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in vivo MR elastography of human liver
Chronic liver disease very often leads to liver fibrosis, the most common cause of chronic liver failure [1]. Early detection of fibrotic changes of the liver is therefore welcome to initiate treatment at the earliest possible time point. Among non-invasive diagnostic modalities [2,3] MR elastography (MRE) is an emerging technique that may be suitable for evaluation of fibrotic changes of the liver.
Current developments of MR elastography of human liver are based on spin-echo MRI, EPI or balanced SSFP-sequences combined with different ways of wave generation by electromagnetic coils or pneumatic drivers [11]. This planar and fractional MRE approach is capable of providing viscoelastic parameters within a few breath-holds.
Balanced SSFP-MRE of a healthy volunteer (left image) and a patient with fibrosis grade 3 (right image). The dashed lines demarcate the manually segmented liver. The solid lines demarcate the ROI used for scalar wave-field inversion.(fv = 51 Hz; through-plane deflections)
see some animated waves
Shear modulus in human liver of 14 subjects. The data are sorted by age within subgroups of females and males (* fibrosis-grade-3 patients).
The proposed fractional bSSFP-MRE was successfully applied for measuring in vivo shear stiffness of human liver. The combination of axial vibrations introduced into the liver below the right costal arch and a transverse image slice through the center of the liver allowed the reconstruction of elasticity from planar waves. Strain waves in the liver are encoded using fractional MRE with a vibration frequency of 51 Hz tuned to 1/(2TR). The MRE signal in the liver is fast sampled with a balanced gradient scheme that incorporates a single bipolar gradient pair for motion sensitization. This technique allowed the acquisition of 20 time-resolved wave images within 4 breath-holds of 17 sec each. Repetition of the protocol in the same volunteer showed good reproducibility. The stiffness of liver varied significantly among healthy male volunteers.
References
[1] Pinzani M, Rombouts K, Colagrande S. Fibrosis in chronic liver diseases: diagnosis and management. J Hepatol 2005;42:S22-S36.
[2] Ziol M, Handra-Luca A, Kettaneh A, et al. Noninvasive assessment of liver fibrosis by measurement of stiffness in patients with chronic hepatitis C. Hepatology 2005;41:48-54.
[3] Corpechot C, El Naggar A, Poujol-Robert A, et al. Assessment of biliary fibrosis by transient elastography in patients with PBC and PSC. Hepatology 2006;43:1118-1124.
[4] Dresner MA, Fidler J, Ehman RL. MR elastography of in vivo human liver. In: Proc 12th Annual Meeting ISMRM. Kyoto. 2004. p 502.
[5] Rouviere O, Yin M, Dresner MA, et al. In vivo MR elastography of the liver: Preliminary results. In: Proc 13th Annual Meeting ISMRM. Miami. 2005. p 340.
[6] Peeters F, Sinkus R, Salameh N, et al. In vivo MR elastography of the liver fibrosis. In: Proc 13th Annual Meeting ISMRM. Miami. 2005. p 339.
[7] Sinkus R, ter Beek LC, Peeters F, et al. Navigator-gated in-vivo 3D liver MR elastography. In: Proc 13th Annual Meeting ISMRM. Miami. 2005. p 339.
[8] Huwart L, Peeters F, Sinkus R, et al. Liver fibrosis: non-invasive assessment with MR elastography. NMR Biomed 2006;19:173-179.
[9] Yin M, Grimm RC, Manduca A, et al. Rapid EPI-based MR Elastography of the Liver. In: Proc 14th Annual Meeting ISMRM. Seattle. 2006. p 2268.
[10] Klatt D, Asbach P, Rump J, et al. Fast planar steady-state free precession MR elastography on human liver. In: Proc 14th Annual Meeting ISMRM. Seattle. 2006. p 399.
[11] Rump J, Klatt D, Papazoglou S, et al. Desynchronized motion encoding in rapid steady-state free precession MR elastography. In: Proc 14th Annual Meeting ISMRM. Seattle. 2006.
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