Background Tension in the spinal cord is a trademark of tethered cord syndrome. Unfortunately, existing tests cannot quantify tension across the bulk of the cord, making the diagnostic evaluation of stretch ambiguous. A potential non-destructive metric for spinal cord tension is ultrasound-derived shear wave velocity (SWV). The velocity is sensitive to tissue elasticity and boundary conditions including strain. We use the term Ultrasound Tensography to describe the acoustic evaluation of tension with SWV. Methods Our solution “Tethered cord Assessment with Ultrasound Tensography (TAUT)” was utilized in three sub-studies: finite element simulations, a cadaveric benchtop validation, and a neurosurgical case series. The simulation computed SWV for given tensile forces. The induced tension cadaveric model validated the SWV-tension relationship. Lastly, SWV was measured intraoperatively in patients diagnosed with tethered cord who underwent surgical treatment (spinal column shortening). The surgery alleviates tension by decreasing the vertebral column length. Results Here we observe a strong linear relationship between tension and squared SWV across the preclinical sub-studies. Higher tension induces faster shear waves in the simulation (R2 = 0.984) and cadaveric (R2 = 0.951) models. The SWV decreases in all neurosurgical procedures (p<0.001). Moreover, TAUT has a c-statistic of 0.962 (0.92-1.00), detecting all tethered cords. Conclusions This study presents the first clinical metric of spinal cord tension. Strong agreement among computational, cadaveric, and clinical studies demonstrates the utility of ultrasound-induced SWV for quantitative intraoperative feedback. This technology is positioned to enhance tethered cord diagnosis, treatment, and post-operative monitoring as it differentiates stretched from healthy cords.

No abstract

Ultrasound holds promise for use in spinal cord injury cases for both diagnostic and therapeutic purposes. Focused ultrasound applications demand an added threshold of study to ensure the safety and efficacy of the therapy. For optimal treatment outcomes, it is crucial to understand whether relevant structures are being targeting with sufficient energy without damaging neighboring tissue and vasculature. However, it is difficult to predict the expected displacement and pressure profile of the ultrasound wavefront due to challenges with visualizing an acoustic beam in real-time and complex patient-specific anatomy. This challenge is particularly prominent in anatomies with varying medium acoustic properties that cause reflection and distortion of the signal, which is inherent to the composition of the spinal cord and is exacerbated by the formations of injury-induced hematomas. Incorrect placement of focused ultrasound transducers can be detrimental to patient health, specifically if therapeutic ultrasound is used at higher intensities, as the beam propagation can target healthy tissue and important structures that could lead to tissue damage and death. We study how computational tools can be leveraged to aid placement of the transducer using an ultrasound simulation software, Wave 3000 Plus, that allows for the visualization of ultrasound propagation through anatomical structures. By simulating the propagation of ultrasound beams through patient-specific Digital Imaging and Communications in Medicine (DICOM) images, we study computational approaches to determine the optimal placement of devices. In this study, we use in vivo porcine spinal cord images following spinal cord injury (as an example medical use case) to determine if the injury site is being targeted appropriately and to visualize the distribution of pressure throughout the simulation. We demonstrate that Wave 3000 Plus is a viable approach for visualizing ultrasound propagation through patient-specific anatomies.