title: A proton beam therapy system dedicated to spot-scanning increases accuracy with moving tumors by real-time imaging and gating and reduces equipment size.
abstract: OBJECTIVE
  A proton beam therapy (PBT) system has been designed which dedicates to spot-scanning and has a gating function employing the fluoroscopy-based real-time-imaging of internal fiducial markers near tumors. The dose distribution and treatment time of the newly designed real-time-image gated, spot-scanning proton beam therapy (RGPT) were compared with free-breathing spot-scanning proton beam therapy (FBPT) in a simulation.
  
  
  METHODS
  In-house simulation tools and treatment planning system VQA (Hitachi, Ltd., Japan) were used for estimating the dose distribution and treatment time. Simulations were performed for 48 motion parameters (including 8 respiratory patterns and 6 initial breathing timings) on CT data from two patients, A and B, with hepatocellular carcinoma and with clinical target volumes 14.6 cc and 63.1 cc. The respiratory patterns were derived from the actual trajectory of internal fiducial markers taken in X-ray real-time tumor-tracking radiotherapy (RTRT).
  
  
  RESULTS
  With FBPT, 9/48 motion parameters achieved the criteria of successful delivery for patient A and 0/48 for B. With RGPT 48/48 and 42/48 achieved the criteria. Compared with FBPT, the mean liver dose was smaller with RGPT with statistical significance (p<0.001); it decreased from 27% to 13% and 28% to 23% of the prescribed doses for patients A and B, respectively. The relative lengthening of treatment time to administer 3 Gy (RBE) was estimated to be 1.22 (RGPT/FBPT: 138 s/113 s) and 1.72 (207 s/120 s) for patients A and B, respectively.
  
  
  CONCLUSIONS
  This simulation study demonstrated that the RGPT was able to improve the dose distribution markedly for moving tumors without very large treatment time extension. The proton beam therapy system dedicated to spot-scanning with a gating function for real-time imaging increases accuracy with moving tumors and reduces the physical size, and subsequently the cost of the equipment as well as of the building housing the equipment.
authors.affiliation: Department of Radiation Oncology, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Department of Medical Physics, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Miyamoto
authors.affiliation: Section of Medical Physics, Hokkaido University Hospital Proton Beam Therapy Center, Sapporo, Hokkaido, Japan.
authors.forename: Taeko
authors.initials: T
authors.lastname: Matsuura
authors.affiliation: Hitachi, Ltd., Hitachi Research Laboratory, Omika, Ibaraki, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Fujii
authors.affiliation: Hitachi, Ltd., Hitachi Research Laboratory, Omika, Ibaraki, Japan.
authors.forename: Masumi
authors.initials: M
authors.lastname: Umezawa
authors.affiliation: Division of Quantum Science and Engineering, Hokkaido University Graduate School of Engineering, Sapporo, Hokkaido, Japan.
authors.forename: Kikuo
authors.initials: K
authors.lastname: Umegaki
authors.affiliation: Hitachi, Ltd., Research & Development Group, Omika, Ibaraki, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Hiramoto
authors.affiliation: Department of Radiation Oncology, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000532:radiotherapy*; D057918:Fiducial Markers; D005471:Fluoroscopy; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000532:radiotherapy*; D009068:Movement; D061766:Proton Therapy / Q000295:instrumentation* / Q000592:standards; D011879:Radiotherapy Dosage; D012119:Respiration; D055425:Respiratory-Gated Imaging Techniques; D017356:Synchrotrons; D014057:Tomography, X-Ray Computed
references.citation: Med Phys. 2012 Sep;39(9):5584-91
references.pmid: 22957624
references.citation: Cancer Sci. 2012 Jan;103(1):1-6
references.pmid: 21954991
references.citation: Med Phys. 2009 Sep;36(9):4068-83
references.pmid: 19810479
references.citation: Acta Radiol Suppl. 1983;364:81-8
references.pmid: 6316745
references.citation: Med Phys. 2013 Jul;40(7):071729
references.pmid: 23822433
references.citation: Phys Med Biol. 2013 Dec 7;58(23):8555-72
references.pmid: 24254249
references.citation: Int J Radiat Oncol Biol Phys. 2006 May 1;65(1):1-7
references.pmid: 16618572
references.citation: Lancet. 1999 Apr 17;353(9161):1331-2
references.pmid: 10218540
references.citation: Med Phys. 2010 Jan;37(1):154-63
references.pmid: 20175477
references.citation: Nat Rev Clin Oncol. 2012 Dec;9(12):688-99
references.pmid: 23165124
references.citation: Phys Med Biol. 2008 Apr 7;53(7):1947-59
references.pmid: 18364549
references.citation: Int J Radiat Oncol Biol Phys. 2002 Jul 15;53(4):822-34
references.pmid: 12095547
references.citation: Radiat Oncol. 2013 Mar 05;8:48
references.pmid: 23497543
references.citation: Int J Radiat Oncol Biol Phys. 2006 Mar 15;64(4):1229-36
references.pmid: 16504762
references.citation: Med Phys. 2010 Feb;37(2):449-60
references.pmid: 20229853
references.citation: Phys Med Biol. 2010 Dec 21;55(24):7633-47
references.pmid: 21113089