En-bloc tumor resection is the standard treatment for locally advanced colorectal cancer (CRC). An extensive histopathological assessment is necessary to evaluate the metastatic spread and adjuvant therapy. Sentinel lymph node biopsy decreases the histopathological burden when only sentinel lymph nodes (SLNs) are examined. This study aims to evaluate the spread of a magnetic tracer throughout the lymphatic system after ex vivo injection in en-bloc resected specimens of patients with CRC. To achieve this, lymph nodes (LNs) were quantified using a new magnetic detection method. Fifteen patients with CRC diagnosed with clinically negative LNs were included in this study and received 2–4 ex vivo magnetic tracer injections (total volume of 2[Formula: see text]mL). Magnetic sample series were acquired to create a look-up table for magnetic tracer quantification. In 80% of the patients, at least one magnetic LN was detected. A total of 33 LNs were marked as magnetic, containing an average of 8.1[Formula: see text][Formula: see text]g iron. In 71% of the patients, metastases were found in nonmagnetic LNs. Ex vivo injection leads to sub-optimal tracer spread and therefore inaccurate diagnosis. This study presents a novel magnetic detection method to quantify magnetic tracer in lymph nodes. Detecting the SLNs in en-bloc resected specimens and involving only these LNs in histopathological investigation enable a decrease in healthcare costs or an increased diagnostic potential.

A recently developed prototype (Laparoscopic Differential Magnetometer, in short LapDiffMag) identifies magnetic tracer accumulated inside sentinel lymph nodes (SLNs) during clinical laparoscopic procedures. The LapDiffMag relies on excitation of superparamagnetic iron oxide nanoparticles (SPIONs) and subsequent laparoscopic detection based on a nonlinear detection principle. The prototype uses an excitation coil to generate a magnetic field needed to activate SPIONs. This study reports on the process of developing a new excitation coil by describing the design choices based upon clinical requirements, by modeling delivered magnetic field using digital twin, and by comparing the magnetic fields of modeled and manufactured prototype. Digital twin technology was used to produce relevant and reliable data to demonstrate the safety and effectiveness of the excitation coil. The magnetic field originating from manufactured prototype was validated at two different heights above the excitation coil and have shown a good concordance to the data generated by its digital twin.Clinical Relevance-Current standard-of-care for a variety of tumor types consists of minimally invasive radical resection of primary tumor and regional lymph nodes (LNs). The newly introduced excitation coil will (after full validation) enable minimally invasive harvesting of sentinel LNs by means of magnetic tracer detection.