DISCRIMINATION BETWEEN LOW ATOMIC-NUMBER MATERIALS FROM THEIR CHARACTERISTIC SCATTERING OF X-RAY-RADIATION

There are many applications within the agricultural, food and medical sciences where it is required to detect targets that absorb X-rays in a similar way to the background material and these are therefore not e asy to detect in a transmission image. Scattered X-rays provide useful additional information as they have interacted with the material in q uestion. Furthermore, the incident and scatter angles can be defined s o as to characterize a small volume element without recourse to comple x computer tomography techniques. The potential of scattering techniqu es has been partially rc:cognized within the medical sciences but rema ins largely unstudied in other application areas. This paper investiga tes the potential of distinguishing between different low atomic numbe r targets from their scattering characteristics with a view to applyin g these techniques to food and agricultural applications. An experimen tal and simulation study are presented. The investigations use a polyc hromatic X-ray source to irradiate several low atomic number samples a nd a small area silicon photodiode to detect the scattered radiation. This geometry is reproduced within a simulation study based on a Monte -Carlo-based program. The results of the simulation and experimental s tudy are shown, qualitatively, to be in close agreement with each othe r. These studies show that the intensity of scattered radiation, over a range of scattering angles, gives a greater contrast measure between low atomic number targets than a traditional transmission image. (C) 1997 Silsoe Research Institute.