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Table 1 Recommended steps for appropriate volume acquisition and postprocessing using 5D CNS+™ (adapted from Dall’Asta et al. 2019 and Abuhamad 2005) [65, 66]

From: Applicability of a semiautomated volumetric approach (5D CNS+™) for detailed antenatal reconstruction of abnormal fetal CNS anatomy

 

General considerations

Specific recommendations

Patient selection

All pregnant women are theoretically eligible

Limitations such as high maternal body mass index, fetal movement, and unfavorable fetal position may occur

No informed consent needed

Volumetric approach may be regularly included in anatomic survey

Ideal gestational age starting from 20 to 34 completed weeks (occasionally even at earlier GA)

Consider that anatomic structures may have not yet fully developed before 20 completed weeks

General machine settings

Presets need to be adjusted at a higher contrast and smaller dynamic range

An initial orienting 2D evaluation of the intracranial anatomy using the same image settings is mandatory (ideally in advance of the volume acquisition)

Volume acquisition

Insonation for 3D transabdominal volume acquisition

A transthalamic axial plane is a prerequisite for proper volumetry

Other scanning planes potentially suitable for 3D brain assessment are not applicable

Region of Interest (ROI) position and size

ROI should capture the entire contour of the fetal head (the box boundaries should be placed outside the skull)

Scanning angle (sweep width of the 3D acquisition) and quality

Scanning angle needs to be adjusted according to the GA (between 60 and 85°), scan quality needs to be highest (‘extreme)

Visualization of the cerebellum is crucial

Intermediate steps

Manipulation of the triplanar volume display along the x, y, and z-axis

The falx cerebri needs to be orientated horizontally in both the a and b planes

Application of 5D CNS+™ and following the onscreen pictograms

Two reference marks need to be placed:

1st seed between the rostralmost third of the thalami,

2nd seed central in the cavum septi pellucidi

Reconstruction

Automatic reslicing of the volume to generate nine diagnostic planes for a complete neurosonogram

Generation of the entire template takes approximately 3–5 s

Evaluation of all planes in a single template or grouped for axial, coronal, and sagittal planes separately

Postprocessing

Optimization of diagnostic plane alignment

If needed manual plane adjustment (plane by plane)

Adjustment of biometric measurement

Manual correction of the calipers for exact biometric assessment of the CNS

Integration of these measures into the structured biometric report