Role of magnetic resonance perfusion imaging (contrast-enhanced dynamic susceptibility imaging) and magnetic resonance spectroscopy, compared to conventional magnetic resonance imaging and histopathology, in grading of cerebral gliomas.

Abstract

Background: The current gold-standard histopathological assessment of gliomas is accompanied by appreciable risks of morbidity and mortality and inherent sampling errors may produce confusing results even for trained pathologists.

Objectives: To evaluate the correlation of relative Cerebral Blood Volume (rCBV), measured by Magnetic Resonance Perfusion Imaging, and metabolite ratios, measured by Magnetic Resonance Spectroscopy, with histopathological grading of cerebral gliomas.

Study design: Prospective observational study.

Participants: Forty-two patients with CT-documented cerebral lesions.

Methods: Patients underwent conventional MRI, dynamic susceptibility contrast perfusion MRI, and proton MR-spectroscopy. Gliomas were graded as low- or high-grade on conventional MRI, rCBV measurements were obtained & metabolite ratios (choline [Cho]/creatine [Cr], Cho/N-acetylaspartate [NAA], and NAA/Cr) were measured at a TE of 135 ms. Tumor grade with the three methods was then compared with histopathologic grading. Logistic regression and receiver operating characteristic analyses were performed to determine optimum thresholds for tumor grading.

Results: Sensitivity, specificity, PPV and NPV for determining a high-grade glioma with conventional MRI were 71%, 63.6%, 84.6% and 43.7%, respectively. Significant differences were noted in the rCBV, Cho/Cr & Cho/NAA between low- and high-grade gliomas (p<0.0001, <0.0001 and 0.049 respectively). A threshold value of 2.17 for rCBV provided sensitivity, specificity, PPV and NPV of 96.8%, 72.7%, 90.9% and 88.9%, respectively. For Cho/Cr, a threshold value of 1.00 provided sensitivity, specificity, PPV and NPV of 93.5%, 45.5%, 82.8% and 71.4%, respectively. For Cho/NAA, a threshold value of 1.03 provided the sensitivity, specificity, PPV, and NPV of 90.3%, 45.5%, 82.3%, and 62.5%, respectively.

Conclusion: rCBV, Cho/Cr and Cho/NAA ratios predict the presense of high-grade glioma, with more than 90% sensitivity when compared with the gold-standard histopathological grading.

Implications: MR perfusion and spectroscopy can be used to grade gliomas non-invasively and provide a means for guiding treatment and determining prognosis.