Assessment of Glioma Response to Radiotherapy Using Multiple MRI Biomarkers with Manual and Semiautomated Segmentation Algorithms

Abstract

Background and Purpose Multi-modality MRI can provide complementary information in the assessment of brain tumors. We aimed to segment tumor in amide proton transfer-weighted (APTw) images and to investigate multi-parametric MRI biomarkers for the assessment of glioma response to radiotherapy. For tumor extraction, we evaluated a semi-automated segmentation method based on region of interest (ROI) results by comparing it with the manual segmentation method. Methods Thirteen nude rats injected with U87 tumor cells were irradiated by an 8-Gy radiation dose. All MRI scans were performed on a 4.7 T animal scanner pre-radiation, and at day 1, day 4, and day 8 post-radiation. Two experts performed manual and semi-automated methods to extract tumor ROIs on APTw images. Multi-modality MRI signals of the tumors, including structural (T2 and T1), functional (apparent diffusion coefficient and blood flow), and molecular (APTw and magnetization transfer ratio or MTR), were calculated and compared quantitatively. Results The semi-automated method provided more reliable tumor extraction results on APTw images than the manual segmentation, in less time. A considerable increase in the ADC intensities of the tumor was observed during the post-radiation. A steady decrease in the blood flow values and in the APTw signal intensities were found after radiotherapy. Conclusions The semi-automated method of tumor extraction showed greater efficiency and stability than the manual method. Apparent diffusion coefficient, blood flow, and APTw are all useful biomarkers in assessing glioma response to radiotherapy.

Implementing diffusion-weighted MRI for body imaging in prospective multicentre trials: current considerations and future perspectives

“…As interobserver concordance is dependent on extent of sampling [ 88 ], the method of segmentation should be clearly recorded, for example, whether whole tumour or selected slices are segmented, and whether necrotic or cystic areas are excluded. A manual, semi-automated or automated method could also introduce variability in the measurement [ 89 ] and should be standardised.…”

Direct radiofrequency saturation corrected amide proton transfer tumor MRI at 3T

“…1 In vivo APT effect in the cancerous tissue has been largely attributed to endogenous cellular protein and peptide content change, which is valuable in tumor grading [2][3][4][5] and prediction of response to treatments. [6][7][8][9][10][11][12] Magnetization transfer (MT) asymmetry (MTR asym ) analysis has been widely used to measure in vivo APT effect because it is simple to calculate yet reasonably corrects the direct radiofrequency (RF) saturation of the bulk water signal (i.e., direct water saturation [DWS]). However, it has been recognized that in vivo MTR asym is complex.…”

Magnetic resonance imaging-guided radiation therapy using animal models of glioblastoma

“…To further increase the accuracy of tumour localization and delineation, a semiautomatic segmentation method was evaluated to provide more reliable MR biomarkers. 32 Comparison between manual and semiautomatic analysis revealed lower intra-and interobserver variability using the semiautomatic methods, improving the accuracy of multiparametric MR. This research group also compared their multiparametric MR approach to contrast-enhanced ultrasound imaging (CEUS) and observed that several CEUS-based metrics correlated well with MR-based metrics.…”

“…31 Pre-clinical, these more advanced MR techniques were used by the MR research group at John Hopkins University for the assessment of response to RT in a rat model of GB. [32][33][34] Hong et al 34 performed longitudinal quantitative multiparametric MRI, in addition to standard T 2 weighted MR. The quantitative MR sequences included T 1 relaxometry, T 2 relaxometry, diffusion-weighted imaging (DWI), arterial spin labelling and chemical exchange-dependent saturation transfer (CEST) techniques.…”