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Abstract
Purpose Using real-time MRI for solid organ embolization provides physiologic and structural information. Current embolization under x-ray guidance only visualizes the vessels and lacks a quantifiable endpoint, which could be overcome by using MRI. The purpose of this study was to use a magnetically assisted remote controlled (MARC) catheter under real-time endovascular MRI to navigate into the renal arteries, embolize with gadolinium (Gd) impregnated microspheres, and measure the reduction in flow.
Method and materials The catheter device was constructed using 4.1Fr custom copper braided catheter (Penumbra Inc., Alameda, CA) with copper wires in the wall connected to a laser-lithographed saddle coil at the distal tip (Figure 1). The copper wires were connected to an in-room MRI compatible cart via an SFTP cable. A foot pedal actuator was used to deliver ± 450mA to deflect the catheter. In vivo navigation was tested in four farm pigs (40–45 kg). The renal arteries were catheterized under a real-time b-SSFP sequence at 1.5T. Embolization was visualized under a real-time contrast enhanced angiographic sequence. Renal artery blood flow rates were assessed with ECG gated velocity-encoded MR imaging before and after embolization with Gd-impregnated microspheres (100–300 μm). Workflow is diagrammed in Figure 2. Statistical analysis was performed and data were presented as mean ± SD.
Results The catheter tip was clearly visible under MRI guidance. Three (75%) out of four renal arteries were successfully catheterized. Overall mean catheterization time was (956 s). The MR signal from the Gd-impregnated spheres was observed under real-time MRI (Figure 3). Flow rate was significantly different (P = 0.025) between pre and post embolization (2.20 ± 0.20 vs. 0.14 ± 0.03 mL/min/kg), accounting for a 94 percent reduction in flow.
A) Schematic of the MARC catheter architecture. B) Profile view of copper traces. C) Coil pattern on alumina tip
XMR suite workflow
Conclusion Using a MARC catheter for renal artery catheterization and embolization under real-time MRI is feasible. The MARC catheter system provides a novel opportunity to perform endovascular procedures in interventional MRI environment. Future work will focus on developing more flexible catheters that can be used for head, neck, and brain embolization applications.
A) Navigation in Aorta with catheter tip inferior to renal artery orgin. B) Navigation into origin of left renal artery. C) Embolization at 600 s
Disclosures S. Hetts: 1; C; NIH-NIBIB, NIH-NCI, Penumbra, Siemens, Stryker, MicroVention Terumo. 2; C; Stryker, Penumbra, Silk Road Medical, Medina Medical. 4; C; Medina Medical. 5; C; UCSF. A. Losey: None. P. Lillaney: None. D. Cooke: None. B. Thorne: None. J. Yang: None. L. Sze: None. L. Do: None. A. Martin: None. M. Saeed: None. M. Wilson: None.