title: Analysis of inter- and intra fractional partial bladder wall movement using implanted fiducial markers.
abstract: BACKGROUND
  Current adaptive and dose escalating radiotherapy for muscle invasive bladder cancer requires knowledge of both inter-fractional and intra-fractional motion of the bladder wall involved. The purpose of this study is to characterize inter- and intra-fractional movement of the partial bladder wall using implanted fiducial markers and a real-time tumor-tracking radiotherapy system.
  
  
  METHODS
  Two hundred fifty one sessions with 29 patients were analysed. After maximal transurethral bladder tumor resection and 40 Gy of whole bladder irradiation, up to six gold markers were implanted transurethrally into the bladder wall around the tumor bed and used for positional registration. We compared the systematic and random uncertainty of positions between cranial vs. caudal, left vs. right, and anterior vs. posterior tumor groups. The variance in intrafractional movement and the percentage of sessions where 3 mm and 5 mm or more of intrafractional wall movement occurring at 2, 4, 6, 8, 10, and at more than 10 min until the end of a session were determined.
  
  
  RESULTS
  The cranial and anterior tumor group showed larger interfractional uncertainties in the position than the opposite side tumor group in the CC and AP directions respectively, but these differences did not reach significance. Among the intrafractional uncertainty of position, the cranial and anterior tumor group showed significantly larger systematic uncertainty of position than the groups on the opposite side in the CC direction. The variance of intrafractional movement increased over time; the percentage of sessions where intrafractional wall movement was larger than 3 mm within 2 min of the start of a radiation session or larger than 5 mm within 10 min was less than 5%, but this percentage was increasing further during the session, especially in the cranial and anterior tumor group.
  
  
  CONCLUSIONS
  More attention for intrafractional uncertainty of position is required in the treatment of cranial and anterior bladder tumors especially in the CC direction. The optimal internal margins in each direction should be chosen or a precise intrafractional target localization system is required depending on the tumor location and treatment delivery time in the setting of partial bladder radiotherapy.
authors.affiliation: Department of Radiation Oncology, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Nishioka
authors.affiliation: Department of Radiation Oncology, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan. sshing@med.hokudai.ac.jp.|Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan. sshing@med.hokudai.ac.jp.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Department of Renal and Genitourinary Surgery, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Shinohara
authors.affiliation: Department of Biostatistics, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Yoichi M
authors.initials: YM
authors.lastname: Ito
authors.affiliation: Department of Renal and Genitourinary Surgery, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.
authors.forename: Takashige
authors.initials: T
authors.lastname: Abe
authors.affiliation: Department of Renal and Genitourinary Surgery, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Maruyama
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Katoh
authors.affiliation: Department of Radiation Oncology, Hokkaido University Hospital, Sapporo, Japan.
authors.forename: Rumiko
authors.initials: R
authors.lastname: Kinoshita
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hashimoto
authors.affiliation: Department of Medical Physics, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Miyamoto
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.
authors.forename: Rikiya
authors.initials: R
authors.lastname: Onimaru
authors.affiliation: Department of Radiation Medicine, Hokkaido University Graduate School of Medicine / School of Medicine, Sapporo, Japan.|Global Station for Quantum Medical Science and Engineering, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, Sapporo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D057918:Fiducial Markers; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D009367:Neoplasm Staging; D011379:Prognosis; D019736:Prostheses and Implants; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D035501:Uncertainty; D001749:Urinary Bladder Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy
keywords: Bladder cancer; Interfractional uncertainty of position; Intrafractional uncertainty of position; Real-time tumor tracking system