Magnetic identification of sentinel lymph nodes

Student thesis: Doctoral ThesisDoctor of Philosophy


Sentinel lymph node biopsy (SLNB) is currently performed using radioisotope and blue dye injections. Drawbacks to using radioisotopes include exposure to radiation, limited global availability and a short half-life. A newly developed magnetic technique for identification of sentinel lymph nodes (SLNs) can overcome these problems. The magnetic technique is nonradioactive as it uses iron oxide particles as a magnetic tracer. The tracer causes a brown colour change in the SLN, which is visualised at surgery and it can be localised intraoperatively using a handheld magnetometer.

The aims of this thesis were to evaluate multiple parameters of the magnetic technique using an animal model and to test the feasibility of this technique to identify the SLN(s) in melanoma. In addition, the imaging characteristics of magnetic tracers were investigated, including pre-operative lymphatic staging and postoperative effects of the injection of the magnetic tracer on MRI.

A porcine animal model was used to test the magnetic technique and a total of 92 magnetic SLNB procedures were performed in 46 mini-pigs. A range of injected volumes, from 0.06 mL to 2.0 mL, was tested. Histological assessment, magnetic counts, iron content, concentration and time elapse since injections were evaluated. The technique was successfully applied to the porcine model, as evidenced by a 100% identification of the SLN(s) (92/92). The magnetic technique was successful using volumes of as low as 0.06 mL and magnetic tracer was taken up in the SLN(s) within minutes.

The MELAMAG trial of the magnetic technique in melanoma, reported in this thesis, evaluated SLN identification rate per patient, with the radioisotope/blue dye and magnetic techniques. The magnetic technique was found to be feasible for SLNB in melanoma with a high SLN identification rate.

The magnetic iron oxide tracer can be used as contrast agent for MRI with high sensitivity and specificity for lymphatic staging. This thesis includes a meta-analysis of contrast enhanced MRI for axillary staging in early breast cancer. Is also includes and investigation of the susceptibility artefact of magnetic tracer in the breast following SLN identification using the magnetic technique and it reports its potential impact on subsequent MRI scans.
Date of Award2017
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorMichael Douek (Supervisor)

Cite this