Christensen G E, Carlson B, Chao K S, Yin P, Grigsby P W, Nguyen K, Dempsey J F, Lerma F A, Bae K T, Vannier M W, Williamson J F
Department of Electrical Engineering, University of Iowa, Iowa City, IA, USA.
Int J Radiat Oncol Biol Phys. 2001 Sep 1;51(1):227-43. doi: 10.1016/s0360-3016(01)01667-4.
To demonstrate that high-dimensional voxel-to-voxel transformations, derived from continuum mechanics models of the underlying pelvic tissues, can be used to register computed tomography (CT) serial examinations into a single anatomic frame of reference for cumulative dose calculations.
Three patients with locally advanced cervix cancer were treated with CT-compatible intracavitary (ICT) applicators. Each patient underwent five volumetric CT examinations: before initiating treatment, and immediately before and after the first and second ICT insertions, respectively. Each serial examination was rigidly registered to the patient's first ICT examination by aligning the bony anatomy. Detailed nonrigid alignment for organs (or targets) of interest was subsequently achieved by deforming the CT exams as a viscous-fluid, described by the Navier-Stokes equation, until the coincidence with the corresponding targets on CT image was maximized. In cases where ICT insertion induced very large and topologically complex rearrangements of pelvic organs, e.g., extreme uterine canal reorientation following tandem insertion, a viscous-fluid-landmark transformation was used to produce an initial registration.
For all three patients, reasonable registrations for organs (or targets) of interest were achieved. Fluid-landmark initialization was required in 4 of the 11 registrations. Relative to the best rigid bony landmark alignment, the viscous-fluid registration resulted in average soft-tissue displacements from 2.8 to 28.1 mm, and improved organ coincidence from the range of 5.2% to 72.2% to the range of 90.6% to 100%. Compared to the viscous-fluid transformation, global registration of bony anatomy mismatched 5% or more of the contoured organ volumes by 15-25 mm.
Pelvic soft-tissue structures undergo large deformations and displacements during the external-beam and multiple-ICT course of radiation therapy for locally advanced cervix cancer. These changes cannot be modeled by the conventional rigid landmark transformation method. In the current study, we found that the deformable anatomic template registration method, based on continuum-mechanics models of deformation, successfully described these large anatomic shape changes before and after ICT. These promising modeling results indicate that realistic registration of the cumulative dose distribution to the organs (or targets) of interest for radiation therapy of cervical cancers is achievable.
证明从盆腔基础组织的连续介质力学模型得出的高维体素到体素变换，可用于将计算机断层扫描（CT）系列检查配准到单个解剖参考框架中，以进行累积剂量计算。
三名局部晚期宫颈癌患者接受了与CT兼容的腔内（ICT）施源器治疗。每位患者均接受了五次容积CT检查：分别在开始治疗前、第一次和第二次ICT插入前及插入后立即进行。通过对齐骨骼解剖结构，将每次系列检查严格配准到患者的第一次ICT检查。随后，通过将CT检查作为粘性流体进行变形（由纳维-斯托克斯方程描述），直到与CT图像上的相应目标的重合度最大化，从而实现对感兴趣器官（或靶区）的详细非刚性对齐。在ICT插入导致盆腔器官发生非常大且拓扑复杂的重排的情况下，例如串联插入后子宫管极端重新定向，使用粘性流体地标变换来产生初始配准。
对于所有三名患者，均实现了对感兴趣器官（或靶区）的合理配准。11次配准中有4次需要流体地标初始化。相对于最佳的刚性骨骼地标对齐，粘性流体配准导致软组织平均位移为2.8至28.1毫米，器官重合度从5.2%至72.2%提高到90.6%至100%。与粘性流体变换相比，骨骼解剖结构的全局配准使5%或更多的轮廓器官体积在15至25毫米范围内不匹配。
在局部晚期宫颈癌的外照射和多次ICT放射治疗过程中，盆腔软组织结构会发生大的变形和位移。这些变化无法用传统的刚性地标变换方法进行建模。在本研究中，我们发现基于连续介质力学变形模型的可变形解剖模板配准方法成功地描述了ICT前后这些大的解剖形状变化。这些有前景的建模结果表明，对于宫颈癌放射治疗，实现对感兴趣器官（或靶区）的累积剂量分布进行真实配准是可行的。
