[ RadSafe ] Z-Backscatter technology
bradkeck at mac.com
Tue Oct 27 10:02:14 CDT 2015
If i understand the Z-backscatter physics correctly, then the dark images of the lungs result from a lesser backscatter signal being generated in the lung cavity versus the thicker surrounding tissues.
Unlike an airport scanner, which does not need to penetrate the side of a truck, the cargo scan uses a higher energy (and intensity, i would think) x-ray source which penetrates humans more than the energies used in airport scans. The detector array - basically the side panel of the truck - is then used to measure the intensity of the x-rays corresponding to those scattered by low-Z material so you build an image of the low-Z materials in the first few centimeters lying along the side of the truck, including humans, drugs, explosives, cantaloupes, etc…. Interestingly, both air and high-Z materials would give a “dark” image, where any organic or low-Z materials would give a “bright” image under the acquisition parameters used.
There are numerous dose estimates on the internet for the airport scanners, but I have not seen estimates for the cargo scans where a human might inadvertently be present.
Hope this helps,
> On Oct 22, 2015, at 11:13 AM, Bradt, Clayton (HEALTH) <clayton.bradt at health.ny.gov> wrote:
> Does anyone know how I might get ahold of technical information on the Z-Backscatter technology as used for example by the AE&S vans mentioned in the above article? I am especially curious as to how the image of the contents of a vehicle is not obscured by backscatter off of the sides of the van and of the vehicle being scanned. Both the beam and scattered x-rays must pass through both vehicles on the way out and back. Also I'm curious about the density information presented in the images of people within a trailer. They appear to show the individuals lungs as dark regions within the thoracic cavities. I would not expect this from a backscatter image.
> Clayton Bradt
> Principal Radiophysicist
> NYS Dept. of Health
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