Reduction of patient dose at medical x-ray diagnosis using scattered x rays.

使用散射 X 射线减少医疗 X 射线诊断中患者的剂量。

• 批准号: 08680524
• 负责人: KANAMORI Hitoshi
• 金额: $ 1.02万
• 依托单位: Fukui University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08680524/
• 关键词: medical x-ray image; image quality; patient dose; granularity; scattered x rays

(1)Measurement of x-ray spectraWe have attempted to perform the direct measurement of x-ray spectra using low-cost CdTe and CdZnTe detectors, which have been developed recently. The results obtained with CdTe detector were less exact than those with a Ge detector, but those with CdZnTe detector agreed with it.(2)Effects of anti-scatter grids on x-ray spectra and radiographic image qualityBy using a conical collimator and a lead beam stopper, primary and scattered x-ray photon spectra through an object and an anti-scatter grid (addreviated as grid, hereafter) were measured separately, varying the irradiation field area. From these results, we obtained the grid ratio, scatter ratio and Bucky factors. The scatter ratio varied with tube voltage but Bucky factors did not. At any spatial frequency, the effects of grids for removing scattered x-rays were almost constant for the tube voltage.(3)Optimum tube voltage of radiographs obtained by psychophysical analysisWe proposed a new method for … More determining the optimum tube voltage of a chest radiograph using psychophysical analysis. The optimum density range of screen-film system was obtained from gradient curve and minimum perceptible contrasts. An optimum tube voltage, by which the highest density in the lung-field and the lowest density in the mediastinum just covered the optimum density range, was obtained using x-ray photon spectrum and sensitivity spectrum of the screen.(4)Modulation transfer function and Wiener spectra for a screen-film systemWe have obtained the tube voltage dependence of the modulation transfer function (MTF) of a rare-earth 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 influence of the crossover effect on the tube voltage dependence of the Wiener spectrum of the quantum mottle for the front and back emulsion has been investigated. It was found that if the crossover effect was appropriately included in the radiographs, the patient exposure and the Wiener spectrum of the quantum mottle could be reduced. Less

(1)X射线能谱的测量我们已经尝试使用最近开发的低成本的CdTe和CdZnTe探测器来直接测量X射线能谱。(2)反散射栅格对X射线能谱和照相图像质量的影响。利用锥形准直器和铅束阻挡，分别测量了物体和反散射栅格(以下简称栅格)的初级和散射X射线光子能谱，改变了照射场面积。由这些结果，我们得到了网格比、散射率和巴基因子。散射率随管电压的变化而变化，而巴基因子变化不大。在任何空间频率下，栅极对去除散射X射线的影响几乎不随管电压而变。(3)通过心理物理分析得到X射线照片的最佳管电压我们提出了一种新的…方法通过心理物理分析进一步确定胸片的最佳管压。由梯度曲线和最小可察觉对比度得到了最佳屏幕-胶片系统的密度范围。利用X射线光子谱和屏的灵敏度谱，得到了一个最佳的管电压，在该管电压下，肺野的最大密度和纵隔的最低密度正好覆盖了最佳的密度范围。(4)屏-膜系统的调制传递函数和维纳谱。在空间频率小于3 mm^~(-1)~(-1)的情况下，正反面的MTF值随管电压的增大而减小。为了解释这一现象，不仅要考虑K-x射线，还要考虑屏面中产生的相干和非相干散射x射线光子。研究了交叉效应对前后乳胶量子斑点维纳谱的管电压依赖性的影响。研究发现，如果在射线照片中适当地包含交叉效应，可以减少患者的暴露和量子斑点的维纳谱。较少

项目成果

H.Arimura, T.Okawa, T.Ikari, M.Okamoto, H.Kubota, M.Matsumoto, A.Takigawa, N.Nakamori and H.Kanamori: "Influence of the crossover effect on x-ray tube voltage dependence of quantum mottle" Journal of Photographic Science. 44[6]. 178-186 (1996)

H.Arimura、T.Okawa、T.Ikari、M.Okamoto、H.Kubota、M.Matsumoto、A.Takikawa、N.Nakamori 和 H.Kanamori：“交叉效应对 X 射线管电压依赖性的影响

A.Asai: "Evaluation of radiographic mottle using a single drequency value of the psychophysical Wiener spectrum" Journal of Photographic Science. 44・3. 89-92 (1996)

A.浅井：“使用心理物理学维纳谱的单一频率值评估放射线斑点”，《摄影科学杂志》44·3（1996）。

浅井 義行: "心理物理的解析から求めた胸部X線写真の最適撮影条件" 日本写真学会雑誌. 60・3. 189-195 (1997)

浅井义行：“根据心理物理学分析确定胸部 X 射线摄影的最佳条件”，日本摄影学会杂志 60・3（1997 年）。

浅井義行: "心理物理的解析を用いたX線写真粒状の評価" 医用画像情報学会雑誌. 14・2. 83-94 (1997)

Yoshiyuki Asai：“使用心理物理分析的 X 射线粒度评估”医学影像和信息科学学会杂志 14・2（1997 年）。

H.Kanamori: "Evaluation of radiographic mottle using psychophysical RMS granularity" Medical & Biological Engineering & Computing. 35・S2. 1131 (1997)

H.Kanamori：“使用心理物理学 RMS 粒度评估放射线斑点”医学与生物工程与计算 35・S2（1997）。