Magnetic resonance-based soft tissue elasticity measurement

Magnetic resonance imaging is a medical imaging technology which has gained widespread popularity in clinical applications.The advantages of MRI as a medical imaging modality include its high image quality,3D imaging and functional imaging capabilities,which render it particularly useful for the diagnosis of diseases in various tissues and organs.With the fast development and fast increasing popularity of this modality,special interest has been attracted to the MRI-based elasticity measurement and imaging techniques(called MR elastography or MRE) and they have also gained many applications nowadays.With the quasi-static loading,MRI can be directly applied to measure the displacement and deformation of the tested tissue.With a dynamic loading,conventional MRI may not be a good choice for this purpose because of its limited imaging speed.In this case,MRE can be achieved by applying the tagging technique or shear wave propagation measurement,the latter of which has been the mainstream of current research.In shear wave-MRE,the motion-sensitive pulses can be designed to measure the spatiotemporal phase information of the propagating shear wave and then to extract its propagation speed for the measurement of tissue elasticity.Compared to traditional ultrasound-based elasticity measurement and imaging methods,MRE has its own advantages such as the more accurate 3D displacement measurement,the larger field of view(limited by the probe size in ultrasound) and the capability in brain elasticity measurement,for which otherwise it is unpractical for ultrasound.This paper mainly introduces the MRI-based techniques for tissue elasticity imaging and measurement(MRE).Firstly the related techniques and their characteristics in MRE are introduced,followed by relevant applications of current MRE in several soft tissues.At the end of this paper we summarize the problems and look forward into some future perspectives of this field.