Muratore Diane M, Russ Jeannette Herring, Dawant Benoît M, Galloway Robert L
Department of Biomedical Engineering, Western New England College, Springfield, Massachusetts 01119, USA.
Comput Aided Surg. 2002;7(6):342-52. doi: 10.1002/igs.10055.
Applications of three-dimensional ultrasound (3D US) are emerging throughout the field of medicine. In this study, tracked, free-hand 3D phantom US images were mapped to computed tomograms (CT) as a development for image-guided surgery (IGS) of the spine. In the operating room, the registration of tracked 3D US images to other imaging modalities, such as CT, could allow the surgeon to identify more precisely the surgical target area prior to the incision. An independent quantitative measure of registration accuracy using a fiducial marker system was provided.
Three-dimensional free-hand US images of a phantom spine were created by tracking the transducer with an optical sensing system. Two sets of images were acquired from three lumbar vertebrae using 4.5- and 7.5-MHz transducers. These images were then segmented for the extraction of the posterior vertebral surface. Next, a surface-based registration of US to the corresponding segmented CT images was performed. Registration errors were computed as the distance between a set of target points transformed using the experimental transformation and the same set of target points transformed using fiducial markers as a gold standard.
Results indicated that alignment of these image sets is feasible using only part of the vertebral surface. In particular, the regions of the spinous process and laminae were used for registration. Target registration errors (TREs) were found to be lowest using the highest resolution CT images. Using the CT scans with 2-mm slice thickness, the TRE was calculated to be 1.33 +/- 0.30 mm for the 7.5-MHz US data set and 2.81 +/- 0.10 mm for the 4.5-MHz US data set. Moreover, residual errors in these surface alignments were 0.69 +/- 0.18 mm and 0.61 +/- 0.20 mm for the 4.5- and 7.5-MHz sets, respectively.
A rigid, surface-based registration of CT images to phantom spinal US images, acquired with a free-hand, tracked transducer, is achievable with a limited, easily obtainable portion of the vertebral surface.
三维超声（3D US）在医学领域的应用正在不断涌现。在本研究中，将跟踪式、徒手3D体模超声图像映射到计算机断层扫描（CT）上，作为脊柱图像引导手术（IGS）的一项进展。在手术室中，将跟踪式3D超声图像与其他成像模态（如CT）进行配准，可使外科医生在切开前更精确地识别手术目标区域。提供了一种使用基准标记系统对配准精度进行独立定量测量的方法。
通过光学传感系统跟踪换能器，创建体模脊柱的三维徒手超声图像。使用4.5兆赫和7.5兆赫的换能器从三个腰椎获取两组图像。然后对这些图像进行分割，以提取椎体后表面。接下来，将超声与相应的分割CT图像进行基于表面的配准。配准误差计算为使用实验变换变换的一组目标点与使用基准标记作为金标准变换的同一组目标点之间的距离。
结果表明，仅使用椎体表面的一部分即可实现这些图像集的对齐。特别是，棘突和椎板区域用于配准。发现使用最高分辨率的CT图像时目标配准误差（TRE）最低。对于2毫米层厚的CT扫描，7.5兆赫超声数据集的TRE计算为1.33±0.30毫米，4.5兆赫超声数据集的TRE计算为2.81±0.10毫米。此外，4.5兆赫和7.5兆赫组在这些表面对齐中的残余误差分别为0.69±0.18毫米和0.61±0.20毫米。
使用徒手跟踪换能器获取的CT图像与体模脊柱超声图像进行基于表面的刚性配准，通过椎体表面有限且易于获取的部分即可实现。
