X. George Xu

Xie George Xu (born June 13, 1962 in Wuhan, China) is currently a Professor and Head of the Nuclear Engineering Program at Rensselaer Polytechnic Institute (RPI), Troy, New York.

George Xu received a B.S. in Physics from Xidian University in Xi’an, China in 1983. After working several years, he came to study in the United States, where he received a Ph.D. in Nuclear Engineering from Texas A&M University in 1994. He then joined RPI as Assistant Professor (with a joint appointment as the Director of the Office Radiation and Nuclear Safety) and was promoted to Associate Professor with tenure in 2001 and then Professor in 2006. In 2011, he was appointed the Head of Nuclear Engineering Program at RPI. In 2012, Xu was elected a Fellow of the American Nuclear Society, making him the first China-born scholar ever to be elected to receive this honor. Xu is also the first China-born to have served as the head of a Nuclear Engineering program at an American university.

Xu heads the Rensselaer Radiation Measurement and Dosimetry Group (RRDMG).^[1] He and his colleagues are interested in novel computational and experimental methods that have important and diverse applications in radiation protection, radiation measurement, shielding design, reactor modeling, medical imaging, and radiotherapy. In particular, he uses Monte Carlo simulations as a research tool and has more than 20 years of experience in various production Monte Carlo codes. His recent research projects have included such diverse topics as parallel Monte Carlo computing using GPU/CUDA, nanomaterials-based x-ray sources, CT imaging and proton radiotherapy, compressive sensing for nuclear detection, and the ARCHER Monte Carlo testbed project. Xu has directed numerous projects, with a total funding of about $15 million from agencies such as the National Science Foundation, Department of Energy, National Institutes of Health, National Institute of Standards and Technology, and Electric Power Research Institute, as well as private nuclear power industry including Entergy Nuclear. Xu has graduated 15 Ph.D. and 10 M.S. students. and he has authored or co-authored 140 peer-reviewed full papers and chapters, 250 conference abstracts, 90 invited seminars and presentations, 5 patents/disclosures and 5 software packages. An internationally recognized leading expert in Monte Carlo computation and radiation protection dosimetry, Xu has co-founded the International Consortium of Computational Human Phantoms and co-edited Handbook of Anatomical Models for Radiation Dosimetry.

Research contributions

Xu and his students pioneered a method to use cadaver images to construct voxel human phantoms that are anatomically realistic. Xu et al. 2000 reported, for the first time, a method in adopting a set of high-fidelity color image dataset from the Visible Human Project to develop the VIP-Man phantom which remains today to be one of the “finest” voxel phantoms with a voxel size of 0.33mm x 0.33mm x 1 mm.^[2] The phantom sets a world record in the total number of voxels in Monte Carlo simulations ¾ 4 billion voxels which required special treatment in the Monte Carlo code. The methodology behind the development of VIP-Man phantom represented a breakthrough in using “voxels” in Monte Carlo dose calculations for the human body. This is the first time when the bone marrow and eye lenses were directly segmented and identified in the phantom for radiation dosimetry purposes. His group was the first to have developed a capability in using four different Monte Carlo codes (MCNP, MCNPX, EGS, GEANT4) for voxel phantom dose calculations involving photons, electrons, protons, and many other heavy ions. The VIP-Man phantom, which has been shared with more than 100 researchers worldwide, made it possible to study radiation dosimetry in health physics as well as medical physics (medical imaging and radiotherapy). As of May 15, 2012, this paper has been cited 266 times and, according to Google Scholar, is the most cited paper in “computational dosimetry phantoms”. For this work, Dr. Xu was awarded the National Science Foundation’s Faculty CAREER Award in 1999. He is one of the few nuclear engineering faculty members who have received this highly selective award.

Xu et al. 2007 reported a method for developing the 3rd-generation computational phantoms using the so-called “boundary representation (BREP)” geometry – NURBS and triangular meshes developed by the computer graphics community.^[3] Dr. Xu and students demonstrated, for the first time, that it was possible to rapidly create phantoms representing a pregnant mother at the end of 3-, 6-, and 9-month gestational periods without relying on patient images that are difficult to obtain for pregnant patients. This innovative method also afforded the ability to simulate changes in human posture as well as physiology-caused organ deformation such as respiration. This paper was rated among 10 of the best and most popular articles by the journal of Physics in Medicine & Biology and was one of the finalists for the Roberts’ Prize in 2007.

Han et al. 2010 investigated a pair of phantoms that represent individuals walking on contaminated ground.^[4]

Ding et al. 2012 examined the effect of obesity on the calculated radiation dose from CT.^[5] Xu and his students developed the first set of overweight and obese phantoms. This was the most downloaded PMB article in 2012. This study received more than 130 pieces of worldwide media coverage about this study (within 30 days after the publication).

In 2005, Dr. Xu co-founded the Consortium of Computational Human Phantoms (CCHP) -- an international collaborative project that promotes research and standardization among researchers. As part of the CCHP’s initiatives, Dr. Xu co-edited the “Handbook of Anatomical Models for Radiation Dosimetry” that provides, for the first time, a comprehensive summary of 50 years of research related to computational phantoms for radiation dosimetry. After two years of preparation involving 60 authors from 13 countries, the 30-chapter book was published in 2009. Following the publication of this important book, Dr. Xu continued to play a leading role in the international community by organizing and chairing The Third International Workshop on Computational Phantoms for Radiation Protection, Imaging and Radiotherapy in Beijing, China on August 8 and 9, 2011.^[6]

Honors and awards

• Radiation Advisory Committee. US Environmental Protection Agency Science Advisory Board (2012)
• Professional Excellence Award, American Nuclear Society Radiation Protection and Shielding Division (RPSD) (2012)
• Fellow, American Nuclear Society (ANS) (2012) - In recognition of “ground-breaking research and technical leadership in computational phantoms and Monte Carlo simulation methods for nuclear engineering, health physics and medical physics problems that resulted in significant advancements in the field of radiation dosimetry and that impacted practices in radiation protection, imaging and radiotherapy both nationally and internationally.”^[7]
• Outstanding Research Team Award, Rensselaer Polytechnic Institute School of Engineering (2012)
• Fellow, American Association of Physicists in Medicine (AAPM) (2009).
• Best Paper Award, American Nuclear Society 14th Biennial Topical Meeting of the Radiation Protection and Shielding Division
• Research Excellence Award, Rensselaer Polytechnic Institute School of Engineering (2006)
• President, Council on Ionizing Radiation Measurements and Standards (1999-2000)
• National Science Foundation / Faculty Early Career Development (CAREER) Award (1999) (formerly known as the Presidential Young Investigator Award)

Book chapters and invited journal reviews

• Xu, Xie George; Eckerman, Kieth F., eds. (2010). Handbook of Anatomical Models for Radiation Dosimetry. CRC. ISBN 978-1-4200-5979-3. 
• Xu XG, Bednarz B, Paganetti H (July 2008). "A review of dosimetry studies on external-beam radiation treatment with respect to second cancer induction". Physics in Medicine and Biology. 53 (13): R193–241. doi:10.1088/0031-9155/53/13/R01. PMC 4009374. PMID 18540047. 
• Zaidi H, Xu XG (2007). "Computational anthropomorphic models of the human anatomy: the path to realistic Monte Carlo modeling in radiological sciences". Annual Review of Biomedical Engineering. 9: 471–500. doi:10.1146/annurev.bioeng.9.060906.151934. PMID 17298237. 
• Xu, X. George (2006). "Modeling of Human Anatomy for Radiation Dosimetry: An Example of the VIP-Man Model". Applied Modeling and Computations in Nuclear Science. ACS Symposium Series. 945. pp. 115–30. doi:10.1021/bk-2007-0945.ch009. ISBN 0-8412-3982-7. 

Professional society membership

American Nuclear Society (ANS)

• Member, Executive Committee, Radiation Protection and Shielding Division (RPSD) (2007-2010)
• Member, ANS-6.4.3 Working Group ANS-6.4.3 "Gamma-Ray Attenuation Coefficients & Buildup Factors for Engineering" (2007–present)
• Chair, Program Committee, Computational Medical Physics Working Group (2006 - 2009)
• Vice Chair, Radiation Protection and Shielding Division (RPSD) (2012–present)
• Member (Executive Committee, nominated), Mathematics and Computation Division (2010 – present)
• Voting member, Nuclear Engineering Dept Head Organization (NEDHO) (2011 – present)

American Association of Physicists in Medicine (AAPM)

• Science Council
  • Therapy Physics, Radiation Safety Subcommittee (2004 – present)
    • Vice-chair (2007 – 2011)
  • Member, Task Group #136 "Hazards due to Induced Radioactivity Produced by Radiotherapy Accelerators" (2006 – present)
  • Chair, Task Group # 158 "Measurements and Monte Carlo Calculations of Whole-Body Organ Doses from External Beam Radiotherapy" (2006–present)
  • Member, Task Group #180 "Modeling and Accounting for the Imaging Guidance Radiation Doses to Radiotherapy Patients in Treatment Planning" (2008 – present)
• Therapy Physics, Therapy Imaging Subcommittee
  • Imaging for Patient Modeling Work Group (2005 – 2006)
• Imaging Physics, Radiation Protection Subcommittee (2005 – 2011)

Health Physics Society (HPS)

• Academic Education Committee, 1997 – 2001
• Publication Committee, 2003 - 2005
• ANSI Standard Committee on Thyroid Modeling, 1998 – present

International Commission on Radiological Protection (ICRP)

• Corresponding Member, Committee 2: Task Group on Dose Calculation, 2002 – present
  • Subgroups on External Dosimetry, Phantom Development, Absorbed Fraction Calculations (Photons, Alphas and Electrons

International Organization of Medical Physics (IOMP)

• Science Committee (2009 – present)

National Council of Radiation Protection and Measurements (NCRP)

• Council member (elected in 2008 for a 6-year term)
• Member, Scientific Committee (1-17) "Second Cancers and Cardiopulmonary Effects After Radiotherapy." (2006-2011)

Society of Nuclear Medicine (SNM)

• Member of The Radiation Dose Assessment Resource (RADAR) Task Group (2007 – present)

Selected publications

• Xu XG, Chao TC, Bozkurt A (May 2000). "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". Health Physics. 78 (5): 476–86. doi:10.1097/00004032-200005000-00003. PMID 10772019. 
• Xu XG, Taranenko V, Zhang J, Shi C (December 2007). "A boundary-representation method for designing whole-body radiation dosimetry models: pregnant females at the ends of three gestational periods--RPI-P3, -P6 and -P9". Physics in Medicine and Biology. 52 (23): 7023–44. doi:10.1088/0031-9155/52/23/017. PMID 18029991. 
• Na YH, Zhang B, Zhang J, Caracappa PF, Xu XG (July 2010). "Deformable adult human phantoms for radiation protection dosimetry: anthropometric data representing size distributions of adult worker populations and software algorithms". Physics in Medicine and Biology. 55 (13): 3789–811. doi:10.1088/0031-9155/55/13/015. PMC 3290660. PMID 20551505. 
• Han B, Zhang J, Na YH, Caracappa PF, Xu XG (October 2010). "Modelling and Monte Carlo organ dose calculations for workers walking on ground contaminated with Cs-137 and Co-60 gamma sources". Radiation Protection Dosimetry. 141 (3): 299–304. doi:10.1093/rpd/ncq184. PMC 3145389. PMID 20663852. 
• Ding A, Mille MM, Liu T, Caracappa PF, Xu XG (May 2012). "Extension of RPI-adult male and female computational phantoms to obese patients and a Monte Carlo study of the effect on CT imaging dose". Physics in Medicine and Biology. 57 (9): 2441–59. doi:10.1088/0031-9155/57/9/2441. PMC 3329718. PMID 22481470. 
• Xu XG, Reece WD, Poston JW (February 1995). "A study of the angular dependence problem in effective dose equivalent assessment". Health Physics. 68 (2): 214–24. doi:10.1097/00004032-199502000-00007. PMID 7814255. 
• Naessens EP, Xu XG (July 1999). "A non-destructive method to determine the depth of radionuclides in materials in-situ". Health Physics. 77 (1): 76–88. doi:10.1097/00004032-199907000-00013. PMID 10376545. 
• Xu XG, Bednarz B, Paganetti H (July 2008). "A review of dosimetry studies on external-beam radiation treatment with respect to second cancer induction". Physics in Medicine and Biology. 53 (13): R193–241. doi:10.1088/0031-9155/53/13/R01. PMC 4009374. PMID 18540047. 
• Bednarz B, Xu XG (February 2009). "Monte Carlo modeling of a 6 and 18 MV Varian Clinac medical accelerator for in-field and out-of-field dose calculations: development and validation". Physics in Medicine and Biology. 54 (4): N43–57. doi:10.1088/0031-9155/54/4/N01. PMC 3376900. PMID 19141879. 
• Gu J, Bednarz B, Caracappa PF, Xu XG (May 2009). "The development, validation and application of a multi-detector CT (MDCT) scanner model for assessing organ doses to the pregnant patient and the fetus using Monte Carlo simulations". Physics in Medicine and Biology. 54 (9): 2699–717. doi:10.1088/0031-9155/54/9/007. PMC 3376893. PMID 19351983. 
• Lieu, Tianyu; Ding, Aiping; Ji, Wei; Xu, X. George; Carothers, Christopher D.; Brown, Forrest B. (2012). A Monte Carlo Neutron Transport Code for Eigenvalue Calculations on a Dual-GPU System and CUDA Environment (PDF). PHYSOR 2012. 

Selected invited talks

• "Biomedical Physics Research at Rensselaer: An Engineering Approach"
  • Keynote presentation, UCLA Biomedical Physics Graduate Program Annual Colloquium, May 9, 2008.
• "Two-dosimeter Algorithms for the Assessment of Effective Dose Equivalent"
  • Plenary presentation, The 41st Annual National Conference on Radiation Control: Advancing Radiation Protection in the 21st Century, Hyatt Regency, Columbus, Ohio, May 18–21, 2009.
• "Recent Progress on Computational Phantoms and Applications to Imaging and Therapy"
  • Seminar, Joint Program in Nuclear Medicine, Harvard Medical School, 8-9am, January 7, 2010.
• "Medical Physics Research at RPI – A Journey in Search of the Next Big Thing"
  • Seminar, Department of Radiation Oncology, Massachusetts General Hospital, Boston, January 12, 2010.
• "Trends in Radiation Protection Dosimetry: The New ICRP-103 Algorithms and Computational Phantoms"
  • Plenary presentation, 2010 American Nuclear Society, Joint RPSD, IRD & BMD International Topical Meeting, Palace Station Hotel & Casino, Las Vegas, NV, April 19–23, 2010.
• "New, Realistic Models of the Adult Female in Pregnancy for Use in Dose Assessment"
  • Invited presentation, Continuous Education Course "New Internal Dose Models – Evaluation and Impact" Society of Nuclear Medicine (SNM) Annual Meeting, Salt Lake City, Utah, June 5–9, 2010.
• "Software Tools for PET and CT Dose Calculations"
  • Invited presentation, Continuous Education Course "Dose Estimation and Reduction in PET/CT Imaging" Society of Nuclear Medicine (SNM) Annual Meeting, Salt Lake City, Utah, June 5–9, 2010.
• "3D/4D Human Modeling and Monte Carlo Dose Calculation for Radiation Protection, Imaging and Radiotherapy"
  • Plenary presentation, The Joint International Conference of the 7th Supercomputing in Nuclear Application and the 3rd Monte Carlo (SNA + MC2010), Tokyo, Japan, October 17–21, 2010.

References