Our current research involves the use of computer-generated phantoms and simulation techniques to investigate and optimize medical imaging systems and methods. Medical imaging simulation involves virtual experiments carried out entirely on the computer using computational models for the patients as well as the imaging devices. Simulation is a powerful tool for characterizing, evaluating, and optimizing medical imaging systems. A vital aspect of simulation is to have realistic models of the subject's anatomy as well as accurate models for the physics of the imaging process. Without this, the results of the simulation may not be indicative of what would occur in actual clinical studies and would, therefore, have limited practical value. We are leading the development of realistic simulation tools for use toward human and small animal imaging research.

These tools have a wide variety of applications in many different imaging modalities to investigate the effects of anatomical, physiological, physical, and instrumentational factors on medical imaging and to research new image acquisition strategies, image processing and reconstruction methods, and image visualization and interpretation techniques. We are currently applying them to the field of x-ray CT. The motivation for this work is the lack of sufficiently rigorous methods for optimizing the image quality and radiation dose in x-ray CT to the clinical needs of a given procedure. The danger of unnecessary radiation exposure from CT applications, especially for pediatrics, is just now being addressed. Optimization is essential in order for new and emerging CT applications to be truly useful and not represent a danger to the patient. Given the relatively high radiation doses required of current CT systems, thorough optimization is unlikely to ever be done in live patients. It would be prohibitively expensive to fabricate physical phantoms to simulate a realistic range of patient sizes and clinical needs especially when physiologic motion needs to be considered.  The only practical approach to the optimization problem is through the use of realistic computer simulation tools developed in our work.

Fung GS, Segars WP, Gullberg GT, Tsui BM. Development of a model of the coronary arterial tree for the 4D XCAT phantom. Phys Med Biol. 2011 Sep 7;56(17):5651-63. Abstract

Hsu CM, Palmeri ML, Segars WP, Veress AI, Dobbins JT 3rd. An analysis of the mechanical parameters used for finite element compression of a high-resolution 3D breast phantom. Med Phys. 2011 Oct;38(10):5756-70. Abstract

Li X, Samei E, Segars WP, Sturgeon GM, Colsher JG, Frush DP. Patient-specific radiation dose and cancer risk for pediatric chest CT. Radiology. 2011 Jun;259(3):862-74. Abstract

Li X, Samei E, Segars WP, Sturgeon GM, Colsher JG, Toncheva G, Yoshizumi TT, Frush DP. Patient-specific radiation dose and cancer risk estimation in CT: part I. development and validation of a Monte Carlo program. Med Phys. 2011 Jan;38(1):397-407. Abstract

Li X, Samei E, Segars WP, Sturgeon GM, Colsher JG, Toncheva G, Yoshizumi TT, Frush DP. Patient-specific radiation dose and cancer risk estimation in CT: part II. Application to patients. Med Phys. 2011 Jan;38(1):408-19. Abstract

Stabin MG, Emmons MA, Segars WP, Fernald MJ. REALISTIC REFERENCE ADULT AND PAEDIATRIC PHANTOM SERIES FOR INTERNAL AND EXTERNAL DOSIMETRY. Radiat Prot Dosimetry. 2011 Nov 28. Abstract

Tang J, Segars WP, Lee TS, He X, Rahmim A, Tsui BM. Quantitative study of cardiac motion estimation and abnormality classification in emission computed tomography. Med Eng Phys. 2011 Jun;33(5):563-72. Abstract

Tward DJ, Ceritoglu C, Kolasny A, Sturgeon GM, Segars WP, Miller MI, Ratnanather JT. Patient Specific Dosimetry Phantoms Using Multichannel LDDMM of the Whole Body. Int J Biomed Imaging. 2011;2011:481064. Abstract

Veress AI, Segars WP, Tsui BM, Gullberg GT. Incorporation of a left ventricle finite element model defining infarction into the XCAT imaging phantom. IEEE Trans Med Imaging. 2011 Apr;30(4):915-27. Abstract

Dey J, Segars WP, Pretorius PH, Walvick RP, Bruyant PP, Dahlberg S, King MA. Estimation and correction of cardiac respiratory motion in SPECT in the presence of limited-angle effects due to irregular respiration. Med Phys. 2010 Dec;37(12):6453-65. Abstract

Keenan MA, Stabin MG, Segars WP, Fernald MJ. RADAR realistic animal model series for dose assessment. J Nucl Med. 2010 Mar;51(3):471-6. Abstract

Lewis JH, Li R, Watkins WT, Lawson JD, Segars WP, Cerviño LI, Song WY, Jiang SB. Markerless lung tumor tracking and trajectory reconstruction using rotational cone-beam projections: a feasibility study. Phys Med Biol. 2010 May 7;55(9):2505-22. Abstract

Segars WP, Sturgeon G, Mendonca S, Grimes J, Tsui BM. 4D XCAT phantom for multimodality imaging research. Med Phys. 2010 Sep;37(9):4902-15. Abstract

Tang J, Lee TS, He X, Segars WP, Tsui BM. Comparison of 3D OS-EM and 4D MAP-RBI-EM reconstruction algorithms for cardiac motion abnormality classification using a motion observer. IEEE Trans Nucl Sci. 2010 Aug 26;57(5):2571. Abstract

He B, Du Y, Segars WP, Wahl RL, Sgouros G, Jacene H, Frey EC. Evaluation of quantitative imaging methods for organ activity and residence time estimation using a population of phantoms having realistic variations in anatomy and uptake. Med Phys. 2009 Feb;36(2):612-9. Abstract

Lee T, Choi JB, Schafer BW, Segars WP, Eckstein F, Kuhn V, Beck TJ. Assessing the susceptibility to local buckling at the femoral neck cortex to age-related bone loss. Ann Biomed Eng. 2009 Sep;37(9):1910-20. Abstract

Li CM, Segars WP, Tourassi GD, Boone JM, Dobbins JT 3rd. Methodology for generating a 3D computerized breast phantom from empirical data. Med Phys. 2009 Jul;36(7):3122-31. Abstract

Segars WP, Lalush DS, Frey EC, Manocha D, King MA, Tsui BM. Improved Dynamic Cardiac Phantom Based on 4D NURBS and Tagged MRI. IEEE Trans Nucl Sci. 2009 Oct 1;56(5):2728-2738. Abstract

Segars WP, Mok SP, Tsui BM. Investigation of Respiratory Gating in Quantitative Myocardial SPECT. IEEE Trans Nucl Sci. 2009 Feb 1;56(1):91-96. Abstract

Li X, Samei E, Segars WP, Sturgeon GM, Colsher JG, Frush DP. Patient-specific dose estimation for pediatric chest CT. Med Phys. 2008 Dec;35(12):5821-8. Abstract

Rahmim A, Cheng JC, Dinelle K, Shilov M, Segars WP, Rousset OG, Tsui BM, Wong DF, Sossi V. System matrix modelling of externally tracked motion. Nucl Med Commun. 2008 Jun;29(6):574-81. Abstract

Rahmim A, Dinelle K, Cheng JC, Shilov MA, Segars WP, Lidstone SC, Blinder S, Rousset OG, Vajihollahi H, Tsui BM, Wong DF, Sossi V. Accurate event-driven motion compensation in high-resolution PET incorporating scattered and random events. IEEE Trans Med Imaging. 2008 Aug;27(8):1018-33. Abstract

Segars WP, Mahesh M, Beck TJ, Frey EC, Tsui BM. Realistic CT simulation using the 4D XCAT phantom. Med Phys. 2008 Aug;35(8):3800-8. Abstract

Smyczynski MS, Gifford HC, Lehovich A, McNamara JE, Segars WP, Tsui BM, King MA. Impact of respiratory motion on the detection of small pulmonary nodules in SPECT imaging. IEEE Nucl Sci Symp Conf Rec (1997). 2007;5:3241-3245. Abstract

Veress AI, Segars WP, Weiss JA, Tsui BM, Gullberg GT. Normal and pathological NCAT image and phantom data based on physiologically realistic left ventricle finite-element models. IEEE Trans Med Imaging. 2006 Dec;25(12):1604-16. Abstract

He B, Du Y, Song X, Segars WP, Frey EC. A Monte Carlo and physical phantom evaluation of quantitative In-111 SPECT. Phys Med Biol. 2005 Sep 7;50(17):4169-85. Abstract

Kraitchman DL, Tatsumi M, Gilson WD, Ishimori T, Kedziorek D, Walczak P, Segars WP, Chen HH, Fritzges D, Izbudak I, Young RG, Marcelino M, Pittenger MF, Solaiyappan M, Boston RC, Tsui BM, Wahl RL, Bulte JW. Dynamic imaging of allogeneic mesenchymal stem cells trafficking to myocardial infarction. Circulation. 2005 Sep 6;112(10):1451-61. Abstract

Lalush DS, Jatko MK, Segars WP. An observer study methodology for evaluating detection of motion abnormalities in gated myocardial perfusion SPECT. IEEE Trans Biomed Eng. 2005 Mar;52(3):480-5. Abstract

Song X, Segars WP, Du Y, Tsui BM, Frey EC. Fast modelling of the collimator-detector response in Monte Carlo simulation of SPECT imaging using the angular response function. Phys Med Biol. 2005 Apr 21;50(8):1791-804. Abstract

Segars WP, Tsui BM, Frey EC, Johnson GA, Berr SS. Development of a 4-D digital mouse phantom for molecular imaging research. Mol Imaging Biol. 2004 May-Jun;6(3):149-59. Abstract

Hauser MA, Walter JW, Walters RW, Maready M, Takeuchi S, Segars WP, Hulette CM, Schmechel DE, Bernba ML, Stajich JM, Hauser ER, Martin E, Scott BL, Stenger J, Li YJ, Beato F, Jensen R, Scherzer C, Gullans S, Vance JM. Identification of candidate genes for Parkinson disease (PD) by the convergence of genetic linkage and association data with gene expression in the substantia nigra. American Journal of Human Genetics, 71(4): 1737 Suppl. S, 2002.

Segars WP and Tsui BMW. 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.

Segars WP, Lalush DS, Tsui BMW. Modeling respiratory mechanics in the MCAT and spline-based MCAT phantoms. IEEE Trans Nucl Sci, 48(1):  89-97, 2001.

Tsui BMW, Segars WP, Lalush DS. Effects of upward creep and respiratory motions in myocardial SPECT. IEEE Trans Nucl Sci, 47(3): 1192-1195, 2000.

Segars WP, Lalush DS and Tsui BMW. A realistic spline-based dynamic heart phantom. IEEE Trans Nucl Sci, 46(3):503-506, 1999.