Relationship of In Vivo MR Parameters to Histopathological and Molecular Characteristics of Newly Diagnosed, Nonenhancing Lower-Grade Gliomas

Abstract

The goal of this research was to elucidate the relationship between WHO 2016 molecular classifications of newly diagnosed, nonenhancing lower grade gliomas (LrGG), tissue sample histopathology, and magnetic resonance (MR) parameters derived from diffusion, perfusion, and ¹H spectroscopic imaging from the tissue sample locations and the entire tumor. A total of 135 patients were scanned prior to initial surgery, with tumor cellularity scores obtained from 88 image-guided tissue samples. MR parameters were obtained from corresponding sample locations, and histograms of normalized MR parameters within the T2 fluid-attenuated inversion recovery lesion were analyzed in order to evaluate differences between subgroups. For tissue samples, higher tumor scores were related to increased normalized apparent diffusion coefficient (nADC), lower fractional anisotropy (nFA), lower cerebral blood volume (nCBV), higher choline (nCho), and lower N-acetylaspartate (nNAA). Within the T2 lesion, higher tumor grade was associated with higher nADC, lower nFA, and higher Cho to NAA index. Pathological analysis confirmed that diffusion and metabolic parameters increased and perfusion decreased with tumor cellularity. This information can be used to select targets for tissue sampling and to aid in making decisions about treating residual disease.

Figure 1

Example of ADC map, T1 contrast (+Gd), CBV perfusion map, T2 FLAIR, and MRSI data from a single LrGG patient. The blue outline on the T1 + Gd image and MRSI grid indicate the T2 lesion ROI. On the CBV map, pink regions reflect higher CBV. The MRSI grid indicates the spectra and CNI values from each voxel, and the color map superimposed on the T2 FLAIR image indicates voxels with abnormally high CNI.

Figure 2

(A) Median nADC, nFA, and nCBV values within tissue sample ROIs with tumor scores of 1, 2, and 3 (indicating the level of tumor cellularity within the sample) for IDH mutant astrocytoma (AS IDH+) and 1p/19q co-deleted oligodendroglioma (OD) LrGG patients. (B) Median nADC, nFA within tissue sample ROIs, and CNI values within T2/CNI >2 lesion ROIs for grade II and grade III LrGG patients.

Figure 3

(A) Median nADC within tissue sample ROIs, (B) nFA within tissue sample ROIs, (C) median CNI within T2/CNI >2 lesion ROIs, and (D) median CCRI values within T2/CNI >2 lesion ROIs for IDH mutant astrocytoma (AS IDH+) and 1p/19q co-deleted oligodendroglioma (OD) LrGG patients.