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Marvellous magnet

If you’ve read the latest Talking Point article on medicalphysicsweb, you’ll have heard how - according to some - MR guidance during radiotherapy could be one of the next big developments in radiation treatment.

Among those currently working on this challenge is Bas Raaymakers of the University Medical Center Utrecht in the Netherlands. I went along to the poster session to talk to Raaymakers about the project’s progress.

The Utrecht team is developing a 6 MV radiotherapy accelerator with an integrated 1.5T MRI functionality. The ultimate goal: real-time, soft-tissue-based image guidance during delivery.

"This started as a system for better position verification, but on the way we realised that if you have this high soft-tissue contrast you can go a step further," Raaymakers told me. He explained that MR guidance during treatment would enable better avoidance of critical structures, and that using such a system to deliver tumour ablation and then treat microscopic infiltrations could "potentially compete with surgery".

According to Raaymakers, it’s the design of the MR magnet that’s critical to this system working. It’s adjusted to have an area of low magnetic field close to the magnet itself. Placing the linac in this low-field region then minimizes the magnetic interference. In addition, all of the magnet components are moved to the edges, leaving an ‘empty’ area through which the beam can travel with minimal absorption.

The magnet is arriving in October of this year, and a prototype system should be operational in January 2009. The initial prototype will be static with the linac mounted in a fixed position next to the magnet. Ultimately, the system will have the accelerator rotating around the MRI.

"We plan to start simple, and see if we can improve position verification and reduce margins," Raaymakers told me. "In the end, we should be able to image continuously during treatment and track the tumour motion with dynamic MRI."
 

Posted by Tami Freeman on July 28, 2008 5:27 PM | Permalink