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Here's an article that talks about Dual-energy CT [1]. And another one talking about material discrimination using DECT [2].

[1] https://en.wikipedia.org/wiki/Spectral_imaging_(radiography)

[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC2719491/

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Neither of those articles seem to support the idea that you can do molecular analysis with x-rays. They are all about elemental analysis, which is not useful for the purpose of detecting explosives.

Not sure if they use dual-energy x-ray as in [0], but you don't need to if you take x-ray shot from different angles. Modern 3D reconstruction algorithms you can detect shape and volume of an object and estimate the material density through its absorption rate. A 100ml liquid explosive in a container will be distinguishable from water (or pepsi) by material density, which can be estimate from volume and absorption rate.

https://en.wikipedia.org/wiki/Dual-energy_X-ray_absorptiomet...

See also beepblap's comments further below where they elaborate on this a bit (it's not just simple dual-energy xray apparently).

Hm, isn't it enough to just detect water and flag everything else as suspicious?

If your liquid is 80%+ water (that covers all juices and soft drinks), it is not going to be an explosive, too much thermal ballast.

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