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Analysis of spectral blur effects in x‐ray scatter imaging
Author(s) -
Leclair Robert J.,
Johns Paul C.
Publication year - 1999
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 - 10.1118/1.598685
Subject(s) - physics , beam (structure) , imaging phantom , photon , optics , fluence , compton scattering , scattering , laser
Previous analysis in our research program investigating the potential use of scattered photons for medical x‐ray imaging has been for monoenergetic beams. In practice, polyenergetic beams are almost always used due to their higher photon fluence rate. The effects of beam polychromaticity on x‐ray scatter imaging are determined with the aid of our semianalytic model that images a target object against a background material of the same dimensions when both are situated within a water phantom. Our analysis involves four different photon beams with constant incident energy fluence: (1) a monoenergetic beam with photon energy E 0 , (2) a dual peak beam with two separate monoenergetic peaks of energies E 1and E 2 , (3) a clinical x‐ray beam, and (4) a rectangular beam with uniform energy fluence between energies E minand E max . A comparison between the polyenergetic spectra is accomplished by matching the centroids and standard deviations of the dual peak and rectangular spectra to those of the clinical x‐ray spectrum. For the task of imaging liver versus fat structures 1 cm thick in a 25‐cm‐diam spherical water phantom with the scattered photons between 2° and 12°, the predicted signal‐to‐noise ratio (SNR) obtained with a 100 kV beam is 87.5 % of the SNR acquired with the optimum monoenergetic beam ( SNR opt) . The SNR for the corresponding dual peak beam is 84.4 % of SNR optand for the rectangular beam is 86.3 % . Our analysis shows that monoenergetic x‐ray beams are not necessary for x‐ray scatter imaging.