X-ray cone-beam computed tomography （CT） has such notable features as high efficiency and precision, and is widely used in the fields of medical imaging and industrial non-destructive testing, but the inherent imagi...X-ray cone-beam computed tomography （CT） has such notable features as high efficiency and precision, and is widely used in the fields of medical imaging and industrial non-destructive testing, but the inherent imaging degradation reduces the quality of CT images. Aimed at the problems of projection image degradation and restoration in cone-beam CT, a point spread function （PSF） modeling method is proposed first. The general PSF model of cone- beam CT is established, and based on it, the PSF under arbitrary scanning conditions can be calculated directly for projection image restoration without the additional measurement, which greatly improved the application convenience of cone-beam CT. Secondly, a projection image restoration algorithm based on pre-filtering and pre-segmentation is proposed, which can make the edge contours in projection images and slice images clearer after restoration, and control the noise in the equivalent level to the original images. Finally, the experiments verified the feasibility and effectiveness of the proposed methods.展开更多
An X-ray pinhole camera has been used to determine the transverse beam size and emittance on the diagnostic beam line of the storage ring at SSRF since2009.The performance of the beam size measurement is determined by...An X-ray pinhole camera has been used to determine the transverse beam size and emittance on the diagnostic beam line of the storage ring at SSRF since2009.The performance of the beam size measurement is determined by the width of the point spread function of the X-ray pinhole camera.Beam-based calibration was carried in 2012 out by varying the beam size at the source point and measuring the image size.However,this calibration method requires special beam conditions.In order to overcome this limitation,the pinhole camera was upgraded and an X-ray quasi-monochromator was installed.A novel experimental method was introduced by combining the pinhole camera with the monochromator to calibrate the point spread function.The point spread function can be accurately resolved by adjusting the angle of the monochromator and measuring the image size.The X-ray spectrum can also be obtained.In this work,the X-ray quasi-monochromator and the novel beam-based calibration method will be presented in detail.展开更多
A pinhole camera for imaging X-ray synchrotron radiation from a dipole magnet is now in operation at the Shanghai Synchrotron Radiation Facility （SSRF） storage ring.The electron beam size is derived by unfolding the...A pinhole camera for imaging X-ray synchrotron radiation from a dipole magnet is now in operation at the Shanghai Synchrotron Radiation Facility （SSRF） storage ring.The electron beam size is derived by unfolding the radiation image and the point spread function （PSF） with deconvolution techniques.The performance of the pinhole is determined by the accuracy of the PSF measurement.This article will focus on a beam-based calibration scheme to measure the PSF system by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes.Applying this method at SSRF,the PSF value of the pinhole is revised from 37 to 44μm.The deviation in beam size between the theoretical value and the measured value isminimized to 4% after calibration.This optimization allows us to observe the horizontal disturbance due to injection down to as small as 0.5μm.展开更多
基金Supported by National Science and Technology Major Project of the Ministry of Industry and Information Technology of China(2012ZX04007021)Young Scientists Fund of National Natural Science Foundation of China(51105315)+1 种基金Natural Science Basic Research Program of Shaanxi Province of China(2013JM7003)Northwestern Polytechnical University Foundation for Fundamental Research(JC20120226,3102014KYJD022)
文摘X-ray cone-beam computed tomography （CT） has such notable features as high efficiency and precision, and is widely used in the fields of medical imaging and industrial non-destructive testing, but the inherent imaging degradation reduces the quality of CT images. Aimed at the problems of projection image degradation and restoration in cone-beam CT, a point spread function （PSF） modeling method is proposed first. The general PSF model of cone- beam CT is established, and based on it, the PSF under arbitrary scanning conditions can be calculated directly for projection image restoration without the additional measurement, which greatly improved the application convenience of cone-beam CT. Secondly, a projection image restoration algorithm based on pre-filtering and pre-segmentation is proposed, which can make the edge contours in projection images and slice images clearer after restoration, and control the noise in the equivalent level to the original images. Finally, the experiments verified the feasibility and effectiveness of the proposed methods.
基金The Natural Science Basic Research Plan in Shaanxi Province of China(Program No.2012JM8008)Scientific Research Program Funded by Shaanxi Provincial Education Department(No.14JK1350)
基金supported by the National Science Foundation of China(No.11375255)
文摘An X-ray pinhole camera has been used to determine the transverse beam size and emittance on the diagnostic beam line of the storage ring at SSRF since2009.The performance of the beam size measurement is determined by the width of the point spread function of the X-ray pinhole camera.Beam-based calibration was carried in 2012 out by varying the beam size at the source point and measuring the image size.However,this calibration method requires special beam conditions.In order to overcome this limitation,the pinhole camera was upgraded and an X-ray quasi-monochromator was installed.A novel experimental method was introduced by combining the pinhole camera with the monochromator to calibrate the point spread function.The point spread function can be accurately resolved by adjusting the angle of the monochromator and measuring the image size.The X-ray spectrum can also be obtained.In this work,the X-ray quasi-monochromator and the novel beam-based calibration method will be presented in detail.
文摘A pinhole camera for imaging X-ray synchrotron radiation from a dipole magnet is now in operation at the Shanghai Synchrotron Radiation Facility （SSRF） storage ring.The electron beam size is derived by unfolding the radiation image and the point spread function （PSF） with deconvolution techniques.The performance of the pinhole is determined by the accuracy of the PSF measurement.This article will focus on a beam-based calibration scheme to measure the PSF system by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes.Applying this method at SSRF,the PSF value of the pinhole is revised from 37 to 44μm.The deviation in beam size between the theoretical value and the measured value isminimized to 4% after calibration.This optimization allows us to observe the horizontal disturbance due to injection down to as small as 0.5μm.
