Effect of Anatomic Changes on Pencil Beam Scanned Proton Dose Distributions for Cranial and Extracranial Tumors

详细信息    查看全文

• 作者：Lorenzo Placidi ; MSc^&lowast ; ; ^{lorenzo.placidi@psi.ch} ; Alessandra Bolsi ; MSc^&lowast ; ; Antony J. Lomax ; PhD^&lowast ; ; ^&dagger ; ; Ralf A. Schneider ; MD^&lowast ; ; Robert Malyapa ; MD ; PhD^&Dagger ; ; Damien C. Weber ; MD ; PhD^&lowast ; ; ^§ ; ; ^‖ ; Francesca Albertini ; PhD^&lowast ;
• 刊名：International Journal of Radiation Oncology*Biology*Physics
• 出版年：2017
• 出版时间：1 March 2017
• 年：2017
• 卷：97
• 期：3
• 页码：616-623
• 全文大小：1394 K
• 卷排序：97

文摘

To estimate the frequency and impact of anatomic changes on the delivered dose in pencil beam scanning proton therapy, to assess the need for repeat CT scanning and adaptive replanning.Methods and MaterialsA total of 730 patients treated at Paul Scherrer Institut between 2007 and 2014 were included in this study, for which the number of patients who had control CT scans and who were replanned as a result of anatomic changes was analyzed. For those that were replanned, the nominal dose distributions (originally optimized on the planning CT scan) were recalculated on the replanning CT scan and differences evaluated using standard dose metrics for planning target volumes and clinical target volumes and organs at risk (OARs).ResultsControl CT studies were acquired for 244 patients (33.5%), and replanning was deemed clinically necessary for 40 (16%) of these (5.5% of the total cohort). The OARs and target dose differences between the nominal and recalculated dose distributions were found to be strongly dependent on the subgroup of patients. Nevertheless, dose differences were found to be ≤ 5% for 88% of all analyzed OARs, and planning target volume/clinical target volume V95% was reduced by ≤5% in 87%/90% of cases.ConclusionsDespite anatomic variations, clinically delivered plans have been found to be robust to anatomic changes, with replanning being deemed necessary in only a small number of cases. However, because the dosimetric effect of such changes can be quite large for some cases, they have to be monitored and evaluated on an individual basis.