Ultrasound Shear-wave Elastography Reveals Biomechanical Heterogeneity Following Acute Spinal Cord Injury

Area of Science:

• Biomedical Engineering
• Neuroscience
• Medical Imaging

Background:

• Traumatic spinal cord injury (SCI) causes secondary tissue damage beyond the initial lesion.
• Current imaging methods lack the ability to assess evolving mechanical properties of injured spinal cord tissue.
• Shear-wave elastography (SWE) offers real-time quantification of tissue stiffness, potentially identifying vulnerable areas.

Purpose of the Study:

• To evaluate the utility of SWE in characterizing biomechanical changes following acute traumatic spinal cord injury (SCI).
• To investigate the temporal and spatial dynamics of tissue stiffness in the peri-lesional area after SCI.
• To determine if SWE can identify regions of altered mechanical properties indicative of secondary injury.

Main Methods:

• A porcine model of thoracic contusion SCI was utilized.
• Shear-wave elastography (SWE) was performed before and after injury at multiple time points (early, mid, late).
• Shear-wave velocity (SWV) heat maps were analyzed to quantify stiffness changes relative to the injury epicenter, with hematoma segmentation.

Main Results:

• Severe SCI induced significant increases in SWV, indicating heightened tissue stiffness.
• SWV changes peaked in early to mid-injury intervals and decreased later, while hematoma size remained stable.
• Spatial SWV patterns evolved from unimodal to bimodal, showing increased stiffness in peri-lesional areas, not solely due to hematoma.

Conclusions:

• SWE effectively visualizes rapid and heterogeneous biomechanical remodeling after acute SCI, independent of structural changes.
• The development of peri-lesional stiffness gradients suggests an identifiable biomechanical zone.
• These findings highlight SWE's potential as a marker for secondary injury processes in SCI.