Multifrequency inversion in magnetic resonance elastography
Multifrequency inversion in magnetic resonance elastography
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DOI：
10.1088/0031-9155/57/8/2329
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发表时间：
2012-04-21
影响因子：
3.5
通讯作者：
Sack, Ingolf
中科院分区：
文献类型：
--
作者：
Papazoglou, Sebastian;Hirsch, Sebastian;Sack, Ingolf
时谐剪切波弹性成像技术能够测量活体组织的粘弹性参数。然而，有限的组织边界和波导效应会引起波的干扰，这是标准的弹性重建方法所不能考虑的。此外，组织的粘弹性导致复数剪切模数的色散，使得恢复的模数依赖于频率。因此，我们建议利用磁共振弹性成像(MRE)的多频波数据，用基于Springpot模型的代数最小二乘解来求解粘弹性重建的反问题。该方法有两个优点：(I)消除了单频驻波方向图中出现的幅度零点；(Ii)通过反演过程考虑了存储和损耗模数随驱动频率的色散，从而避免了后续的模型拟合。因此，与标准的单频参数恢复相比，多频反演在粘弹性参数图中产生的伪影更少，因此可以支持基于图像的粘弹性测量。通过对人体模型和活体人脑的模拟波形数据和MRE实验，验证了该方法的可行性。作为一种临床方法，多频倒置可以提高时间谐波MRE在各种应用中的诊断价值。
Time-harmonic shear wave elastography is capable of measuring viscoelastic parameters in living tissue. However, finite tissue boundaries and waveguide effects give rise to wave interferences which are not accounted for by standard elasticity reconstruction methods. Furthermore, the viscoelasticity of tissue causes dispersion of the complex shear modulus, rendering the recovered moduli frequency dependent. Therefore, we here propose the use of multifrequency wave data from magnetic resonance elastography (MRE) for solving the inverse problem of viscoelasticity reconstruction by an algebraic least-squares solution based on the springpot model. Advantages of the method are twofold: (i) amplitude nulls appearing in single-frequency standing wave patterns are mitigated and (ii) the dispersion of storage and loss modulus with drive frequency is taken into account by the inversion procedure, thereby avoiding subsequent model fitting. As a result, multifrequency inversion produces fewer artifacts in the viscoelastic parameter map than standard single-frequency parameter recovery and may thus support image-based viscoelasticity measurement. The feasibility of the method is demonstrated by simulated wave data and MRE experiments on a phantom and in vivo human brain. Implemented as a clinical method, multifrequency inversion may improve the diagnostic value of time-harmonic MRE in a large variety of applications.