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. 2012 Jul;22(3):e12-9.
doi: 10.1111/j.1552-6569.2011.00629.x. Epub 2011 Aug 19.

Approaches to normalization of spinal cord volume: application to multiple sclerosis

Brian C Healy  1 , Ashish Arora, Douglas L Hayden, Antonia Ceccarelli, Shahamat S Tauhid, Mohit Neema, Rohit Bakshi
Affiliations

Approaches to normalization of spinal cord volume: application to multiple sclerosis

Brian C Healy et al. J Neuroimaging. 2012 Jul.

Abstract

Background and purpose: To determine the proper method for the normalization of spinal cord volume.

Materials and methods: A group of 34 multiple sclerosis (MS) patients (28 relapsing and 6 progressive) and 15 healthy controls had whole spinal cord 3-mm thick T2-weighted axial fast spin-echo magnetic resonance imaging (MRI) images obtained at 3T. For each participant, four volumes were measured (C2-3 volume, cervical cord volume, thoracic cord volume, and whole cord volume). The volumes were normalized by the number of slices and three potential measures of body size (intracranial volume [ICV], body mass index, and body surface area) using the proportional method.

Results: All raw volumes and volumes normalized by number of slices or ICV were significantly lower in progressive MS patients compared to relapsing MS patients/healthy controls (P < .05). In addition, C2-3 volume and cervical cord volume were significantly correlated with Expanded Disability Status Scale score (P < .05). All regional volumes showed high intercorrelation, and normalization by the number of slices significantly increased some correlations. Regarding reliability, whole cord volume regardless of normalization technique had lower coefficient of variation than C2-3 volume.

Conclusions: Since normalization factor had limited impact on reliability and the ability to detect differences, normalization by the number of slices is recommended.

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Figures

Figure 1
Figure 1. Representative spinal cord image
Representative MRI images: The figure shows the native axial T2-weighted image (B) and the reconstructed sagittal view of the data set provided by a reslicing orthogonal tool (A). The localizing lines in the sagittal view were used to identify the anatomic level of the axial slices. Then using an edge finding tool based on local thresholding, the spinal cord contour was identified, resulting in a region of interest (in red) in the axial image.
Figure 2
Figure 2. Comparison of regional cord volumes/whole cord volume and EDSS
All volumes (mm3) were normalized by the number of slices. Spearman correlation coefficients between the two measures and p-values are reported in each graph. First row: Relationship between Expanded Disability Status Scale (EDSS) score and A) C2-3 or B) cervical cord volume. Second row: Relationship between EDSS and C) thoracic or D) whole cord volume.
Figure 3
Figure 3. Comparison of regional cord volumes and whole cord volume
All volumes (mm3) were normalized by the number of slices. Pearson correlation coefficients between the two measures are reported in each graph, and p-values for each correlation were less than 0.0001. First row: Relationship between C2-3 volume and A) cervical, B) thoracic, or C) whole cord volume. Second row: Relationship between D) cervical and thoracic cord volume, E) cervical and whole cord volume and F) thoracic and whole cord volume.
See this image and copyright information in PMC

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