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A K edge filter technique for optimization of the coherent‐to‐Compton scatter ratio method
Author(s) -
Harding G.,
Armstrong R.,
McDaid S.,
Cooper M. J.
Publication year - 1995
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.597497
Subject(s) - compton scattering , optics , scattering , physics , photon , atomic number , attenuation , inelastic scattering , computational physics , radiation , semiconductor detector , effective atomic number , filter (signal processing) , incoherent scatter , detector , atomic physics , computer science , computer vision
The ratio method involves forming the ratio of the elastic to inelastic x‐ray scatter signals from a localized region of a scattering medium to determine its mean atomic number. An analysis is presented of two major error sources influencing the ratio method: firstly statistical (photon) noise and secondly multiple scattering and self‐attenuation of the primary and scatter radiations in the medium. It is shown that a forward scattering geometry minimizes errors of both types for substances composed of elements with low and medium atomic number. However, owing to the small energy separation (∼100 eV) of coherent and Compton scatter for this geometry, they cannot be distinguished directly with semiconductor (e.g., Ge) detectors. A novel K edge filter technique is described which permits separation of the elastic and Compton signals in the forward‐scatter geometry. The feasibility of this method is demonstrated by experimental results obtained with Ta fluorescence radiation provided by a fluorescent x‐ray source filtered with an Er foil. The extension of this technique to the “ in vivo ” measurement of low momentum transfer inelastic scattering from biological tissues, possibly providing useful diagnostic information, is briefly discussed.