Lung stereotactic body radiotherapy with an MR-linac - Quantifying the impact of the magnetic field and real-time tumor tracking.
Abstract
BACKGROUND AND PURPOSE: There are concerns that radiotherapy doses delivered in a magnetic field might be distorted due to the Lorentz force deflecting secondary electrons. This study investigates this effect on lung stereotactic body radiotherapy (SBRT) treatments, conducted either with or without multileaf collimator (MLC) tumor tracking. MATERIAL AND METHODS: Lung SBRT treatments with an MR-linac were simulated for nine patients. Two different treatment techniques were compared: conventional, non-tracked deliveries and deliveries with real-time MLC tumor tracking, each conducted either with or without a 1.5T magnetic field. RESULTS: Slight dose distortions at air-tissue-interfaces were observed in the presence of the magnetic field. Most prominently, the dose to 2% of the skin increased by 1.4Gy on average. Regardless of the presence of the magnetic field, MLC tracking was able to spare healthy tissue, for example by decreasing the mean lung dose by 0.3Gy on average, while maintaining the target dose. CONCLUSIONS: Accounting for the magnetic field during treatment plan optimization allowed for design and delivery of clinically acceptable lung SBRT treatments with an MR-linac. Furthermore, the ability of MLC tumor tracking to decrease dose exposure of healthy tissue, was not inhibited by the magnetic field.
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http://dx.doi.org/10.1016/j.radonc.2016.04.019Collections
Subject
Humans
Lung Neoplasms
Magnetic Resonance Imaging
Radiosurgery
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Electrons
Particle Accelerators
Aged
Aged, 80 and over
Female
Male
Magnetic Fields
Research team
Radiotherapy Physics Modelling
Language
eng
Date accepted
2016-04-11
License start date
2016-06
Citation
Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, 2016, 119 (3), pp. 461 - 466
Publisher
ELSEVIER IRELAND LTD