Fetal MRI

What it does

Fetal MRI reads the fetal brain examination performed after a suspicious anomaly scan, above all for ventriculomegaly and other central nervous system malformations. The fetus moves between and during slices, so the stacks of single-shot T2 images acquired in different planes are each motion-corrupted and incomplete on their own. The run first combines them by slice-to-volume reconstruction into one motion-corrected, high-resolution 3D brain volume.

On that volume it segments the brain tissues and reports their volumes, and it measures the standard fetal brain biometry: biparietal and occipitofrontal diameters, transcerebellar diameter and the atrial width of the lateral ventricles. Each measurement is placed against gestational-age reference values, so a borderline atrial width or a small cerebellum is reported with how far it sits from the expected range.

Intended use

Decision support for physicians reading fetal MRI in specialised centres and for those who see the exam only occasionally: reproducible biometry taken on a reconstructed volume rather than on oblique slices, and tissue volumes that cannot be measured by hand in clinical time. Measurements are shown on the reconstructed images.

Who it is for

Paediatric and fetal neuroradiologists, general radiologists covering prenatal imaging, maternal-fetal medicine specialists and fetal neurologists who counsel families after an abnormal scan. Researchers use the reconstruction and tissue volumes for fetal brain development studies.

Accepted input

• DICOM MR study (MR Image, Enhanced MR or Legacy Converted Enhanced MR) containing the fetal brain stacks, zipped or sent by DICOMweb STOW-RS. NIfTI stacks with a BIDS-style sidecar are accepted on the API.
• A reconstructed fetal brain volume can be uploaded instead of the raw stacks; reconstruction is then skipped.

Requirements

Requirement	Why
Several single-shot T2 stacks of the fetal brain in different orientations	Slice-to-volume reconstruction needs overlapping views to correct motion
Gestational age in clinical_context	Biometry and volumes are interpreted against age-specific references

Motion between stacks is expected and corrected; a study whose stacks cannot be reconstructed into a usable volume returns a quality block instead of measurements.

Optional context

Besides gestational age, the anomaly-scan finding that prompted the MRI (for example ventriculomegaly measured on ultrasound) goes in clinical_context.

The result

Section	Content
Brain tissue segmentation	Tissue labels on the reconstructed volume with per-tissue volumes
Brain biometry	Biparietal and occipitofrontal diameters, transcerebellar diameter and atrial width against gestational-age references
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

Standards

• DICOM: SEG for tissue labels, SR TID 1500 for diameters and volumes, KOS key images and Encapsulated PDF.
• Measurements: millimetres for diameters, millilitres for volumes, each with its gestational-age reference and position relative to it.
• Terminology: RadLex and SNOMED CT codes for structures and findings.

Why reconstruction matters

Diameters measured on a single motion-corrupted slice depend on how the slice happens to cut the head. On a reconstructed volume, the diameters are measured in planes aligned to the fetal brain itself, so they depend less on slice angle and can be compared between examinations.