Laparoscopic Probe for Sentinel Lymph Node Harvesting using Magnetic Nanoparticles

A new bimodal approach for sentinel lymph node imaging in prostate cancer using a magnetic and fluorescent hybrid tracer

PURPOSE

To obtain initial data on sentinel lymph node (SLN) visualisation by pre-operative magnetic resonance imaging (MRI) and intra-operative bimodal SLN identification using a new magnetic fluorescent hybrid tracer in prostate cancer (PCa) patients.

METHODS

Ten patients at > 5% risk for lymph node (LN) invasion were included. The day before surgery, a magnetic fluorescent hybrid tracer consisting of superparamagnetic iron oxide nanoparticles (SPION) and indocyanine green was transrectally injected into the prostate. Five hours after injection, transversal pelvic MRI scans were recorded and T2*-weighed images were screened for pelvic LNs with SPION uptake. Intra-operatively, magnetically active and/or fluorescent SLNs were detected by a handheld magnetometer and near-infrared fluorescence imaging (FI). Extended pelvic lymph node dissection (PLND) and radical prostatectomy completed the surgery. All resected specimens were checked ex situ for magnetic activity and fluorescence and were histopathologically examined.

RESULTS

Pre-operative MRI identified 145 pelvic LNs with SPION uptake. In total, 75 (median 6, range 3‒13) magnetically active SLNs were resected, including 14 SLNs not seen on MRI. FI identified 89 fluorescent LNs (median 8.5, range 4‒13) of which 15 LNs were not magnetically active. Concordance of the different techniques was 70% for pre-operative MRI vs. magnetometer-guided PLND and 88% for magnetic vs. fluorescent SLN detection.

CONCLUSION

These are the first promising results of bimodal, magnetic fluorescent SLN detection in PCa patients. Our magnetic fluorescent hybrid approach provides the surgeon a pre-operative lymphatic roadmap by using MRI and intra-operative visual guidance through the application of a fluorescent lymphatic agent. The diagnostic accuracy of our new hybrid approach has to be evaluated in further studies.

TRIAL REGISTRATION

DRKS00032808. Registered 04 October 2023, retrospectively registered.

Sentinel Lymph Node Techniques in Urologic Oncology: Current Knowledge and Application

Lymph node (LN) metastases have a significant negative impact on the prognosis of urological malignancies. Unfortunately, current imaging modalities are insufficient when it comes to detecting micrometastases; thus, surgical LN removal is commonly used. However, there is still no established ideal lymph node dissection (LND) template, leading to unnecessary invasive staging and the possibility of missing LN metastases located outside the standard template. To address this issue, the sentinel lymph node (SLN) concept has been proposed. This technique involves identifying and removing the first group of draining LNs, which can accurately stage cancer. While successful in breast cancer and melanoma, the SLN technique in urologic oncology is still considered experimental due to high false-negative rates and lack of data in prostate, bladder, and kidney cancer. Nevertheless, the development of new tracers, imaging modalities, and surgical techniques may improve the potential of the SLN procedures in urological oncology. In this review, we aim to discuss the current knowledge and future contributions of the SLN procedure in the management of urological malignancies.

Excitation coil for sentinel lymph node harvesting: design, digital twin and prototype

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.