Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
Ideguchi Tadamitsu Last modified date:2021.06.25

Associate Professor / Department of Health Sciences / Faculty of Medical Sciences


Presentations
1. Souichiro Kawaguchi, Yoshiki Yamaguchi, Hidetaka Arimura, Junji Morishita, Masafumi Ohki, Yoshinori Uno, Tadamitsu Ideguchi, Yoshiharu Higashida, Fukai Toyofuku, Reconstruction of mammography x-ray spectrum by using Rayleigh and Compton scattering corrections, World Congress on Medical Physics and Biomedical Engineering: Diagnostic Imaging, 2009.12, The analysis of the x-ray spectrum is important for quality assurance (QA) and quality control (QC) of a radiographic system such as mammography. In the case of mammography, the direct measurement of the primary x-ray spectra under clinical conditions is very difficult and time-consuming mainly because it is almost impossible to increase the longitudinal distance between the focal spot and x-ray detector in order to make the photon counting measurement possible. An alternative way of measuring the primary spectra is to correct the 90 degree scattered x-ray spectra which can be measured without photon pile-up since the intensity of the scattered x-rays is significantly lowered. The scattered x-ray spectrum is composed of two components, Compton scattered photons and Rayleigh scattered photons. We have developed a new method of reconstructing the primary x-ray spectrum from the scattered x-ray spectrum taking into account both Rayleigh and Compton scattered photons . The 90 degree scattered x-ray spectrum from a 28 kV mammography x-ray unit was measured at a tube voltage by using a CdTe semiconductor detector. The reconstructed spectrum agreed fairly well with a directly measured primary x-ray spectrum. The Rayleigh and Compton scattering correction method could be suitable for measuring the mammography x-ray spectra under clinical conditions and useful for QA and QC of the mammography x-ray units..
2. Yoshiki Yamaguchi, Souichiro Kawaguchi, Hidetaka Arimura, Junji Morishita, Masafumi Ohki, Yoshinori Uno, Tadamitsu Ideguchi, Kenji Tokumori, Yoshiharu Higashida, Fukai Toyofuku, Rayleigh and Compton scattering analysis for PMMA in the mammography energy range, World Congress on Medical Physics and Biomedical Engineering: Diagnostic Imaging, 2009.12, The method of obtaining the primary x-ray spectrum by the Compton scattering correction has been practically established for relatively high x-ray tube voltages. However, for mammography, the tube voltages are less than 30 to 35 kV and there exists an intense characteristic x-ray peak at 17.5 keV from the molybdenum target. The influence of Rayleigh scattering can not be neglected in this mammography energy range. Accurate data of Rayleigh and Compton cross sections for the scatterer material are required for obtaining the primary x-ray spectrum by correcting the scattered x-ray spectrum of mammography. The purpose of this study is to investigate the Rayleigh and Compton scattering cross sections for PMMA scatterer material in the mammography energy range theoretically and experimentally. Fluorescent x-rays of 15 to 25 keV were generated by exciting four metal targets including molybdenum by synchrotron radiation. The produced fluorescent x-rays were incident on a sphere of PMMA (polymethyl methacrylate), and scattered x-rays at 90, 120, 150, and 165 degrees, respectively, were measured with a CdTe detector. The scattered fluorescent x-ray spectrum was separated into the Rayleigh and Compton scattering peaks by using a curve fitting technique with two Gaussian functions. We compared the measured cross section data to those obtained from theoretical values. In addition, we calculated the scattered fluorescent x-ray spectra using the Monte Carlo simulation and compared them to the measured spectra. As a result, the ratio of the Rayleigh to the total scattering ratio agreed to theoretical value within 10%. The shapes of the scattered spectra calculated by Monte Carlo simulation agreed fairly well with those of measured spectra..