Pitfalls
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Symmetry is vital.
Oblique section
This diagram shows an oblique section. This will result in an inaccurate measurement – but you can guard against this by ensuring that the landmarks are clearly seen on the image.
Fig 1a Copyright Phillipe Jeanty 1994
These two images show an oblique plane through the skull. Although the scan plane passes through the parietal eminence, it is angled downwards towards the skull base (sb). The normal anatomical landmarks are not seen. Only one choroid plexus (cp) is demonstrated because the scan plane passes through only one lateral ventricle. Neither the thalami nor the cavum septi pellucidi are seen.
Oblique section
This diagram shows an oblique section. This will result in an inaccurate measurement – but you can guard against this by ensuring that the landmarks are clearly seen on the image.
These two images show an oblique plane through the skull. Although the scan plane passes through the parietal eminence, it is angled downwards towards the skull base (sb). The normal anatomical landmarks are not seen. Only one choroid plexus (cp) is demonstrated because the scan plane passes through only one lateral ventricle. Neither the thalami nor the cavum septi pellucidi are seen.
Axial section
This diagram shows an axial section but the anatomy is not well seen because the plane is not the true fronto occipital plane described on the previous page (scan plane D).
Fig 2a Copyright Phillipe Jeanty 1994
On this image, look at the distorted position of the cavum – this should lie a third of the way from the front of the skull and two-thirds from the back. This plane begins to show part of the roof of the eye socket (arrow).
Axial section
This diagram shows an axial section but the anatomy is not well seen because the plane is not the true fronto occipital plane described on the previous page (scan plane D).
On this image, look at the distorted position of the cavum – this should lie a third of the way from the front of the skull and two-thirds from the back. This plane begins to show part of the roof of the eye socket (arrow).