William Paul Segars, Ph.D.   Assistant Professor of Radiology, Biomedical Engineering, and   Environmental Health Sciences   Johns Hopkins Outpatient Center   601 N. Caroline Street   Baltimore, MD 21287-0859   Email: wsegars@jhmi.edu  Recently moved to Johns Hopkins with the:   Medical Imaging Research Group   Department of Biomedical Engineering   The University of North Carolina at Chapel Hill

Research & Publications A Realistic Spline-Based Dynamic Heart Phantom, IEEE Trans Nucl Sci, 46(3):503-506, 1999. Effects of upward creep and respiratory motions in myocardial SPECT, IEEE Trans Nucl Sci, 47(3): 1192-1195, 2000. Modeling respiratory mechanics in the MCAT and spline-based MCAT phantoms, IEEE Trans Nucl Sci, 48(1): 89-97, 2001. Development and Application of the New Dynamic NURBS-based Cardiac-Torso (NCAT) Phantom, Ph.D. Dissertation, The University of North Carolina, 2001. Study of the efficacy of respiratory gating in myocardial SPECT using the new 4D NCAT Phantom, IEEE Trans Nucl Sci, 49(3): 675-679, 2002. CT-PET image fusion using the 4D NCAT phantom with the purpose of attenuation correction, Submitted to IEEE Trans Nucl Sci, 2002. Development of a 4D Digital Mouse Phantom for Molecular Imaging Research, Molecular Imaging and Biology, 2004. Education BS in Computer Engineering, University of South Carolina, 1996 PhD in Biomedical Engineering, University of North Carolina, 2001

4D NURBS-BASED CARDIAC-TORSO (NCAT) PHANTOM     Simulation is a powerful tool for characterizing, evaluating, and optimizing medical imaging systems. An important aspect of simulation is to have a realistic phantom or model of the human anatomy. The four-dimensional (4D) NURBS-based cardiac-torso (NCAT) phantom was developed to provide a realistic and flexible model of the human anatomy and physiology to be used in nuclear medicine imaging research. The organ models are based on NURBS, non-uniform rational B-splines, as used in computer graphics. NURBS, which define continuous surfaces, allow the phantom to be defined at any spatial resolution. An important innovation is the extension of NURBS to a fourth dimension, time, to model the cardiac and respiratory motions.     NURBS surfaces for the various organs in the torso and for the skeletal system are shown at the right.  All of the organ and skeletal models with the exception of the heart are based on CT scans from the Visible Human male data set.  The heart is based on gated MRI cardiac scans of a normal patient.      The phantom is a hybrid between the realism of pixel-based phantoms and the flexibility of geometry-based phantoms.  By fitting NURBS to actual patient data, the phantom is more realistic than those based on solid geometry.  In addition, the NURBS primitives give the phantom a mathematical basis allowing the phantom to be very flexible. NURBS surfaces can be altered easily via affine and other transformations to realistically model variations in anatomy and to simulate patient motion.     Given a model of the physics of the medical imaging process, medical images of the computerized patient provided by the NCAT can be generated using computational methods. This forms the basis of simulation techniques. The main advantage to using computerized patients in simulation studies is that the exact anatomy and physiological functions of the phantom are known, thus providing a gold standard from which to evaluate and improve medical imaging devices and image processing and reconstruction techniques.

3D RENDERINGS OF THE NCAT PHANTOM Anterior View Posterior View Right Lateral View

 

Simulated Patient Motions with the 4D NCAT:

NCAT beating heart (exterior)	NCAT beating heart (interior chambers)
NCAT respiration (anterior)	NCAT respiration (right lateral)

Copyright © 2002, William Paul Segars
Revised - Dec. 1, 2002
http://www.bme.unc.edu/wsegars/index.html