The potassium LIDAR at Arecibo Observatory utilizes the Light Age alexandrite high power laser which requires a well synchronized system and steady trigger repetition rate to achieve correct height determination and to extend the lifetime of the equipment. The system includes an optical chopper that prevents the detector from saturating before the altitude of interest is reached and a sequence of delayed pulses that execute the laser trigger which are generated by an external pulse/delay generator. The accuracy of the optical chopper limits the accuracy of the laser repetition rate as well as other equipment in the synchronized system. This work describes the implementation of a new microcontroller based single instrument optical chopper and laser trigger controller to improve stability and functionality. By programming a unifying USB user interface, the new capability of monitoring the system and manipulating relevant variables was achieved. This includes changing the repetition rate, moving the optical chopper edge to block out different altitudes, tuning PID constants, and more. The new system centralizes control, increasing ease of operation and allowing more flexible and efficient use. Furthermore, a laser only mode for testing has been implemented to send out a laser trigger sequence to the rest of the system without the need of an optical chopper. The new implementation has reduced steady state frequency jitter of the laser trigger by 60% and startup time by 77%.
This technical note provides an overview of our work to explore the combination of photoacoustic imaging with the da Vinci surgical robot, which is often used to perform teleoperated hysterectomies (i.e., surgical removal of the uterus). Hysterectomies 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. By introducing photoacoustic imaging, we aim to visualize the uterine arteries (and potentially the ureter) during this surgery. 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 resulting acoustic signals. Photoacoustic images were acquired while sweeping the tool across a custom 3D uterine vessel model covered in ex vivo bovine tissue that was placed between the 3D model and the light delivery system, as well as between the ultrasound probe and the 3D model (to introduce optical and acoustic scattering). Four tool orientations were explored with the scissors in either open or closed configurations. The optimal tool orientation was determined to be closed scissors with no bending of the tool’s wrist, based on measurements of signal contrast and background signal-to-noise ratios in the corresponding photoacoustic images. We also introduce a new metric, dθ, to determine when the image will change during a sweep, based on the tool position and orientation (i.e., pose), relative to previous poses. Overall, results indicate that photoacoustic imaging is a promising approach to enable visualization of the uterine arteries and thereby guide hysterectomies (and other gynecological surgeries). In addition, results can be extended to other minimally invasive da Vinci surgeries and laparoscopic instruments with similar tip geometry.
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 >10 dB and background signal-to-noise ratios (SNRs) >1.7, 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.
Death and paralysis are significant risks of modern surgeries, caused by injury to blood vessels and nerves hidden by bone and other tissue. We propose an approach to surgical guidance that relies on photoacoustic (PA) imaging to determine the separation between these critical anatomical features and to assess the extent of safety zones during surgical procedures. Images were acquired as an optical fiber was swept across vessel-mimicking targets, in the absence and presence of teleoperation with a research da Vinci Surgical System. Vessel separation distances were measured directly from PA images. Vessel positions were additionally recorded based on the fiber position (calculated from the da Vinci robot kinematics) that corresponded to an observed PA signal, and these recordings were used to indirectly measure vessel separation distances. Amplitude- and coherence-based beamforming were used to estimate vessel separations, resulting in 0.52- to 0.56-mm mean absolute errors, 0.66- to 0.71-mm root-mean-square errors, and 65% to 68% more accuracy compared to fiber position measurements obtained through the da Vinci robot kinematics. Similar accuracy was achieved in the presence of up to 4.5-mm-thick ex vivo tissue. Results indicate that PA image-based measurements of the separation among anatomical landmarks could be a viable method for real-time path planning in multiple interventional PA applications.
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