Real-Time Visualization of an Acoustically Active Injection Catheter With Ultrasound Imaging: Algorithm and In Vivo Validation in a Swine Model

Objective: To independently visualize a catheter and needle during minimally invasive surgery in order to aid in precisely guiding them to their intended location. Methods: Symmetric frequency detection allows for the visualization of the acoustically active catheter tip as a unique color in live imaging. This study extends the algorithm to identify two different crystals by unique colors, validating the algorithm with in vivo pig experiments while simulating the human condition using different attenuation pads. Results: The catheter and needle tip were identified with unique colors, differentiable from common Doppler colors, with a frame rate varying between 8 and 10 Hz. Both were visible at graded levels of attenuation induced by interposed polymer pads. Reducing ensemble length increased the frame rate and decreased the signal-to-noise ratio (SNR), though not significantly. At the highest in-path attenuation of 12 dB at 5 MHz, the catheter spot marker was visible whereas the needle was not. The SNR of the catheter signal varied between 12.50 and 18.24 dB and the size of the spot marker varied between 149 and 1015 mm
²
. The SNR of the needle signal varied between 6.37 and 16.3 dB and the size of the spot marker between 59 and 169 mm
²
. A reliability index greater than 50% was achieved for all cases except for the needle crystal at the highest attenuation setting. Conclusion: Modified symmetric frequency detection algorithm can uniquely visualize both catheter and needle in real time with in-path attenuation. Significance: Unambiguous and distinct visualization of separate locations on the catheter facilitates real-time tracking of minimally invasive procedures.