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Whole shaft visibility and mechanical performance for active MR catheters using copper-nitinol braided polymer tubes.

Kocaturk O, Saikus CE, Guttman MA, Faranesh AZ, Ratnayaka K, Ozturk C, McVeigh ER, Lederman RJ - J Cardiovasc Magn Reson (2009)

Bottom Line: Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability.We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability) and antenna (signal attenuation) properties.This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures.

View Article: PubMed Central - HTML - PubMed

Affiliation: Translational Medicine Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA. kocaturko@nhlbi.nih.gov

ABSTRACT

Background: Catheter visualization and tracking remains a challenge in interventional MR.Active guidewires can be made conspicuous in "profile" along their whole shaft exploiting metallic core wire and hypotube components that are intrinsic to their mechanical performance. Polymer-based catheters, on the other hand, offer no conductive medium to carry radio frequency waves. We developed a new "active" catheter design for interventional MR with mechanical performance resembling braided X-ray devices. Our 75 cm long hybrid catheter shaft incorporates a wire lattice in a polymer matrix, and contains three distal loop coils in a flexible and torquable 7Fr device. We explored the impact of braid material designs on radiofrequency and mechanical performance.

Results: The incorporation of copper wire into in a superelastic nitinol braided loopless antenna allowed good visualization of the whole shaft (70 cm) in vitro and in vivo in swine during real-time MR with 1.5 T scanner. Additional distal tip coils enhanced tip visibility. Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability. We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability) and antenna (signal attenuation) properties. With this configuration, the temperature increase remained less than 2 degrees C during real-time MR within 10 cm horizontal from the isocenter. The design was conspicuous in vitro and in vivo.

Conclusion: We have engineered a new loopless antenna configuration that imparts interventional MR catheters with satisfactory mechanical and imaging characteristics. This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures.

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(a) Flexibility test setup and result. The catheter distal tip was fixed perpendicular to force meter that was mounted on a motorized stage. (b) The schematic representation of tip flexibility measurement setup. (c) Distal tip flexibility for different braiding layer configurations. Resistance force at the catheter distal tip was measured while the shaft was bent from 5 cm away until the tip reaches 1.5 cm vertical displacement.
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Figure 2: (a) Flexibility test setup and result. The catheter distal tip was fixed perpendicular to force meter that was mounted on a motorized stage. (b) The schematic representation of tip flexibility measurement setup. (c) Distal tip flexibility for different braiding layer configurations. Resistance force at the catheter distal tip was measured while the shaft was bent from 5 cm away until the tip reaches 1.5 cm vertical displacement.

Mentions: The aim of this test is to compare the force required to deflect the distal tip of the catheter the same amount for different nitinol/copper wire ratio braiding configurations. The catheter distal tip was connected to the force meter in a way that the tip is perpendicular to force meter (Figure 2a). The force meter was mounted onto motorized linear stage that moves at a constant speed. The catheter was fixed 5 cm away from the distal tip to prevent any damage on two solenoid coils at the tip. The force required to deflect the catheter tip up to 1.5 cm was measured using the digital force meter as shown in the schematic representation in Figure 2b.


Whole shaft visibility and mechanical performance for active MR catheters using copper-nitinol braided polymer tubes.

Kocaturk O, Saikus CE, Guttman MA, Faranesh AZ, Ratnayaka K, Ozturk C, McVeigh ER, Lederman RJ - J Cardiovasc Magn Reson (2009)

(a) Flexibility test setup and result. The catheter distal tip was fixed perpendicular to force meter that was mounted on a motorized stage. (b) The schematic representation of tip flexibility measurement setup. (c) Distal tip flexibility for different braiding layer configurations. Resistance force at the catheter distal tip was measured while the shaft was bent from 5 cm away until the tip reaches 1.5 cm vertical displacement.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2743675&req=5

Figure 2: (a) Flexibility test setup and result. The catheter distal tip was fixed perpendicular to force meter that was mounted on a motorized stage. (b) The schematic representation of tip flexibility measurement setup. (c) Distal tip flexibility for different braiding layer configurations. Resistance force at the catheter distal tip was measured while the shaft was bent from 5 cm away until the tip reaches 1.5 cm vertical displacement.
Mentions: The aim of this test is to compare the force required to deflect the distal tip of the catheter the same amount for different nitinol/copper wire ratio braiding configurations. The catheter distal tip was connected to the force meter in a way that the tip is perpendicular to force meter (Figure 2a). The force meter was mounted onto motorized linear stage that moves at a constant speed. The catheter was fixed 5 cm away from the distal tip to prevent any damage on two solenoid coils at the tip. The force required to deflect the catheter tip up to 1.5 cm was measured using the digital force meter as shown in the schematic representation in Figure 2b.

Bottom Line: Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability.We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability) and antenna (signal attenuation) properties.This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures.

View Article: PubMed Central - HTML - PubMed

Affiliation: Translational Medicine Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA. kocaturko@nhlbi.nih.gov

ABSTRACT

Background: Catheter visualization and tracking remains a challenge in interventional MR.Active guidewires can be made conspicuous in "profile" along their whole shaft exploiting metallic core wire and hypotube components that are intrinsic to their mechanical performance. Polymer-based catheters, on the other hand, offer no conductive medium to carry radio frequency waves. We developed a new "active" catheter design for interventional MR with mechanical performance resembling braided X-ray devices. Our 75 cm long hybrid catheter shaft incorporates a wire lattice in a polymer matrix, and contains three distal loop coils in a flexible and torquable 7Fr device. We explored the impact of braid material designs on radiofrequency and mechanical performance.

Results: The incorporation of copper wire into in a superelastic nitinol braided loopless antenna allowed good visualization of the whole shaft (70 cm) in vitro and in vivo in swine during real-time MR with 1.5 T scanner. Additional distal tip coils enhanced tip visibility. Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability. We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability) and antenna (signal attenuation) properties. With this configuration, the temperature increase remained less than 2 degrees C during real-time MR within 10 cm horizontal from the isocenter. The design was conspicuous in vitro and in vivo.

Conclusion: We have engineered a new loopless antenna configuration that imparts interventional MR catheters with satisfactory mechanical and imaging characteristics. This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures.

Show MeSH