Simultaneous Visualization of Sentinel Lymph Nodes and Ureters Using a Dual Fluorescence Laparoscopic System With Indocyanine Green and Methylene Blue: An Animal Study
This animal study demonstrates that a dual-fluorescence laparoscopic system using indocyanine green and methylene blue can simultaneously and effectively visualize sentinel lymph nodes and ureters in real-time without signal interference, offering a promising tool for enhancing navigation in complex gynecologic oncology surgeries.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the delicate landscape of gynecologic surgery, where a surgeon navigates the intricate pathways of the female pelvis to treat cancer, two tasks stand out as critical yet challenging. The first is finding the sentinel lymph nodes, the tiny gatekeepers that act as the first stop for cancer cells spreading from a tumor. Identifying these nodes allows surgeons to remove only the necessary tissue, sparing patients from the heavy toll of removing entire chains of lymph nodes. The second task is protecting the ureters, the slender tubes that carry urine from the kidneys to the bladder. These tubes run dangerously close to the surgical field, and even a minor nick can lead to serious complications. For decades, surgeons have relied on different tools to solve these problems separately: a dye that glows under special light to find the lymph nodes, and a different dye to highlight the ureters. However, current technology usually forces the surgeon to switch back and forth between these two views, like changing lenses on a camera, which breaks the flow of the operation and risks losing track of where things are in relation to one another.
A team of researchers at the Shenzhen People's Hospital in China sought to solve this juggling act by testing a new way to see both structures at the same time. They worked with a dual-fluorescence laparoscopic system, a specialized camera that can detect two different colors of light simultaneously. In their experiment, they used a young female pig, a standard model for human anatomy, to see if they could inject two different dyes and watch both the lymph nodes and the ureters glow in real time without the signals mixing up. The first dye, indocyanine green, was injected into the cervix to map the lymphatic system, while the second dye, methylene blue, was given through a vein to light up the ureters. The goal was to see if the camera could display the lymph nodes in one color and the ureters in another on the same screen, fused with the normal white-light view of the surgery, allowing the surgeon to see everything at once.
The results showed that the system worked exactly as hoped. After the methylene blue was injected, the ureters began to glow with a blue light within six minutes. The signal grew stronger, reaching its brightest point about twenty to twenty-five minutes after the injection, and remained clearly visible for over an hour. At the same time, the indocyanine green injected into the cervix began to travel through the lymphatic vessels, lighting up the sentinel lymph nodes in a distinct green color. These nodes appeared within ten minutes, and the green glow became strong enough to clearly identify even the second layer of nodes about twenty-eight minutes later. Crucially, the two colors did not interfere with each other. The blue light of the ureters and the green light of the lymph nodes stayed separate and distinct, allowing the researchers to see the exact path of the ureter right next to the glowing lymph nodes without any confusion.
Throughout the procedure, the pig remained stable, and the camera provided a seamless view where the surgeon could see the white-light image of the organs overlaid with the blue and green signals. This meant that the surgeon never had to toggle between different modes or lose their place in the anatomy. The study demonstrated that this dual-view approach is safe and effective in a living animal, offering a way to keep both the lymph nodes and the ureters in clear view simultaneously. While this was a test on a single animal with normal anatomy, the findings suggest that this technology could one day help surgeons perform complex cancer operations with greater precision and safety, reducing the risk of accidental injury to the urinary system while ensuring cancer is not left behind. The researchers noted that future work would need to test this in more complex situations, such as in patients with tumors or scar tissue, but the initial experiment proved that seeing two critical structures at once is not only possible but practical.
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