Journal of X-Ray Science and Technology - Volume 14, issue 4

Authors: Li, Liang | Kang, Kejun | Chen, Zhiqiang | Zhang, Li | Xing, Yuxiang | Wang, Ge

Article Type: Research Article

Abstract: The FDK algorithm is a widely used filtered-backprojection (FBP) algorithm for 3D image reconstruction from circular cone-beam projections. In this paper, we redefine the x-ray transform and expand the definition domain of FDK reconstruction to all points in 3D space. We prove that the FDK reconstruction, in this expanded definition domain, preserves the value of integrals along oblique lines in an angular range larger than the original FDK reconstruction proven by Rodet et al. Based on …this result, an efficient FBP-type method is proposed to synthesize radiographs from cone-beam projections. Finally, numerical experiments are done to validate this stereogram synthesis algorithm. Show more

Keywords: Cone-beam CT, FDK, FBP, stereogram, line integral

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 4, pp. 217-233, 2006

Authors: Ying, Zhengrong | Naidu, Ram | Crawford, Carl R.

Article Type: Research Article

Abstract: Single energy computed tomography (CT) scanners use measurements of densities to detect explosives in luggage. It is desirable to apply dual energy techniques to these CT scanners to obtain atomic number measurements to reduce false alarm rates. However, the direct application of existing dual energy techniques has practical problems, such as, approximation errors and lack of boundary constraints in dual energy decomposition, image artifacts, and x-ray spectral drifts. In this paper, we present methods to reduce …these problems. The methods include constrained dual energy decomposition, adaptive scatter correction, nonlinear filtering of decomposed projections, and real-time image-based correction for x-ray spectral drifts. We demonstrate the effectiveness of the methods using simulated data and real data obtained from a commercial dual energy CT scanner. Show more

Keywords: Computed tomography, dual energy, photoelectric effect, Compton scatter, effective atomic number, destreaking, spectral correction

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 4, pp. 235-256, 2006

Authors: Li, Changqing | Jiang, Huabei

Article Type: Research Article

Abstract: We present a method that optimizes the source intensity distribution in three-dimensional (3D) diffuse optical tomography (DOT). We evaluate this method using a series of phantom experiments where different contrast levels between the target and background are considered. With the new method, while the quality of both absorption and scattering images is quantitatively improved, the improvement in absorption image reconstruction is especially substantial: a relative error of less than 0.95% for recovered peak value in …the target region is achieved for high contrast case and of less than 18.0% for low contrast case. Show more

Keywords: Diffuse optical tomography, calibration, three dimensional optical imaging, source intensity optimization, Near Infrared

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 4, pp. 257-272, 2006

Authors: Zhang, Da | Rong, John | Chu, Robert | Wu, Xizeng | Liu, Hong

Article Type: Research Article

Abstract: The objective of this study is to characterize the imaging performance of a high resolution computed radiography (CR) system. The finest pixel pitch of the system is 43.75 μm. The Modulation Transfer Function (MTF) of the CR system was measured on both scan and subscan directions. The Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE) were also determined under different conditions. The MTF results on subscan direction showed 90%, 45% and 10% modulation at 1, …3, and 7 lp/mm resolutions, respectively; on scan direction the MTF values are slightly lower. The DQE value of this CR system at low frequency under 26 kVP is as high as 45%. As a comparison, these measurements were repeated with a CCD based system (48 μm pixel pitch) using the same x-ray source. The unique features of this CR system, such as its high limiting spatial resolution and detective quantum efficiency, make it attractive in applications such as mammography. Show more

Keywords: Digital x-ray imaging, computed radiography, CCD, noise power spectrum, modulation transfer function, detective quantum efficiency

Citation: Journal of X-Ray Science and Technology, vol. 14, no. 4, pp. 273-282, 2006