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 |