Non-invasive characterization of intracranial tumors by magnetic resonance elastography

M Simon,H Scholand-Engler,C Erdmann,J Braun,D Petersen,I Sack,J Guo,S Papazoglou,J Wuerfel,U Melchert,M Bonsanto

doi:10.1088/1367-2630/15/8/085024

Abstract

Presurgical, non-invasive methods of differentiating brain tumors have remained unsatisfactory even for specialized academic hospitals. Despite major advances in clinical and neuroradiological diagnostic techniques, the majority of neurooncology patients still need to undergo a brain biopsy for diagnosis. Recent single cell experiments suggested that biomechanical cell properties might be very sensitive in detecting cellular malignancy. Accordingly, we investigated magnetic resonance elastography (MRE) as an investigative tool for the clinical routine diagnostic work-up of intracranial neoplasm. In order to obtain sufficient spatial resolution for the biomechanical characterization of intracranial tumors, we modified a recently introduced least-squares solution of the stationary wave equation, facilitating stable solutions of the magnitude |G*| and the phase angle φ of the complex shear modulus G*. MRE was added to a routine diagnostic or presurgical neuroradiological magnetic resonance imaging work-up in 16 prospective patients and it was well tolerated in all cases. Our preliminary tumor MRE data revealed alterations in viscoelastic constants, e.g. a loss of stiffness in malignancies compared to healthy reference tissue, or benign variants. Based on larger studies on selected tumor entities to establish threshold and reference values for future diagnostic purposes, MRE may thus provide a predictive marker for tumor malignancy and thereby contribute to an early non-invasive clinical assessment of suspicious cerebral lesions.

Highlights

Representative morphological details and anatomical locations are demonstrated by T2w and contrast-enhanced T1w images, comprising an oligastrocytoma World Health Organization (WHO) III, a meningeoma WHO I and a glioblastoma WHO IV
Regarding tumor entity and WHO classification, we found that those primary brain tumors of highest malignancy WHO IV presented with the highest loss of stiffness (33.6–52% softer than normal appearing white matter (NAWM))
The presurgical diagnostic tools available for the neuroradiological work-up of intracranial neoplasms are limited and a diagnosis, as well as the visualization of tumor margins based on current non-invasive imaging techniques, has remained challenging and sometimes insufficient, even for specialized university hospitals

Summary

Introduction

We modified a recently introduced least-squares solution of the stationary wave equation (Papazoglou et al 2012) in order to facilitate stable solutions of the magnitude |G∗| and the phase angle φ of the complex shear modulus G∗. In this pilot study we used the improved capability of MRE to obtain spatially resolved maps of viscoelastic constants for the biomechanical characterization of cerebral tumors in their natural environment. Motion sensitivity in MRE is acquired in the phase of the complex MRI signal (Muthupillai et al 1995). The motion field components u j can be obtained from the spin phase φ j by solving equation (1) numerically or by analytical expressions, as can be readily derived if both u j and

Methods

Results

Conclusion