Cotton balls are used in neurosurgical procedures to assist with hemostasis and improve vision within the operative field. Although the surgeon can reshape pieces of cotton for multiple intraoperative uses, this customizability and scale also places them at perpetual risk of being lost, as blood-soaked cotton balls are visually similar to raw brain tissue. Retained surgical cotton can induce potentially life-threatening immunologic responses, impair postoperative imaging, lead to a textiloma or misdiagnosis, and/or require reoperation. This study investigated three imaging modalities (optical, acoustic, and radiographic) to find the most effective method of identifying foreign bodies during neurosurgery. First, we examined the use of dyes to increase contrast between cotton and surrounding parenchyma (optical approach). Second, we explored the ability to distinguish surgical cotton on or below the tissue surface from brain parenchyma using ultrasound imaging (acoustic approach). Lastly, we analyzed the ability of radiography to differentiate between brain parenchyma and cotton. Our preliminary testing demonstrated that dark-colored cotton is significantly more identifiable than white cotton on the surface level. Additional testing revealed that cotton has noticeable different acoustic characteristics (eg, speed of sound, absorption) from neural tissue, allowing for enhanced contrast in applied ultrasound imaging. Radiography, however, did not present sufficient contrast, demanding further examination. These solutions have the potential to significantly reduce the possibility of intraoperative cotton retention both on and below the surface of the brain, while still providing surgeons with traditional cotton material properties without affecting the surgical workflow.
Spinal cord injury (SCI) affects approximately 2.5 million people worldwide. The primary phase of SCI is initiated by mechanical trauma to the spinal cord, while the secondary phase involves the ensuing tissue swelling and ischemia that worsen tissue damage and functional outcome. Optimizing blood flow to the spinal cord after SCI can mitigate injury progression and improve outcome. Accurate, sensitive, real-time monitoring is critical to assessing the spinal cord perfusion status and optimizing management, particularly in those with injuries severe enough to require surgery. However, the complex anatomy of the spinal cord vasculature and surrounding structures present significant challenges to such a monitoring strategy. In this study, Doppler ultrasound was hypothesized to be a potential solution to detect and monitor spinal cord tissue perfusion in SCI patients who required spinal decompression and/or stabilization surgeries. This approach could provide real-time visual blood flow information and pulsatility of the spinal cord as biomarkers of tissue perfusion. Importantly, Doppler ultrasound could be readily integrated into the surgical workflow, because the spinal cord was exposed during surgery, thereby allowing easy access for Doppler deployment, while keeping the dura intact. Doppler ultrasound successfully measured blood flow in single and bifurcated microfluidic channels at physiologically relevant flow rates and dimensions in both in-vitro and in-vivo porcine SCI models. Furthermore, perfusion was quantified from the obtained images. Our results provide a promising and viable solution to intraoperatively assess and monitor blood flow at the SCI site to optimize tissue perfusion and improve functional recovery in SCI patients.