Study of measuring system of x-ray spectrum for reduction of patient dose at medical x-ray diagnosis.
Grant-in-Aid for Scientific Research (C)
|Allocation Type||Single-year Grants|
|Research Institution||Osaka University|
MATSUMOTO Masao Osaka University, Faculty of Medicine, associate professor, 医学部, 助教授 (50149944)
KANAMORI Hitoshi Fukui University of Technology, Electrical Engineering, professor, 工学部, 教授 (70027770)
OGATA Yuji Osaka University, Faculty of Medicine, research associate, 医学部, 助手 (60281127)
|Project Period (FY)
1996 – 1997
Completed(Fiscal Year 1997)
|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1997 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1996 : ¥1,300,000 (Direct Cost : ¥1,300,000)
|Keywords||CdTe detector / CdZnTe detector / stripping procedure / diagnostic x-ray spectrum / photon spectrum|
(1) Correction of diagnostic x-ray spectra measured with CdTe and CdZnTE detectors
We have attempted to perform the direct measurement of diagnostic x-ray spectra using low-cost CdTe and CdZnTe detectors, which have been developed recently. Since detected spectra did not coincide with the true photon spectra, a correction by stripping procedure was applied. The results obtained with CdTe detector were less exact than those with a Ge detector, but those with CdZnTe detector agreed with it.
We analyzed mammographic x-ray spectra penetrated through 0.03mmMo or 0.025mmRh filter and objects measured using 50-mu m pinhole colimator system at 28kV and 50mAs. The obtainable results with CdZnTe detector agree with mammographic x-ray spectral shape measured using Ge detector published by Bureau of Radiological Health (BRH) in U.S.A..
(2) Measurement of scattered x-ray spectra
By using a conical collimator and a lead beam stopper, primary and scattered x-ray photon spectra through an object and an an
ti-scatter grid (abbreviated as grid, hereafter) were measured separately, varying the irradiation field area. From these results, the effects of grids for removing scattered x-rays were able to estimate.
(3) Analysis of optimum radiographic factors
We proposed a new method for determining the optimum tube voltage of a chest radiograph using psychophysical analysis. An optimum tube voltage, by which the highest density in the lung-field and the lowest density in the mediastin just covered the optimum density range, was obtained using x-ray photon spectrum and sensitivity spectrum of the screen.
(4) Analysis of image quality (MTF,granularity) of a screen-film system
We have obtained the tube voltage dependence of the modulation transfer function (MTF) of a rate-erath screen-film system. The values of the MTFs for the front and back sides at spatial frequencies of less than 3mm^<-1> decreased with the tube voltage. We showed that to explain this phenomenon, not only K-x rays but coherent and incoherent scattered x-ray photons yielded in the screens had to be taken into consideration.
The value of psychophysical Wiener spectrum at a frequency of 2.0mm^<-1> can be used for the evaluation of radiographic mottle instead of the psychophysical RMS granularity. The time to obtain the psychophysical Wiener spectrum can be reduced more than it to obtain the psychophysical RMS granularity. Less
Research Output (21results)