The overall goal of the following experiment is to develop and test a control system for improved steering of endovascular catheters in interventional MRI. This is achieved by fabricating microcatheters with tiny electromagnets on their tips as a second step. The microcatheters are attached to a custom built control system for remote controlled navigation.
Next microcatheters are controllably deflected in water baths and navigated in phantoms, which simulate conditions in the blood vessels of patients. Results from water bath experiments show predictable catheter tip deflections based on the amount and polarity of electrical current applied to the steering micro coils. Successful navigation in vessel phantoms demonstrates catheter steering ability.
The main advantage of MRI guided navigation as compared to conventional x-ray endovascular catheter navigation is that MRI allows the interventionist important information like perfusion and diffusion information in real time, thus helping to make the best possible intraprocedural decisions. This method can help answer key questions in the interventional MRI field, such as if the ability to control the catheter tip remotely can improve the efficacy of current interventional MRI procedures, Among the angel of the technology is to further develop M MRI as a therapeutic modality. Potential applications include the endovascular treatment of stroke tumor and cardiac arrhythmia.
Generally, individuals new to this method will struggle because it's a very unique approach to interventional guidance. To begin micro coil fabrication, obtain a commercially available microcatheter for a substrate. Ensure catheters have no Ferris components are considered magnetic resonance or mr.
Safe and range in size from 2.3 to 3.0 French size. Use a sputtering system to apply a seed layer of copper to a polyamide or Illumina one to two millimeter outer diameter insulating tube. Applying the photo resist and patterning the copper as described in the text protocol, allows fabrication of both solenoid and helm holt's copper patterns.
Continue to follow the assembly instructions in the text protocol for adding the insulating tube to the tip of the microcatheter with shrink wrap and inserting the copper wire. After attaching the micro coil wires to a modified three foot phone jack transmission line, the micro coil fabrication is complete for in vitro testing of the micro coil in a water bath. First, make a small hole in the center of the side of a plastic basin about five centimeters from the bottom.
Insert an 11 French Avanti cordes vascular sheath through the hole. Cut the distal tip of the vascular sheath leaving a four centimeter long piece extending into the basin. At the end of the sheath, attach a rotating hemostatic or two EORs valve to stabilize the location of the microcatheter.
Fill the basin with distilled water ensuring complete submersion of the apparatus. Insert the catheter with coiled tip through the vascular sheath and valve. Measure and record the unrestrained length of the microcatheter extending from the valve into the water bath.
Place the water bath with microcatheter system within the magnet of the MR scanner and orient with respect to the bore of the magnet. Connect the modified three foot phone cable attached to the catheter to a 25 foot RJ 11 phone cable transmission line using a two-way phone jack. Next, place the transmission lines through a wave guide.
Now connect the other end of the 25 foot phone cable to a dual regulated power supply to deliver up to one amp of current to the device and then place the power source outside of the MR scanner. Outside of the five gauss line. Perform imaging with a 1.5 Tesla clinical MR system.
Apply less than 50 milliamps of current to visualize the catheter tip position under MRI. A small magnetic moment will be produced at the catheter tip to visualize a distinct artifact, a varying shape depending on which coils are energized. Apply variable amounts of current in the range of plus or minus 100 milliamps from the Lambda dual power source to the coils and observe tip deflection in the water bath setup because tip deflection is almost instantaneous current only needs to be applied for about one to two seconds.
To visualize maximum deflection, repeat and record consecutive applications of set amounts of current acquire MR.Using a 2D snapshot flash sequence, which can be found in the text. As a final step, analyze and measure angle deflections of images captured with various computer applications for in vitro testing of the micro coil in a vessel phantom construct, a hollow vessel phantom with a Y shaped intersection from rubber tubing. Prior to experimentation, fill the vessel phantom with a 0.0102 molar solution of gadolinium contrast agent in distilled water.
To create contrast between the phantom vessels and background, assemble the microcatheter system. Connect the catheter to the power supply and position as demonstrated earlier in the video. Position the tip of the microcatheter at the base of the vessel opening.
Place the phantom within the magnet of the MR scanner and orient with respect to the bore of the magnet. Use the same MR procedure as for the water bath except to simultaneously push the catheter's hub end by hand, allowing mechanical advancement through the vessel phantom at the vessel branch point. Apply a sufficient amount of current to successfully deflect the catheter tip into the desired vessel.
Advance the catheter tip into this vessel by manually pushing the catheter end. Retract the catheter tip to the vessel bifurcation and repeat in the opposite branch. An angle of deflection between zero and 90 degrees should be observed from application of 50 to 300 milliamps of current delivered simultaneously to both coils of a combined solenoid and helm hols coil microcatheter system.
Catheter tip deflection is observable with application of current here. A blooming artifact from the energized coil is clearly visible. An increase in applied current should result in an increase in microcatheter deflection angle while a reversal in current polarity should result in deflection in the exact opposite direction as observed with positive current.
This video shows the anterior posterior catheter deflection in the water bath applications of 50 milliamps and 100 milliamps of current resulted consistent 10 degree and 14.5 degree deflections respectively. Positive current causes tip deflection in the anterior plane and negative current results in deflection in the posterior plane. Shown here is right left catheter deflection in a water bath applications of 50 milliamps and 100 milliamps of current resulted in consistent 11.5 degree and 17 degree deflections respectively.
Positive current causes tip deflection in the right plane and negative current results in deflection in the left plane as shown here. Catheter deflection and steering can be controlled through a vessel. Phantom current is applied to the coiled catheter tip producing visualization blooming.
The catheter is mechanically advanced and current is applied to cause deflection into the bottom vessel branch. The catheter is then retracted by reversed current polarity. The catheter is deflected and advanced into the top vessel branch catheter deflection in a bifurcation phantom is shown here.
Current applied to the catheter allows successful targeting and advancement into the left vessel branch of the phantom. The catheter is then retracted to the branching point and directed into the right vessel branch. Following this procedure, catheter deflection can be performed in more complex vessel phantoms under MRI guidance to further explore catheter system navigability After its development.
This technique paved the way for researchers in the field of neurointerventional radiology and interventional radiology to explore interventional MRI as a therapeutic modality. After watching this video, you should have a good understanding of how predictable catheter tip deflections are produced with this micro coil tipped catheter system. Don't forget that working with a laser blade can be extremely hazardous and that proper protective equipment should be worn at all times.
