P09.04 T2 hyperintense regions on MRI in gliomas: a comparison between routine clinical MRI and 7T MRI

Abstract

Abstract BACKGROUND Gliomas can be highly heterogeneous on brain MRI, especially at higher grades. These tumors often include a low-grade component and/or surrounding edema. Both these components appear as hyperintense regions on clinical T2-weighted MR images and cannot be accurately distinguished. Ultrahigh field 7T MR systems have the potential for a higher sensitivity due to its increase signal-to-noise ratio (SNR). This could allow for enhanced detailed visualization of gliomas. Therefore our goal was to assess the difference in extent of T2 hyperintense regions in glioma patients between clinical (1.5T/3T) and 7T MR images. MATERIAL AND METHODS We prospectively scanned 6 glioma patients (3 glioblastomas (GBM) WHO grade IV post-operative, 1 anaplastic diffuse glioma (ADG) WHO grade III, 1 biopsied oligodendroglioma (OD) WHO grade II and 1 suspected low-grade glioma (LGG); 4 Females, mean age: 56.8 years and 2 Males, mean age: 45.5 years) on a routine clinical MRI scanner (3T or 1.5T) and on a 7T MRI scanner (Philips Achieva). Resolution of the T2-weighted image at 7T, 3T and 1.5T: 0.75mm3, 3mm3 and 5mm3, respectively. T2-weighted scans were visually assessed by an independent researcher and experienced neuro-radiologist. The T2 hyperintense regions were measured in 3 directions and compared brain structures as reference points between the clinical and 7T scans (e.g. brain stem, gyri), also considering differences in slice thickness and spatial resolution. RESULTS T2 hyperintensity lesion measurements in the AP direction were as follows: GBM: 114.7mm (clinical field strength) vs 115.56mm (7T); ADG: 45mm vs 58.87mm and 24.7mm vs 25.55mm; OD: 45.1mm vs 48.5mm; GBM: 45.3mm vs 44.75mm; suspected LGG: 47.4mm vs 51.57mm; GBM: 105.8mm vs 114.5mm. We observed the largest difference between 3T and 7T T2 hyperintense region measurement to be 13.87mm (30%), belonging to a GBM WHO grade IV patient. For all patients the T2 hyperintense region was measured on average 8.3% larger at 7T MRI compared to the routine clinical MRI scan. Overall the T2 hyperintense regions at 7T appeared sharper and tumor boundaries were better defined. Likewise, the contrast between the tumor and healthy tissue was enhanced, most likely because of the increase in spatial resolution. CONCLUSION In gliomas the T2 hyperintense regions were more extensive at 7T MRI compared to the routine clinical MRI. These preliminary results might indicate that at clinical field strength the extent of the lesion is underestimated and that 7T MRI can potentially aid in detecting this more extensive disease process. Therefore, 7T MRI scan in gliomas might have a future role in treatment decisions regarding the extent of tumor resection and radiotherapy planning.