Open AccessChanges in Rectal Dose Due to Alterations in Beam Angles for Setup Uncertainty and Range Uncertainty in Carbon-Ion Radiotherapy for Prostate Cancer
Author(s) -
Yoshiki Kubota,
Hidemasa Kawamura,
Makoto Sakai,
Ryou Tsumuraya,
Mitsuru Tashiro,
K. Yusa,
Nobuteru Kubo,
Hiro Sato,
Masahiro Kawahara,
Hiroyuki Katoh,
Tatsuaki Kanai,
Tatsuya Ohno,
Takashi Nakano
Publication year - 2016
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0153894
Subject(s) - prostate cancer , carbon ion radiotherapy , range (aeronautics) , radiation therapy , physics , beam (structure) , prostate , ion beam , medicine , nuclear medicine , optics , cancer , materials science , composite material
Background and Purpose Carbon-ion radiotherapy of prostate cancer is challenging in patients with metal implants in one or both hips. Problems can be circumvented by using fields at oblique angles. To evaluate the influence of setup and range uncertainties accompanying oblique field angles, we calculated rectal dose changes with oblique orthogonal field angles, using a device with fixed fields at 0° and 90° and a rotating patient couch. Material and Methods Dose distributions were calculated at the standard angles of 0° and 90°, and then at 30° and 60°. Setup uncertainty was simulated with changes from −2 mm to +2 mm for fields in the anterior-posterior, left-right, and cranial-caudal directions, and dose changes from range uncertainty were calculated with a 1 mm water-equivalent path length added to the target isocenter in each angle. The dose distributions regarding the passive irradiation method were calculated using the K2 dose algorithm. Results The rectal volumes with 0°, 30°, 60°, and 90° field angles at 95% of the prescription dose were 3.4±0.9 cm 3 , 2.8±1.1 cm 3 , 2.2±0.8 cm 3 , and 3.8±1.1 cm 3 , respectively. As compared with 90° fields, 30° and 60° fields had significant advantages regarding setup uncertainty and significant disadvantages regarding range uncertainty, but were not significantly different from the 90° field setup and range uncertainties. Conclusions The setup and range uncertainties calculated at 30° and 60° field angles were not associated with a significant change in rectal dose relative to those at 90°.