Technical design and concept of a 0.35 T MR-Linac

Abstract

The integration of magnetic resonance (MR) imaging and linear accelerators into hybrid treatment systems has made MR-guided radiation therapy a clinical reality. This work summarizes the technical design of a 0.35 T MR-Linac and corresponding clinical concepts. The system facilitates 3D-conformal as well as IMRT treatments with 6MV photons. Daily MR imaging provides superior soft-tissue contrast for patient setup and also enables on-table adaption of treatment plans, which is fully integrated into the treatment workflow of the system. Automated beam gating during delivery is facilitated by cine MR imaging and structure tracking. Combining different novel features compared to conventional image-guided radiotherapy, this technology offers the potential for margin reduction as well as dose escalation.

Fig. 1

Photograph of the MRIdian Linac system that has been installed at Heidelberg University Hospital in 2017.

Fig. 2

(a) Schematic drawing of the system depicting the main hardware components: superconducting double-donut magnet, circular radiation gantry and patient couch; (b) schematic drawing of the radiation gantry with linac components and MLC. Images courtesy of ViewRay Inc.