We have previously described miniature 2D array transducers integrated into a Cook Medical, Inc. vena cava fi ter deployment device. While functional, the fabrication technique was very labor intensive and did not lend itself well to efficient fabrication of large numbers of devices. We developed two new fabrication methods that we believe can be used to efficiently manufacture these types of devices in greater than prototype numbers. One transducer consisted of 55 elements operating near 5 MHz. The interelement spacing is 0.20 mm. It was constructed on a flat piece of copper-clad polyimide and then wrapped around an 11 French catheter of a Cook Medical, Inc. inferior vena cava (IVC) filter deployment device. We used a braided wiring technology from Tyco Electronics Corp. to connect the elements to our real-time 3D ultrasound scanner. Typical measured transducer element band width was 20% centered at 4.7 MHz and the 50 Ω round trip insertion loss was -–82 dB. The mean of the nearest neighbor cross talk was –37.0 dB. The second method consisted of a 46-cm long single layer flex circuit from MicroConnex that terminates in an interconnect that plugs directly into our system cable. This transducer had 70 elements at 0.157 mm interelement spacing operating at 4.8 MHz. Typical measured transducer element bandwidth was 29% and the 50 Ω round trip insertion loss was –83 dB. The mean of the nearest neighbor cross talk was –33.0 dB.
As a treatment for aortic stenosis, several companies have recently introduced prosthetic heart valves designed to be deployed through a catheter using an intravenous or trans-apical approach. This procedure can either take the place of open heart surgery with some of the devices, or delay it with others. Real-time 3D ultrasound could enable continuous monitoring of these structures before, during and after deployment. We have developed a 2D ring array integrated with a 30 French catheter that is used for trans-apical prosthetic heart valve implantation. The transducer array was built using three 46 cm long flex circuits from MicroConnex (Snoqualmie, WA) which terminate in an interconnect that plugs directly into our system cable, thus no cable soldering is required. This transducer consists of 210 elements at .157 mm inter-element spacing and operates at 5 MHz. Average measured element bandwidth was 26% and average round-trip 50 Ohm insertion loss was -81.1 dB. The transducer were wrapped around the 1 cm diameter lumen of a heart valve deployment catheter. Prosthetic heart valve images were obtained in water tank studies.
We have previously developed 2D ring array transducers for real-time volumetric imaging guidance of minimally invasive procedures. These transducers were integrated with an 11 French catheter sheath of a Cook Medical, Inc. vena cava filter deployment kit. We have expanded on these devices and developed a 2D ring array integrated with a 30 French catheter that is used for trans-apical prosthetic heart valve implantation. This transducer consists of 210 elements at .157 mm interelement spacing and operates at 5 MHz. Average measured element bandwidth was 26% and average round-trip 50 ohm insertion loss was -81.1 dB. Update to Previous WorkFigure 1. A completed 55 element 12 French ring array transducer (A), a 5 cm deep Doppler flow image of agitated saline in a porcine model (B), and the fluoroscopy image confirming the position of the transducer (T) in the inferior vena cava (fig. 1C). There is a sheath (S) in the aorta and another catheter (C) in the renal vein used to inject the contrast shown in fig. 1B) Based on our previously developed ring array transducers [1], we conducted an animal study placing the 2D transducer into the inferior vena cava (IVC) of a fully grown pig. This study conformed with the animal use protocol of our institution. We placed the 55 element, 12 French transducer using a femoral vein approach, stopping inferior to the renal vein. Agitated saline was used as contrast and applied through another catheter directly into the renal vein. The completed transducer is shown in figure 1A. Figure 1B shows the Doppler B-scan of the contrast as it comes out the renal vein and moving into the IVC. Figure 1C shows a fluoroscopic image confirming the placement of the transducer (T) and the catheter (C) that was used to introduce the contrast. Also in the image is a sheath (S) in the renal artery.
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