title: Compensation method for respiratory motion in proton treatment planning for mobile liver cancer.
abstract: We evaluated the dosimetric effect of a respiration motion, and sought an effective planning strategy to compensate the motion using four-dimensional computed tomography (4D CT) dataset of seven selected liver patients. For each patient, we constructed four different proton plans based on: (1) average (AVG) CT, (2) maximum-intensity projection (MIP) CT, (3) AVG CT with density override of tumor volume (OVR), and (4) AVG CT with field-specific proton margin which was determined by the range difference between AVG and MIP plans (mAVG). The overall effectiveness of each planning strategy was evaluated by calculating the cumulative dose distribution over an entire breathing cycle. We observed clear differences between AVG and MIP CT-based plans, with significant underdosages at expiratory and inspiratory phases, respectively. Only the mAVG planning strategy was fully successful as the field-specific proton margin applied in the planning strategy complemented both the limitations of AVG and MIP CT-based strategies. These results demonstrated that respiration motion induced significant changes in dose distribution of 3D proton plans for mobile liver cancer and the changes can be effectively compensated by applying field-specific proton margin to each proton field.
authors.affiliation: Proton Therapy Center, Research Institute and Hospital, National Cancer Center, Goyang, Korea.
authors.forename: Hojin
authors.initials: H
authors.lastname: Jeong
authors.forename: Se Byeong
authors.initials: SB
authors.lastname: Lee
authors.forename: Seung Hoon
authors.initials: SH
authors.lastname: Yoo
authors.forename: Young Kyung
authors.initials: YK
authors.lastname: Lim
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.forename: Seyjoon
authors.initials: S
authors.lastname: Park
authors.forename: Gyu Young
authors.initials: GY
authors.lastname: Chai
authors.forename: Ki Mun
authors.initials: KM
authors.lastname: Kang
authors.forename: Dongho
authors.initials: D
authors.lastname: Shin
mesh_terms: D016477:Artifacts; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D009038:Motion; D061766:Proton Therapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D011522:Protons
chemical_list: D011522:Protons