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Technical Note: Quantification of blood‐spinal cord barrier permeability after application of magnetic resonance‐guided focused ultrasound in spinal cord injury
Author(s) -
Cross Chloe G.,
Payne Allison H.,
Hawryluk Gregory W.,
HaagRoeger Riley,
Cheeniyil Rahul,
Brady Dalton,
Odéen Henrik,
Minoshima Satoshi,
Cross Donna J.,
Anzai Yoshimi
Publication year - 2021
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1002/mp.14947
Subject(s) - spinal cord , magnetic resonance imaging , medicine , evans blue , spinal cord injury , cord , nuclear medicine , microbubbles , ultrasound , radiology , surgery , psychiatry
Purpose To demonstrate that magnetic resonance‐guided focused ultrasound (MRgFUS) facilitates blood‐spinal cord barrier (BSCB) permeability and develop observer‐independent MRI quantification of BSCB permeability after MRgFUS for spinal cord injury (SCI). Methods Noninjured Sprague‐Dawley rats (n = 3) underwent MRgFUS and were administered Evans blue post‐MRgFUS to confirm BSCB opening. Absorbance was measured by spectrophotometry and correlated with its corresponding image intensity. Rats (n = 21) underwent T8–T10 laminectomy and extradural compression of the spinal cord (23g weighted aneurysm‐type clip, 1 min). The intervention group (n = 11) was placed on a preclinical MRgFUS system, administered microbubbles (Optison, 0.2 mL/kg), and received 3 MRgFUS sonications (25 ms bursts, 1 Hz pulses for 3 min, 3 acoustic W, approximately 1.0–2.1 MPa peak pressure as measured via hydrophone). The sham group (n = 10) received equivalent procedures with no sonications. T1w MRI was obtained both pre‐ and post‐MRgFUS BSCB opening. Spinal cords were segmented manually or semiautomatically and a Pearson correlation with P ≤ 0.001 was used to correlate the two segmentation methods. MRgFUS sonication and control regions intensity values were evaluated with a paired t ‐test with a P ≤ 0.01. Results Semiautomatic segmentation reduced computational time by 95% and was correlated with manual segmentation (Pearson = 0.92, P < 0.001, n = 71 regions). In the noninjured rat group, Evans blue absorbance correlated with image intensity in the MRgFUS and control regions (Pearson = 0.82, P = 0.02, n = 6). In rats that underwent the SCI procedure, an increase in signal intensity in the MRgFUS targeted region relative to control was seen in all SCI rats (10.65 ± 12.4%, range: 0.96–43.9%, n = 11, P = 0.002). SCI sham MRgFUS revealed no change (0.63 ± 0.52%, 95% CI 0.320.95, n = 10). This result was significant between both groups ( P = 0.003). Conclusion The implemented semiautomatic segmentation procedure improved data analysis efficiency. Quantitative methods using contrast‐enhanced MRI with histological validation are sensitive for detection of blood‐spinal cord barrier opening induced by magnetic resonance‐guided focused ultrasound.