Answer to Question #4427 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I wish to carry out tomography on a gas-liquid (water)-solid system, wherein, a gas (air) and a solid (quartz/sand or glass beads) having wide variations in density are encountered, thereby requiring special attention towards the type of source and its strength for a particular material. In short I wish to conduct dual-energy tomography. Can you help me with some suggestions or references wherein I can find out the basics about dual-energy tomography and related things about it?
Would it be necessary to use two different types of sources at the same time?
Can the attenuation caused by air and sand/quartz or glass beads be quantified separately?
It sounds like the materials (water, air, glass) that you want examined are suitable for conventional/medical CT examination (computed-tomography examination), unless you desire extremely fine spatial resolution. If you can transport the sample to a nearby hospital that has a CT scanner, you might ask if someone there could check it out for you. If you have other special considerations that absolutely require dual-energy tomography, see the following references for more details:
- Papers found on the Nondestructive-Testing (NDT) net website, and search "dual-energy computed tomography."
- Publications available on the ESRF - The European Synchrotron Radiation Facility website, search "Micro-Imaging and Micro-Tomography."
- ACCENT PRO 2000 and click on Digital Radiography.
It appears a single x-ray source can be used for dual-energy tomography.
Attenuation by the different densities of various materials is the factor that makes computed tomography possible in the construction of the image of the item being x rayed.
John P. Hageman, MS, CHP