Spiral Scanning – Biomedical Imaging Division, VT / WFU School of Biomedical Engineering and Sciences
http://www.bid.sbes.vt.edu
Biomedical Imaging Division, VT / WFU SBESSun, 27 Mar 2016 22:44:19 +0000en-UShourly1https://wordpress.org/?v=4.5.2Wang G, Ye Y, Yu HY: Approximate and exact cone-beam reconstruction with standard and non-standard spiral scanning. Physics in Medicine and Biology. 52:R1-R13, 2007
http://www.bid.sbes.vt.edu/2007/01/wang-g-ye-y-yu-hy-approximate-and-exact-cone-beam-reconstruction-with-standard-and-non-standard-spiral-scanning-physics-in-medicine-and-biology-52r1-r13-2007/
http://www.bid.sbes.vt.edu/2007/01/wang-g-ye-y-yu-hy-approximate-and-exact-cone-beam-reconstruction-with-standard-and-non-standard-spiral-scanning-physics-in-medicine-and-biology-52r1-r13-2007/#respondMon, 01 Jan 2007 18:00:28 +0000http://localhost/wordpress/?p=617The long object problem is practically important and theoretically challenging. To solve the long object problem, spiral cone-beam CT was first proposed in 1991, and has been extensively studied since then. As a main feature of the next generation medical CT, spiral cone-beam CT has been greatly improved over the past several years, especially in terms of exact image reconstruction methods. Now, it is well established that volumetric images can be exactly and efficiently reconstructed from longitudinally truncated data collected along a rather general scanning trajectory. Here we present an overview of some key results in this area. Click here for full article….
]]>http://www.bid.sbes.vt.edu/2007/01/wang-g-ye-y-yu-hy-approximate-and-exact-cone-beam-reconstruction-with-standard-and-non-standard-spiral-scanning-physics-in-medicine-and-biology-52r1-r13-2007/feed/0Ye Y, Zhu JH, Wang G: Geometric studies on variable radius spiral cone-beam scanning. Medical Physics 31:1473-1480, 2004
http://www.bid.sbes.vt.edu/2004/05/ye-y-zhu-jh-wang-g-geometric-studies-on-variable-radius-spiral-cone-beam-scanning-medical-physics-311473-1480-2004/
http://www.bid.sbes.vt.edu/2004/05/ye-y-zhu-jh-wang-g-geometric-studies-on-variable-radius-spiral-cone-beam-scanning-medical-physics-311473-1480-2004/#respondMon, 24 May 2004 18:00:38 +0000http://localhost/wordpress/?p=528The goal is to perform geometric studies on cone-beam CT scanning along a three-dimensional (3D) spiral of variable radius. First, the background for variable radius spiral cone-beam scanning is given in the context of electron-beam CT/micro-CT. Then, necessary and sufficient conditions are proved for existence and uniqueness of PI lines inside the variable radius 3D spiral. These results are necessary steps toward exact cone-beam reconstruction from a 3D spiral scan of variable radius, adapting Katsevich’s formula for the standard helical cone-beam scanning. It is shown in the paper that when the longitudinally projected planar spiral is not always convex toward the origin, the PI line may not be unique in the envelope defined by the tangents of the spiral. This situation can be avoided by using planar spirals whose curvatures are always positive. Using such a spiral, a longitudinally homogeneous region inside the corresponding 3D spiral is constructed in which any point is passed by one and only one PI line, provided the angle w between planar spiral’s tangent and radius is bounded by |ω – 90°| ≤ Ɛ for some positive ω ≤ 32.48°. If the radius varies monotonically, this region is larger and one may allow Ɛ ≤ 51.85°. Examples for 3D spirals based on logarithmic and Archimedean spirals are given. The corresponding generalized Tam–Danielsson detection windows are also formulated. Click here for full article….
]]>http://www.bid.sbes.vt.edu/2004/05/ye-y-zhu-jh-wang-g-geometric-studies-on-variable-radius-spiral-cone-beam-scanning-medical-physics-311473-1480-2004/feed/0Liu V, Lariviere N, Wang G: X-ray micro-CT with a displaced detector array: An application for helical cone-beam reconstruction. Medical Physics 30:2758-2761, 2003
http://www.bid.sbes.vt.edu/2003/09/liu-v-lariviere-n-wang-g-x-ray-micro-ct-with-a-displaced-detector-array-an-application-for-helical-cone-beam-reconstruction-medical-physics-302758-2761-2003/
http://www.bid.sbes.vt.edu/2003/09/liu-v-lariviere-n-wang-g-x-ray-micro-ct-with-a-displaced-detector-array-an-application-for-helical-cone-beam-reconstruction-medical-physics-302758-2761-2003/#respondWed, 24 Sep 2003 18:00:47 +0000http://localhost/wordpress/?p=510In x-ray micro-CT applications, it is useful to increase the field of view by offsetting a two-dimensional (2D) detector array. In this technical note, we briefly review the methods for image reconstruction with an asymmetric 2D detector array, elaborate on the use of an associated weighting scheme in the case of helical/spiral cone-beam scanning, and perform a series of numerical tests to demonstrate helical cone-beam image reconstruction with such an arrangement. Click here for full article….
]]>http://www.bid.sbes.vt.edu/2003/09/liu-v-lariviere-n-wang-g-x-ray-micro-ct-with-a-displaced-detector-array-an-application-for-helical-cone-beam-reconstruction-medical-physics-302758-2761-2003/feed/0Wang G, Lee SW: Grangeat-type and Katsevich-type algorithms for cone-beam CT. Journal of CT Theory and Applications 12:45-55, 2003
http://www.bid.sbes.vt.edu/2003/05/wang-g-lee-sw-grangeat-type-and-katsevich-type-algorithms-for-cone-beam-ct-journal-of-ct-theory-and-applications-1245-55-2003/
http://www.bid.sbes.vt.edu/2003/05/wang-g-lee-sw-grangeat-type-and-katsevich-type-algorithms-for-cone-beam-ct-journal-of-ct-theory-and-applications-1245-55-2003/#respondThu, 01 May 2003 18:00:26 +0000http://localhost/wordpress/?p=516Abstract: Cone-beam image reconstruction algorithms are in rapid development for major biomedical and industrial applications. In this report, we primarily focus on those algorithms that allow exact and efficient reconstruction and have potential for dynamic studies, which are recently developed Grangeat-type and Katsevich-type algorithms. This preference is due to the needs for quantitative and functional CT/micro-CT applications. Last year, Lee and Wang developed Grangeat-type half-scan cone-beam algorithms in the circular and helical scanning cases to solve the short object problem. In both the circular and helical half-scan cases, the boundaries between regions of different sample redundancies are first determined. Then, corresponding weighting functions are formulated for evaluation at various characteristic point. It was demonstrated that the Grangeat-type half-scan reconstruction clearly outperformed the Feldkamp-type half-scan reconstruction in terms of intensity dropping artifacts. In 2001, Katsevich derived the first theoretically exact reconstruction formula for the spiral cone-beam geometry in the filtered backprojection format. The limitations of this formula include a large detector window and a small radius of the object to be reconstructed. Last year, Katsevich improved his first formula remarkably. The new formula imposes little restriction on the size of the patient, and assumes a smaller detector array than the old formula. Recently, Katsevich generalized his method from the spiral scanning case to other trajectories, and proved that the earlier two formulas are special cases of his general formula. There are important needs to improve current Grangeat.type and Katsevich-type algorithms for dynamic volumetric imaging in the long object cone-beam geometry. Click here for full article….
]]>http://www.bid.sbes.vt.edu/2003/05/wang-g-lee-sw-grangeat-type-and-katsevich-type-algorithms-for-cone-beam-ct-journal-of-ct-theory-and-applications-1245-55-2003/feed/0Wang G, Vannier MW: Helical CT image noise – Analytical results. Medical Physics 20:1635-1640, 1993
http://www.bid.sbes.vt.edu/1993/12/wang-g-vannier-mw-helical-ct-image-noise-analytical-results-medical-physics-201635-1640-1993/
http://www.bid.sbes.vt.edu/1993/12/wang-g-vannier-mw-helical-ct-image-noise-analytical-results-medical-physics-201635-1640-1993/#respondWed, 01 Dec 1993 18:00:47 +0000http://localhost/wordpress/?p=374Helical CT is an important recent development in x-ray CT. In helical CT, planar projection sets arc synthesized from raw projection data via interpolation. Among various interpolation schemes, linear interpolation is usually preferred due to its efficiency and performance. In this paper, image noise variance is derived for typical helical CT linear interpolation techniques, including the full scan (FS), under-scan (US), full scan with interpolation (FI), half-scan (HS), half-scan with interpolation (HI) and half-scan with extrapolation (HE) methods. Image noise deviation ratios of helical CT to conventional 360 degree reconstruction (CR) are tabulated. These are consistent with previously reported simulation results. The theoretical results provide further understanding of helical CT noise performance. It is shown that helical CT image noise deviation is independent of transaxial position, proportional to the raw projection noise deviation, and not affected by the fan angle (approximately for the HE method). Also, helical CT image noise variation is proportional to the area under the square of the reconstruction filter. Click here for full article….
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