title: Evaluation of the radiobiological gamma index with motion interplay in tangential IMRT breast treatment.
abstract: The purpose of this study was to evaluate the impact of the motion interplay effect in early-stage left-sided breast cancer intensity-modulated radiation therapy (IMRT), incorporating the radiobiological gamma index (RGI). The IMRT dosimetry for various breathing amplitudes and cycles was investigated in 10 patients. The predicted dose was calculated using the convolution of segmented measured doses. The physical gamma index (PGI) of the planning target volume (PTV) and the organs at risk (OAR) was calculated by comparing the original with the predicted dose distributions. The RGI was calculated from the PGI using the tumor control probability (TCP) and the normal tissue complication probability (NTCP). The predicted mean dose and the generalized equivalent uniform dose (gEUD) to the target with various breathing amplitudes were lower than the original dose (P < 0.01). The predicted mean dose and gEUD to the OARs with motion were higher than for the original dose to the OARs (P < 0.01). However, the predicted data did not differ significantly between the various breathing cycles for either the PTV or the OARs. The mean RGI gamma passing rate for the PTV was higher than that for the PGI (P < 0.01), and for OARs, the RGI values were higher than those for the PGI (P < 0.01). The gamma passing rates of the RGI for the target and the OARs other than the contralateral lung differed significantly from those of the PGI under organ motion. Provided an NTCP value <0.05 is considered acceptable, it may be possible, by taking breathing motion into consideration, to escalate the dose to achieve the PTV coverage without compromising the TCP.
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan sumida@radonc.med.osaka-u.ac.jp.
authors.forename: Iori
authors.initials: I
authors.lastname: Sumida
authors.affiliation: Department of Radiation Oncology, NTT West Osaka Hospital, 2-6-40 Karasugatsuji, Tennoji-ku, Osaka 543-8922, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Yamaguchi
authors.affiliation: Department of Radiation Oncology, New York University Medical Center, 160 E, 34th Street, New York, NY 10016, USA.
authors.forename: Indra J
authors.initials: IJ
authors.lastname: Das
authors.affiliation: Department of Radiation Oncology, NTT West Osaka Hospital, 2-6-40 Karasugatsuji, Tennoji-ku, Osaka 543-8922, Japan.
authors.forename: Hisao
authors.initials: H
authors.lastname: Kizaki
authors.affiliation: Department of Radiation Oncology, NTT West Osaka Hospital, 2-6-40 Karasugatsuji, Tennoji-ku, Osaka 543-8922, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Aboshi
authors.affiliation: Department of Radiation Oncology, NTT West Osaka Hospital, 2-6-40 Karasugatsuji, Tennoji-ku, Osaka 543-8922, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Tsujii
authors.affiliation: Department of Radiation Oncology, NTT West Osaka Hospital, 2-6-40 Karasugatsuji, Tennoji-ku, Osaka 543-8922, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamada
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Kiesuke
authors.initials: K
authors.lastname: Tamari
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Suzuki
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Seo
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Isohashi
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yoshioka
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ogawa
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008168:Lung / Q000528:radiation effects; D009038:Motion; D011785:Quality Assurance, Health Care; D011829:Radiation Dosage; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D015203:Reproducibility of Results; D012119:Respiration
keywords: IMRT; dose prediction; quality assurance; radiobiological gamma index