Lung infections: The radiologist's perspective - ScienceDirectwww.sciencedirect.com › science › article › pii
Pneumatoceles manifest as single or multiple thin-walled air-filled lucencies ... which points to an exudate, with the extra-pleural fat demonstrating hyperdensity.
by C Beigelman-Aubry · ‎2012 · ‎Cited by 40 · ‎Related articles

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Basics of X-ray Physics - Tissue densitieswww.radiologymasterclass.co.uk › tutorials › x-ray_ph...
The 5 X-ray densities Low density material such as air is represented as black on the final radiograph. Very dense material such as metal or contrast material is represented as white.
Missing: gas ‎| Must include: gas

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Reference: see

Reference information:
https://cyberlearn.hes-so.ch/mod/glossary/view.php?id=94926&...

CLARTÉ
L'image thoracique étant définie par sa transparence due notamment à l'air contenu dans les voies et les espaces aériens, le concept de clarté est ambigu. En radiologie pulmonaire, on parle surtout d'hyperclarté, ce qui sous-entend que l'image décrite est relativement plus "noire" que celle du parenchyme environnant. Le terme hypertransparence est également accepté.

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Lors de l'analyse d'une radiographie, on parle d'hypodensité ou de clarté quand c'est « noir » et d'hyperdensité ou opacité quand c'est « blanc ». L'image a donc différents contrastes qui dépendent de l'épaisseur et des tissus du corps qui absorbent (ou laissent passer !) les rayons X.

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Chapitre 23 Imagerie thoracique - Wiki-SIDESwiki.side-sante.fr › doku
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29 May 2018 — Une clarté est une diminution de la densité, c'est-à-dire une image plus « noire ». La clarté est due à un remplacement du parenchyme ...

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Associating liver partition and portal vein ligation for staged ...www.ncbi.nlm.nih.gov › pmc › articles › PMC5785687
27 Jan 2018 — Liver resection is often precluded by the fact that disease reaches ... 4 and right hepatic lobe and contains air densities (black arrow) and ...
by S Akbulut · ‎2018 · ‎Cited by 7 · ‎Related articles

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so

there is an air/air-filled density above the collection

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X-Ray Exam: Abdomen (for Parents) - Nemours KidsHealthkidshealth.org › parents › xray-abdomen
Dense body parts that block the passage of the X-ray beam through the body, such as bones, appear white ... ****Gas in the stomach and intestines appears black****.

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Base Physique de la Radiologie - Jamiatiwww.jamiati.ma › sites › default › files
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Clarté = zone de moindre densité : (sombre ou noire). • Structure dense (Z élevé), comme l'os, atténue (absorbe) beaucoup le RX, et s'exprime en blanc: « il est ...

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Structures which are not very dense, such as air, absorb very little of the x-ray beam. Most of the beam passes through the air and strikes the detector. As a result, these structures appear black on x-rays, termed 'radiolucent'.

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https://medical-dictionary.thefreedictionary.com/radiolucenc...
radiolucent adjective Referring to a material or tissue that allows the facile passage of X-rays (i.e., has an air or near-air density); radiolucent structures are black or near black on conventional X-rays

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adjective Referring to a material or tissue that allows the facile passage of X-rays (i.e., has an air or near-air density); radiolucent structures are black or near black on conventional X-rays


so

air density

looks good to me

"Discreet increase (surcharge) in the hepatectomy (hepatocytomy) lodge measuring 23 mm surmounted from an aerial clarity for a previous (preceding) reading."
(Hepatectomy is a surgicla resection of the liver.)

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(surgical resection)

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https://www.thefreedictionary.com/aerial

I can't find a definition of the fixed phrase 'aerial clarity', deduced from "une clarté aérique" in French, but of the two words separately.
In the medical sense, whilst 'aerial' can be an aerial with antenna used for transmitting or reading radio waves, it can also be relating to, connected with or resembling air.
The source text states specifically that the clarity is of a 14.4mm preceding measurement in the air.