Incorporation of treatment plan spatial and temporal dose patterns into a prostate intrafractional motion management strategy Journal Article

   

Authors:	Zhang, P.; Hunt, M.; Happersett, L.; Cox, B.; Mageras, G.
Article Title:	Incorporation of treatment plan spatial and temporal dose patterns into a prostate intrafractional motion management strategy
Abstract:	Purpose: Periodic MVKV radiographs taken during volumetric modulated arc therapy (VMAT) for hypofractionated treatment provide guidance in intrafractional motion management. The choice of imaging frequency and timing are key components in delivering the desired dose while reducing associated overhead such as imaging dose, preparation, and processing time. In this project the authors propose a paradigm with imaging timing and frequency based on the spatial and temporal dose patterns of the treatment plan. Methods: A number of control points are used in treatment planning to model VMAT delivery. For each control point, the sensitivity of individual target or organ-at-risk dose to motion can be calculated as the summation of dose degradations given the organ displacements along a number of possible motion directions. Instead of acquiring radiographs at uniform time intervals, MVKV image pairs are acquired indexed to motion sensitivity. Five prostate patients treated via hypofractionated VMAT are included in this study. Intrafractional prostate motion traces from the database of an electromagnetic tracking system are used to retrospectively simulate the VMAT delivery and motion management. During VMAT delivery simulation patient position is corrected based on the radiographic findings via couch movement if target deviation violates a patient-specific 3D threshold. The violation rate calculated as the percentage of traces failing the clinical dose objectives after motion correction is used to evaluate the efficacy of this approach. Results: Imaging indexed to a 10 s equitime interval and correcting patient position accordingly reduces the violation rate to 19.5 with intervention from 44.5 without intervention. Imaging indexed to the motion sensitivity further reduces the violation rate to 12.1 with the same number of images. To achieve the same 5 violation rate, the imaging incidence can be reduced by 40 by imaging indexed to motion sensitivity instead of time. Conclusions: The simulation results suggest that image scheduling according to the characteristics of the treatment plan can improve the efficiency of intrafractional motion management. Using such a technique, the accuracy of delivered dose during image-guided hypofractionated VMAT treatment can be improved. © 2012 American Association of Physicists in Medicine.
Keywords:	radiation treatment planning; volumetric modulated arc therapy; prostate radiotherapy; radiofrequency tracking; intrafractional motion management
Journal Title:	Medical Physics
Volume:	39
Issue:	9
ISSN:	0094-2405
Publisher:	American Association of Physicists in Medicine
Date Published:	2012-09-01
Start Page:	5429
End Page:	5436
Language:	English
DOI:	10.1118/1.4742846
PROVIDER:	scopus
PUBMED:	22957610
PMCID:	PMC6961698
DOI/URL:	http://www.scopus.com/inward/record.url?eid=2-s2.0-84866102821&partnerID=40&md5=b3ce1a4670f2c88a34d016013af6f68a
Notes:	--- - "Export Date: 1 October 2012" - "CODEN: MPHYA" - "Source: Scopus"

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