title: [Impact of setup error and anatomical change on dose distribution during conventional radiation therapy].
abstract: The purpose of this study was to evaluate the impact of setup error and anatomical change on dose distribution during conventional radiation therapy. We performed regional irradiation (Plan1) using opposing pair fields, and then we planned local irradiation (Plan2) with a computed tomography (CT) acquired at that time in 10 patients with advanced oral cancer. To consider the setup error, a minimum dose of gross tumor volume (GTV) and a maximum dose for the spinal cord were re-calculated with isocenter shifts of ±5 mm. We also evaluated an alteration of reference dose due to anatomical changes during radiation therapy. A minimum dose of GTV was decreased with isocenter shifts; the trend was stronger in Plan2 than Plan1 (-5.7% vs. -1.2%, p=0.02). Similarly, a maximum dose of spinal cord was increased with isocenter shifts, especially in Plan2 (12.2% vs. 0.5%, p<0.01). Anatomical changes during radiation therapy were observed in all patients, and the mean difference for depth was -4 mm in Plan1; the reference dose was increased in Plan1 and Plan2. Precise setup is necessary, especially for local irradiation in spite of anatomical changes during radiation therapy. Reimaging and replanning are recommended for patients with marked anatomical changes.
authors.affiliation: Division of Radiology, Department of Medical Technology, Kyushu University Hospital.
authors.forename: Naoko
authors.initials: N
authors.lastname: Tsujita
authors.forename: Saki
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Ryuji
authors.initials: R
authors.lastname: Murakami
authors.forename: Takafumi
authors.initials: T
authors.lastname: Hattori
authors.forename: Masato
authors.initials: M
authors.lastname: Maruyama
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakaguchi
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Kakei
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Saito
authors.forename: Keiko
authors.initials: K
authors.lastname: Teshima
mesh_terms: D001823:Body Composition; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy; D006801:Humans; D009062:Mouth Neoplasms / Q000532:radiotherapy; D058958:Organs at Risk; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000009:adverse effects / Q000379:methods*; D061106:Radiotherapy Setup Errors; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013116:Spinal Cord / Q000528:radiation effects