Realistic CT simulation using the 4D XCAT phantom.

The authors develop a unique CT simulation tool based on the 4D extended cardiac-torso (XCAT) phantom, a whole-body computer model of the human anatomy and physiology based on NURBS surfaces. Unlike current phantoms in CT based on simple mathematical primitives, the 4D XCAT provides an accurate representation of the complex human anatomy and has the advantage, due to its design, that its organ shapes can be changed to realistically model anatomical variations and patient motion. A disadvantage to the NURBS basis of the XCAT, however, is that the mathematical complexity of the surfaces makes the calculation of line integrals through the phantom difficult. They have to be calculated using iterative procedures; therefore, the calculation of CT projections is much slower than for simpler mathematical phantoms. To overcome this limitation, the authors used efficient ray tracing techniques from computer graphics, to develop a fast analytic projection algorithm to accurately calculate CT projections directly from the surface definition of the XCAT phantom given parameters defining the CT scanner and geometry. Using this tool, realistic high-resolution 3D and 4D projection images can be simulated and reconstructed from the XCAT within a reasonable amount of time. In comparison with other simulators with geometrically defined organs, the XCAT-based algorithm was found to be only three times slower in generating a projection data set of the same anatomical structures using a single 3.2 GHz processor. To overcome this decrease in speed would, therefore, only require running the projection algorithm in parallel over three processors. With the ever decreasing cost of computers and the rise of faster processors and multi-processor systems and clusters, this slowdown is basically inconsequential, especially given the vast improvement the XCAT offers in terms of realism and the ability to generate 3D and 4D data from anatomically diverse patients. As such, the authors conclude that the efficient XCAT-based CT simulator developed in this work will have applications in a broad range of CT imaging research.

[1]  Dieter Lasser,et al.  Intersection of parametric surfaces in the Bernstein—Be´zier representation , 1986 .

[2]  Michael A. King,et al.  Impact of respiratory motion on the detection of solitary pulmonary nodules with SPECT tumor imaging of NeoTect , 2002, 2002 IEEE Nuclear Science Symposium Conference Record.

[3]  Wesley E Bolch,et al.  REVISIONS TO THE ORNL SERIES OF ADULT AND PEDIATRIC COMPUTATIONAL PHANTOMS FOR USE WITH THE MIRD SCHEMA , 2006, Health physics.

[4]  Eric C. Frey,et al.  Comparison of 180° and 360° acquisition for myocardial perfusion SPECT with compensation for attenuation, detector response, and scatter: Monte Carlo and mathematical observer results , 2006 .

[5]  Chandrajit L. Bajaj,et al.  Tracing surface intersections , 1988, Comput. Aided Geom. Des..

[6]  P B Hoffer,et al.  Computerized three-dimensional segmented human anatomy. , 1994, Medical physics.

[7]  D. Manocha,et al.  Development and application of the new dynamic Nurbs-based Cardiac-Torso (NCAT) phantom. , 2001 .

[8]  Les A. Piegl,et al.  On NURBS: A Survey , 2004 .

[9]  B.M.W. Tsui,et al.  Impact of respiratory motion on the detection of small pulmonary nodules in SPECT imaging , 2007, 2007 IEEE Nuclear Science Symposium Conference Record.

[10]  Deanna Hasenauer,et al.  Hybrid computational phantoms of the male and female newborn patient: NURBS-based whole-body models , 2007, Physics in medicine and biology.

[11]  James T. Kajiya,et al.  Ray tracing complex scenes , 1986, SIGGRAPH.

[12]  M. King,et al.  A mathematical model of motion of the heart for use in generating source and attenuation maps for simulating emission imaging. , 1999, Medical physics.

[13]  Peter Shirley,et al.  An Efficient and Robust Ray-Box Intersection Algorithm , 2005, J. Graph. Tools.

[14]  Elaine Cohen,et al.  Practical Ray Tracing of Trimmed NURBS Surfaces , 2000, J. Graphics, GPU, & Game Tools.

[15]  Richard F. Riesenfeld,et al.  A Theoretical Development for the Computer Generation and Display of Piecewise Polynomial Surfaces , 1980, IEEE Transactions on Pattern Analysis and Machine Intelligence.

[16]  Chapman,et al.  Aspects of the Kinematic Simulation of Human Movement , 1982, IEEE Computer Graphics and Applications.

[17]  Richard H. Bartels,et al.  Ray Tracing Free-Form B-Spline Surfaces , 1986, IEEE Computer Graphics and Applications.

[18]  Chengyu Shi,et al.  Development of a 30-week-pregnant female tomographic model from computed tomography (CT) images for Monte Carlo organ dose calculations. , 2004, Medical physics.

[19]  Tom Lyche,et al.  Discrete B-splines and subdivision techniques in computer-aided geometric design and computer graphics , 1980 .

[20]  B.M.W. Tsui,et al.  Development of a dynamic model for the lung lobes and airway tree in the NCAT phantom , 2002 .

[21]  J. H. Hubbell,et al.  Photon mass attenuation and energy-absorption coefficients , 1982 .

[22]  B.M.W. Tsui,et al.  A mathematical observer study for the evaluation and optimization of compensation methods for myocardial SPECT using a phantom population that realistically models patient variability , 2004, IEEE Transactions on Nuclear Science.

[23]  B.M.W. Tsui,et al.  Extension of the 4D NCAT phantom to dynamic X-ray CT simulation , 2003, 2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515).

[24]  A. Requicha,et al.  Piecewise-circular curves for geometric modeling , 1987 .

[25]  Nicholas M. Patrikalakis,et al.  Topological and differential-equation methods for surface intersections , 1992, Comput. Aided Des..

[26]  D. R. White,et al.  Tissue substitutes in experimental radiation physics. , 1978, Medical physics.

[27]  Wesley E Bolch,et al.  The UF series of tomographic computational phantoms of pediatric patients. , 2005, Medical physics.

[28]  C. Yang.  On speeding up ray tracing of B-spline surfaces , 1987 .

[29]  J. W. Vieira,et al.  MAX06 and FAX06: update of two adult human phantoms for radiation protection dosimetry , 2006, Physics in medicine and biology.

[30]  Michael A. King,et al.  Modeling the respiratory motion of solitary pulmonary nodules for investigating SPECT tumor imaging , 2001, 2001 IEEE Nuclear Science Symposium Conference Record (Cat. No.01CH37310).

[31]  Nina Petoussi-Henss,et al.  The GSF family of voxel phantoms , 2002, Physics in medicine and biology.

[32]  J. W. Vieira,et al.  All about FAX: a Female Adult voXel phantom for Monte Carlo calculation in radiation protection dosimetry. , 2003, Physics in medicine and biology.

[33]  Ronald J. Jaszczak,et al.  Four-dimensional superquadric-based cardiac phantom for Monte Carlo simulation of radiological imaging systems , 1999 .

[34]  Tomoyuki Nishita,et al.  Ray tracing trimmed rational surface patches , 1990, SIGGRAPH.

[35]  Benjamin M. W. Tsui,et al.  Modeling respiratory mechanics in the MCAT and spline-based MCAT phantoms , 1999 .

[36]  A. Bozkurt,et al.  VIP-MAN: AN IMAGE-BASED WHOLE-BODY ADULT MALE MODEL CONSTRUCTED FROM COLOR PHOTOGRAPHS OF THE VISIBLE HUMAN PROJECT FOR MULTI-PARTICLE MONTE CARLO CALCULATIONS , 2000, Health physics.

[37]  Robert E. Barnhill,et al.  A marching method for parametric surface/surface intersection , 1990, Comput. Aided Geom. Des..

[38]  Rida T. Farouki,et al.  The characterization of parametric surface sections , 1986, Comput. Vis. Graph. Image Process..

[39]  Ge Wang,et al.  Computed tomography simulation with superquadrics. , 2005, Medical physics.

[40]  Les A. Piegl,et al.  The NURBS Book , 1995, Monographs in Visual Communication.

[41]  W. Boehm.  Inserting New Knots into B-spline Curves , 1980 .

[42]  William P. Segars,et al.  A realistic spline-based dynamic heart phantom , 1998 .

[43]  Philip J. Willis,et al.  A Picture Archive Browser , 1991, Comput. Graph. Forum.