Rohlfing Torsten, Maurer Calvin R, O'Dell Walter G, Zhong Jianhui
Image Guidance Laboratories, Department of Neurosurgery, Stanford University, Stanford, California 94305-5327, USA.
Med Phys. 2004 Mar;31(3):427-32. doi: 10.1118/1.1644513.
We present a technique for modeling liver motion during the respiratory cycle using intensity-based nonrigid registration of gated magnetic resonance (MR) images. Three-dimensional MR images of the abdomens of four volunteers were acquired at end-inspiration, end-expiration, and eight time points in between using respiratory gating. The deformation fields between the images were computed using intensity-based rigid and nonrigid registration algorithms. Global motion is modeled by a rigid transformation while local motion is modeled by a free-form deformation based on B-splines. Much of the liver motion was cranial-caudal translation, which was captured by the rigid transformation. However, there was still substantial residual deformation (approximately 10 mm averaged over the entire liver in four volunteers, and 34 mm at one place in the liver of one volunteer). The computed organ motion model can potentially be used to determine an appropriate respiratory-gated radiotherapy window during which the position of the target is known within a specified excursion.
我们提出了一种技术，通过对门控磁共振（MR）图像进行基于强度的非刚性配准，来模拟呼吸周期中的肝脏运动。使用呼吸门控技术，在四名志愿者吸气末、呼气末以及两者之间的八个时间点采集了腹部的三维MR图像。使用基于强度的刚性和非刚性配准算法计算图像之间的变形场。全局运动通过刚性变换建模，而局部运动通过基于B样条的自由形式变形建模。肝脏的大部分运动是头-尾平移，这通过刚性变换捕获。然而，仍存在大量残余变形（四名志愿者整个肝脏平均约为10毫米，一名志愿者肝脏的一个位置为34毫米）。计算得到的器官运动模型有可能用于确定合适的呼吸门控放射治疗窗口，在此窗口内目标位置在指定偏移范围内是已知的。
