Fetal Brain Biometric Measurements on 3D Super-Resolution Reconstructed T2-Weighted MRI: An Intra- and Inter-observer Agreement Study

Abstract

We present the comparison of two-dimensional (2D) fetal brain biometry on magnetic resonance (MR) images using orthogonal 2D T2-weighted sequences (T2WSs) vs. one 3D super-resolution (SR) reconstructed volume and evaluation of the level of confidence and concordance between an experienced pediatric radiologist (obs1) and a junior radiologist (obs2). Twenty-five normal fetal brain MRI scans (18–34 weeks of gestation) including orthogonal 3-mm-thick T2WSs were analyzed retrospectively. One 3D SR volume was reconstructed per subject based on multiple series of T2WSs. The two observers performed 11 2D biometric measurements (specifying their level of confidence) on T2WS and SR volumes. Measurements were compared using the paired Wilcoxon rank sum test between observers for each dataset (T2WS and SR) and between T2WS and SR for each observer. Bland–Altman plots were used to assess the agreement between each pair of measurements. Measurements were made with low confidence in three subjects by obs1 and in 11 subjects by obs2 (mostly concerning the length of the corpus callosum on T2WS). Inter-rater intra-dataset comparisons showed no significant difference (p > 0.05), except for brain axial biparietal diameter (BIP) on T2WS and for brain and skull coronal BIP and coronal transverse cerebellar diameter (DTC) on SR. None of them remained significant after correction for multiple comparisons. Inter-dataset intra-rater comparisons showed statistical differences in brain axial and coronal BIP for both observers, skull coronal BIP for obs1, and axial and coronal DTC for obs2. After correction for multiple comparisons, only axial brain BIP remained significantly different, but differences were small (2.95 ± 1.73 mm). SR allows similar fetal brain biometry as compared to using the conventional T2WS while improving the level of confidence in the measurements and using a single reconstructed volume.

A Fetal Brain magnetic resonance Acquisition Numerical phantom (FaBiAN)

“…We have designed this open-source simulator to aid in the development and validation of advanced image processing techniques dedicated to improving the analysis of fetal brain MR images and support accurate diagnosis. Despite SR reconstruction has already demonstrated its potential for accurate biometric measurements in the fetal brain 18 – 20 , some parameters still need to be adjusted to the nature of the input LR images to provide optimal evaluation and support computer-assisted diagnosis. In fetal MRI, the level of regularization is commonly set empirically based on visual perception 12 – 14 , 17 .…”

“…Typical fetal brain HASTE images are acquired on patients at 1.5 T (MAGNETOM Aera, Siemens Healthcare, Erlangen, Germany) with an 18-channel body coil and a 32-channel spine coil at CHUV. At least three T2w series (3–11 series, series) of 2D thick slices are acquired in three orthogonal orientations (axial, coronal and sagittal) with respect to the fetal brain using an ultra-fast multi-slice HASTE sequence (TR/TE, 1200 ms/90 ms; flip angle, 90°; echo train length, 224; echo spacing, 4.08 ms; field-of-view, 360 360 mm ; voxel size, 1.13 1.13 3.00 mm ; inter-slice gap, 10%) 20 , 73 . Twenty-two to thirty slices are needed to cover the whole fetal brain depending on the GA (between 21 and 33 weeks) and size of the fetus, which corresponds to an acquisition time of between 26 to 36 seconds.…”

“…Especially, super-resolution (SR) reconstruction techniques take advantage of the redundancy between low-resolution (LR) series acquired in orthogonal orientations to reconstruct an isotropic high-resolution (HR) volume of the fetal brain with reduced intensity artefacts and motion sensitivity 12 – 17 . Navigating through the resulting SR volume provides valuable information on the developing brain anatomy, including consistent biometric measurements 18 – 20 . Besides, fetal brain tissue segmentation is critical for further investigation of brain development, especially for volumetric evaluation 21 – 25 .…”

ISUOG Practice Guidelines (updated): performance of fetal magnetic resonance imaging

“…Normal values for several cerebral structures have been defined by MRI 44 . Super‐resolution images 45 and machine‐learning‐based automatic measurement methods have been developed 46 . When measuring fluid‐containing structures, it is important to remember that MRI measurements are usually around 10% greater than the corresponding ultrasound measurements 47 .…”

Assessment of fetal corpus callosum biometry by 3D super-resolution reconstructed T2-weighted MRI

“…However, like any other reconstruction method, SR may distort the real anatomy (3). Thus, previous works have explored the value of SR reconstruction to perform fetal brain biometry, for whole brain and posterior fossa (20)(21)(22) in comparison to clinical T2WS MRI, ocular biometry (23), as well as in normative fetal brain atlases (12,24). To our knowledge, apart from the length of the CC, detailed CC biometry has not yet been evaluated on SR reconstructed fetal brain MRI.…”