Background
Radioactive seed localisation (RSL) is a preoperative localisation method using a small titanium seed containing iodine-125. The method is increasingly applied for localising non-palpable lesions in the treatment of breast cancer. We believe that RSL has the potential to be used in various surgical specialties. The aim of this feasibility study was to test RSL as a preoperative localisation of non-palpable lymph nodes.

Methods
Between November 24, 2015 and October 26, 2016, 15 patients with suspicious lymph nodes on imaging were included in the study. The lymph nodes were located in the axillary region (n = 9), the head and neck region (n = 5) and the inguinal region (n = 1). The seeds were placed in the centre of the lymph node, in the capsule or just outside the capsule guided by ultrasound. During surgery, incision and localisation of the lymph nodes were performed based on the auditory signal of the gamma probe. After excision, lymph nodes including iodine seeds were sent for pathologic examination and the seeds were returned to the Department of Nuclear Medicine.

Results
The non-palpable lymph nodes were all successfully marked using ultrasound. The lymph nodes were successfully localised and excised during surgery, and the procedure was performed without complications in the majority of the cases.

Conclusion
Localisation of suspicious non-palpable lymph nodes using RSL is feasible. RSL may ease the surgical procedure, minimise trauma to the surrounding tissue and ultimately benefit the patient. Future prospective studies are necessary to determine the further use of RSL within different surgical specialties.