The lungs are one of the most difficult organs for doctors to navigate. They have a dense network of blood vessels, bronchi and other critical anatomical structures that facilitate access to distant lungs. nodules with a conventional bronchoscope challenging.
To overcome these limitations, researchers from the University of North Carolina at Chapel Hill, Vanderbilt University, and the University of Utah have built a compact robotic system that can autonomously steer a flexible needle around these anatomical obstacles within the lungs of living animals.
“The robotic system is innovative because it incorporates autonomous navigation guidance that allows for more precise movement of the needle through the lungs. Reducing human error could lead to better outcomes for patients,” said Moria Bittmann, Ph.D., program director in NIBIB’s Division of Discovery and Applied Sciences.
Scientists demonstrated in their preclinical study published in Scientific robotics that the robot-guided bronchoscopy needle consistently outperformed a physician-guided bronchoscopy needle in achieving selected objectives. The orientation errors were so small that the robot could be used to biopsy the smallest clinically relevant nodules, the researchers said.
They chose pig lungs for their study because of their similar size and structure to human lungs.
“This is the biggest milestone we’ve reached so far. This robot is the first that has autonomous needle steering, works in vivo, and can avoid anatomical obstacles,” said Ron Alterovitz, Ph.D., principal investigator and corresponding author of the study, and professor of computer science at the University of North Carolina at Chapel Hill.
Designing the robot
The least invasive way to diagnose lung nodules is bronchoscopy, a procedure in which a doctor passes an endoscope through the patient’s mouth and through the airways. From there, a straight needle is inserted into the lung tissue to a target site, removing a small sample of the nodule for analysis.
However, current manual bronchoscopy techniques have several limitations. Straight needles are not designed to navigate anatomical obstacles or pass through lung tissue that moves when people breathe. These barriers have limited biopsies of small nodules or nodules deep in the lungs and further away from the main airways.
“We’re trying to target a pea-sized object that moves when the person breathes, so it’s like trying to hit a moving target that’s very small,” said Jason Akulian, MD, study co-author and pulmonary interventionalist at the University of North Carolina at Chapel Hill.
While robot-assisted bronchoscopy has made progress in reaching distant nodules, the doctor still must operate the bronchoscope and current systems do not offer needles that can pass through lung tissue.
The researchers addressed these limitations when designing their semi-autonomous robotic system. The system has three stages: the first two require a doctor to insert a bronchoscope into the airways and then operate a targeting device (along with software) to launch the needle to the desired target in the lungs; The last stage is where the robot autonomously directs the needle towards its destination.
The system’s hardware components include flexible, laser-engineered needles that curve around anatomical obstacles, a mechanical control of needle thrust and rotation, and a aiming device.
The system software independently operates the needle direction and semi-operates the aiming device. Using a 3D map of the pig’s lungs acquired from a previous computed tomography (CT) scan, it plans the shortest path for the steerable needle that safely avoids obstacles such as blood vessels and takes into account respiratory motion caused by the animal’s breathing.
Testing the performance of the robot.
The researchers wanted to test how well the autonomic system controlled the direction of the needle in living, breathing lung tissue, which is more difficult to navigate than deceased lung tissue or phantom lung tissue.
The first series of experiments evaluated whether the robot-directed needle accurately followed a pre-planned path in the pig’s living lung tissue. The results of three switch deployments showed that the automated steering stayed true to the route with only small deviations.
The steerable needle safely avoided anatomical obstacles and hit targets with an average error of 2.7 millimeters. The smallest nodule that doctors will try to biopsy is about 8 millimeters in diameter, so the result was within the target range of an actual biopsy.
The second set of experiments compared the needle accuracy of robotic-directed bronchoscopy on ex vivo lung tissue with a manual diagnostic bronchoscopy technique. The results of 21 total needle deployments showed that, on average, the robot-guided needle had a significantly smaller orientation error (about 3.5 millimeters) than the hand tool (about 13 millimeters).
“The results demonstrate the potential to improve the precision of medical procedures when using medical robots with autonomous capabilities,” Alterovitz said.
The researchers plan to test their robot next in lungs from human cadavers, followed by trials in living humans. They also plan to fully automate the operation of the aiming device.
The researchers’ ultimate goal is to leverage new technology to improve patient care. This study was funded in part by NIBIB (R01EB024864) and the National Science Foundation.
This prominent scientist describes a basic research finding. Basic research increases our understanding of human behavior and biology, which is critical to promoting new and better ways to prevent, diagnose, and treat diseases. Science is an unpredictable and incremental process: each research advance builds on past discoveries, often in unexpected ways. Most clinical advances would not be possible without knowledge of fundamental basic research.
Study reference: Alan Kuntz et al. Autonomous medical needle direction in vivo. Scientific robotics (2023). Doi/10.1126/scirobotics.adf7614
