title: Improved beam angle arrangement in intensity modulated proton therapy treatment planning for localized prostate cancer.
abstract: OBJECTIVE
  This study investigates potential gains of an improved beam angle arrangement compared to a conventional fixed gantry setup in intensity modulated proton therapy (IMPT) treatment for localized prostate cancer patients based on a proof of principle study.
  
  
  METHODS
  Three patients with localized prostate cancer retrospectively selected from our institution were studied. For each patient, IMPT plans were designed using two, three and four beam angles, respectively, obtained from a beam angle optimization algorithm. Those plans were then compared with ones using two lateral parallel-opposed beams according to the conventional planning protocol for localized prostate cancer adopted at our institution.
  
  
  RESULTS
  IMPT plans with two optimized angles achieved significant improvements in rectum sparing and moderate improvements in bladder sparing against those with two lateral angles. Plans with three optimized angles further improved rectum sparing significantly over those two-angle plans, whereas four-angle plans found no advantage over three-angle plans. A possible three-beam class solution for localized prostate patients was suggested and demonstrated with preserved dosimetric benefits because individually optimized three-angle solutions were found sharing a very similar pattern.
  
  
  CONCLUSIONS
  This study has demonstrated the potential of using an improved beam angle arrangement to better exploit the theoretical dosimetric benefits of proton therapy and provided insights of selecting quality beam angles for localized prostate cancer treatment.
authors.affiliation: Department of Industrial Engineering, University of Houston, Houston, TX 77204, USA. wcao@central.uh.edu.
authors.forename: Wenhua
authors.initials: W
authors.lastname: Cao
authors.affiliation: Department of Industrial Engineering, University of Houston, Houston, TX 77204, USA. ginolim@central.uh.edu.
authors.forename: Gino J
authors.initials: GJ
authors.lastname: Lim
authors.affiliation: Applied Research, Varian Medical Systems, Palo Alto, CA 94304, USA. Yupeng.Li@varian.com.
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. xrzhu@mdanderson.org.
authors.forename: X Ronald
authors.initials: XR
authors.lastname: Zhu
authors.affiliation: Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. xizhang@mdanderson.org.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhang
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