Real-time 3D ultrasound laparoscopy
We have previously described 2D array ultrasound transducers operating up to 13.5 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time transesophageal echocardiography (TEE) and real time 3D intravascular ultrasound (IVUS) imaging. We have recently built a pair of 2D array transducers for real time 3D laparoscopic ultrasound imaging. These transducers are intended to be placed down a trocar during minimally invasive surgery. Both transducers were built using Gore MicroFlat cables consisting of 18 wires spaced at 0.10 mm and attached to a polyimide backing. The first is a forward viewing 5 MHz, 19 × 11 array with 198 operating elements. It was built on an 8 layer multi-layer flex circuit. The interelement spacing is 0.20 mm yielding an aperture that is 2.2 mm × 3.8 mm. The O.D. of the completed transducer is 10.2 mm , and includes a 2 mm tool port. The average measured center frequency is 4.5 MHz, and the -6 dB bandwidth ranges from 15% to 30%. The 50 Ohm insertion loss, including the MicroFlat cabling, is -81.2 dB. The second transducer is a 7 MHz, 36 × 36 array with 504 operating elements. It was built upon a 10 layer multi-layer flex circuit. This transducer is in the forward viewing configuration, and the interelement spacing is 0.18 mm. The total aperture size is 6.48 mm × 6.48 mm. The O.D. of the completed transducer is 11.4 mm. The average measured center frequency is 7.2 MHz, and the -6 dB bandwidth ranges from 18% to 33%. The 50 Ohm insertion loss is -79.5 dB, including the MicroFlat cable. Real time in vivo 3D images of a canine heart have been made including an apical 4 chamber view from a substernal access with the first transducer to monitor cardiac function. In addition we produced real time 3D rendered images of the right pulmonary veins from a right parasternal access with the second transducer which would be valuable in the guidance of cardiac ablation catheters for treatment of atrial fibrillation. © 2005 IEEE.
