Objec0ve: Superparamagne0c nanopar0cles (SPIONs) can be combined with tumor chemoemboliza-0on agents to form magne0c drug-elu0ng beads (MDEBs), which are navigated magne0cally in the MRI scanner through the vascular system. We aim to develop a method to accurately quan0fy and localize these par0cles and to validate the method in phantoms and swine models. Meth-ods: MDEBs were made of Fe3O4 SPIONs. Aaer injected known numbers of MDEBs, suscep0bility ar0facts in three-dimensional (3D) volumetric interpolated breath-hold ex-amina0on (VIBE) sequences were acquired in glass and Polyvinyl alcohol (PVA) phantoms, and two living swine. Image processing of VIBE images provided the volume rela0onship between MDEBs and their ar0fact at different VIBE acquisi0ons and post-processing parameters. Sim-ulated hepa0c-artery emboliza0on was performed in vivo with an MRI-condi0onal magne0c-injec0on system, using the volume rela0onship to locate and quan0fy MDEB distri-bu0on. Results: Individual MDEBs were spa0ally identified, and their ar0facts quan0fied, showing no correla0on with magne0c-field orienta0on or sequence bandwidth, but ex-hibi0ng a rela0onship with echo 0me and providing a lin-ear volume rela0onship. Two MDEB aggregates were mag-ne0cally steered into desired liver regions while the other 19 had no steering, and 25 aggregates were injected into another swine without steering. The MDEBs were spa0ally iden0fied and the volume rela0onship showed accuracy in assessing the number of the MDEBs, with small errors (≤ 8.8%). Conclusion and Significance: MDEBs were able to be steered into desired body regions and then localized using 3D VIBE sequences. The resul0ng volume rela0onship was linear, robust, and allowed for quan0ta0ve analysis of the MDEB distribu0on.
Introduction Magnetic resonance navigation (MRN) uses MRI gradients to steer magnetic drug-eluting beads (MDEBs) across vascular bifurcations. We aim to experimentally verify our theoretical forces balance model (gravitational, thrust, friction, buoyant and gradient steering forces) to improve the MRN targeted success rate. Method A single-bifurcation phantom (3 mm inner diameter) made of poly-vinyl alcohol was connected to a cardiac pump at 0.8 mL/s, 60 beats/minutes with a glycerol solution to reproduce the viscosity of blood. MDEB aggregates (25 6 6 particles, 200 lm) were released into the main branch through a 5F catheter. The phantom was tilted horizontally from 2 10 to +25 to evaluate the MRN performance. Results The gravitational force was equivalent to 71.85 mT/m in a 3T MRI. The gradient duration and amplitude had a power relationship (amplitude=78.717 ðdurationÞ À0:525 ). It was possible, in 15 elevated vascular branches, to steer 87% of injected aggregates if two MRI gradients are simultaneously activated (G x = +26.5 mT/m, G y = +18 mT/m for 57% duty cycle), the flow velocity was minimized to 8 cm/s and a residual pulsatile flow to minimize the force of friction. Conclusion Our experimental model can determine the maximum elevation angle MRN can perform in a single-bifurcation phantom simulating in vivo conditions.
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