@misc{oai:repo.qst.go.jp:00069089,
 author = {Ohno, Yumiko and 大野 由美子},
 month = {Sep},
 note = {Monochromatic x-ray CT has advantages over conventional x-ray CT when using the data in treatment planning for radiotherapy. Monochromatic x-rays make CT images free from uncertainty due to the x-ray beam hardening effect. Two CT images taken with two different monochromatic x-rays directly provide the information on electron density and further additionally the information on effective atomic numbers. The quantitative electron density is expected to make the treatment planning more accurate. The goal is to develop techniques of the dual-energy x-ray CT(DECT) for medical applications. The previous studies have proved that the DECT provides quantitative and accurate electron density with synchrotron radiation. One of important factors for the medical application is to scan a large size object. The SR is highly collimated as its one of features. It is necessary therefore to widen the irradiation field in order to take a whole image at once. In these experiments, we tried to make wide fields employing a method of asymmetry reflection. The experiments were carried out at the BL20B2 beamline at SPring-8. The crystals for the expansion were set in the 1st hutch. CT images were taken in the 3rd hatch using the beam that was expanded in the method of asymmetric Bragg reflection. The field were obtained with 2D array of scintillator Gd2O2S. The measured magnifying powers roughly agree with the calculated ones. In the CT scanning, the obtained image quality was almost same as that taken in the unexpanded field. An electron density image and an effective atomic number image are derived based on CT images taken with X-rays of 40 and 70 keV. As well as the direct use of DECT, it is one of our purposes to acquire data helping a treatment planning of radiotherapy. It becomes a problem in a treatment planning that the property of medical materials implanted in the body change as time passes. We'll report on experimental results contributing to the treatment planning and discuss an application possibility to material identification., Medical Applications of Synchrotron Radiation},
 title = {Practical use of Dual-Energy X-ray CT},
 year = {2007}
}