開發以醫學影像為基礎之創新技術以量測活體三維椎體運動

Abstract

精確量測脊椎於功能性動作時的椎體運動將有助於對脊椎功能之了解與許多臨床醫療與研究之應用。雖然許多量測技術已被提出且用來量測椎體運動，至今能夠在符合生理荷重的情況下，以非侵入式的方法精確量測三維、動態椎間運動的方法仍然很有限。近年來，少數基於椎骨模型之二維對三維影像契合方法被提出，但是這些關節運動量測方法仍有其精度上或使用上的侷限性，且這些方法之精確度從未在相同的實驗平台上接受評估與比較。 因此，本研究建構並評估比較四種主要的二維對三維影像契合之方法(基於投影的方法)，包含了STS (表面模型對單平面X光)，VTS (實體模型對單平面X光)，STB (表面模型對雙平面X光)，VTB (實體模型對雙平面X光)等四種方法。並開發一整合VTS與椎骨模型碰撞偵測與約束限制之方法，進一步增加實體模型對單平面X光之契合方法的精確度。基於經實驗驗證的影像契合方法，進一步將其運用於量測正常受試者之頸椎在屈曲/伸展、側彎和軸向旋轉等三種功能性動作時的三維椎體運動。另一方面，除了基於投影的影像契合技術，本研究另發展並驗證一影像切片對實體模型的對位方法，該方法整合三維靜態核磁共振影像與一創新的單切片、即時的徑向FLASH核磁共振影像。 透過實驗驗證評估，VTB被證明具有最高的精確度，VTS可達到與該方法接近的旋轉精度，STB可達到與該方法接近的位移精度，而STS則擁有最低的精確度。整合VTS與椎骨模型碰撞限制的方法成功降低了椎間運動量測時的出影像平面位移誤差，同時保持其他自由度的量測精確度。運用上述開發之影像契合方法，正常人受試者在執行三種不同頸椎功能性動作時的活體三維椎間運動可以被精確測量與分析。影像切片對實體模型的對位方法的精確度與重覆性，亦透過實驗之驗證評估而得到了確立，該方法在可避免輻射照射的優勢下，將有望成為評估三維椎體運動時的一項非侵入式且低風險量測工具。

Accurate measurement of in vivo vertebral kinematics of the spine during functional activities is essential for better understanding of its function and for many clinical applications. While several techniques have been developed to measure the spinal kinematics, not many allow for non-invasive measurement of the 3D and dynamic intervertebral motion under physiological weight-bearing conditions. Although a few model-based 2D-to-3D registration methods are available in measuring 3D vertebral motion recently, their performance has not been evaluated under the same experimental protocol. The existing methods are also limited either in their accuracy or difficulties in implementation. Four major types of 2D-to-3D registration methods (projection-based methods) were established and experimentally evaluated, namely STS (surface, single-plane), VTS (volumetric, single-plane), STB (surface, bi-plane) and VTB (volumetric, bi-plane). A new single-plane fluoroscopy-to-CT registration method (VTS) integrated with intervertebral anti-collision constraints was proposed. The validated registration methods were then applied to measure the 3D motion of cervical vertebrae during the flexion/extension, lateral bending and axial rotation in normal subjects. In addition to the projection-based registration methods, a new slice-to-volume registration method that integrated 3D static MRI volumes of the vertebrae with an advanced single-slice, real-time radial FLASH MRI was developed and experimentally evaluated. It was concluded that (a) The VTB was found to have the highest precision, comparable with the VTS in rotations, and the STB in translations. The STS had the lowest precision. (b) The fluoroscopy-to-CT registration (i.e. VTS) integrated with anti-collision constraints successfully reduced the out-of-plane translation errors for intervertebral kinematic measurements while keeping the measurement accuracies for the other five degrees-of-freedom more or less unaltered. (c) With the validated volumetric model-based registration methods, the 3D kinematics of the sub-axial cervical spine during activities had been accurately measured. (d) With the accuracy and repeatability achieved, and without the use of ionizing radiation, the slice-to-volume registration combining the real-time radial FLASH MR imaging is potential to be a low-risk, valuable tool for studying 3D vertebral kinematics non-invasively.