IEEE Trans Biomed Eng. 2021 Aug;68(8):2479-2489. doi: 10.1109/TBME.2020.3046370. Epub 2021 Jul 19.
Spinal fusion surgeries require accurate placement of pedicle screws in anatomic corridors without breaching bone boundaries. We are developing a combined ultrasound and photoacoustic image guidance system to avoid pedicle screw misplacement and accidental bone breaches, which can lead to nerve damage.
Pedicle cannulation was performed on a human cadaver, with co-registered photoacoustic and ultrasound images acquired at various time points during the procedure. Bony landmarks obtained from coherence-based ultrasound images of lumbar vertebrae were registered to post-operative CT images. Registration methods were additionally tested on an ex vivo caprine vertebra.
Locally weighted short-lag spatial coherence (LW-SLSC) ultrasound imaging enhanced the visualization of bony structures with generalized contrast-to-noise ratios (gCNRs) of 0.99 and 0.98-1.00 in the caprine and human vertebrae, respectively. Short-lag spatial coherence (SLSC) and amplitude-based delay-and-sum (DAS) ultrasound imaging generally produced lower gCNRs of 0.98 and 0.84, respectively, in the caprine vertebra and 0.84-0.93 and 0.34-0.99, respectively, in the human vertebrae. The mean ± standard deviation of the area of -6 dB contours created from DAS photoacoustic images acquired with an optical fiber inserted in prepared pedicle holes (i.e., fiber surrounded by cancellous bone) and holes created after intentional breaches (i.e., fiber exposed to cortical bone) was 10.06 ±5.22 mm and 2.47 ±0.96 mm , respectively (p 0.01).
Coherence-based LW-SLSC and SLSC beamforming improved visualization of bony anatomical landmarks for ultrasound-to-CT registration, while amplitude-based DAS beamforming successfully distinguished photoacoustic signals within the pedicle from less desirable signals characteristic of impending bone breaches.
These results are promising to improve visual registration of ultrasound and photoacoustic images with CT images, as well as to assist surgeons with identifying and avoiding impending bone breaches during pedicle cannulation in spinal fusion surgeries.
脊柱融合手术需要在解剖学通道中准确放置椎弓根螺钉，而不突破骨边界。我们正在开发一种结合超声和光声图像引导系统，以避免椎弓根螺钉错位和意外的骨突破，这可能导致神经损伤。
在人体尸体上进行椎弓根插管，在手术过程中的不同时间点获取配准的光声和超声图像。从腰椎基于相干性的超声图像获得的骨性标志与术后 CT 图像进行配准。还在离体山羊椎骨上测试了配准方法。
局部加权短滞后空间相干（LW-SLSC）超声成像增强了骨性结构的可视化，山羊和人体椎骨的广义对比噪声比（gCNR）分别为 0.99 和 0.98-1.00。短滞后空间相干（SLSC）和基于幅度的延迟和求和（DAS）超声成像在山羊椎骨中通常产生较低的 gCNR，分别为 0.98 和 0.84，在人体椎骨中分别为 0.84-0.93 和 0.34-0.99。从插入准备好的椎弓根孔（即光纤被松质骨包围）和故意穿透孔（即光纤暴露于皮质骨）中获得的 DAS 光声图像创建的-6 dB 轮廓的平均值±标准偏差分别为 10.06±5.22 mm 和 2.47±0.96 mm（p<0.01）。
基于相干性的 LW-SLSC 和 SLSC 波束形成改善了超声到 CT 配准的骨性解剖标志的可视化，而基于幅度的 DAS 波束形成成功地区分了椎弓根内的光声信号与不太理想的即将发生骨突破的信号。
这些结果有望改善超声和光声图像与 CT 图像的视觉配准，并帮助外科医生在脊柱融合手术中进行椎弓根插管时识别和避免即将发生的骨突破。
