Real-time 3T MRI-guided cardiovascular catheterization in a porcine model using a glass-fiber epoxy-based guidewire

Abstract

Purpose: Real-time magnetic resonance imaging (MRI) is a promising alternative to X-ray fluoroscopy for guiding cardiovascular catheterization procedures. Major challenges, however, include the lack of guidewires that are compatible with the MRI environment, not susceptible to radiofrequency-induced heating, and reliably visualized. Preclinical evaluation of new guidewire designs has been conducted at 1.5T. Here we further evaluate the safety (device heating), device visualization, and procedural feasibility of 3T MRI-guided cardiovascular catheterization using a novel MRI-visible glass-fiber epoxy-based guidewire in phantoms and porcine models.

Methods: To evaluate device safety, guidewire tip heating (GTH) was measured in phantom experiments with different combinations of catheters and guidewires. In vivo cardiovascular catheterization procedures were performed in both healthy (N = 5) and infarcted (N = 5) porcine models under real-time 3T MRI guidance using a glass-fiber epoxy-based guidewire. The times for each procedural step were recorded separately. Guidewire visualization was assessed by measuring the dimensions of the guidewire-induced signal void and contrast-to-noise ratio (CNR) between the guidewire tip signal void and the blood signal in real-time gradient-echo MRI (specific absorption rate [SAR] = 0.04 W/kg).

Results: In the phantom experiments, GTH did not exceed 0.35°C when using the real-time gradient-echo sequence (SAR = 0.04 W/kg), demonstrating the safety of the glass-fiber epoxy-based guidewire at 3T. The catheter was successfully placed in the left ventricle (LV) under real-time MRI for all five healthy subjects and three out of five infarcted subjects. Signal void dimensions and CNR values showed consistent visualization of the glass-fiber epoxy-based guidewire in real-time MRI. The average time (minutes:seconds) for the catheterization procedure in all subjects was 4:32, although the procedure time varied depending on the subject's specific anatomy (standard deviation = 4:41).

Conclusions: Real-time 3T MRI-guided cardiovascular catheterization using a new MRI-visible glass-fiber epoxy-based guidewire is feasible in terms of visualization and guidewire navigation, and safe in terms of radiofrequency-induced guidewire tip heating.

Fig 1. MRI scanner room setup for cardiac catheterization experiments.

The guidewire maneuvering was performed by operator 1 in the MRI scanner room and the real-time scan was controlled by operator 2 in the MRI control room.

Fig 2. Cardiac catheterization devices evaluated in the phantom and porcine model experiments.

(a) diameter 0.035” × length 260 cm MRI-visible glass-fiber epoxy-based guidewire (MaRVis). (b) 0.035” × 260 cm stainless steel guidewire (Rosen, Cook Medical) (c) 7 French (Fr) x 110 cm non-metallic balloon-wedge pressure catheter (Arrow, Teleflex) (d) 7 Fr x 110 cm non-metallic Swan-Ganz catheter (True Size Double Lumen Monitoring Catheter, Edwards Lifesciences). (e) 6 Fr x 100 cm braided catheter (Expo, Boston Scientific).

Fig 3. Experimental setup for evaluating device heating in the ASTM torso phantom.

(a) Coronal and (b) Sagittal views of the experimental setup. (c) Zoomed-in view of the phantom. The MRI-visible glass-fiber epoxy-based guidewire (MR guidewire) tip and thermal probe were placed at three positions to mimic the spatial locations of the descending aorta (position 1), the aortic arch (position 2), and the left ventricle (position 3).

Fig 4. Representative examples of real-time MR images from porcine model experiments.

Glass-fiber epoxy-based guidewire (MR guidewire) visualization examples during the left ventricle (LV) catheterization procedure in healthy subjects (a, b) and subjects with an infarct (c, d). The first three columns show the MR guidewire in the descending aorta, aortic arch, and LV during steps 2–4. The corresponding signal void dimensions (e.g., a4) measured in the LV cavity are shown in the last column. The signal void intensity (e.g., region of interest [ROI] 1 in c4), surrounding blood signal intensity (e.g., ROI 2 in c4), and background noise (e.g., ROI 3 in c4) were measured to calculate the contrast-to-noise ratio (CNR) of the guidewire tip.

Fig 5. Guidewire Tip Heating (GTH) during phantom experiments.

GTH measured with GRE (blue) and TSE (red) sequences during phantom experiments for a stainless-steel guidewire (left), the glass-fiber epoxy-based MR guidewire (center), and the same MR guidewire in combination with three different catheters (right). GTH was measured at three different positions representing the descending aorta (DA, position 1, top), the aortic arch (AA, position 2, middle), and the left ventricle (LV, position 3, bottom).

Fig 6. Examples of temperature recordings over time in phantom heating experiments.

Guidewire tip heating (GTH) for stainless steel guidewire only, glass-fiber epoxy-based guidewire only, and glass-fiber epoxy-based guidewire with braided catheter over time during the phantom heating experiments using the gradient echo (GRE, blue line) and turbo spin echo (TSE, red line) sequences. The guidewire tip was placed at position 1 to mimic the descending aorta (DA) location, position 2 to mimic the aortic arch (AA) location, and position 3 to mimic the left ventricle (LV) location. A clear increase in temperature is detected at the tip of the stainless-steel guidewire at positions 1 and 3 during imaging with the TSE sequence. The red zone represents a GTH greater than 2°C, which is not considered procedurally safe. Note that only positive temperature changes above baseline are shown since they correspond to the RF-induced heating.