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Laparoscopic Probe for Sentinel Lymph Node Harvesting using Magnetic Nanoparticles

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The sentinel lymph node (SLN) procedure decreases the number of lymph nodes necessary to remove during primary cancer treatment. This is standard-of-care for several cancer types (including breast cancer) and is mainly used during open surgery in combination with a radioactive tracer. Using a radioactive tracer during minimal invasive (laparoscopic) surgery is possible but suboptimal due to the shine-through effect, radiation, strict regulations, relative short decay time, and availability. This research presents a novel laparoscopic magnetic detector (LapDiffMag) and evaluates its clinical possibilities. The LapDiffMag uses a nonlinear detection principle, enabling selective measurements of only magnetic nanoparticles, negating human tissue and surgical instruments. The prototype consists of three main parts: an excitation coil to activate magnetic nanoparticles, a detection probe to locate magnetic nanoparticles, and a control unit to control the system. To analyze the performance of the LapDiffMag, the iron content sensitivity, depth & spatial sensitivity, and angular sensitivity were determined. Measurements were performed with aid of a robotic arm to ensure precise and concise movement of the detection probe with respect to the sample, as can be seen in the figure above. The minimal detectable amount of iron was 9.8 µg at a distance of 1 mm. The detection depth was 5, 8, and 10 mm and the maximum lateral detection distance was 5, 7, and 8 mm, both for samples containing 126, 252, and 504 µg iron, respectively. A sample of 504 µg iron was detectable at 0, 30, 60, and 90 degree angles. These first results with the LapDiffMag are promising, giving a viable alternative for executing a minimal invasive SLN procedure while using a magnetic tracer.

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