Multimodal Imaging to Delineate Tumor Heterogeneity in Cerebral Gliomas

Abstract

Purpose: Magnetic resonance imaging (MRI) is the gold standard in visualizing brain tumors and their effects on adjacent structures. However, no reliable information concerning different tumor components and borders between perifocal edema and infiltration areas can be received. The aim of the study was to establish and evaluate a multimodal imaging concept, in order to differentiate different biological tumor components and to determine tumor borders. Materials and Methods: 12 patients with cerebral gliomas (four low and eight high grade) received a "morphological" MRI, a 3D MR spectroscopy and a T2* MR perfusion examination prior to surgery. Data was evaluated by defining different tumor components, which were entitled based upon their multimodal characteristics and histological data. Results: In high grade gliomas different components can be differentiated, which were described as: "true edema", "cellular proliferation", "vascular proliferation", "cellular infiltration", "tumor" and "necrosis". In low grade gliomas, four different tumor components were found: "true edema", "cellular infiltration", "cellular proliferation" and "tumor". Conclusion: With the applied multimodal imaging and a novel evaluation concept, it was possible to detect different tumor components, which could be helpful in detecting the optimal sites for tumor biopsy. Especially in morphological "edema appearing" sites, this knowledge could be important for the adaption of tumor resection borders and the planning of radiation therapy. Further studies with more patients and histological correlation are needed.

Convex-Envelope Based Automated Quantitative Approach to Multi-Voxel 1H-MRS Applied to Brain Tumor Analysis

“…An overview of the recent literatures on brain tumor diagnosis using an in vivo 1 H-MRS quantitative method shows that most authors presented the statistical analysis results for tumor type-specific or for tumor grading based on 1 H-MRS quantitative results using MRI application software provided by GE, Siemens and Philips [ 25 – 32 ]. Their various results imply that although 1 H-MRS can be used as an auxiliary tool for brain tumor diagnosis, the MRS data processing methods are not robust enough for in vivo complex tissues.…”

“…As current research reports on glioma grading show, MRS quantitative analysis may be the simplest, safest, and most effective method. However, the accuracy is not as high as the combination analysis of MRS and PWI [ 32 , 34 – 36 ].…”

Diffusion and perfusion weighted magnetic resonance imaging for tumor volume definition in radiotherapy of brain tumors

“…Accurate margin definition for gliomas has been a challenge in radiotherapy. The tumor perfusion parameter maps derived from DSC and DCE imaging, including rCBV, rMTT and K trans , provide information about tumor vascularity that is reflective of tumor invasion and allows for improved tumor volume delineation [ 55 – 58 ], as well as determination of aggressive or infiltrating tumor sub-volume in radiotherapy treatment planning [ 59 , 60 ].…”

“…There are different components in a glial neoplasm, including cancerous tissue, pure edema, cellular proliferation, vascular proliferation, cellular infiltration and necrosis, and the number of components increases with the tumor grade. To differentiate different biological tumor components and to determine tumor borders between peritumoral edema and infiltration areas, rCBV values in different morphological areas (e.g., solid appearing, edematous appearing) were evaluated [ 55 ]. In the perienhancing areas with abnormal signals on conventional contrast-enhanced MR images for gliomas, rCBV proved significantly higher in cancerous tissue, lower in normal tissue, and intermediate in the infiltrating tumor, perhaps providing useful information for improving the definition of glioma extent and grade [ 56 ].…”

“…By evaluating the spatial distribution of substances correlated with metabolic activity in tumor tissue, including choline (Cho), N-acetylaspartate (NAA), creatine (Cr), lipids and/or lactate (LL), 1 H-MRSI was used to differentiate different biological tumor components and to determine tumor borders for radiotherapy planning [ 74 ]. In a recent report, Grams et al established and evaluated a multimodal imaging concept that included Cho/Cr ratio, NAA-concentration and rCBV derived from 1 H-MRSI and DSC [ 55 ]. With this method, different groups of tumors with different multimodal imaging characteristics such as “true edema,” “cellular infiltration,” “cellular proliferation” and “tumor” were identified for patients with gliomas.…”