Quantitative magnetic resonance imaging in a naturally occurring canine model of spinal cord injury

Abstract

Study design: Retrospective cohort study. Objectives: To analyze magnetic resonance imaging (MRI) evaluator agreement in dogs with spinal cord injury (SCI) caused by intervertebral disk herniation (IVDH) using semiautomated and manual lesion segmentation and to analyze the associations between MRI and functional outcome. Setting: United States of America. Methods: T2-weighted MRIs from dogs with SCI resulting from thoracolumbar IVDH were identified from a database. Evaluators categorized MRIs on the basis of the presence or absence of a T2-hyperintense spinal cord lesion in axial and sagittal images. A semiautomated segmentation algorithm was developed and used to estimate the lesion volume. Agreement between evaluators and between semiautomated and manual segmentation was analyzed. The relationships of qualitative and quantitative MRIs with behavioral functional outcome were analyzed. Results: Axial images more commonly depicted lesions compared with sagittal images. Lesions in axial images had more consistent associations with functional outcome compared with sagittal images. There was imperfect qualitative agreement, and lesion volume estimation was imprecise. However, there was improved precision using semiautomated segmentation compared with manual segmentation. Conclusion: Lesion volume estimation in dogs with naturally occurring SCI caused by IVDH is challenging, and axial images have important advantages compared with sagittal images. The semiautomated segmentation algorithm described herein shows promise but may require further refinement. INTRODUCTIONSpinal cord injury (SCI) is a devastating disease process that results in disability, loss of quality of life and cost to the health-care system. Currently, there are no therapies that robustly improve functional outcomes. 1 Magnetic resonance imaging (MRI) has been used in humans to diagnose SCI for three decades and has been proposed as a viable in vivo biomarker. 2-4 High T2 signal intensity within the spinal cord following injury is correlated with identifiable edema, necrosis, cellular infiltrates and hemorrhage. 5,6 The presence of such lesions has been associated with slowed recovery across a number of model systems and in humans. 2,7,8 More recently, spinal cord lesion volume as measured by MRI has been used to quantitatively characterize SCI following clinical interventions. 9 Canine intervertebral disk herniation (IVDH) is a common, naturally occurring SCI that is seen in pet dogs. 10,11 Canine IVDH shares many features with human SCI including lesion histopathology, presence of compressive/contusive facets of injury and use of surgical/ rehabilitative treatment modalities. 10,11 As is the case in humans, data from dogs with IVDH suggest that T2-hyperintense lesions within the spinal cord are correlated with behaviorally severe injuries and poorer long-term motor recovery. 11

Single‐shot Turbo Spin Echo Pulse Sequence Findings in Dogs With and Without Progressive Myelomalacia

“…These two ratios were not statistically significant between groups, possibly because cerebrospinal fluid signal loss and/or intramedullary hyperintensity could be underestimated or missed entirely on standard T2 sagittal images alone. Both qualitative and quantitative assessment of cerebrospinal fluid attenuation and intramedullary hyperintensity may have been more accurate if multiplanar images were evaluated in the current study, as was suggested by a recent report in which agreement for identification and measurement of intramedullary spinal cord lesions was better on T2 images in the transverse plane compared to the sagittal plane …”

Comparison of Preoperative Quantitative Magnetic Resonance Imaging and Clinical Assessment of Deep Pain Perception as Prognostic Tools for Early Recovery of Motor Function in Paraplegic Dogs with Intervertebral Disk Herniations

“…For this study, dogs admitted to the Department of Small Animal Medicine and Surgery of the University of Veterinary Medicine Hannover between June 2013 and April 2015 were prospectively recruited. The dogs had to fulfill the following inclusion criteria: acute paraplegia (0-7 days since observed onset of clinical signs) or subacute paraplegia (8-28 days since onset of clinical signs), 23,37,38 SCI confined to the T3-L3 spinal cord segments and a body weight <20 kg. Onset of clinical signs was defined and recorded as the time point when owners noticed a nonambulatory state of their dog.…”

Transcranial magnetic motor evoked potentials and magnetic resonance imaging findings in paraplegic dogs with recovery of motor function

“…Identification of T2‐weighted intramedullary hyperintensities was performed upon assessment of sagittal images . Corresponding transverse T2‐weighted images were evaluated for detection of hyperintensities' length expansion to increase accuracy of measurements . T1‐weighted sequences were assessed in transverse planes to exclude presence of T1‐weighted hyperintensities .…”