'll be able to treat a greater population of epileptic patients more effectively," said Henry.
The research team examined the principle pathology of hippocampal lesions with a 7T MRI system housed at the University of Minnesota’s Center for MR Research. The study involved 11 healthy subjects and eight patients with temporal lobe epilepsy between April 2009 and January 2010.
In designing the study, the researchers hypothesized that the higher-field system could show subregional distributions of hippocampal atrophy and allow detection of associated malformations. The results demonstrated the concept.
By leveraging the additional signal to noise ratio of 7T MRI, the researchers better visualized subtle alterations in patients with mild degrees of hippocampal sclerosis. Such structures might appear normal on a lower-strength MRI system, Henry explained. In addition, the researchers could see contours and surface details, including digitations, more clearly.
The increased spatial and contrast resolution provided by the 7T system could inform and enable surgical treatment by helping neurologists better identify and diagnose patients who appear to be MR-negative for temporal lobe epilepsy using existing imaging technology. Images produced by the 7T system also could be used to identify patients with unilateral hippocampal abnormalities, who are not candidates for surgical resection, thus sparing them from unnecessary surgery.
A third benefit of the approach, Henry offered, is that the 7T system depicted internal structures of the hippocampus. In the past, the only method for viewing resected tissue was through a microscope after surgery or autopsy. “It’s a very major early application of 7T MRI and possibly one that could establish the correlation between actual brain structure and brain images,” Henry confirmed.
Although the current study was limited by a small sample size and incomplete development of 7T brain imaging techniques, Henry expressed high confidence in the technology. “It appears extremely promising for future development,” he opined.
Henry and fellow researchers plan to study other forms of epilepsy using 7T MRI. In addition, he pointed to other potential applications of 7T MRI such as early brain tumor imaging.