ABSTRACT
Acoustoelectric imaging (AEI) is a technique that combines ultrasound (US) with radio frequency recording to detect and map local current source densities. This study demonstrates a new method called acoustoelectric time reversal (AETR), which uses AEI of a small current source to correct for phase aberrations through a skull or other US-aberrating layers with applications to brain imaging and therapy. Simulations conducted at three different US frequencies (0.5, 1.5, and 2.5 MHz) were performed through media layered with different sound speeds and geometries to induce aberrations of the US beam. Time delays of the acoustoelectric (AE) signal from a monopole within the medium were calculated for each element to enable corrections using AETR. Uncorrected aberrated beam profiles were compared with those after applying AETR corrections, which demonstrated a strong recovery (29%-100%) of lateral resolution and increases in focal pressure up to 283%. To further demonstrate the practical feasibility of AETR, we further conducted bench-top experiments using a 2.5 MHz linear US array to perform AETR through 3-D-printed aberrating objects. These experiments restored lost lateral restoration up to 100% for the different aberrators and increased focal pressure up to 230% after applying AETR corrections. Cumulatively, these results highlight AETR as a powerful tool for correcting focal aberrations in the presence of a local current source with applications to AEI, US imaging, neuromodulation, and therapy.
ABSTRACT
Hysterectomies (i.e., surgical removal of the uterus) are the prevailing solution to treat medical conditions such as uterine cancer, endometriosis, and uterine prolapse. One complication of hysterectomies is accidental injury to the ureters located within millimeters of the uterine arteries that are severed and cauterized to hinder blood flow and enable full uterus removal. This work explores the feasibility of using photoacoustic imaging to visualize the uterine arteries (and potentially the ureter) when this imaging method is uniquely combined with a da Vinci® surgical robot that enables teleoperated hysterectomies. We developed a specialized light delivery system to surround a da Vinci® curved scissor tool, and an ultrasound probe was placed externally, representing a transvaginal approach, to receive the acoustic signals. Photoacoustic images were acquired while sweeping the tool across our custom 3-D uterine vessel model covered in ex vivo bovine tissue that was placed between the 3-D model and the fiber, as well as between the ultrasound probe and the 3-D model. Four tool orientations were explored, and the robot kinematics were used to provide tool position and orientation information simultaneously with each photoacoustic image acquisition. The optimal tool orientation produced images with contrast [Formula: see text] and background signal-to-noise ratios (SNRs) [Formula: see text], indicating minimal acoustic clutter from the tool tip. We achieved similar contrast and SNR measurements with four unique wrist orientations explored with the scissor tool in open and closed configurations. Results indicate that photoacoustic imaging is a promising approach to enable visualization of the uterine arteries to guide hysterectomies (and other gynecological surgeries). These results are additionally applicable to other da Vinci® surgeries and other surgical instruments with similar tip geometry.
