Multimodal Analysis of Vasogenic Edema in Glioblastoma Patients for Radiotherapy Planning

Matthieu Lê,Nicholas Ayache,Elizabeth Gerstner,Tracy Batchelor,Jan Unkelbach,Jayashree Kalpathy-Cramer,Hervé Delingette,Helen Shih

doi:10.54294/i2w39x

Abstract

Glioblastoma (GBM) is the most common type of primary brain tumor, which is characterized by an infiltrative growth pattern. In current practice, radiotherapy planning is primarily based upon T2 FLAIR MRI despite its known lack of specificity in the detection of tu- mor infiltration. While hyperintensity on T2 FLAIR is widely considered to represent infiltrative tumor, it may also be caused by the presence of vasogenic edema (VE), caused by a leakage of fluid into the brain parenchyma. Distinguishing VE from infiltrative tumor could have im- pact on improving radiotherapy planning. In this paper we study a data set of 17 GBM patients treated with anti-angiogenic therapy for which a fast decrease of T2 FLAIR hypersignal is observed, which indicates the resolution of VE. We investigate if multimodal MRI acquisitions in- cluding diffusion tensor imaging can distinguish between VE and tumor infiltration prior to therapy. Using a random forest classifier, we show that, in this study, morphological information based on the contrast en- hanced T1 image explains up to 75% of the extent of VE. The information from different imaging modalities did not significantly improve the clas- sification. We then show that delineating the VE prior to therapy can have substantial impact on radiotherapy target delineation, leading to smaller treatment volumes and reducing potentially harmful radiation dose to normal brain tissue.

Highlights

Glioblastoma (GBM) is an infiltrative brain tumor whose cells invade the adjacent brain tissue which is only partially revealed by MRI [1]
ROC curves were computed by changing the voting threshold of the prediction output of the random forest (RF)
Many GBM patients present extensive T2 FLAIR hyperintensity on brain imaging that is known in part to represent peritumoral edema and to less well understood extent, represent infiltrative tumor cells

Summary

Introduction

Glioblastoma (GBM) is an infiltrative brain tumor whose cells invade the adjacent brain tissue which is only partially revealed by MRI [1]. The signal abnormality on T2 FLAIR and contrast enhanced T1 (T1Gd) images is only a surrogate for tumor invaded tissue but not per se indicative of the presence of tumor cells. The T2 FLAIR abnormality is a signal resulting from the combination of the bulk of the tumor, tumor cell infiltration, and vasogenic edema (VE) [2]. Discarding VE from the T2 FLAIR abnormality could possibly result in a better surrogate for GBM cell infiltration and, as such, provide a better guide for radiotherapy planning by eliminating targeting of radiation to neighboring regions of normal uninvolved brain and other healthy tissues

Methods

Results

Conclusion