School of Computing, Queen's University, Ontario K7L 3N6, Canada.
Med Phys. 2010 Jun;37(6):2749-60. doi: 10.1118/1.3416937.
In prostate brachytherapy, transrectal ultrasound (TRUS) is used to visualize the anatomy, while implanted seeds can be visualized by fluoroscopy. Intraoperative dosimetry optimization is possible using a combination of TRUS and fluoroscopy, but requires localization of the fluoroscopy-derived seed cloud, relative to the anatomy as seen on TRUS. The authors propose to develop a method of registration of TRUS images and the implants reconstructed from fluoroscopy.
A phantom was implanted with 48 seeds then imaged with TRUS and CT. Seeds were reconstructed from CT yielding a cloud of seeds. Fiducial-based ground-truth registration was established between the TRUS and CT. TRUS images are filtered, compounded, and registered to the reconstructed implants by using an intensity-based metric. The authors evaluated a volume-to-volume and point-to-volume registration scheme. In total, seven TRUS filtering techniques and three image similarity metrics were analyzed. The method was also tested on human subject data captured from a brachytherapy procedure.
For volume-to-volume registration, noise reduction filter and normalized correlation metrics yielded the best result: An average of 0.54 +/- 0.11 mm seed localization error relative to ground truth. For point-to-volume registration, noise reduction combined with beam profile filter and mean squares metrics yielded the best result: An average of 0.38 +/- 0.19 mm seed localization error relative to the ground truth. In human patient data, C-arm fluoroscopy images showed 81 radioactive seeds implanted inside the prostate. A qualitative analysis showed clinically correct agreement between the seeds visible in TRUS and reconstructed from intraoperative fluoroscopy imaging. The measured registration error compared to the manually selected seed locations by the clinician was 2.86 +/- 1.26 mm.
Fully automated registration between TRUS and the reconstructed seeds performed well in ground-truth phantom experiments and qualitative observation showed adequate performance on early clinical patient data.
在前列腺近距离放射治疗中，经直肠超声（TRUS）用于可视化解剖结构，而植入的种子则可以通过透视成像来可视化。通过将 TRUS 和透视成像相结合，可以进行术中剂量优化，但需要对透视成像中种子云相对于 TRUS 上所见解剖结构的位置进行定位。作者提出了一种将 TRUS 图像和透视成像重建的植入物进行配准的方法。
在一个体模中植入 48 颗种子，然后用 TRUS 和 CT 进行成像。从 CT 重建种子以获得种子云。使用基于基准的真实注册在 TRUS 和 CT 之间建立基准注册。通过使用基于强度的度量标准，对 TRUS 图像进行滤波、复合，并与重建的植入物进行配准。作者评估了体积到体积和点到体积的配准方案。总共分析了七种 TRUS 滤波技术和三种图像相似性度量标准。该方法还在从近距离放射治疗过程中捕获的人体受试者数据上进行了测试。
对于体积到体积的配准，降噪滤波器和归一化相关度量标准产生了最佳结果：相对于真实值，种子定位误差的平均值为 0.54 +/- 0.11 毫米。对于点到体积的配准，降噪与束状滤波和均方根度量相结合产生了最佳结果：相对于真实值，种子定位误差的平均值为 0.38 +/- 0.19 毫米。在人体患者数据中，C 臂透视成像显示 81 颗放射性种子植入前列腺内。定性分析表明，在 TRUS 中可见的种子与术中透视成像重建的种子之间存在临床正确的一致性。与临床医生手动选择的种子位置相比，测量的配准误差为 2.86 +/- 1.26 毫米。
TRUS 和重建种子之间的全自动配准在真实实验和定性观察中表现良好，早期临床患者数据显示出足够的性能。
