MU Fluence Reconstruction based-on Delivered Leaf Position: for IMRT Quality Assurance

세기조절방사선치료의 정도관리를 위한 모니터유닛 공간분포 재구성의 효용성 평가

  • Park, So-Yeon (Department of Radiation Applied Life Science, Seoul National University Graduate School) ;
  • Park, Yang-Kyun (Department of Radiation Applied Life Science, Seoul National University Graduate School) ;
  • Park, Jong-Min (Department of Radiation Applied Life Science, Seoul National University Graduate School) ;
  • Choi, Chang-Heon (Department of Radiation Applied Life Science, Seoul National University Graduate School) ;
  • Ye, Sung-Joon (Department of Radiation Oncology, Seoul National University College of Medicine)
  • 박소연 (서울대학교 대학원 방사선응용생명과학 협동과정) ;
  • 박양균 (서울대학교 대학원 방사선응용생명과학 협동과정) ;
  • 박종민 (서울대학교 대학원 방사선응용생명과학 협동과정) ;
  • 최창헌 (서울대학교 대학원 방사선응용생명과학 협동과정) ;
  • 예성준 (서울대학교 의과대학 방사선종양학교실)
  • Received : 2011.02.14
  • Accepted : 2011.03.22
  • Published : 2011.03.30


The measurement-based verification for intensity modulated radiation therapy (IMRT) is a time-and labor-consuming procedure. Instead, this study aims to develop a MU fluence reconstruction method for IMRT QA. Total actual fluences from treatment planning system (TPS, Eclipse 8.6, Varian) were selected as a reference. Delivered leaf positions according to MU were extracted by the dynalog file generated after IMRT delivery. An in-house software was develop to reconstruct MU fluence from the acquired delivered leaf position data using MATLAB. We investigated five patient's plans delivered by both step-and-shoot IMRT and sliding window technologies. The total actual fluence was compared with the MU fluence reconstructed by using commercial software (Verisoft 3.1, PTW) and gamma analysis method (criteria: 3%/3 mm and 2%/1 mm). Gamma pass rates were $97.8{\pm}1.33$% and the reconstructed fluence was shown good agreement with RTP-based actual fluence. The fluence from step and shoot IMRT was shown slightly higher agreement with the actual fluence than that from sliding window IMRT. If moving from IMRT QA measurements toward independent computer calculations, the developed method can be used for IMRT QA. A point dose calculation method from reconstructed fluences is under development for the routine IMRT QA purpose.


  1. Hong CS, Lim J, Ju SG, Shin E, Han Y, Ahn YC. Comparison of the Efficacy of 2D Dosimetry Systems in the Pre-treatment Verification of IMRT. J. Korean Soc. Ther. Radiol. Oncol. 2009;27(2):91-102.
  2. Wiersma RD, Xing L. Examination of geometric and dosimetric accuracies of gated step-and-shoot intensity modulated radiation therapy. Phys, Med. 2007 October;34(10):3962-3969.
  3. Zygmanski P, Kung JH, Jiang SB, Chin L. Dependence of fluence errors in dynamic IMRT in leaf-positional errors varying with time and leaf number. Phys, Med. 2003 October; 30(10):2736-2749.
  4. Litzenbeg DW, Moran JM, Fraass BA. Verification of dynamic and segmental IMRT delivery by dynamic log file analysis. J. Appl, Clin. Med. Phys, 2002;3(2):63-72.
  5. Spirou SV, Chui CS. Delivery of Intensity-Modulated Beam Profiles With A Multileaf Collimator. In: Samuel Hellman. A Practical Guide To Intensity-Modulated Radiation Therapy. 1st ed. Madison, Wisconsin; Medical Physics Publishing. 2003:71-82.
  6. Varian Medical System, Inc. Varian Medical Systems. Eclipse Inverse Planning Administration and Physics. 2009.
  7. Kumar MD, Thirumavalavan N, Krishan DV, Babaiah M. QA of intensity-modulated beams using dynamic MLC log files. Journal of Medical Physics 2006;31(1):36-41.
  8. Lee JW, Park JH, Chung JB, Park JY, Choe BY, Suh TS, Lee DH, Hong S, Kang MY, Choi KS. Inverse Verification of the Dose Distribution for Intensity Modulated Radiation Therapy Patient-Specific Quality Assurance Using Dynamic MLC Log Files. J. Korean Phys, Soc. 2009 October;55(4):1649-1656.
  9. Varian Medical System, Inc. Varian Medical Systems. Dynalog File Viewer reference guide. 2003.
  10. Chen X, Yue NJ, Chen W, Saw CB, Heron DE, Stefanik D, Antemann R, Huq MS. A dose verification method using a monitor unit matrix for dynamic IMRT on Varian linear accelerators. Phy. Med. Biol. 2005;50:5641-5652.
  11. Kung JH, Chen GTY, Kuchnir FK. A monitor unit verification calculation in intensity modulated radiotherapy as a dosimetry quality assurance. Phys, Med. 2000 October;27(10):2226-2230.
  12. Xing L, Li JG. Computer verification of fluence map for intensity modulated radiation therapy. Phys, Med. 2000 September;27(9):2084-2092.
  13. Langer M, Thai V, Papiez L. Improved leaf sequencing reduces segments of monitor units needed to deliver IMRT using multileaf collimators. Phys, Med. 2001 December;28(12):2450-2458.
  14. Xing L, Chen Y, Luxton G, Li JG, Boyer AL. Monitor unit calculation for intensity modulated photon field by a simple scatter-summation algorithm. Phy. Med. Biol. 2000;45:N1-N7.
  15. Low DA, Harms WB, Mutic S, Purdy JA. A technique for the quantitative evaluation of dose distribution. Phys, Med. 1998 May;25(5):656-661.