Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
권호 표지
DOI QR코드

DOI QR Code

DEVELOPMENT AND EVALUATION OF A PHANTOM FOR MULTI-PURPOSE DOSIMETRY IN INTENSITY-MODULATED RADIATION THERAPY

  • Jeong, Hae-Sun (Department of Nuclear Engineering, Hanyang University) ;
  • Han, Young-Yih (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Kum, O-Yeon (Department of Radiation Oncology, Yonsei University College of Medicine) ;
  • Kim, Chan-Hyeong (Department of Nuclear Engineering, Hanyang University) ;
  • Park, Joo-Hwan (Korea Atomic Energy Research Institute)
  • Received : 2010.10.02
  • Accepted : 2011.04.02
  • Published : 2011.08.31
Download PDF
⟨ Previous Next ⟩

Abstract

A LEGO-type multi-purpose dosimetry phantom was developed for intensity-modulated radiation therapy (IMRT), which requires various types of challenging dosimetry. Polystyrene, polyethylene, polytetrafluoroethylene (PTFE), and polyurethane foam (PU-F) were selected to represent muscle, fat, bone, and lung tissue, respectively, after considering the relevant mass densities, elemental compositions, effective atomic numbers, and photon interaction coefficients. The phantom, which is composed of numerous small pieces that are similar to LEGO blocks, provides dose and dose distribution measurements in homogeneous and heterogeneous media. The phantom includes dosimeter holders for several types of dosimeters that are frequently used in IMRT dosimetry. An ion chamber and a diode detector were used to test dosimetry in heterogeneous media under radiation fields of various sizes. The data that were measured using these dosimeters were in disagreement when the field sizes were smaller than $1.5{\times}1.5\;cm^2$ for polystyrene and PTFE, or smaller than $3{\times}3\;cm^2$ for an air cavity. The discrepancy was as large as 41% for the air cavity when the field size was $0.7{\times}0.7\;cm^2$, highlighting one of the challenges of IMRT small field dosimetry. The LEGO-type phantom is also very useful for two-dimensional dosimetry analysis, which elucidates the electronic dis-equilibrium phenomena on or near the heterogeneity boundaries.

Keywords

References

  1. Y. Han, et al., "Dosimetry in an IMRT phantom designed for a remote monitoring program," Medical Physics, 35, 2519-2527 (2008). https://doi.org/10.1118/1.2903440
  2. F. Sanchez-Doblado, et al., "Micro ionization chamber dosimetry in IMRT verification: Clinical implications of dosimetric errors in the PTV," Radiotherapy and Oncology 75, 342-348 (2005). https://doi.org/10.1016/j.radonc.2005.04.011
  3. R. Capote, F. Sánchez-Doblado, A. Leal, J. I. Lagares, and R. Arráns, "An EGSnrc Monte Carlo study of the microionization chamber for reference dosimetry of narrow irregular IMRT beamlets," Medical Physics, 31, 2416-2422 (2004). https://doi.org/10.1118/1.1767691
  4. C. Y. Han, J. K. Kim, and K. S. Chung, "An Epithermal Neutron Beam Design for BNCT Using $^{2}H(d,n)^{3}He$ Reaction," Nucl. Eng. & Tech., 31, 512-521 (1976).
  5. L. B. Leybovich, A. Sethi, and N. Dogan, "Comparison of ionization chambers of various volumes for IMRT absolute dose verification," Medical Physics, 30, 119-123 (2003). https://doi.org/10.1118/1.1536161
  6. E. E. Wilcox and G. M. Daskalov, "Accuracy of dose measurements and calculations within and beyond heterogeneous tissues for 6 MV photon fields smaller than 4 cm produced by Cyberknife," Medical Physics, 35, 2259-2266 (2008). https://doi.org/10.1118/1.2912179
  7. H. S. Jeong, Y. Han, O Kum, and C. H. Kim, "Study on Small Field Dosimetry for High Energy Photon-based Radiation Therapy," Korean J Med Phys., 20, 290-297 (2009).
  8. J. W. Sohn, J. F. Dempsey, T. S. Suh, and D. A. Low, "Analysis of various beamlet sizes for IMRT with 6 MV Photons," Medical Physics, 30, 2432-2439 (2003). https://doi.org/10.1118/1.1596785
  9. I. J. Das, G. X. Ding, and A. Ahnesjö, "Small fields: Nonequilibrium radiation dosimetry," Medical Physics, 35, 206-215 (2008). https://doi.org/10.1118/1.2815356
  10. H. S. Jeong, Y. Han, O Kum, and C. H. Kim, "Deconvolution of Ion Chamber Volume Effect for IMRT Absolute Dose Evaluation," The 5th KOREA-JAPAN Joint Meeting on Medical Physics, Jeju, Korea, Sept. 10-12, (2008).
  11. C. Martens, C. D. Wagter, and W. D. Neve, "The Value of the PinPoint ion chamber for characterization of small field segments used in intensity-modulated radiotherapy," Physics in Medicine and Biology, 45 2519-2530 (2000). https://doi.org/10.1088/0031-9155/45/9/306
  12. D. Radford, D. S. Followill, and W. F. Hanson, "Design of an Anthropomorphic Intensity Modulated Radiation Therapy Quality Assurance Phantom," The 22nd Annual EMBS International Conference, Chicago IL, USA, Jul. 23-28, (2000).
  13. C. Ma, et al., "A quality assurance phantom for IMRT dose verification," Physics in Medicine and Biology, 48, 561-572 (2003). https://doi.org/10.1088/0031-9155/48/5/301
  14. C. Lee, and J. Lee., "Computational Anthropomorphic Phantoms for Radiation Protection Dosimetry: Evolution and Prospects," Nucl. Eng. & Tech., 38, 239-250 (2006).
  15. Photon, Electron, Proton and Neutron Interaction Data for Body Tissues, ICRU report 46, International Commission on Radiation Units and Measurements, (1992).
  16. C. Shin, A Dual Energy Double Beam Method for Detection of Illicit Materials in $90^{\circ}$ Compton Scattering Inspection System, Doctoral Dissertation, Hanyang University, Seoul, Korea, (2007).
  17. National Institute of Standards and Technology (NIST), http://physics.nist.gov/PhysRefData/XrayMassCoef/cover.html
  18. F. H. Attix, Introduction to Radiological Physics and Radiation Dosimetry, 1st ed, Wiley-Interscience, New York, pp. 259-260, (1986).
  19. F. M. Khan, The physics of radiation therapy, 3rd ed, Lippincott Williams & Wilkins, Philadelphia, pp. 254-255, (2003).