Dose enhancement in radiotherapy of small lung tumors using inline magnetic fields: A Monte Carlo based planning study

Abstract

Monte Carlo methods have described significant and predictable dose enhancement effects in small lung tumor plans for 6 MV radiotherapy when an external inline magnetic field is included. Results of this study indicate that future clinical inline MRI-guided radiotherapy systems will be able to deliver a dosimetrically superior treatment to small (PTV < 15 cm(3)), isolated lung tumors over non-MRI-Linac systems. This increased efficacy coincides with the reimbursement in the United States of lung CT screening and the likely rapid growth in the number of patients with small lung tumors to be treated with radiotherapy.

Planning feasibility of extremely hypofractionated prostate radiotherapy on a 1.5 T magnetic resonance imaging guided linear accelerator

“…Our findings are in line with studies investigating this effect in conventional or moderately hypofractionated prostate radiotherapy [35][36][37]. Also for other tumor sites, as lung, (partial) breast, rectum and pancreas, the influence of the magnetic field has been evaluated and resulted in small dose differences and clinically acceptable plans [34,35,[38][39][40][41][42][43].…”

Experimental characterization of magnetically focused electron contamination at the surface of a high‐field inline MRI‐linac

“…The Australian MRI‐linac is currently setup as an inline system. This configuration has the advantages of penumbral trimming and enhanced dose to lung tumors compared to without a magnetic field. However, this orientation can lead to higher dose to the patient surface due to the magnet’s fringe field .…”

Technical Note: Experimental results from a prototype high‐field inline MRI‐linac

“…In low density medium such as lung, the penumbral flaring that occurs due to electron disequilibrium will be reduced by the forward focusing. While there is no simple quantification of this effect, it is significant enough to have an impact on target coverage and has been shown using Monte Carlo methods to provide a significant dose enhancement effect 14 which warrants further investigation. In future work, we will replace the 1.5 T magnet with a specially designed 1.0 T split bore magnet to allow the construction of a fully integrated second prototype and extend these preliminary findings.…”