title: Robust plan optimization using edge-enhanced intensity for intrafraction organ deformation in prostate intensity-modulated radiation therapy.
abstract: This study evaluated a method for prostate intensity-modulated radiation therapy (IMRT) based on edge-enhanced (EE) intensity in the presence of intrafraction organ deformation using the data of 37 patients treated with step-and-shoot IMRT. On the assumption that the patient setup error was already accounted for by image guidance, only organ deformation over the treatment course was considered. Once the clinical target volume (CTV), rectum, and bladder were delineated and assigned dose constraints for dose optimization, each voxel in the CTV derived from the DICOM RT-dose grid could have a stochastic dose from the different voxel location according to the probability density function as an organ deformation. The stochastic dose for the CTV was calculated as the mean dose at the location through changing the voxel location randomly 1000 times. In the EE approach, the underdose region in the CTV was delineated and optimized with higher dose constraints that resulted in an edge-enhanced intensity beam to the CTV. This was compared to a planning target volume (PTV) margin (PM) approach in which a CTV to PTV margin equivalent to the magnitude of organ deformation was added to obtain an optimized dose distribution. The total monitor units, number of segments, and conformity index were compared between the two approaches, and the dose based on the organ deformation of the CTV, rectum, and bladder was evaluated. The total monitor units, number of segments, and conformity index were significantly lower with the EE approach than with the PM approach, while maintaining the dose coverage to the CTV with organ deformation. The dose to the rectum and bladder were significantly reduced in the EE approach compared with the PM approach. We conclude that the EE approach is superior to the PM with regard to intrafraction organ deformation.
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Iori
authors.identifier: http://orcid.org/0000-0001-7669-0325
authors.initials: I
authors.lastname: Sumida
authors.affiliation: Department of Radiation Oncology, NTT West Osaka hospital, Tennoji-ku, Osaka, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Yamaguchi
authors.affiliation: Department of Radiation Oncology, New York University Langone Medical Center, New York, New York, United States of America.
authors.forename: Indra J
authors.initials: IJ
authors.lastname: Das
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Anetai
authors.affiliation: Department of Radiation Oncology, NTT West Osaka hospital, Tennoji-ku, Osaka, Japan.
authors.forename: Hisao
authors.initials: H
authors.lastname: Kizaki
authors.affiliation: Department of Radiation Oncology, NTT West Osaka hospital, Tennoji-ku, Osaka, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Aboshi
authors.affiliation: Department of Radiation Oncology, NTT West Osaka hospital, Tennoji-ku, Osaka, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Tsujii
authors.affiliation: Department of Radiation Oncology, NTT West Osaka hospital, Tennoji-ku, Osaka, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamada
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Tamari
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Seo
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Isohashi
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yoshioka
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ogawa
mesh_terms: D006801:Humans; D008297:Male; D011467:Prostate / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000473:pathology; D001743:Urinary Bladder / Q000473:pathology