Optimized cervical spinal cord perfusion MRI after traumatic injury in the rat

Abstract

Despite the potential to guide clinical management of spinal cord injury and disease, noninvasive methods of monitoring perfusion status of the spinal cord clinically remain an unmet need. In this study, we optimized pseudo-continuous arterial spin labeling (pCASL) for the rodent cervical spinal cord and demonstrate its utility in identifying perfusion deficits in an acute contusion injury model. High-resolution perfusion sagittal images with reduced imaging artifacts were obtained with optimized background suppression and imaging readout. Following moderate contusion injury, perfusion was clearly and reliably decreased at the site of injury. Implementation of time-encoded pCASL confirmed injury site perfusion deficits with blood flow measurements corrected for variability in arterial transit times. The noninvasive protocol of pCASL in the spinal cord can be utilized in future applications to examine perfusion changes after therapeutic interventions in the rat and translation to patients may offer critical implications for patient management.

Comparison and optimization of pCASL and VSASL for rat thoracolumbar spinal cord MRI at 9.4 T

“…Instead, because cardiac motion was the predominant source of motion, and cardiac gating was required to improve tSNR to levels similar to those acceptable for measuring SCBF as in our prior cervical cord study. 6 For pCASL, the end of the long label duration is not easily synchronized to the cardiac cycle. Gating introduces variable delay times, and we used an external device to measure the actual PLDs in real time for retrospective data screening.…”

“…For VSI, α was obtained from simulations of the full sequence that included effects of T 2 during the labeling module and the global presaturation pulse and was estimated at 0.58. The longitudinal relaxation time of arterial blood (T 1b = 2380 ms) used constant values from the literature for 9.4 T. 6,27 The temporal SNR (tSNR) was computed as the mean ΔM divided by the standard deviation across all repetitions. For voxelwise analysis of SCBF, ROIs were determined on the M 0 images that best delineated the spinal cord using FSL.…”

“…ASL is an established technique for perfusion measurements of the brain and other organs such as kidney, lung, placenta, and liver. [1][2][3][4] However, its application to the spinal cord is largely limited to animal models, and few studies of ASL exist in spinal cord injury (SCI) [5][6][7] despite its potential use to monitor blood flow changes common after SCI. Pseudo-continuous arterial spin labeling (pCASL) is the recommended MRI approach to measure perfusion in the brain because of its high SNR.…”

“…8 pCASL uses a train of RF pulses to invert spins flowing perpendicular to the labeling plane. pCASL was recently optimized for the rat cervical spinal cord to evaluate spinal cord blood flow (SCBF) as a biomarker for acute SCI 6 by labeling the ascending vertebral arteries. The goal of the current work was to refine ASL methods in the rodent thoracic spinal cord.…”

Diffusion‐prepared fast spin echo for artifact‐free spinal cord imaging

“…DW prep -RARE was motivated, in part, to obtain diffusion and perfusion contrasts with a precisely matched FOV that follows prior pCASL-RARE optimizations. 32 In the future, a direct comparison of these 2 contrasts with unique and potentially important relationships in a rodent contusion SCI model is needed to appreciate the insight on injury mechanisms and relationship to neurological dysfunction. It is anticipated that improved quality of sagittal DWI with matched perfusion weighted imaging can be utilized to study the mechanisms of traumatic injuries as well as evaluate and optimize potential medical interventions.…”