Magnetic Resonance Navigation of a Bead Inside a Three-Bifurcation PMMA Phantom Using an Imaging Gradient Coil Insert

This paper reports the successful navigation of a 1-mm Chrome-Steel bead along three consecutive polymethyl methacrylate channels inside the bore of a 1.5-T magnetic resonance imaging (MRI) scanner. The bead traveled at a mean velocity of 14 cm·s-1. This was accomplished using an imaging gradient coil (IGC) insert located inside the MRI tube. While targeting one side of a bifurcation has been previously demonstrated using unidirectional gradient coils, this is the first time that magnetic resonance navigation (MRN) of a bead along consecutive channels is reported. Experimental results confirm that a clinical regular MRI can be used to propel a 1-mm device. In addition, when used at maximum power, IGC temperature rise becomes a serious issue that can ultimately damage the insert and limit the overall performance. Consequently, this paper aims to give some insight into coil temperature management for IGC-assisted procedures. A 33-min thermal stress test was carried out using 100% of the IGC power. Steady-state oscillation can be reached by interleaving propulsion periods with cooling periods, thus enabling longer propulsion procedures. Experimental data showed that the cooling time can be used for imaging purposes with no performance loss, thus enabling MRN-assisted procedures with multiplexed particle distribution assessment.