Journal of X-Ray Science and Technology - Volume 13, issue 2

Authors: Li, Xiang | Ni, Jun | Wang, Ge

Article Type: Research Article

Abstract: The iterative reconstruction (IR) algorithms are able to generate CT images with higher quality compared with the filtered backprojection method when the projection data is noisy or the radiation dose is low. IR can also be used when the data is incomplete. The major disadvantage of the IR is its high demand on computation and slow reconstruction. To improve the time performance of the IR we parallelized four representative iterative algorithms: EM, SART and their ordered …subset (OS) versions on a Linux PC cluster. A micro-forward-back-projector was implemented for increased parallelization. Parameters are cached at the ray level during forward-projection to further reduce time used for back-projection. The speed-up and efficiency factors of our parallel implementation are reported. Show more

Citation: Journal of X-Ray Science and Technology, vol. 13, no. 2, pp. 63-72, 2005

Authors: Wu, Dee H. | Mayr, Nina A. | Zheng, Yi | Wolff, James D. | Edwards, Susan M. | Liu, Hong | Yuh, William T.C.

Article Type: Research Article

Abstract: Purpose/Objective: Dynamic Contrast Enhanced (DCE) Magnetic Resonance Imaging (MRI) has been reported to be valuable in the evaluation of perfusion patterns throughout the entire tumor bed. Tumor cell heterogeneity over the entire structure has been well described in the literature. However, regional heterogeneity of DCE-MRI within the tumor has not been previously investigated until this point. The purpose of this study was to assess the topographical pattern of DCE-MRI among different subdivisions within tumors …evaluated by DCE-MRI in cervical cancer patients. Materials/Methods: The DCE-MRI data from subdivisions of cervical cancer patients were evaluated prior to radiation therapy (n = 18). Each tumor was sectioned into eight three-dimensional subdivision wedge "regions" arrayed around the tumor center-of-volume. The orientation of the wedges was based upon uterine direction as determined by the projection of the endometrial canal and spatial orientation of the uterus. Tumor perfusion was estimated by the Relative Signal Intensity (RSI), which was defined by the ratio of the plateau post-injection signal intensity (SI) (at 75 seconds post-injection) divided by the pre-contrast SI on a pixel-by-pixel basis. Perfusion in each of eight regions of the cervical cancers was estimated by the mean RSI within each region. Statistical differences among the various regions were computed from RSI distributions within each three-dimensional wedge evaluated in cervical cancer patients pre-radiotherapy. Results: Significant differences over the eight regional subdivisions were found via a repeated-measures analysis of variance (ANOVA) design that produced an F-value = 18.37 with Degrees of Freedom – DOF(7,119) such that p < 0.0001. In addition, a planned comparison between tumor segments closest to the uterine corpus as compared to segments closest to the cervix demonstrated significant differences t-value = 3.19, p < 0.002. Show more

Citation: Journal of X-Ray Science and Technology, vol. 13, no. 2, pp. 73-80, 2005

Authors: Kochubey, V.I. | Konyukhova, Ju. G.

Article Type: Research Article

Abstract: Effect of competition in excitation between luminescence centres and the rest of a sample on intensity of luminescence in the visual range under exciting with synchrotron radiation is considered. It is shown that the competition gives rise to distortion of XEOL spectra. In this case the obtained structure data are incorrect. An algorithm of data correction is proposed. It is demonstrated that, to apply this algorithm, it is necessary to use three-detector circuit of recording XEOL …spectra. The examples of correction of XEOL spectra of KBr and NaCl-Ni samples are given. Show more

Keywords: XEOL, EXAFS, spectrum correction

Citation: Journal of X-Ray Science and Technology, vol. 13, no. 2, pp. 81-84, 2005

Authors: Liu, Julian J. | Watt-Smith, Stephen R. | Smith, Stephen M.

Article Type: Research Article

Abstract: Computed tomography has played a key role in bone structure imaging for over two decades. However, when a metal implant is present in the sample, the reconstructions are seriously distorted by artifact, and no method has successfully met the clinical demands. This paper presents a new method for metal artifact reduction in Computed Tomography based on sinusoidal description with the concentration of clinical applications. A piece of pig's leg with a lead nail placed inside the …bone was scanned, generating 224 slices, in 177 of which the metal implant was present. The method includes detection of the correspondence of metal implants, fitting, amendment, and reconstruction based on sinusoidal description. Simulation and statistical error analysis show that the method improves PSNR (Peak Signal-to-Noise Ratio). A 3D modeling based on the reconstruction using the sinusoidal amendment method for a real case demonstrates that most of the metal artifact has been removed, which is compared with that based on the default output of the scanner. Metal artifacts in CT can be reduced effectively by the method based on the sinusoidal description, which isolates the correspondence of a metal implant from the original projection, so that a high quality reconstruction can be obtained. Show more

Citation: Journal of X-Ray Science and Technology, vol. 13, no. 2, pp. 85-96, 2005

Authors: Qiang, Yong Gang | Liao, Yong Hua | Li, Jian | Zhang, Xiu Ping | Huang, Zheng

Article Type: Research Article

Abstract: This study described a novel radioactive probe for SPECT imaging of lung cancer. The probe was consisted of ^{99m} Tc labeled cartilage link protein (CLP). The CLP, a hyaluronate binding protein, was isolated from bovine nose cartilage and purified on a chromatography column. ^{99m} Tc labeling was carried out by pre-treating CLP with SnCl_2 . The feasibility of this probe for lung cancer imaging was tested in vivo in an animal model. The …hyaluronate probe showed a fairly good binding activity towards both natural and tumor hyaluronic acid in in vitro and in vivo assays. The preliminary feasibility study in a human lung cancer bearing mouse model showed that the probe might be useful for tumor imaging. Show more

Keywords: hyaluronate probe, cartilage link protein, SPECT, lung cancer

Citation: Journal of X-Ray Science and Technology, vol. 13, no. 2, pp. 97-106, 2005

Article Type: Other

Citation: Journal of X-Ray Science and Technology, vol. 13, no. 2, pp. 107-108, 2005