Diagnostic Accuracy of Magnetic Resonance Spectroscopy in Predicting the Grade of Glioma Keeping Histopathology as the Gold Standard

Abstract

Background Gliomas are the most prevalent intrinsic tumors of the central nervous system and are categorized from grade I to grade IV. Magnetic resonance imaging (MRI) provides exact diagnosis, prognosis, and assessment of tumor response to current chemotherapy/immunotherapy and radiation therapy. With histopathology serving as the gold standard, we aimed to assess the diagnostic accuracy of magnetic resonance spectroscopy (MRS) in predicting glioma grade. Methodology This cross-sectional study was conducted in the Department of Radiology, KRL Hospital, Islamabad, from December 15, 2019, to September 30, 2021. After providing written consent, 80 patients with untreated gliomas were included in this study. The voxel of interest was identified using MRI brain conventional contrast-enhanced sequences to assess the grade of the gliomas and link it to the histology report. Following this identification, tissue metabolites were calculated using MRS. Results The patients' age ranged from 13 to 80 years, with a mean age of 49.5 years. Male patients comprised 57.5% of the total study population, while female patients comprised 42.5%. Overall, 23.75% of patients had low-grade tumors, while 76.25% had high-grade tumors. Low-grade tumors had a choline (Cho)/creatine (Cr) metabolite ratio of 1.7421, whereas high-grade tumors had an average Cho/Cr metabolite ratio of 2.5575. N-acetyl aspartate (NAA)/Cr ratio was 1.6368 in low grade and 0.6734 in high-grade tumors. Sensitivity of 77% and specificity of 84.2% were noted, with 78.75% diagnostic accuracy for the Cho/Cr ratio. Conclusions Multivoxel MRS has been shown to reliably predict the grade of gliomas despite its non-invasive nature and lack of procedural challenges. When used together Cho/Cr and NAA/Cr ratios and histopathology can accurately determine tumor grade and can be used as a supplementary non-invasive technique.

Keywords: diagnostic accuracy; glioma; magnetic resonance imaging; sensitivity; specificity.

Figure 1. Color mapping of different metabolites according to flip angle and chemical data shift image. The choline peak at 3.3 corresponds to the red area in the map.

Figure 2. MRI brain of a 70-year-old male showing high-grade glioma (GBM) seen involving the bilateral frontal horns (arrows in a and b) and body and occipital horns (arrowheads in a and b) appearing high on T2WI and showing significant post-contrast enhancement on T2WI in b.

MRI: magnetic resonance imaging; GBM: glioblastoma; T2WI: T2-weighted images

Figure 3. MRI with TIWI (a), T2WI (b), and FLAIR (c) showing low-grade glioma (histopathologically proven) in a 14-year-old female in the right temporal lobe (arrows in a, b, and c) appearing low on TIWI (a), high on T2WI (b), and FLAIR (c).

MRI: magnetic resonance imaging; T1WI: T1-weighted images; T2WI: T2-weighted images; FLAIR: fluid-attenuated inversion recovery

Figure 4. The multivoxel technique used to locate the area with a high Cho/Cr ratio of >4 (same patient as shown in Figure 2).

Cho: choline; Cr: creatine

Figure 5. MRS using the multivoxel technique with Cho/Cr ratio of less than 2 (same patient as shown in Figure 3).

Cho: choline; Cr: creatine

Figure 6. Tumor grades by histopathology in association with metabolite ratio Cho/Cr.

Y-axis: Mean and standard deviation. Cho: choline; Cr: creatine