Magnetic Resonance Elastography: Preliminary Experimental Study
10.3969/j.issn.1005-202X.2006.04.006
- VernacularTitle:磁共振弹性成像的初步实验研究
- Author:
Lei XU
;
Peiyi GAO
;
Yan LIN
;
Zhinong XI
;
Wei SUN
;
Hao SHEN
- Publication Type:Journal Article
- Keywords:
Magnetic resonance elastography;
Shear wave;
Shear modulus
- From:Chinese Journal of Medical Physics
2006;23(4):253-257
- CountryChina
- Language:Chinese
-
Abstract:
Objective: To study magnetic resonance elastography (MRE) technique. Methods: An external force actuator was developed, the imaging pulse sequence of MRE was designed,and tissue simulating phantoms were constructed. The actuator controlled by the pulse sepuence produced shear waves at low frequency on the surface of the phantoms. A modified gradient echo sequence was developed with motion sensitizing gradient (MSG)imposed along X,Y or Z direction.Cyclic displacement within the medium induced by shear waves caused a measurable phase shift in the received MR signal.From the measured phase shift,the displacement at each voxel could be calculated,and the propatating shear waves within the medium were directly imaged. By adjusting the phase offsets,the dynamic propagation of shear waves in a wave cycle was obtained.The phase images were processed to aquire quantitative elasticity image using local frequency estimation(LFE)method. The experiments were implemented with 1.0% and 1.5% tissue simulating agarose gel. Shear waves at frequency of 150 Hz,200 Hz,250 Hz,and 300 Hz were applied. Results: The phase images of MRE directly imaged the propagating shear waves within the phantoms.The wavelength of shear waves varied with the change of exciting frequency and stiffness of the phantoms. The wavelength of shear waves was exactly proportional to the frequency and stiffness of the phantom. The contrast of elasticity in agarose gel with two concentrations was clearly demonstrated on elasticity images.Conclusion: The phase images of MRE can directly visualize the propagation of shear waves in the medium. The elasticity image of MRE can quantitatively image the elastic modulus of the medium
