Choroid plexus volume in multiple sclerosis can be estimated on structural MRI avoiding contrast injection

Abstract

We compared choroid plexus (ChP) manual segmentation on non-contrast-enhanced (non-CE) sequences and reference standard CE T1- weighted (T1w) sequences in 61 multiple sclerosis patients prospectively included. ChP was separately segmented on T1w, T2-weighted (T2w) fluid-attenuated inversion-recovery (FLAIR), and CE-T1w sequences. Inter-rater variability assessed on 10 subjects showed high reproducibility between sequences measured by intraclass correlation coefficient (T1w 0.93, FLAIR 0.93, CE-T1w 0.99). CE-T1w showed higher signal-to-noise ratio and contrast-to-noise ratio (CE-T1w 23.77 and 18.49, T1w 13.73 and 7.44, FLAIR 13.09 and 10.77, respectively). Manual segmentation of ChP resulted 3.073 ± 0.563 mL (mean ± standard deviation) on T1w, 3.787 ± 0.679 mL on FLAIR, and 2.984 ± 0.506 mL on CE-T1w images, with an error of 28.02 ± 19.02% for FLAIR and 3.52 ± 12.61% for T1w. FLAIR overestimated ChP volume compared to CE-T1w (p < 0.001). The Dice similarity coefficient of CE-T1w versus T1w and FLAIR was 0.67 ± 0.05 and 0.68 ± 0.05, respectively. Spatial error distribution per slice was calculated after nonlinear coregistration to the standard MNI152 space and showed a heterogeneous profile along the ChP especially near the fornix and the hippocampus. Quantitative analyses suggest T1w as a surrogate of CE-T1w to estimate ChP volume.Relevance statement To estimate the ChP volume, CE-T1w can be replaced by non-CE T1w sequences because the error is acceptable, while FLAIR overestimates the ChP volume. This encourages the development of automatic tools for ChP segmentation, also improving the understanding of the role of the ChP volume in multiple sclerosis, promoting longitudinal studies.Key points • CE-T1w sequences are considered the reference standard for ChP manual segmentation.• FLAIR sequences showed a higher CNR than T1w sequences but overestimated the ChP volume.• Non-CE T1w sequences can be a surrogate of CE-T1w sequences for manual segmentation of ChP.

Keywords: Choroid plexus; Gadolinium-based contrast media; Image segmentation; Magnetic resonance imaging; Multiple sclerosis.

Fig. 1

a Coronal view of choroid plexus of a representative patient. First row, from left to right: contrast-enhanced (CE) T1-weighted (T1w), non-CE T1w, and fluid-attenuated inversion-recovery (FLAIR) sequences. Second row, from left to right; previous images with overlapped, respectively, CE-T1w manual segmentation (MSeg) in red, T1w MSeg in green, and FLAIR MSeg in blue. b Study workflow: (1) data acquisition (for details, see the “Data acquisition” section); (2) MSeg performed by neuroradiologists on ITK-snap for each available sequence for each subject (for details, see the “Manual segmentation and inter-rater agreement” section); (3) metrics evaluation: analyses performed in the study (for details, see the “Quantitative contrast metrics,” “Quantitative segmentation metrics,” and “Spatial variability” sections). ANTs, Advanced Normalization Toolbox

Fig. 2

a Quantitative contrast metrics. Boxplot of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) between the choroid plexus and the ventricles for the three compared sequences: T1-weighted (T1w), fluid-attenuated inversion-recovery (FLAIR), and contrast-enhanced (CE) T1w. The asterisk indicates that the metrics between the two groups are statistically different (p < 0.05). b Quantitative segmentation metrics, from left to right: boxplot of the absolute volume of the manual segmentations (MSegs); boxplot of the percentage volume difference (ΔVol%) for T1w and FLAIR MSegs (reference CE-T1w); boxplot of the absolute percentage volume difference (|ΔVol%|) for T1w and FLAIR MSegs (reference CE-T1w). The asterisk indicates statistically significant differences between groups (p < 0.05)

Fig. 3

a Slice-wise evaluation of performance metrics in MNI Talairach ICBM 152 2009c nonlinear symmetric template (MNI152) coordinate system. The graph represents the error distribution per slice between non-contrast-enhanced (CE) manual segmentations (MSegs)—fluid-attenuated inversion-recovery (FLAIR) in red, T1-weighted (T1w) in blue—and the reference CE-T1w computed axial-wise along the z-coordinate (on the left) and coronal-wise along the y-coordinate (on the right) of the MNI152 coordinate system. The vertical green lines highlight three representative axial (z = -12: temporal horn near the head of the hippocampus; z = 10: atrium of the lateral ventricle; z = 18: body of the lateral ventricles near the fornix) and coronal (y = -35: anterior portion of the atrium of the lateral ventricles; y = -42: posterior portion of the atrium of the lateral ventricles; y = -7: anterior portion of the fornix) slices reported in b. b Probability frequency maps of MSegs overlapped to the MNI Talairach ICBM 152 2009c nonlinear symmetric template (MNI152). From left to right, three axial views (z = -12: temporal horn near the head of the hippocampus; z = 10: atrium of the lateral ventricle; z = 18: body of the lateral ventricles near the fornix) and three coronal views (y = -35: anterior portion of the atrium of the lateral ventricles; y = -42: posterior portion of the atrium of the lateral ventricles; y = -7: anterior portion of the fornix). Reported coordinates are centered at the origin of the MNI space. The first row represents the frequency map of the CE-T1w MSeg for representative slices overlapped to the MNI152 template. The second and third rows show the difference between the frequency map of MSegs depicted on non-CE sequences (T1w and FLAIR) and the MSeg obtained from the CE-T1w sequence overlapped to the MNI152, respectively