Preclinical feasibility of robot‐assisted sentinel lymph node biopsy using multi‐modality magnetic and fluorescence guidance in the head and neck

Abstract

Background: Sentinel lymph node biopsy (SLNB) is a staging procedure dependent on accurate mapping of draining lymphatics via tracers. Robotassisted SLNB enables access to multiple neck levels with a single incision and intraoperative fluorescence guidance to the SLN.Methods: Lymphatic mapping in swine was done using a magnetic tracer and fluorescent dye, injected into the tongue. MRI preoperatively mapped lymphatic spread of the magnetic tracer. Dissection was performed using a da Vinci Xi robot guided by fluorescence-imaging of the dye. Results: Robot-assisted SLNB was successfully performed in all animals (n = 5). A novel MRI protocol differentiated SLNs (n = 6) from lower echelon nodes (n = 11) based on flow progression. Fluorescence imaging provided valuable intraoperative guidance and correlated with magnetic-positive nodes.Conclusions: This study demonstrates preclinical feasibility of a robot-assisted approach to SLNB using magnetic and fluorescent tracers in the head and neck, enabling both preoperative mapping and intraoperative guidance.

Preclinical evaluation of sentinel node localization in the stomach via mannose-labelled magnetic nanoparticles and indocyanine green

“…The present study investigated the pairing of FerroTrace and ICG for more accurate gastric SLN localization. This concept was initially tested using robot-assisted dissection ( n = 2) given the promising results previously obtained with this tracer combination in the head and neck [ 17 ]. The robot-assisted investigation demonstrated concurrence of magnetic and fluorescent signals and the ability to use MRI to plan surgery, but was more akin to the conservative pick-up method of SLNB, as the draining lymphatic basin was only partially dissected.…”

“…In our dual-modality paradigm, it is accepted that the ICG will not be specific to the SLNs, and will likely highlight a relatively high number of LNs in a short period of time. However, ICG has proven effective at highlighting the pathways leading from the injection site to SLNs, and from SLNs to 2nd echelon LNs and beyond to guide dissection [ 17 , 30 ]. During the laparotomy phase of this study, sensitive fluorescence imaging guidance yielded an additional advantage: rapid identification of draining LNs, with a mean time of 2.5 ± 1.7 min between starting the ICG mapping to first LN removal.…”

“…At the onset of this preclinical investigation, a da Vinci Xi robotic system (Intuitive Surgical Inc., Sunnyvale, CA, USA) was utilised to perform the tracer injection and lymphatic dissection on 2 animals. A dose of 0.25 mL combination tracer (0.15 mL FerroTrace and 0.1 mL ICG dye) was used in both animals, with the objective of initially assessing the feasibility of ICG-guided surgical dissection of gastric LNs—as had been demonstrated previously in the head and neck [ 17 ].…”

“…All dissected LNs were measured using the magnetometer, and a semi-quantitative signal recorded for each. For each animal, SLNs were identified as the LNs with the highest magnetic signal [ 16 , 17 ] and which received direct lymphatic flow from the injection site (determined via fluorescence imaging). In instances where there was bilateral drainage, a SLN was identified for each side.…”

“…As with the combination of radiocolloids and blue dyes, we aim to pair two complementary modalities in order to take advantage of the strengths of each, while overcoming the limitations of individual tracers. A novel mannose-labelled iron oxide nanoparticle ‘FerroTrace’ (Ferronova, Adelaide, SA Australia) has previously demonstrated efficacy as a lymphotropic magnetic tracer in the swine head and neck, given the strong signal contrast created in MRI allowing preoperative mapping, and its high specificity to SLNs as a result of macrophage binding between the CD206 receptor and the tracer’s mannose label [ 16 , 17 ]. While FerroTrace is capable of differentiating SLNs (based on magnetic signals measured by a handheld magnetometer probe [ 16 ]), it is not easily visualised or detected in vivo in the gastric environment.…”