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multimodal imaging images

Real-time surgical guidance system enables multimodal tissue monitoring

For the first time, researchers at Children’s National Hospital successfully demonstrated a label-free tissue perfusion imaging in a pre-clinical model, according to a study published in IEEE Transactions on Biomedical Engineering.

Richard Jaepyeong Cha, Ph.D., research faculty associate professor at Children’s National, and colleagues combined visible, near-infrared laser speckle contrast imaging (LSCI) and snapshot hyperspectral (HSI) cameras into a single clinical multimodal imaging device suitable for real-time intraoperative visualization and demonstrated such a device in a surgical model for the first time, to the best knowledge of the authors. This system provides instant microcirculation information about the ischemic regions, normal tissue and transitional ischemic zones with quantitative values that are reproducible.

“Our pre-clinical work demonstrated a novel, dye-free imaging platform for quantitatively assessing bowel perfusion. The ability to identify optimal surgical resection margins can improve surgical performance and patient outcome in terms of more targeted bowel resection and bowel preservation without anastomotic leakage,” Cha said. “This new optical imaging and quantitative assessment technology holds great promise to solving the long-standing issue of suboptimal assessment of intestinal viability.”

Intraoperative imaging techniques for the precise monitoring of blood flow, hemorrhage and oxygen saturation are needed to minimize errors caused by blood vessel ligation to reduce surgical blood loss and successfully isolate and resect ischemic regions.

When the blood flow, hemorrhage and oxygen are not monitored properly, anastomotic leak (AL) is a serious complication of intestinal surgery that can occur due to a technical error, and most frequently because of poorly vascularized intestine.

This complication of intestinal surgery carries with it a reported mortality ranging from 6 to 39%. The best time to prevent a possible AL is during its creation in the operating room.

Creating a healthy and safe intestinal anastomosis requires a good blood supply to the two ends of bowel to be joined. The tools for diagnosing well-perfused bowel intraoperatively are limited and often rely on the subjective evaluation of the surgeon.

“We are hoping that the use and application of multimodal LSCI/HSI imaging, capable of both non-invasive and quantitative gross tissue perfusion assessment, will provide colorectal/general surgeons with a convenient and objective method for assessment of bowel perfusion characteristics and facilitate surgical transection in tissues requiring colorectal anastomosis,” Cha said.

Recently, indocyanine green fluorescence angiography (ICG-FA) was introduced for intraoperative assessment of anastomotic perfusion. Preliminary evidence suggests that ICG-FA may reduce the rate of anastomotic leakage in gastrointestinal surgery.

Perfusion assessment at the site of anastomosis may alter surgical strategy and possibly reduce anastomotic leakage rates. However, ICG-FA evaluation requires an exogenous fluorophore and the surgeon must subjectively assess the quality of perfusion. For an ideal intestinal viability test, it is essential that the technique is easily performed by the surgeon, minimally invasive, objective and reproducible—which is what Lee et al. demonstrate with their new approach.

multimodal imaging system

schematic of Mueller polarimetric imaging

Novel technique improved nerve visualization in head and neck surgery

In a pre-clinical model, researchers from Children’s National Hospital found that the Mueller polarimetric imaging, a novel technique that improves image contrast, may help identify nerves from other surrounding tissues during neck and head surgical procedures, avoiding accidental nerve damage.

“This technology holds great promise for the possibility of a truly noninvasive imaging approach and may help improve surgical outcomes by potentially reducing inadvertent, ill effects of nerve injuries in head and neck surgery,” said Bo Ning, Ph.D., R&D engineer at Children’s National and lead author of the study.

This pre-clinical study presents the first application of a full-field polarimetric imaging technique in vivo during head and neck surgery to highlight the vagus nerve (VN) and a branch that supplies all the intrinsic muscles to the larynx, known as recurrent laryngeal nerve (RLN).

“Unlike conventional nerve identification devices, this technique is noninvasive and less interruptive to intact tissues without disrupting surgical workflows,” said Ning et al. “Since the technique has an easy mechanism and promising performance in our study, this novel method holds great potential for real-time, noninvasive, and convenient nerve visualization.”

While some promising methods use polarimetric imaging for tissue characterizations, the current literature is still limited to ex vivo conditions due to the system complications and prolonged acquisition speeds.

“Recently, the industry released a new polarimetric camera, which is compact and allows fast and high-definition polarimetric imaging through simple snapshots. Enlightened by this technical advance, we have developed a practical polarimetric imaging method,” said Ning, who also develops compact and practical imaging systems for surgical innovation, including 3D, fluorescent, laser speckle and hyperspectral techniques. “It allows fast polarimetric analysis and can acquire birefringence maps over the whole field of view within 100 milliseconds, which provides an appropriate speed for directly surgical use.”

The new approach proofs that the concept is feasible to set up in live subjects during head and neck surgery, which can also be easily adapted for other surgeries. Among the seven subjects, the VNs and RLNs were successfully differentiated from arteries and other surrounding tissues.

Additional co-authors from Children’s National include Itai Katz, Ph.D., M.S., R&D staff engineer III; Anthony D. Sandler, M.D., Senior Vice President and Surgeon-in-Chief; Richard Jaepyeong Cha, Ph.D., research faculty assistant professor.

schematic of Mueller polarimetric imaging

Researchers at Children’s National used a novel technique that improves image contrast, which may help improve surgical outcomes.