Optimizing Hippocampal Segmentation in Infants Utilizing MRI Post-Acquisition Processing
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This study aims to determine the most reliable method for infant hippocampal segmentation by comparing magnetic resonance (MR) imaging post-acquisition processing techniques: contrast to noise ratio (CNR) enhancement, or reformatting to standard orientation. MR scans were performed with a 1.5 T GE scanner to obtain dual echo T2 and proton density (PD) images at term equivalent (38–42 weeks’ gestational age). 15 hippocampi were manually traced four times on ten infant images by 2 independent raters on the original T2 image, as well as images processed by: a) combining T2 and PD images (T2-PD) to enhance CNR; then b) reformatting T2-PD images perpendicular to the long axis of the left hippocampus. CNRs and intraclass correlation coefficients (ICC) were calculated. T2-PD images had 17% higher CNR (15.2) than T2 images (12.6). Original T2 volumes’ ICC was 0.87 for rater 1 and 0.84 for rater 2, whereas T2-PD images’ ICC was 0.95 for rater 1 and 0.87 for rater 2. Reliability of hippocampal segmentation on T2-PD images was not improved by reformatting images (rater 1 ICC = 0.88, rater 2 ICC = 0.66). Post-acquisition processing can improve CNR and hence reliability of hippocampal segmentation in neonate MR scans when tissue contrast is poor. These findings may be applied to enhance boundary definition in infant segmentation for various brain structures or in any volumetric study where image contrast is sub-optimal, enabling hippocampal structure-function relationships to be explored.
KeywordsNeonate Preterm Magnetic resonance imaging Volume Hippocampus Brain
The authors gratefully thank Merilyn Bear, Michael Kean, Katherine Lee, Gregory A. Lodygensky, Hong X. Wang, Michael J.Farrell, Peter J. Anderson, and Rodney W. Hunt, the VIBeS and Developmental Imaging teams at the Murdoch Childrens Research Institute, as well as the families and infants who participated in this study.
National Medical and Health Research Council of Australia; Grant number: 237117; Grant sponsor: NIH; Grant number: R01 RR021885, R01 GM074068, R01 EB008015, P30 HD018655; Grant sponsor: NHMRC Research Fellowship; Grant number: 400317; Grant sponsors: United Cerebral Palsy Foundation (USA), Mather Foundation (USA), Brown Foundation (USA), NHMRC Clinical Career Development Award, NARSAD Young Investigator Award, Victorian Government’s Operational Infrastructure Support Program.
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