Speaker
Description
The focus of this project is on the design of a new, dedicated upright MR
scanner for real-time imaging of patients during proton therapy treatment.
Historically, MR imaging and proton therapy (PT) were done with patients
in a recumbent position. Recently, the concept of performing PT in an upright position has gained interest in the PT community.[1, 2] Although the P3 in-beam MR scanner at the OncoRay in Dresden, Germany, would allow for upright MR integrated PT (MRiPT), its magnet has a narrow air gap between the magnet poles, restricting the degrees of freedom for couch movements with an upright patient positioning device.
In order to facilitate upright rotational MRiPT, it is desirable to widen the gap size from 60 cm to ca. 80 cm such that an average-sized adult patient can be fully rotated around a vertical axis in a seated position. However, simply increasing the distance between the magnetic poles will deteriorate the magnetic field homogeneity and thus impact the geometrical fidelity of the MR images. Hence, a redesign of the magnet is required.
Using the finite element analysis (FEA) software COMSOL, simulations of
the current P3 scanner are modeled and run. Various mesh sizes, shapes, and model geometries are considered. Focus is given to the homogeneity of the magnetic field in the field of view (FOV) region, the Ampere-turns of the coil, and the electromagnetic (EM) forces acting on the coils. Results are confirmed by comparison with values obtained from testing.
Additional models are explored. A scaled-up model of the P3, with every part scaled by a factor of 1.3, is simulated. Another model with an increased gap size but the same coil and magnet head geometry as the P3 is also considered. Results are compared to the P3 simulations. Future work for this project will include simulations of new, unique geometries and coil analysis to identify the ideal coil placement and current density in order to to reduce the amount of coil material and energy (and therefore the weight and cost) required in the next generation scanner.
References
1. Volz, L; Yinxiangzi, S; Durante, M; Graeff, C. Considerations for upright particle therapy patient positioning and associated image guidance. Front Oncol. 2022.
2. Volz, L; Korte, J; Martire, M C; Zhang, Y; Hardcastle, N; Durante, M; Kron, T; Graeff, C. Opportunities and challenges of upright patient positioning in radiotherapy. Phys Med Biol. 2024