Journal of X-Ray Science and Technology - Volume 12, issue 3

Authors: Li, Guangming | Tian, Jie | Zhao, Mingchang | He, Huiguang

Article Type: Research Article

Abstract: Virtual endoscopy is a new development of diagnostic imaging, covering a wide range of potential clinical applications. This paper introduced a system framework for virtual endoscopy. Our research efforts concentrated on mesh smoothing, automated centerline extraction and view-dependent level-of-detail rendering techniques. First, the fairing surface was obtained by smoothing the normal vectors of the reconstructed model. Then, the modified reliable path method was used to generate the accurate skeleton. After that, the …view-dependent level-of-detail rendering techniques, including mesh simplification, mesh parameterization and mesh subdivision, were used to achieve the purpose of real time rendering. Experimental results for the images of cerebral blood vessels, knees, and trachea using our solution were given. Show more

Keywords: virtual endoscopy, mesh smoothing, path planning, mesh simplification, view-dependent subdivision, virtual navigation

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 3, pp. 129-141, 2004

Authors: Gutierrez, L. | Alvarez, S. | Senor, P. | Caselli, E. | Pecelis, M. | Santiago, M.

Article Type: Research Article

Abstract: In this paper an algorithm is reported for enhancing low contrast features in mammograms. Some features barely visible or not visible to the naked eye in original images can be observed clearly in the corresponding filtered images along with those features that are readily seen. The main characteristic of the filter is that it allows the simultaneous visualisation of low contrast anatomical features in both the dense mammary gland and the breast periphery. The contribution of …the filter to a better interpretation of mammograms is illustrated with examples. Show more

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 3, pp. 143-150, 2004

Authors: Schmithorst, Vincent J. | Endorf, Robert J. | Kulatunga, Sunil | Spelic, David C. | DiBianca, Frank A. | Rodriguez, Carlos | Zeman, Herbert D. | Zhu, Zeping | Giakos, George C.

Article Type: Research Article

Abstract: The Kinestatic Charge Detector (KCD) technique of projection radiography shows promise when used for dual-energy imaging, which may be performed either by taking two separate exposures at different kVp settings (the dual-kVp method) or by taking a single exposure with the KCD segmented into a front and back region (the split-detector method), as the higher energy photons will be preferentially absorbed in the back region. Using computer simulations, we have optimized the dual-energy performance …of a segmented KCD using the split-detector method for chest radiography. Theoretical optimization of imaging parameters and determination of contrast resolution were performed by minimizing pixel variances of the basis materials. The expected contrast resolution of the aluminum and plexiglas basis material images was found to be acceptable for purposes of clinical diagnosis. A detector medium of krypton produced better results than xenon at the same density, and the optimal kVp setting was in the range of 120–150 kVp. Preliminary dual-energy images were taken with a small field-of-view split-detector imaging KCD system. The experimentally obtained aluminum and plexiglas basis material pixel variances agree with the theoretical results. Show more

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 3, pp. 151-159, 2004

Authors: Nagabhushan, N.M. | Kerur, B.R. | Lagare, M.T. | Nathuram, R. | Abani, M.C. | Thontadarya, S.R. | Hanumaiah, B.

Article Type: Research Article

Abstract: A new and accurate method to determine the mass attenuation coefficient, μm, for low photon energy employing NaI(Tl) X-ray detector and radioactive source is described. Effect of size of collimator and the selection of width of photopeak for integration on the contribution from scattered photons to the transmitted intensity is studied systematically and optimum size of collimator and photopeak limits for integration are established. With a 6 mm diameter collimator and FWHM for photopeak limits it …was found that Beer-Lambert's law was rigorously valid over transmission range of 50–2%. Using this method μm was determined for six elements that covered a wide atomic number range (12 < Z < 73) and two biological equivalent materials. The values so obtained agreed with theoretical values within 1% establishing the validity and accuracy of the present method which uses inexpensive moderate resolution detector. As the method permits higher transmission range better counting statistics is an added advantage. Show more

Keywords: X-ray attenuation coefficient, X-ray cross section, X-rays

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 3, pp. 161-168, 2004

Authors: Wang, Ge | Jiang, Ming

Article Type: Research Article

Abstract: In this paper, we first demonstrate that two ordered-subset simultaneous algebraic reconstruction techniques (OS-SART) can be heuristically derived from the perspective of data rectification. Then, we study the convergence in the framework of our recent work on the OS version of the Landweber scheme. The first OS-SART is the same as the BSSART formula, which is a special case of the OS version of the Landweber scheme. Hence, it converges in the weighted least square sense …even in the case of inconsistent data. Both the OS-SART formulas are tested for reconstruction of CT images from practical data. Show more

Keywords: computed tomography (CT), iterative reconstruction, ordered-subsets (OS), simultaneous algebraic reconstruction techniques (SART), convergence

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 3, pp. 169-177, 2004

Authors: Zhu, Daan | Razaz, Moe | Hemmings, Andrew | Wang, Bin Hai

Article Type: Research Article

Abstract: X-ray diffraction imaging is an important analytical tool in a variety of biological and medical imaging applications. However, the images obtained are often degraded by the point spread function (PSF) of the imaging system. An accurate knowledge of the system PSF is essential for a successful deconvolution of the degraded images. In this paper, we present a novel modeling procedure to determine the PSF of an X-ray diffraction (XRD) system based on experimental data. Different regions …of an XRD pattern have different orientations due to the diffuse light distortion (DLD). A new multiple PSF model is introduced and used to restore XRD data. Raw PSFs are collected using isolated spots from XRD data in high resolution regions. An adaptive ridge regression (ARR) technique is first used to remove noise and baseline from the raw PSF data. A target Gaussian function is used to model the raw PSFs. A gradient descent algorithm is used to find optimum parameters of the Gaussian function. A set of XRD data are restored by a nonlinear iterative deconvolution algorithm using the modeled PSFs. Experimental results using a single and multiple PSFs are presented and discussed. We show that by using a multiple PSF model in the deconvolution algorithm, improved restored XRD data are obtained and as a result the symmetry estimator and integration error are enhanced. Show more

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 3, pp. 179-194, 2004