https://fr.wikipedia.org/wiki/Système_de_référence_en_anatom...

[...] L'une des difficultés vis-à-vis de l'imagerie médicale de la tête chez l'être humain tient au fait que l'encéphale n'est pas dans le prolongement du rachis mais forme un angle de telle sorte que, par exemple, la direction du regard est horizontale lorsqu'on se tient debout. Par conséquent, ce qui est en avant (antérieur) est ventral pour le reste du corps mais rostral (du côté du nez et de la bouche) s'agissant de la tête.

https://en.wikipedia.org/wiki/Anatomical_terms_of_location
Anterior and posterior
Anterior refers to what is in front (from Latin ante, meaning "before") and posterior, what is to the back of the subject (from Latin post, meaning "after"). For example, in a dog the nose is anterior to the eyes and the tail is considered the most posterior part; in many fish the gill openings are posterior to the eyes, but anterior to the tail. In projectional radiography terminology, an anteroposterior (AP) projection is taken with the X-ray generator anteriorly (such as in the front of a human), and the X-ray detector posteriorly. In contrast, a posteroanterior (PA) projection is taken with the X-ray generator posteriorly.

[...]
The terms of zootomy and anatomy came into use at a time when all scientific communication took place in Latin. In their original Latin forms the respective meanings of "anterior" and "posterior" are in front of (or before) and behind (or after), those of "dorsal" and "ventral" are toward the spine and toward the belly, and those of "superior" and "inferior" are above and below.

http://www.tamingthesru.com/aorta-module
...Identify the Aorta, which will appear as a hypoechoic, pulsatile, thick walled circular structure just anterior to the vertebral shadow.

https://www.sciencedirect.com/topics/medicine-and-dentistry/...
Abdominal aorta (AA) represents the segment between aortic hiatus of the diaphragm, situated at the level of the 12th thoracic vertebra, and the division into the common iliac arteries, at the level of the fourth lumbar vertebra. In the longitudinal plane, AA descends anterior to the vertebral column and left to the cava vein, from which it can be distinguished by thicker and pulsatile walls...

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Note added at 31 mins (2019-10-13 20:44:31 GMT)
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https://www.medbox.org/Manual-of-Diagnostic-Ultrasound-in-In...
(p. 42)
2.3.4.1
Examination Technique
[...]
– Measurements: longitudinal diameter right mid-clavicular line (right
of the gall bladder). Thickness of the left lobe in front of the aorta.
Diameter of the portal vein.

2.3.4.2
Normal Findings
– Vertical diameter in the right MCL < 12 cm, but wide variations depending on the shape of the liver. Thickness of the left lobe < 6 cm, measured in front of the aorta.


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Note added at 34 mins (2019-10-13 20:47:25 GMT)
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https://www.medbox.org/manual-of-diagnostic-ultrasound-in-in...


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Note added at 2 days 21 hrs (2019-10-16 17:13:36 GMT) Post-grading
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My pleasure!