Lung stereotactic body radiotherapy with an MR-linac - Quantifying the impact of the magnetic field and real-time tumor tracking

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• 作者：Martin J. Menten ; ^{martin.menten@icr.ac.uk" class="auth_mail" title="E-mail the corresponding author} ; Martin F. Fast ; Simeon Nill ; Cornelis P. Kamerling ; Fiona McDonald ; Uwe Oelfke ^{uwe.oelfke@icr.ac.uk" class="auth_mail" title="E-mail the corresponding author}
• 关键词：MR-linac ; MR-guided radiotherapy ; Real-time adaptive radiotherapy ; Tumor tracking ; Lung stereotactic body radiotherapy
• 刊名：Radiotherapy and Oncology
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：119
• 期：3
• 页码：461-466
• 全文大小：1070 K

文摘

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 1.5 T 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 1.4 Gy 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 0.3 Gy 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.