Skip to Content

Geoffrey S. Ibbott, Ph.D.

Present Title & Affiliation

Primary Appointment

Professor and Chairman, Department of Radiation Physics, Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX

Education & Training

Degree-Granting Education

1993 Colorado State University, Ft. Collins, CO, PHD, Radiation Biology
1981 University of Colorado Health Sciences Center, Denver, CO, MS, Medical Physics
1979 University of Colorado, Denver, CO, BA, Physics

Board Certifications

6/1994 American Board of Radiology, Diagnostic and Medical Nuclear Physics
6/1983 American Board of Radiology, Therapeutic Radiological Physics


Academic Appointments

Professor, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, 2005-present
Associate Professor, The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX, 9/2001-8/2005

Other Appointments/Responsibilities

Vice-Chair, Commission on Medical Physics, American College of Radiology, Fairfax, VA, 2014-2018
Trustee, American Board of Radiology, Tucson, AZ, 2007-present
Member, Council Steering Committee, American College of Radiology, Reston, VA, 2004-2010

Institutional Committee Activities

Member, GSBS Medical Physics Steering Committee, 2004-2010

Professional Memberships

American Association of Physicists in Medicine
Chairman of the Board, 2000
President, 1999
President-Elect, 1998
Member, 1972-present
American Board of Radiology
Oral Examiner in Radiological Physics, 2009
Oral Examiner in Radiological Physics, 2008
Member, Board of Trustees, 2007-present
Oral Examiner in Radiological Physics, 2007
Oral Examiner in Radiological Physics, 2005
Oral Examiner in Radiological Physics, 2003
Oral Examiner in Radiological Physics, 2002
Oral Examiner in Radiological Physics, 2000
Oral Examiner in Radiological Physics, 1998
Oral Examiner in Radiological Physics, 1996
Member, Radiation Oncology written examination committee, 1994-present
American College of Radiology
Member, Quality Task Force, QRRO, 2007-2009
Councilor at Large, 2004-present
Fellow, 1998
Councilor at Large, 1996-2001
Member, 1984-present
American Society for Therapeutic Radiology and Oncology
Member, Whole Breast Irradiation Task Force, American Society of Therapeutic Radiology and Oncology, Fairfax, VA, 2009-present
Fellow, 2007
Member, Government Relations Committee, 2001-2009
Member, 1980-present
International Electrotechnical Commission
Chair, Subcommittee 62C, 2008-present
Chair, U.S. Technical Advisory Group, 1993-present
Member, Working Group 1, 62C, 1993-present
Member, U.S. Technical Advisory Group, 1990-present

Selected Publications

Peer-Reviewed Original Research Articles

1. Baldock C, Deene YD, Doran S, Ibbott G, Jirasek A, Lepage M, McAuley KB, Oldham M, Schreiner LJ. Polymer Gel Dosimetry. Physics in Medicine and Biology 55:R1-R63, 2/2010.
2. Sherry C, Bowkley C, Ibbott G, Kaye A, Short B. In Through the Out Door: AMCLC 2009 Council Perceptions of Self-Referral. Journal of the American College of Radiology 6(12):832-836, 12/2009.
3. Mettler FA, Bhargavan M, Faulkner K, Gilley DB, Fray JE, Ibbott GS, Lipoti JA, Mahesh M, McCrohan JL, Stabin MG, Thomadsen BR, Yoshizumi TT. Radiologic and Nuclear Medicine Studies in the United States and Worldwide: Frequency, Radiation Dose, and Comparison with Other Radiation Sources - 1950-2007. Radiology 253(2):520-31, 11/2009. e-Pub 9/2009. PMID: 19789227.
4. Sakhalkar H, Sterling D, Adamovics J, Ibbott G, Oldham M. Investigation of the feasibility of relative 3D dosimetry in the Radiologic Physics Center head and Neck IMRT phantom using presage/optical-CT. Med Phys 36(7):3371-7, 7/2009. PMID: 19673232.
5. Sakhalkar HS, Adamovics J, Ibbott G, Oldham M. A comprehensive evaluation of the PRESAGE/optical-CT 3D dosimetry system. Med Phys 36(1):71-82, 1/2009. PMCID: PMC2673667.
6. Hartford AC, Palisca MG, Eichler TJ, Beyer DC, Devineni VR, Ibbott GS, Kavanagh B, Kent JS, Rosenthal SA, Schultz CJ, Tripuraneni P, Gaspar LE. American Society for Therapeutic Radiology and Oncology (ASTRO) and American College of Radiology (ACR) Practice Guidelines for Intensity-Modulated Radiation Therapy (IMRT). Int J Radiat Oncol Biol Phys 73(1):9-14, 1/2009. PMID: 19100920.
7. Pourfallah TA, Allahverdi M, Alam NR, Ay MR, Zahmatkesh MH, Ibbott GS. Performance evaluation of MRI-based PAGAT polymer gel dosimeter in an inhomogeneous phantom using EGSnrc code on a Co-60 machine. Appl Radiat Isot 67(1):186-91, 1/2009. e-Pub 9/2008. PMID: 18951810.
8. Tailor R, Ibbott G, Lampe S, Bivens Warren W, Tolani N. Dosimetric characterization of a 131Cs brachytherapy source by thermoluminescence dosimetry in liquid water. Med Phys 35(12):5861-68, 12/2008. PMID: 19175142.
9. Davidson SE, Popple RA, Ibbott GS, Followill DS. Technical note: Heterogeneity dose calculation accuracy in IMRT: Study of five commercial treatment planning systems using an anthropomorphic thorax phantom. Med Phys 35(12):5434-39 [Erratum published in Med. Phys. 35, 5434-5438 (2008)], 12/2008. PMCID: PMC2736720.
10. Tailor RC, Ibbott GS, Tolani N. Thermoluminescence dosimetry measurements of brachytherapy sources in liquid water. Med Phys 35(9):4063-9, 9/2008. PMID: 18841858.
11. Butler WM, Bice WS, DeWerd LA, Hevezi JM, Huq MS, Ibbott GS, Palta JR, Rivard MJ, Seuntjens JP, Thomadsen BR. Third-party brachytherapy source calibrations and physicist responsibilities: report of the AAPM Low Energy Brachytherapy Source Calibration Working Group. Med Phys 35(9):3860-5, 9/2008. PMID: 18841836.
12. Han Y, Shin EH, Lim C, Kang SK, Park SH, Lah JE, Suh TS, Yoon M, Lee SB, Cho SH, Ibbott GS, Ju SG, Ahn YC. Dosimetry in an IMRT phantom designed for a remote monitoring program. Med Phys 35(6):2519-27, 6/2008. PMID: 18649485.
13. Ibbott G, Ma CM, Rogers DW, Seltzer SM, Williamson JF. Anniversary paper: fifty years of AAPM involvement in radiation dosimetry. Med Phys 35(4):1418-27, 4/2008. PMID: 18491537.
14. Huq MS, Fraass BA, Dunscombe PB, Gibbons JP, Ibbott GS, Medin PM, Mundt A, Mutic S, Palta JR, Thomadsen BR, Williamson JF, Yorke ED. A method for evaluating quality assurance needs in radiation therapy. Int J Radiat Oncol Biol Phys 71(1 Suppl):S170-3, 2008. PMID: 18406920.
15. Ibbott GS, Followill DS, Molineu HA, Lowenstein JR, Alvarez PE, Roll JE. Challenges in Credentialing Institutions and Participants in Advanced Technology Multi-institutional Clinical Trials. Int J Radiat Oncol Biol Phys 71(1):S71-S75, 2008. PMCID: PMC2409281.
16. Frey GD, Ibbott GS, Morin RL, Paliwal BR, Thomas SR, Bosma J. The American Board of Radiology perspective on maintenance of certification: Part IV: Practice quality improvement in radiologic physics. Med Phys 34(11):4158-63, 11/2007. PMID: 18072479.
17. Ibbott GS, Hanson WF, O'Meara E, Kuske RR, Arthur D, Rabinovitch R, White J, Wilensick RM, Harris I, Tailor R. Dose Specification and Quality Assurance of Radiation Therapy Oncology Group Protocol 95-17; A Cooperative Group Study of Iridium-192 Breast Implants as Sole Therapy. Int J Radiat Oncol Biol Phys (*Listed in "Issue Highlights) 69(5):1572-78, 8/2007. PMCID: PMC2180157.
18. Rivard MJ, Butler WM, DeWerd LA, Huq MS, Ibbott GS, Meigooni AS, Melhus CS, Mitch MG, Nath R, Williamson JF. Supplement to the 2004 update of the AAPM Task Group No. 43 Report. Med Phys 34(6):2187-2205, 6/2007. PMID: 17654921.
19. Davidson SE, Ibbott GS, Prado KL, Dong L, Liao Z, Followill DF. Accuracy of two heterogeneity dose calculation algorithms for IMRT in treatment plans designed using an anthropomorphic thorax phantom. Med Phys 34(5):1850-7, 5/2007. PMID: 17555266.
20. Followill D, Radford DA, Cherry C, Molineu A, Fisher G, Hanson WF, Ibbott GS. Design, development, and implementation of the Radiological Physics Center's pelvis and thorax anthropomorphic quality assurance phantoms. Med Phys 34(6):2070-6, 5/2007. PMID: 17654910.
21. Li Z, Das RK, Dewerd LA, Ibbott GS, Meigooni AS, Perez-Calatayud J, Rivard MJ, Sloboda RS, Williamson JF. Dosimetric prerequisites for routine clinical use of photon emitting brachytherapy sources with average energy higher than 50 Kev. Med Phys 34(1):37-40, 1/2007. PMID: 17278487.
22. Ibbott GS, Molineu A, Followill DS. Independent evaluations of IMRT through the use of an anthropomorphic phantom. Technol Cancer Res Treat 5(5):481-7, 10/2006. PMID: 16981790.
23. Timmerman R, Galvin J, Michalski J, Straube W, Ibbott G, Martin E, Abdulrahman R, Swann S, Fowler J, Choy H. Accreditation and quality assurance for Radiation Therapy Oncology Group: Multicenter clinical trials using stereotactic body radiation therapy in lung cancer. Acta Oncologica 45(7):779-86, 9/2006. PMID: 16982540.
24. Randall ME, Ibbott GS. Intensity-modulated radiation therapy for gynecologic cancers: pitfalls, hazards, and cautions to be considered. Semin Radiat Oncol 16(3):138-43, 7/2006. PMID: 16814153.
25. Gillin MT, Dunning BF, Lawton CA, Foley WD, Byhardt RW, Morton G, Baikadi M, Pisansky TT, Michalski JM, Ibbott G, Lopez F. Quality assurance methods for the first Radiation Therapy Oncology Group permanent prostate implant protocol. Brachytherapy 5(3):152-6, Jul-Sep, 7/2006. PMID: 16864066.
26. Tailor RC, Hanson WF, Wells N, Ibbott GS. Consistency of absorbed dose to water measurements using 21 ion-chamber models following the AAPM TG51 and TG21 calibration protocols. Med Phys 33(6):1818-28, 6/2006. PMID: 16872089.
27. Minniti R, Chen-Mayer H, Seltzer SM, Huq MS, Bryson L, Slowey T, Micka JA, DeWerd LA, Wells N, Hanson WF, Ibbott GS. The US radiation dosimetry standards for 60Co therapy level beams, and the transfer to the AAPM accredited dosimetry calibration laboratories. Med Phys 33(4):1074-7, 4/2006. PMID: 16696484.

Invited Articles

1. Morin RL, Ibbott GS. Gel dosimetry. J Am Coll Radiol 3(2):144-6, 2/2006. PMID: 17412026.
Other Articles
1. Ibbott GS, Heard MP. 3D Dosimetry for Brachytherapy and Heterogeneities. J. Phys. Conf. Ser. 250 012088 250(1), 2010.
2. Ibbott GS. QA in Radiation Therapy: The RPC Perspective. J. Phys. Conf. Ser. 250 012001 250(1), 2010.
3. Grant RL, Crowder ML, Ibbott GS, Simon J, Frank RK, Rogers J, Loy HM, Adamovics J, Newton J, Oldham M, Stearns S, Wendt RE. Three-Dimensional Dosimetry of a Beta-Emitting Radionuclide Using PRESAGE® Dosimeters. J. Phys. Conf. Ser. 250 012095 250(1), 2010.
4. Sakhalkar HS, Adamovics J, Ibbott G, Oldham M. An Investigation into the Robustness of Optical-CT Dosimetry of a Radiochromic Dosimeter Compatible with the RPC Head-and-Neck Phantom. Journal of Physics: Conference Series 164:012059, 2009.
5. Heard M, Ibbott G, Followill D, White RA, Jackson E, Salehpour S. Characterization of a normoxic polyacrylamide gel using MRI and optical CT. Journal of Physics: Conference Series 164:012005, 2009.
6. Sakhalkar HS, Sterling D, Adamovics J, Ibbott G, Oldham M. Investigating the Feasibility of 3D Dosimetry in the RPC IMRT H&N Phantom. Journal of Physics: Conference Series 164:012058, 2009.
7. Davidson S, Cui J, Followill D, Ibbott S. A Flexible Monte Carlo Tool for Patient or Phantom Specific Calculations: Comparison with Preliminary Validation Measurements. Journal of Physics: Conference Series 102:012004, 2008.
8. Ibbott GS. Clinical applications of gel dosimeters. Journal of Physics: Conference Series 56:108-31, 2006.

Book Chapters

1. FitzGerald TJ, Bishop-Jodoin M, Urie M, Ulin K, Ibbott G, Purdy J, Saltz J, Peters L, Schnall M, Deasy J, Bosch W, Knopp M, Schwartz L, White K, Hanusik R, Kessel S, Morano K, Laurie F. Quality Assurance of Clinical Trials in the Management of Cancer in the Head and Neck. In: Head and Neck Cancer: Multimodality Management, 1. Ed(s) Bernier J. Springer; 1st Edition: New York, 687-694, 2011. ISBN: 978-1-4419-9463-9.
2. Ibbott G. QA for Clinical Dosimetry. with Emphasis on Clinical Trials. In: Clinical Dosimetry Measurements in Radiotherapy. Ed(s) DWO Rogers, JE Cygler. Medical Physics Publishing: Madison, 577-604, 2009.
3. Ibbott GS. Radiation Physics. In: Handbook of Radiation Oncology. Ed(s) Haffty BG, Wilson LD. Jones & Bartlett: Sudbury, 1-40, 2009.
4. Fitzgerald TJ, White K, Saltz J, Sharma A, Siegel E, Urie M, Ulin K, Purdy J, Bosch W, Matthews J, Deasy J, Ibbott G, Laurie F, Hanusik R, Yorty J, Bishop-Jodoin M, Kessel S, Cicchetti MG, McCarten K, Rosen N, Pieters R, Voss S, Reaman G, Schnall M, Schilsky R, Knopp M, Schwartz L, Baker L, Comis R, Kun L, boyett J, Ramamurthy U, Parliament M, Nelson H, Ota D. Development of a Queriable Database for Oncology Outcome Analysis. In: Cured II - LENT Cancer Survivorship Research and Education. Ed(s) P Rubin, SL Constine, LB Marks, P Okunieff. Springer: New York, 55-66, 2008.

Books (edited and written)

1. Hendee WR, Ibbott GS, Hendee EG. Radiation Therapy Physics., 3rd. John Wiley and Sons: Hoboken, 2004.
2. Hendee WR Ibbott GS. Radiation Therapy Physics., 2nd. Mosby Year-Book Publishers: Philadelphia, 1996.

Grant & Contract Support

Title: Improving the clinical effectiveness and understanding of the biophysical basis - Core A: Administrative
Funding Source: NIH/NCI
Role: Co-Investigator
Principal Investigator: Radhe Mohan
Duration: 9/25/2014 - 8/31/2015
Title: Imaging and Radiation Oncology Core (IROC Group) – IROC Houston QA
Funding Source: American College of Radiology
Role: Co-Investigator
Principal Investigator: Followill
Duration: 3/1/2014 - 2/28/2019

Last updated: 6/9/2015