Visualization and quantification of breast cancer biomechanical properties with magnetic resonance elastography

Abstract

A quasistatic magnetic resonance elastography (MRE) method for the evaluation of breast cancer is proposed. Using a phase contrast, stimulated echo MRI approach, strain imaging in phantoms and volunteers is presented. First-order assessment of tissue biomechanical properties based on inverse strain mapping is outlined and demonstrated. The accuracy of inverse strain imaging is studied through simulations in a two-dimensional model and in an anthropomorphic, three-dimensional finite-element model of the breast. To improve the accuracy of modulus assessment by elastography, inverse methods are discussed as an extension to strain imaging, and simulations quantify MRE in terms of displacement signal/noise required for robust inversion. A direct inversion strategy providing information on tissue modulus and pressure distribution is described along with a novel iterative method utilizing a priori knowledge of tissue geometry. It is shown that through the judicious choice of information from previous contrast-enhanced MRI breast images, MRE data acquisition requirements can be significantly reduced while maintaining robust modulus reconstruction in the presence of strain noise. An experimental apparatus for clinical breast MRE and preliminary images of a normal volunteer are presented.

Magnetic resonance elastography of the brain

“…For example, static and quasi-static MRE (Plewes et al 2000) techniques require compression of the tissue through hundreds of microns for tens or hundreds of milliseconds, which is not practical to do non-invasively. Ultrasound elasticity (Cespedes et al 1993;Ophir et al 1991) imaging of the in vivo brain would be extremely difficult due to the lack of an acoustic window through the skull.…”

Non-identifiability of the Rayleigh damping material model in Magnetic Resonance Elastography

“…Magnetic Resonance Elastography (MRE) can directly visualise and measure tissue elasticity [5][6][7][8], and has been applied to resolve stiffness characteristics of a variety human tissues and organs, such as muscle [9][10][11][12], breast [13][14][15][16][17], liver [18][19][20] and the brain [21][22][23][24][25][26][27][28][29]. MRE acquisition requires application of mechanical waves to tissue within the MRI, phase-contrast MR pulse sequence extended with motion encoding gradient (MEGs), and sophisticated inverse problem methods to identify an elastic modulus map of the tissue.…”

Diffraction-biased shear wave fields generated with longitudinal magnetic resonance elastography drivers

“…Measurement of motion with MR in medical applications was originally directed at blood flow measurement and vascular imaging (1)(2)(3)(4). Dynamic Magnetic Resonance Elastography is a technique in which propagating shear waves are generated in tissue, typically by an external mechanical driver, and the waves are imaged using a modified phase-contrast technique (5,6).…”