Open magnetic resonance imaging using titanium-zirconium needles: improved accuracy for interstitial brachytherapy implants?

Abstract

To evaluate the benefit of using an open magnetic resonance (MR) machine and new MR-compatible needles to improve the accuracy of brachytherapy implants in pelvic tumors. The open MR machine, foreseen for interventional procedures, allows direct visualization of the pelvic structures that are to be implanted. For that purpose, we have developed MR- and CT-compatible titanium-zirconium (Ti-Zr) brachytherapy needles that allow implantations to be carried out under the magnetic field. In order to test the technical feasibility of this new approach, stainless steel (SS) and Ti-Zr needles were first compared in a tissue-equivalent phantom. In a second step, two patients implanted with Ti-Zr needles in the brachytherapy operating room were scanned in the open MR machine. In a third phase, four patients were implanted directly under open MR control. The artifacts induced by both materials were significantly different, strongly favoring the Ti-Zr needles. The implantation in both first patients confirmed the excellent quality of the pictures obtained with the needles in vivo and showed suboptimal implant geometry in both patients. In the next 4 patients, the tumor could be punctured with excellent accuracy, and the adjacent structures could be easily avoided. We conclude that open MR using MR-compatible needles is a very promising tool in brachytherapy, especially for pelvic tumors.