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Author Notes:

Corresponding author: Liyong Lin, Department of Radiation Oncology, University of Pennsylvania, 2308 W TRC, PCAM, 3400 Civic Center Blvd., Philadelphia, PA 19104, USA; phone: (215) 615 5638; fax: (215) 615 1658; email: linl@uphs.upenn.edu

he authors would like to thank Olivier De Wilde from Research and Development Division of Ion Beam Applications to extract the delivery log of the PBS treatment plan and Kevin Teo from University of Pennsylvania for deformable image registration using MIM software, respectively.

Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the US Army.


Research Funding:

This work was supported in part by the US Army Medical Research and Materiel Command under Contract Agreement No. DAMD17‐W81XWH‐07‐2‐0121 and W81XWH‐09‐2‐0174, and in part by a Varian industry grant.


  • Science & Technology
  • Life Sciences & Biomedicine
  • Radiology, Nuclear Medicine & Medical Imaging
  • 4D CT
  • beam-specific PTV
  • treatment planning
  • proton therapy
  • pencil beam scanning
  • interplay

Beam-specific planning target volumes incorporating 4D CT for pencil beam scanning proton therapy of thoracic tumors


Journal Title:

Journal of Applied Clinical Medical Physics


Volume 16, Number 6


, Pages 281-292

Type of Work:

Article | Final Publisher PDF


The purpose of this study is to determine whether organ sparing and target coverage can be simultaneously maintained for pencil beam scanning (PBS) proton therapy treatment of thoracic tumors in the presence of motion, stopping power uncertain-ties, and patient setup variations. Ten consecutive patients that were previously treated with proton therapy to 66.6/1.8 Gy (RBE) using double scattering (DS) were replanned with PBS. Minimum and maximum intensity images from 4D CT were used to introduce flexible smearing in the determination of the beam specific PTV (BSPTV). Datasets from eight 4D CT phases, using ± 3% uncertainty in stop-ping power and ± 3 mm uncertainty in patient setup in each direction, were used to create 8 × 12 × 10 = 960 PBS plans for the evaluation of 10 patients. Plans were normalized to provide identical coverage between DS and PBS. The average lung V20, V5, and mean doses were reduced from 29.0%, 35.0%, and 16.4 Gy with DS to 24.6%, 30.6%, and 14.1 Gy with PBS, respectively. The average heart V30 and V45 were reduced from 10.4% and 7.5% in DS to 8.1% and 5.4% for PBS, respectively. Furthermore, the maximum spinal cord, esophagus, and heart doses were decreased from 37.1 Gy, 71.7 Gy, and 69.2 Gy with DS to 31.3 Gy, 67.9 Gy, and 64.6 Gy with PBS. The conformity index (CI), homogeneity index (HI), and global maximal dose were improved from 3.2, 0.08, 77.4 Gy with DS to 2.8, 0.04, and 72.1 Gy with PBS. All differences are statistically significant, with p-values < 0.05, with the exception of the heart V45 (p = 0.146). PBS with BSPTV achieves better organ sparing and improves target coverage using a repainting method for the treatment of thoracic tumors. Incorporating motion-related uncertainties is essential.

Copyright information:

© 2015 The Authors.

This is an Open Access work distributed under the terms of the Creative Commons Attribution 3.0 Unported License (http://creativecommons.org/licenses/by/3.0/).

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