Impact of respiratory motion on variable relative biological effectiveness in 4D-dose distributions of proton therapy.
Background:Organ motion during radiation therapy with scanned protons leads to deviations between the planned and the delivered physical dose. Using a constant relative biological effectiveness (RBE) of 1.1 linearly maps these deviations into RBE-weighted dose. However, a constant value cannot accou...
| Published in: | Acta Oncologica Vol. 56; no. 11; pp. 1420 - 1428 |
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| Main Authors: | , , , , |
| Format: | diagnostic images equations & formulas research tables/charts Journal Article |
| Published: |
Medical Journals Sweden AB
Nov2017
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| Online Access: | View this record in EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=ccm&AN=126287897&site=ehost-live header: @attributes: shortDbName: ccm uiTerm: 126287897 longDbName: CINAHL Complete uiTag: AN controlInfo: bkinfo: dissinfo: jinfo: jid: 0284186X B84 jtl: Acta Oncologica issn: 0284186X maglogo: N pubinfo: dt: Nov2017 vid: 56 iid: 11 pid: 59195 pub: Medical Journals Sweden AB artinfo: ui: 126287897 126287897 126287897 10.1080/0284186X.2017.1354131 126287897 ppf: 1420 ppct: 8 formats: tig: atl: Impact of respiratory motion on variable relative biological effectiveness in 4D-dose distributions of proton therapy. aug: au: Ulrich, Silke Wieser, Hans-Peter Cao, Wenhua Mohan, Radhe Bangert, Mark affil: Department of Medical Physics in Radiation Therapy, German Cancer Research Center (DKFZ), Heidelberg, Germany; sug: subj: Proton Therapy Methods Radiation Dosage Respiration Human Radiation Monitoring Liver Neoplasms Cancer Patients Linear Regression ab: Background:Organ motion during radiation therapy with scanned protons leads to deviations between the planned and the delivered physical dose. Using a constant relative biological effectiveness (RBE) of 1.1 linearly maps these deviations into RBE-weighted dose. However, a constant value cannot account for potential nonlinear variations in RBE suggested by variable RBE models. Here, we study the impact of motion on recalculations of RBE-weighted dose distributions using a phenomenological variable RBE model. Material and methods:4D-dose calculation including variable RBE was implemented in the open source treatment planning toolkit matRad. Four scenarios were compared for one field and two field proton treatments for a liver cancer patient assuming (α∕β)x = 2 Gy and (α∕β)x = 10 Gy: (A) the optimized static dose distribution with constant RBE, (B) a static recalculation with variable RBE, (C) a 4D-dose recalculation with constant RBE and (D) a 4D-dose recalculation with variable RBE. For (B) and (D), the variable RBE was calculated by the model proposed by McNamara. For (C), the physical dose was accumulated with direct dose mapping; for (D), dose-weighted radio-sensitivity parameters of the linear quadratic model were accumulated to model synergistic irradiation effects on RBE. Results:Dose recalculation with variable RBE led to an elevated biological dose at the end of the proton field, while 4D-dose recalculation exhibited random deviations everywhere in the radiation field depending on the interplay of beam delivery and organ motion. For a single beam treatment assuming (α∕β)x = 2 Gy, D95%was 1.98 Gy (RBE) (A), 2.15 Gy (RBE) (B), 1.81 Gy (RBE) (C) and 1.98 Gy (RBE) (D). The homogeneity index was 1.04 (A), 1.08 (B), 1.23 (C) and 1.25 (D). Conclusion:For the studied liver case, intrafractional motion did not reduce the modulation of the RBE-weighted dose postulated by variable RBE models for proton treatments. pubtype: Academic Journal doctype: diagnostic images equations & formulas research tables/charts Journal Article ougenre: Article language: English refInfo: holdings: @attributes: islocal: N |
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