Ultrafast Doppler Vascular Imaging for Intraoperative Physiological Monitoring of Human Spinal Cord

Summary

This study presents the application of ultrafast Doppler vascular imaging for physiological monitoring during human spinal cord surgery.

Abstract

Monitoring physiological parameters is essential for assessing the patient's condition during intraoperative scenarios. Hemodynamic information, such as blood pressure and heart rate, can be derived from ultrasound Doppler signals, reflecting vascular function and indicating pathological risks in real-time. Compared to oscillometry, magnetic resonance imaging (MRI), conventional Doppler, and piezoelectric methods, ultrafast Doppler provides superior temporal resolution and high sensitivity for small vessels. In this study, an intraoperative application of ultrafast Doppler imaging in the spinal cord of a patient with Chiari malformation is described. Post-processing of the data generated power Doppler images of the spinal cord vasculature and physiological parameters, including detailed mapping of the resistivity index (RI) and pulsatility index (PI). Both RI and PI showed significant reductions after surgical intervention (RI mean: 0.47 → 0.32; PI mean: 0.63 → 0.39; p < 0.001), with consistent trends observed in the medians, indicating improved spinal cord hemodynamics. Evaluation of changes in PI/RI parameters using this method may offer a broader understanding of disease progression and treatment efficacy, potentially guiding surgical strategies and therapeutic approaches.

Introduction

Blood pressure dynamics, as an important intraoperative physiological indicator, provides valuable guidance for surgical strategy and ensures operational safety¹. Pulse waves, generated by the periodic contraction and relaxation of the heart, propagate through the arterial vascular system from the aorta as pressure waves². These waves can be regarded as a direct manifestation of cardiovascular function, offering critical information for understanding blood pressure dynamics and overall hemodynamics³. In clinical practice, pulse waves are extensively utilized for continuous assessment of hemodynami....

Protocol

This study involved human subjects, and all procedures were conducted in accordance with protocols approved by the Human Research Ethics Committee, Huashan Hospital affiliated with Fudan University (2021-065). Informed consent was obtained from all participants. The implementation was solely intended for preliminary research and validation purposes, not for clinical diagnosis. Relevant FDA-recommended safety indices were assessed to ensure compliance with established safety standards. Patients included in this study were diagnosed with Chiari malformation. The inclusion, exclusion, and withdrawal criteria for participants are provided in Supplementary File 1

Results

Ultrafast Doppler offers high sensitivity, enabling high temporal resolution imaging of the spinal cord vasculature network. Compared to color Doppler, power Doppler offers a higher signal-to-noise ratio (SNR)⁴². An appropriate threshold range was used for the SVD-based spatiotemporal filter, enabling the identification of valid blood flow signals and the imaging of blood flow direction. Figure 3E,F presents the power Doppler images of the spinal cord.......

Discussion

In this study, ultrafast Doppler imaging was employed intraoperatively to extract the blood flow of the human spinal cord. Spectral analysis and calculation of the RI and PI were subsequently performed on the blood flow signals, providing power Doppler images of spinal cord vasculature and corresponding RI and PI maps of the patient with Chiari malformation. In the context of ultrafast ultrasound, small vessels refer to vessels with diameters on the order of 100 micrometers, while vessels smaller than 100 micrometers wer.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
MATLAB  R2022b	MathWorks	N/A	For post-processing of data
Microscope	ZEISS	PENTERO 8O0 S	For intraoperative microscopic observation
Programmable ultrasound system	Verasonics	Vantage 256	For ultrasound imaging of spinal vessels
Robotic arm	Aesculap	RT060R	For fixing the probe
Single crystal high frequency linear array transducers	Verasonics	L22-14vX	For ultrasound imaging of spinal vessels
Ultrasound gel	Baby Fun	Type M	Eliminate the air gap between the probe and the contact surface