Location

Brunswick, ME

Start Date

1-1-1997 12:00 AM

Description

Palpation is routinely used for the evaluation of mechanical properties of tissue in regions that are accessible to touch. This means of detecting pathology using the “stiffness” of the tissue is more that 2000 years old. Even today it is common for surgeons to find lesions during surgery that have been missed by advanced imaging methods. Palpation is subjective and limited to individual experience and to the accessibility of the tissue region to touch. It appears that a means of noninvasively imaging elastic modulus (the ratio of applied stress to strain) may be useful to distinguish tissues and pathologic processes based on mechanical properties such as elastic modulus [1]. To this end many approaches have been developed over the years [2–9]. The approaches have been to use conventional imaging methods to measure the mechanical response of tissue to mechanical stress. Static, quasi-static or cyclic stresses have been applied. The resulting strains have been measured using ultrasound [1–9] or MRI [10–15] and the related elastic modulus has been computed from visco-elastic models of tissue mechanics. Recently a new MRI phase contrast technique has been reported in which transverse strain waves propagating in tissue are imaged [13, 14, 16]. Because the wavelengths of propagating waves are related to density and the shear modulus and because the wavelengths of transverse waves for low frequency is on the order of millimeters this method promises to have good resolution and to be sensitive to the shear modulus. This paper reviews the theory of the method, presents some applications and discusses the implications of the method.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

16A

Chapter

Minisymposium

Pages

19-26

DOI

10.1007/978-1-4615-5947-4_3

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Measurement of Tissue Elasticity Using Magnetic Resonance Elastography

Brunswick, ME

Palpation is routinely used for the evaluation of mechanical properties of tissue in regions that are accessible to touch. This means of detecting pathology using the “stiffness” of the tissue is more that 2000 years old. Even today it is common for surgeons to find lesions during surgery that have been missed by advanced imaging methods. Palpation is subjective and limited to individual experience and to the accessibility of the tissue region to touch. It appears that a means of noninvasively imaging elastic modulus (the ratio of applied stress to strain) may be useful to distinguish tissues and pathologic processes based on mechanical properties such as elastic modulus [1]. To this end many approaches have been developed over the years [2–9]. The approaches have been to use conventional imaging methods to measure the mechanical response of tissue to mechanical stress. Static, quasi-static or cyclic stresses have been applied. The resulting strains have been measured using ultrasound [1–9] or MRI [10–15] and the related elastic modulus has been computed from visco-elastic models of tissue mechanics. Recently a new MRI phase contrast technique has been reported in which transverse strain waves propagating in tissue are imaged [13, 14, 16]. Because the wavelengths of propagating waves are related to density and the shear modulus and because the wavelengths of transverse waves for low frequency is on the order of millimeters this method promises to have good resolution and to be sensitive to the shear modulus. This paper reviews the theory of the method, presents some applications and discusses the implications of the method.