Table 4 –

Comparison of magnetic resonance and ultrasound elastography, with applications in neurosurgery, advantages, and limitations for each modality

Modality	Applications	Advantages	Limitations
Magnetic resonance elastography	Preoperative assessment:  •Diagnose abnormal lesions  •Tumor consistency and heterogeneity  •Classify tumors as hard or soft  •Tumor-brain adhesion  •Differentiate types of tumors •Postoperative monitoring after shunt treatment for hydrocephalus •Investigate pathophysiology of disease	•Penetrates bone non-invasively  •Can perform routinely as part of follow-up care at scheduled intervals  •Samples large area of tissue	•Expensive  •May require sedation in pediatric patients  •Motion artifacts  •Long acquisition times  •Availability can be challenging for intraoperative cases
Ultrasound elastography (Shear-wave or strain)	Intraoperative assessment:  •Tumor boundaries  •Tumor consistency and heterogeneity  •Tumor-brain adhesion  •Differentiate high- and low-grade gliomas  •Presence of residual tumor  •MRI-negative epileptogenic lesions  •Spinal cord compression Preoperative and postoperative assessment:  •Stiffness of intervertebral disks in scoliosis patients  •Neonatal hydrocephalus (<1 year old)	•Inexpensive  •Ultrasound readily available intraoperatively  •Fast acquisition time  •Real-time imaging	•Invasive, requires bone removal (exceptions: infants, intervertebral disk pathology)  •Sample limited to acoustic window in plane of the probe  •Limited depth of measurements due to tissue attenuation, tradeoff between spatial resolution and depth of penetration  •Interobserver variability  •Applies pressure to tissue, requires care for fragile tissue