Evaluation of the Tumor-brain Interface of Intracranial Meningiomas on MR Imaging including FLAIR Images

Abstract

The usefulness of fluid-attenuated inversion recovery (FLAIR) imaging for the evaluation of brain diseases has been reported. The purpose of this study was to evaluate the brain-meningioma interface with MRI including FLAIR imaging. This study involved 48 patients with 50 intracranial meningiomas. We retrospectively evaluated the brain-meningioma interface by various imaging method including FLAIR. If a thin layer with a signal intensity different from that of the tumor and brain was observed in the areas of the tumor-brain interface in T(1)-weighted IR (T(1)WIR) and T(2)-weighted turbo SE (T(2)WTSE) images, we defined this structure as the rim. The presence or absence of the rim and the signal intensity were evaluated, and the length and the signal intensity of the rim observed with FLAIR and contrast-enhanced T(1)WIR (CE-T(1)WIR) images were evaluated. In 35 of the 50 lesions (70.0%), the rim was observed in the tumor-brain interface as a layer of low signal intensity in T(1)WIR images and high signal intensity in T(2)WTSE images. In 13 lesions (26.0%), no rim was detected. Flow voids were observed at the tumor-brain interface in 20 of the 50 lesions (40.0%). No rim showed a low signal intensity of the tumor-brain interface in both T(1)WIR and T(2)WTSE images. The rim exhibited an iso-to-high signal intensity compared to the tumor parenchyma in FLAIR images and an enhanced signal intensity in CE-T(1)WIR images. In contrast to T(1)WIR images, the rim in FLAIR images tended to be identified across the entire circumference. The rim at the brain-meningioma interface revealed as low signal intensity in T(1)WIR images and high signal intensity in T(2)WTSE images, which was conventionally considered to be the CSF cleft, was often revealed in FLAIR images as high signal intensity compared to the tumor parenchyma, and an enhanced signal intensity in CE-T(1)WIR images. Therefore, the presence of CSF in such rims is unlikely, and the rims might reflect the capsule structure of the tumor surface.