Automating Quantitative Measures of an Established Conventional MRI Scoring System for Preterm-Born Infants Scanned between 29 and 47 Weeks’ Postmenstrual Age

Article Figures & Data

Download figure
Open in new tab
Download powerpoint
FIG 1.
Automated MR imaging measures of biparietal width (BPW), interhemispheric distance (IHD), thickness of the corpus callosum (CC), transcerebellar diameter (TCD), left and right LVD, and DGMA. IHD, Blue to orange represents the distance (closest and farthest, respectively) for each voxel to the segmentation in the opposite hemisphere. CC, Upper image, T2WI with the CC segmentation border (red); lower panel, segmentation border (blue), skeleton (red), and distance between the upper and lower borders of the segmentation for each voxel on the skeleton (green). R indicates right; L, left; A, anterior; P, posterior.
Download figure
Open in new tab
Download powerpoint
FIG 2.
Associations between the 6 raw conventional MR imaging measures with postmenstrual age (left) and gestational age at birth (right) in the Pearson r, displayed separately for preterm-born infants at early MR imaging (n = 94) and TEA MR imaging (n = 81), as well as term-born controls at TEA MR imaging (PPREMO, n = 22; dHCP, n = 455). Manual measures were available for PPREMO only. Double asterisks indicate P ≤ .001; asterisk, P ≤ .05. BPW indicates biparietal width; CC, callosal thickness (at the genu (CCg), midbody (CCm), and splenium (CCs)); IHD, interhemispheric distance; TCD, transcerebellar diameter; R, right; L, left.

Table 1:

Six manual measures of distance and area

Measure	How to Measure
Biparietal width	Greatest distance between left and right parietal cortices, measured on a single coronal slice identifying bilateral cochlea and basilar truncus
Interhemispheric distance	Distance between crowns of superior frontal gyri, measured on the same coronal slice as biparietal width
Callosal thickness	Thinning at the genu, midbody, splenium
Transcerebellar diameter	Single coronal slice at level of ventricular atrium
Lateral ventricular diameter	Same coronal slice as transcerebellar diameter
Deep grey matter area	Single axial slice showing caudate heads, lentiform nuclei, and thalami

Table 2:

Automated measures of distance and area

Measure	How to Measure
Biparietal width	Identify most lateral sagittal slices of parietal GM (regionprops3) For each GM voxel, calculate distance to voxels in opposite hemisphere Calculate maximum distance
Interhemispheric distance	Calculate distance from each voxel of superior frontal gyrus label in left hemisphere to each voxel label in right hemisphere (bwmorph3, bwdist) Derive minimum distance
Callosal thickness	Combine 2D corpus callosum segmentation of the 11 most medial slices Increase resolution (imresize) and improve mask (bwmorph3, bwmorph) Derive skeleton (bwskel); for every voxel, calculate normal vector, identify intersection with borders of segmentation (points2contour, polyfit) Derive distance between upper/lower segmentation borders for every voxel Apply smoothing (nanfastsmooth), make 3 divisions Obtain 97th percentile for each division (prctile)
Transcerebellar diameter	Model cerebellum segmentation as 3D ellipsoid (bwmorph3, regionprops3) Calculate length of principal axis (regionprops3)
Lateral ventricular dilation	Identify coronal slice at level of ventricular atrium (regionprops3): find maximum surface area using ventricle label (bwmorph, regionprops) Model 2D ventricle as ellipse, calculate length of minor axes (regionprops)
Deep grey matter area	Identify axial slice: centroid of caudate, thalamus, and lentiform nucleus (bwmorph, regionprops) Combine labels to calculate area (regionprops)

Table 3:

Demographic and clinical characteristics

↵a P < .05 for 2-sided t test comparing preterm infants at 40 weeks with term-born controls (PPREMO). Continuous variables are given as median ± interquartile range (range). Scans with poor quality (PPREMO, n = 39), realignment errors (PPREMO, n = 1; dHCP, n = 39), and severe pathology (PPREMO, n = 16; dHCP, n = 12) were excluded.