Noninvasively Predicting Gene Status of Glioma

Overview

Malignant gliomas are the most common and deadly primary brain tumors in adults. The clinical outcome of patients with glioblastoma depends on key molecular genetic alteration. Specifically, Isocitrate Dehydrogenase Gene Mutation, an independent favorable prognostic factor, serve as diagnostic and prognostic markers of glioma. Thus, accurate grading of a glioma is fundamental in order to determine the treatment strategy. Amide proton transfer (APT) imaging is a noninvasive molecular MRI technique based on chemical exchange saturation transfer mechanism that detects endogenous mobile proteins and peptides in biological tissues. Preliminary studies have shown that APT-weighted (APTw) signal intensity could serve as a new imaging biomarker, by revealing significantly higher signal intensities in the high-grade gliomas compared with the low-grade gliomas. The purpose of this study was to investigate the value of amide proton transfer imaging (APT) in the noninvasive evaluation of isocitrate dehydrogenase (IDH) gene status in glioma.

Materials and Methods: The whole brain MRI examinations were performed on a 3.0-T MRI system (Discovery MR750, General Electric Medical System, Milwaukee, WI, USA) with an eight-channel head coil (General Electric Medical System). Conventional MRI, contrast-enhanced MRI, DWI and amide proton transferimaging were performed in regular sequence during the same examination. Finally, contrast-enhanced T1-weighted spin echo sequence was acquired in the transverse, sagittal, and coronal planes after intravenous administration of 0.01 mmol/kg gadodiamide (Omniscan; GE Healthcare, Co. Cork, Ireland). MRI data processing and image analysis: All data were transferred to a workstation (Advantage Workstation 4.6, General Electric Medical System, Milwaukee, Wisconsin, USA) for processing.The MR imaging of all the patients were assessed independently by two experienced neuroradiologist (HYC and YLF, who have 12 and 6 years of experience, respectively, in neurologic-oncologic imaging) who were blinded to the patient's information. Next, a region of interest (ROI) was drawn manually on the solid part of the tumor with the relatively higher signal intensity on APT image. Statistical analysis: Categorical data obtained from image were calculated using the Fisher's exact test. Quantitative data were denoted as the mean and standard deviation. The Kolmogorov-Smirnov (K-S) test was used to assess the normality of data distribution.APT-weighted (APTw) signal intensity were tested for differences between the IDH mutation and the IDH wild-type by using independent sample t test.