• Ahn, Beom Seok (Department of Radiation Oncology, Seoul National University Hospital) ;
  • Wu, Hong-Gyun (Department of Radiation Oncology, Seoul National University Hospital) ;
  • Yoo, Sook Hyun (Department of Radiation Oncology, Seoul National University Hospital) ;
  • Park, Jong Min (Department of Radiation Oncology, Seoul National University Hospital)
  • Received : 2014.11.21
  • Accepted : 2015.02.17
  • Published : 2015.03.31


To improve accuracy of dose calculation on kilovoltage cone beam computed tomography (kV CBCT) images, a custom-made phantom was fabricated to acquire an accurate CT number to electron density curve by full scatter of cone beam x-ray. To evaluate the dosimetric accuracy, 9 volumetric modulated arc therapy (VMAT) plans for head and neck (HN) cancer and 9 VMAT plans for lung cancer were generated with an anthropomorphic phantom. Both CT and CBCT images of the anthropomorphic phantom were acquired and dose-volumetric parameters on the CT images with CT density curve (CTCT), CBCT images with CT density curve ($CBCT_{CT}$) and CBCT images with CBCT density curve ($CBCT_{CBCT}$) were calculated for each VMAT plan. The differences between $CT_{CT}$ vs. $CBCT_{CT}$ were similar to those between $CT_{CT}$ vs. $CBCT_{CBCT}$ for HN VMAT plans. However, the differences between $CT_{CT}$ vs. $CBCT_{CT}$ were larger than those between $CT_{CT}$ vs. $CBCT_{CBCT}$ for lung VMAT plans. Especially, the differences in $D_{98%}$ and $D_{95%}$ of lung target volume were statistically significant (4.7% vs. 0.8% with p = 0.033 for $D_{98%}$ and 4.8% vs. 0.5% with p = 0.030 for $D_{95%}$). In order to calculate dose distributions accurately on the CBCT images, CBCT density curve generated with full scatter condition should be used especially for dose calculations in the region of large inhomogeneity.


  1. Maund IF, Benson RJ, Fairfoul J, Cook J, Huddart R, Poynter A. Image Guided Radiotherapy of the Prostate using Daily Cone Beam CT - The Feasibility and Likely Benefit of Implementing a Margin Reduction. Brit J Radiol. 2014;87:20140459.
  2. Ding GX, Duggan DM, Coffey CW. Characteristics of kilovoltage x-ray beams used for cone-beam computed tomography in radiation therapy. Phys Med Biol. 2007; 52(6):1595- 615.
  3. Yan D, Ziaja E, Jaffray D, Wong J, Brabbins D, Vicini F, Martinez A. The use of adaptive radiation therapy to reduce setup error: a prospective clinical study. Int J Radiat Oncol. 1998;41(3):715-20.
  4. Veiga C, McClelland J, Moinuddin S, Lourenco A, Ricketts K, Annkah J, Modat M, Ourselin S, D'Souza D, Royle G. Toward adaptive radiotherapy for head and neck patients: Feasibility study on using CT-to-CBCT deformable registration for "dose of the day" calculations. Med Phys. 2014;41(3):031703.
  5. Guan H, Dong H. Dose calculation accuracy using cone-beam CT (CBCT) for pelvic adaptive radiotherapy. Phys Med Biol. 2009;54(20):6239-50.
  6. Rong Y, Smilowitz J, Tewatia D, Tome WA, Paliwal B. Dose calculation on kV cone beam CT images: an investigation of the Hu-density conversion stability and dose accuracy using the site-specific calibration. Med Dosim. 2010;35(3): 195-207.
  7. Yang Y, Schreibmann E, Li T, Wang C and Xing L, Evaluation of on-board kV cone beam CT (CBCT)-based dose calculation. Phys Med Biol, 2007. 52(3): p. 685-705.
  8. Qian J, Lee L, Liu W, Chu K, Mok E, Luxton G, Le QT, Xing L. Dose reconstruction for volumetric modulated arc therapy (VMAT) using cone-beam CT and dynamic log files. Phys Med Biol. 2010;55(13):3597-610.
  9. Reggiori G, Mancosu P, Tozzi A, Cantone MC, Castiglioni S, Lattuada P, Lobefalo F, Cozzi L, Fogliata A, Navarria P, Scorsetti M. Cone beam CT pre- and post-daily treatment for assessing geometrical and dosimetric intrafraction variability during radiotherapy of prostate cancer. J Appl Clin Med Phys. 2011;12(1):141-152.
  10. Jin X, Hu W, Shang H, Han C, Yi J, Zhou Y, Xie C. CBCT-based volumetric and dosimetric variation evaluation of volumetric modulated arc radiotherapy in the treatment of nasopharyngeal cancer patients. Radiat Oncol. 2013;8:279.

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