title: Optimal beam design on intensity-modulated radiation therapy with simultaneous integrated boost in nasopharyngeal cancer.
abstract: This study aims to determine the optimal beam design among various combinations of field numbers and beam trajectories for intensity-modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB) technique for the treatment of nasopharyngeal cancer (NPC). We used 10 fields with gantry angles of 155°, 130°, 75°, 25°, 0° L, 0° R, 335°, 285°, 230°, and 205° denoted as F10. To decrease doses in the spinal cord, the F10 technique was designed by featuring 2 pairs of split-opposed beam fields at 155° to 335° and 205° to 25°, as well as one pair of manually split beam fields at 0°. The F10 technique was compared with 4 other common field arrangements: F7E, 7 fields with 50° equally spaced gantry angles; F7, the basis of F10 with 155°, 130°, 75°, 0°, 285°, 230°, and 205°; F9E, 9 fields with 40° equally spaced gantry angles; and FP, 7 posterior fields with 180°, 150°, 120°, 90°, 270°, 240°, and 210°. For each individual case of 10 patients, the customized constraints derived after optimization with the standard F10 technique were applied to 4 other field arrangements. The 4 new optimized plans of each individual case were normalized to achieve the same coverage of planning target volume (PTV)63Gy as that of the standard F10 technique. The F10 field arrangement exhibited the best coverage in PTV70Gy and the least mean dose in the trachea-esophagus region. Furthermore, the F10 field arrangement demonstrated the highest level of conformity in the low-dose region and the least monitor unit. The F10 field arrangement performed more outstandingly than the other field arrangements in PTV70Gy coverage and spared the central organ. This arrangement also exhibited the highest conformity and delivery efficiency. The F10 technique is recommended as the standard beam geometry for the SIB-IMRT of NPC.
authors.affiliation: Division of Radiation Oncology, Department of Oncology Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Mei-Chun
authors.initials: MC
authors.lastname: Cheng
authors.affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Hu
authors.affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Ching-Sheng
authors.initials: CS
authors.lastname: Liu
authors.affiliation: Division of Radiation Oncology, Department of Oncology Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Jeun-Shenn
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Pin-I
authors.initials: PI
authors.lastname: Huang
authors.affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Sang-Hue
authors.initials: SH
authors.lastname: Yen
authors.affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Yuh-Lin
authors.initials: YL
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan.
authors.forename: Chun-Mei
authors.initials: CM
authors.lastname: Hsieh
authors.affiliation: Department of Radiation Oncology, Taichung Veterans General Hospital, Taichung, Taiwan. Electronic address: cyshiau@vghtpe.gov.tw.
authors.forename: Cheng-Ying
authors.initials: CY
authors.lastname: Shiau
mesh_terms: D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
keywords: Beam design; Intensity-modulated radiation therapy (IMRT); Nasopharyngeal cancer (NPC); Simultaneous integrated boost (SIB)