期刊文献+
共找到1篇文章
< 1 >
每页显示 20 50 100
The Measurement Accuracy of Ball Bearing Center in Portal Images Using an Intensity-Weighted Centroid Method 被引量:1
1
作者 Mutian Zhang joseph driewer +2 位作者 Yichi Zhang Sumin Zhou Xiaofeng Zhu 《International Journal of Medical Physics, Clinical Engineering and Radiation Oncology》 2015年第4期273-283,共11页
Medical linac based imaging modalities such as portal imaging can be utilized for highly accurate measurements. An intensity-weighted centroid method for determining object center is proposed that can detect the posit... Medical linac based imaging modalities such as portal imaging can be utilized for highly accurate measurements. An intensity-weighted centroid method for determining object center is proposed that can detect the position of small object at subpixel accuracy. The principles and algorithms of the intensity-weighted centroid method are presented. Analytical results are derived for positional accuracy of a rod and a sphere in digital images, and the theoretical accuracy limits are calculated. The method was experimentally examined using phantoms with embedded ball bearings (BBs). Images of the phantoms were taken by the MV portal imager of a medical linac. The image pixel size was 0.26 mm when projected at the linac isocenter plane. The BB coordinates were calculated by applying the intensity-weighted centroid method after removing the background. The reproducibility of BB position detection was measured with 3 monitor unit (MU) exposures at various dose rates. A stationary BB, of 0.25 image contrast, showed position reproducibility in the range of 0.004 - 0.013 mm. When the method was used to measure the displacement of a moving BB, the difference between the measured and expected BB position had a standard deviation of 0.006 mm. The effect of image noise on the BB detection accuracy was measured using a phantom with multiple BBs. The overall detection accuracy, represented by standard deviation, steadily improved from 0.13 mm at 0.03 MU to 0.008 mm at 5.0 MU, and showed an inverse correlation with contrast-to-noise ratio. We demonstrated that intensity-weighted centroid method can achieve subpixel accuracy in position detection. With a linac based imaging system, precise mechanical measurement with accuracy of microns could be achieved. 展开更多
关键词 SUBPIXEL Detection Intensity-Weighted CENTROID PORTAL Image Medical LINAC Ball Bearing
下载PDF
上一页 1 下一页 到第
使用帮助 返回顶部