Baldewsing Radj A, Schaar Johannes A, Mastik Frits, Oomens Cees W J, van der Steen Antonius F W
Biomedical Engineering, room Ee 23.02, Thoraxcenter, Erasmus Medical Center Rotterdam, PO Box 1738, 3000 DR Rotterdam, The Netherlands.
IEEE Trans Med Imaging. 2005 Apr;24(4):514-28. doi: 10.1109/tmi.2005.844170.
Intravascular ultrasound (IVUS) elastography visualizes local radial strain of arteries in so-called elastograms to detect rupture-prone plaques. However, due to the unknown arterial stress distribution these elastograms cannot be directly interpreted as a morphology and material composition image. To overcome this limitation we have developed a method that reconstructs a Young's modulus image from an elastogram. This method is especially suited for thin-cap fibroatheromas (TCFAs), i.e., plaques with a media region containing a lipid pool covered by a cap. Reconstruction is done by a minimization algorithm that matches the strain image output, calculated with a parametric finite element model (PFEM) representation of a TCFA, to an elastogram by iteratively updating the PFEM geometry and material parameters. These geometry parameters delineate the TCFA media, lipid pool and cap regions by circles. The material parameter for each region is a Young's modulus, EM, EL, and EC, respectively. The method was successfully tested on computer-simulated TCFAs (n = 2), one defined by circles, the other by tracing TCFA histology, and additionally on a physical phantom (n = 1) having a stiff wall (measured EM = 16.8 kPa) with an eccentric soft region (measured EL = 4.2 kPa). Finally, it was applied on human coronary plaques in vitro (n = 1) and in vivo (n = 1). The corresponding simulated and measured elastograms of these plaques showed radial strain values from 0% up to 2% at a pressure differential of 20, 20, 1, 20, and 1 mmHg respectively. The used/reconstructed Young's moduli [kPa] were for the circular plaque EL = 50/66, EM = 1500/1484, EC = 2000/2047, for the traced plaque EL = 25/1, EM = 1000/1148, EC = 1500/1491, for the phantom EL = 4.2/4 kPa, EM = 16.8/16, for the in vitro plaque EL = n.a./29, EM = n.a./647, EC = n.a./1784 kPa and for the in vivo plaque EL = n.a./2, EM = n.a./188, Ec = n.a./188 kPa.
血管内超声（IVUS）弹性成像技术通过所谓的弹性图来显示动脉的局部径向应变，以检测易破裂斑块。然而，由于动脉应力分布未知，这些弹性图不能直接解读为形态和材料成分图像。为克服这一局限性，我们开发了一种从弹性图重建杨氏模量图像的方法。该方法特别适用于薄帽纤维粥样斑块（TCFA），即具有含脂质池的中膜区域且由帽覆盖的斑块。重建通过一种最小化算法完成，该算法将用TCFA的参数有限元模型（PFEM）表示计算得到的应变图像输出与弹性图进行匹配，通过迭代更新PFEM的几何形状和材料参数来实现。这些几何参数通过圆来描绘TCFA的中膜、脂质池和帽区域。每个区域的材料参数分别是杨氏模量(E_M)、(E_L)和(E_C)。该方法已在计算机模拟的TCFA（(n = 2)）上成功测试，一个由圆定义，另一个通过追踪TCFA组织学定义，此外还在一个具有硬壁（测量得到的(E_M = 16.8)kPa）和偏心软区域（测量得到的(E_L = 4.2)kPa）的物理模型（(n = 1)）上进行了测试。最后，该方法应用于体外（(n = 1)）和体内（(n = 1)）的人体冠状动脉斑块。这些斑块相应的模拟和测量弹性图在压力差分别为20、20、1、20和1 mmHg时显示出从0%到2%的径向应变值。所使用/重建的杨氏模量[kPa]分别为：圆形斑块的(E_L = 50/66)，(E_M = 1500/1484)，(E_C = 2000/2047)；追踪斑块的(E_L = 25/1)，(E_M = 1000/1148)，(E_C = 1500/1491)；模型的(E_L = 4.2/4) kPa，(E_M = 16.8/16)；体外斑块的(E_L = 未给出/29)，(E_M = 未给出/647)，(E_C = 未给出/1784) kPa；体内斑块的(E_L = 未给出/2)，(E_M = 未给出/188)，(E_C = 未给出/188) kPa。
