Purpose: To develop and compare an automated detection system for ischemic lesions in a neonatal model of bilateral carotid artery occlusion with hypoxia (BCAO-H) from T2 weighted MRI (T2WI) to the currently used ''gold standard'' of manual segmentation.Materials and Methods: Forty-three P10 BCAO-H rat pups and 8 controls underwent T2WI at 1 day and 28 days. A computational imaging method, Hierarchical Region Splitting (HRS), was developed to automatically and rapidly detect and quantify 3D lesion and normal appearing brain matter (NABM) volumes.Results: HRS quantified lesion and NABM volumes within 15 s in comparison to 3 h for its manual counterpart, with a high correlation for injury (r 2 ¼ 0. 95; P ¼ 8.6 Â 10 À7 ) and NABM (r 2 ¼ 0. 92; P ¼ 1.4 Â 10 À22 ). Average lesion volumes for mild, moderate, and severe injuries were 3.85%, 28.85%, and 52.98% for HRS and 0.51%, 24.22%, and 48.74% for manual detection. Lesion volumes and locations were similar for both methods (sensitivity: 0.82, specificity: 0.86, and similarity: 1.47). Conclusion:HRS is an accurate, objective, and rapid method to quantify injury evolution in neonatal hypoxic ischemic injury models.
Neonatal hypoxic-ischemic brain injury (HII) and arterial ischemic stroke (AIS) result in irreversibly injured (core) and salvageable (penumbral) tissue regions. Identification and reliable quantification of salvageable tissue is pivotal to any effective and safe intervention. Magnetic resonance imaging (MRI) is the current standard to distinguish core from penumbra using diffusionperfusion mismatch (DPM). However, subtle MR signal variations between core-penumbral regions make their visual delineation difficult. We hypothesized that computational analysis of MRI data provides a more accurate assessment of core and penumbral tissue evolution in HII/AIS. We used two neonatal rat-pup models of HII/AIS (unilateral and global hypoxic-ischemia) and clinical data sets from neonates with AIS to test our noninvasive, automated computational approach, Hierarchical Region Splitting (HRS), to detect and quantify ischemic core-penumbra using only a single MRI modality (T2-or diffusion-weighted imaging, T2WI/DWI). We also validated our approach by comparing core-penumbral images (from HRS) to DPM with immunohistochemical validation of HII tissues. Our translational and clinical data results showed that HRS could accurately and reliably distinguish the ischemic core from penumbra and their spatiotemporal evolution, which may aid in the vetting and execution of effective therapeutic interventions as well as patient selection.
We compared the efficacy of three automated brain injury detection methods, namely symmetry-integrated region growing (SIRG), hierarchical region splitting (HRS) and modified watershed segmentation (MWS) in human and animal magnetic resonance imaging (MRI) datasets for the detection of hypoxic ischemic injuries (HII). Diffusion weighted imaging (DWI, 1.5T) data from neonatal arterial ischemic stroke (AIS) patients, as well as T2-weighted imaging (T2WI, 11.7T, 4.7T) at seven different time-points (1, 4, 7, 10, 17, 24 and 31 days post HII) in rat-pup model of hypoxic ischemic injury were used to check the temporal efficacy of our computational approaches. Sensitivity, specificity, similarity were used as performance metrics based on manual (‘gold standard’) injury detection to quantify comparisons. When compared to the manual gold standard, automated injury location results from SIRG performed the best in 62% of the data, while 29% for HRS and 9% for MWS. Injury severity detection revealed that SIRG performed the best in 67% cases while HRS for 33% data. Prior information is required by HRS and MWS, but not by SIRG. However, SIRG is sensitive to parameter-tuning, while HRS and MWS are not. Among these methods, SIRG performs the best in detecting lesion volumes; HRS is the most robust, while MWS lags behind in both respects.
Neuroimaging is commonly used for the assessment of children with traumatic brain injury and has greatly advanced how children are acutely evaluated. More recently, emphasis has focused on how advanced magnetic resonance imaging methods can detect subtler injuries that could relate to the structural underpinnings of the neuropsychological and behavioral alterations that frequently occur. We examine several methods used for the assessment of pediatric brain injury. Susceptibility-weighted imaging is a sensitive 3-dimensional high-resolution technique in detecting hemorrhagic lesions associated with diffuse axonal injury. Magnetic resonance spectroscopy acquires metabolite information, which serves as a proxy for neuronal (and glial, lipid, etc) structural integrity and provides sensitive assessment of neurochemical alterations. Diffusion-weighted imaging is useful for the early detection of ischemic and shearing injury. Diffusion tensor imaging allows better structural evaluation of white matter tracts. These methods are more sensitive than conventional imaging in demonstrating subtle injury that underlies a child’s clinical symptoms. There also is an increasing desire to develop computational methods to fuse imaging data to provide a more integrated analysis of the extent to which components of the neurovascular unit are affected. The future of traumatic brain injury neuroimaging research is promising and will lead to novel approaches to predict and improve outcomes.
The aims of this study were to evaluate longitudinal metabolite changes in traumatic brain injury (TBI) subjects and determine whether early magnetic resonance spectroscopic imaging (MRSI) changes in discrete brain regions predict 1year neuropsychological outcomes. Three-dimensional (3D) proton MRSI was performed in pediatric subjects with complicated mild (cMild), moderate, and severe injury, acutely (6-17 days) and 1-year post-injury along with neurological and cognitive testing. Longitudinal analysis found that in the cMild/Moderate group, all MRSI ratios from 12 regions returned to control levels at 1 year. In the severe group, only cortical gray matter regions fully recovered to control levels whereas N-acetylaspartate (NAA) ratios from the hemispheric white matter and subcortical regions remained statistically different from controls. A factor analysis reduced the data to two loading factors that significantly differentiated between TBI groups; one included acute regional NAA variables and another consisted of clinically observed variables (e.g., days in coma). Using scores calculated from the two loading factors in a logistic regression model, we found that the percent accuracy for classification of TBI groups was greatest for the dichotomized attention measure (93%), followed by Full Scale Intelligence Quotient at 91%, and the combined memory Z-score measure (90%). Using the acute basal ganglia NAA/creatine (Cr) ratio alone achieved a higher percent accuracy of 94.7% for the attention measure whereas the acute thalamic NAA/Cr ratio alone achieved a higher percent accuracy of 91.9% for the memory measure. These results support the conclusions that reduced NAA is an early indicator of tissue injury and that measurements from subcortical brain regions are more predictive of long-term cognitive outcome.
BACKGROUND Gender is increasingly recognized as an important influence on brain development, disease susceptibility, and response to pharmacologic/rehabilitative treatments. In regenerative medicine, it remains entirely unknown whether there is an interaction between transplanted stem cells and host gender that might bias efficacy and safety in some patients but not others. METHODS We examined the role of recipient gender in a neonatal rat hypoxia-ischemic injury (HII) model, treated with human female neural stem cells (hNSCs), labeled with superparamagnetic iron-oxide (SPIO) particles implanted into the contralateral cerebral ventricle. We monitored HII evolution (by MRI, histopathology, behavioral testing) and hNSC fate (migration, replication, viability). RESULTS Recipient gender after implantation did not influence the volume or location of ischemic injury (1, 30, or 90d) or behavior (90d). SPIO labeling did not influence HII evolution. Implantation had its greatest benefit on mild/moderate injuries which remained stable rather than increasing as in severe HII as is the natural history for such lesions. CONCLUSIONS Our results suggest that hNSC treatment (including using hNSCs that are pre-labeled with iron to allow tracking in real time by MRI) would be equally safe and effective for male and female human newborns with mild-to-moderate HII.
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