Alterovitz Ron, Goldberg Ken, Pouliot Jean, Hsu I-Chow Joe, Kim Yongbok, Noworolski Susan Moyher, Kurhanewicz John
Department of Industrial Engineering and Operations Research, University of California, Berkeley, 4141 Etcheverry Hall, Berkeley, California 94720-1777, USA.
Med Phys. 2006 Feb;33(2):446-54. doi: 10.1118/1.2163391.
Magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) have been shown to be very useful for identifying prostate cancers. For high sensitivity, the MRI/MRSI examination is often acquired with an endorectal probe that may cause a substantial deformation of the prostate and surrounding soft tissues. Such a probe is removed prior to radiation therapy treatment. To register diagnostic probe-in magnetic resonance (MR) images to therapeutic probe-out MR images for treatment planning, a new deformable image registration method is developed based on biomechanical modeling of soft tissues and estimation of uncertain tissue parameters using nonlinear optimization. Given two-dimensional (2-D) segmented probe-in and probe-out images, a finite element method (FEM) is used to estimate the deformation of the prostate and surrounding tissues due to displacements and forces resulting from the endorectal probe. Since FEM requires tissue stiffness properties and external force values as input, the method estimates uncertain parameters using nonlinear local optimization. The registration method is evaluated using images from five balloon and five rigid endorectal probe patient cases. It requires on average 37 s of computation time on a 1.6 GHz Pentium-M PC. Comparing the prostate outline in deformed probe-out images to corresponding probe-in images, the method obtains a mean Dice Similarity Coefficient (DSC) of 97.5% for the balloon probe cases and 98.1% for the rigid probe cases. The method improves significantly over previous methods (P < 0.05) with greater improvement for balloon probe cases with larger tissue deformations.
磁共振成像（MRI）和磁共振波谱成像（MRSI）已被证明在识别前列腺癌方面非常有用。为了获得高灵敏度，MRI/MRSI检查通常使用直肠内探头进行，这可能会导致前列腺和周围软组织发生显著变形。在放射治疗前会移除这种探头。为了在治疗计划中将诊断性探头在位的磁共振（MR）图像与治疗性探头移除后的MR图像进行配准，基于软组织的生物力学建模以及使用非线性优化估计不确定的组织参数，开发了一种新的可变形图像配准方法。给定二维（2-D）分割的探头在位和探头移除后的图像，使用有限元方法（FEM）来估计由于直肠内探头产生的位移和力而导致的前列腺和周围组织的变形。由于有限元方法需要组织刚度特性和外力值作为输入，该方法使用非线性局部优化来估计不确定参数。使用来自五个球囊和五个刚性直肠内探头患者病例的图像对配准方法进行评估。在1.6 GHz奔腾-M个人电脑上，该方法平均需要37秒的计算时间。将变形后的探头移除图像中的前列腺轮廓与相应的探头在位图像进行比较，对于球囊探头病例，该方法获得的平均骰子相似系数（DSC）为97.5%，对于刚性探头病例为98.1%。该方法比以前的方法有显著改进（P < 0.05），对于组织变形较大的球囊探头病例改进更大。
