# "X-ray" doesn't look like one **URL:** \ **Category:** Factual Questions\ **Created:** [July 25, 2013, 12:32am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440 "2013-07-25T00:32:28Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [July 25, 2013, 12:32am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/1 "2013-07-25T00:32:28Z")
What kind of “X-ray” is this? Flesh and fuel are opaque and metal is transparent? > **[Mexico rescues migrants crammed into truck in 'subhuman' conditions | CNN](https://www.cnn.com/2013/07/23/world/americas/mexico-migrants-rescued/index.html)** > > Mexican authorities say they’ve rescued 94 migrants who were crammed into the back of a hauling truck in “subhuman conditions.” I think this is t-ray or some other, not x-ray. Any strong guesses? ---
**Author:** ![USCDiver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uscdiver/32/354_2.png) [@USCDiver](https://boards.straightdope.com/u/USCDiver)\ **Post date:** [July 25, 2013, 12:43am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/2 "2013-07-25T00:43:52Z")
Probably X-ray with black and white reversed. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [July 25, 2013, 12:48am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/3 "2013-07-25T00:48:14Z")
If we could see the engine it would be definitive, but I presume this is some sort of thermal imaging. ---
**Author:** ![Attack\_from\_the\_3rd\_dimension](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@Attack\_from\_the\_3rd\_dimension](https://boards.straightdope.com/u/Attack_from_the_3rd_dimension)\ **Post date:** [July 25, 2013, 1:18am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/4 "2013-07-25T01:18:52Z")
The wheel hubs are in the image and are quite dark. They would be bright on a standard x-ray, dark on a reversed image. On thermal imaging, the rubber should be bright, as it is, while the hub would be darker. Several people, notably the person standing on the left, have a bright central chest (mediastinum) and dark lungs. This is how a standard x-ray would look, dark lungs, bright heart. Thermal imaging should also give this appearance, as the lungs are full of relatively cool air, but the abdomen is warmer. The ground should be dark on x-ray, bright on thermal, so again, thermal. I don’t understand while the boxy thing on the left - fuel tank ? - is bright, unless it’s from sloshing. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [July 25, 2013, 2:03am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/5 "2013-07-25T02:03:46Z")
I’m pretty sure this is a backscatter x-ray image. So the x-rays didn’t pass through the truck and the people in it. Rather the x-rays were scattered back from them. So you don’t get the classic absorption images one associates with x-rays. It is more akin to shining light onto them and getting the scattered light back - except that the light will pass through things as well. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [July 25, 2013, 2:46am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/6 "2013-07-25T02:46:05Z")
**Francis Vaughan** is right. It’s [backscatter X-ray](http://en.wikipedia.org/wiki/Backscatter_X-ray), which is commonly used to inspect trucks and shipping containers. It’s the same technology used at some airports as full-body scanners. (Though [millimeter wave](http://en.wikipedia.org/wiki/Millimeter_wave_scanner) seems to be more common for this application.) ---
**Author:** ![Projammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/projammer/32/559_2.png) [@Projammer](https://boards.straightdope.com/u/Projammer)\ **Post date:** [July 25, 2013, 2:50am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/7 "2013-07-25T02:50:20Z")
And the backscatter x-ray is completely digital. So the rendering can be done in whatever style the operator chooses. Or that the software supports any way. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [July 25, 2013, 4:19am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/8 "2013-07-25T04:19:37Z")
I saw a similar picture in an article on border security, in Pop Sci I think. They said it can see piston heads in an engine. ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [July 25, 2013, 4:21am UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/9 "2013-07-25T04:21:09Z")
I concur, backscatter X-ray. There are similar pictures in this Forbes article: [Full-Body Scan Technology Deployed In Street-Roving Vans](http://www.forbes.com/sites/andygreenberg/2010/08/24/full-body-scan-technology-deployed-in-street-roving-vans/) ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [July 25, 2013, 12:23pm UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/10 "2013-07-25T12:23:08Z")
So it IS an X-ray, though not a typical shadowgraph type. Ignorance fought! Thanks! ---
**Author:** ![Attack\_from\_the\_3rd\_dimension](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@Attack\_from\_the\_3rd\_dimension](https://boards.straightdope.com/u/Attack_from_the_3rd_dimension)\ **Post date:** [July 25, 2013, 10:14pm UTC](https://boards.straightdope.com/t/x-ray-doesnt-look-like-one/664440/11 "2013-07-25T22:14:39Z")
Cool. Thanks.