2 The technology



The Magtrace and Sentimag system (Endomag) comprises a magnetic liquid tracer (Magtrace) and a handheld magnetic sensing probe (Sentimag). Magtrace is intended for use only with the Sentimag system. Magtrace is a non-radioactive dark brown liquid containing superparamagnetic iron oxide with a carboxydextran coating. It is both a magnetic marker and a visual dye. Magtrace is injected into the tissue beneath the areola or interstitial tissue around a tumour. The particles are then absorbed into lymphatics and become trapped in sentinel lymph nodes that can then be detected by the magnetic sensing probe and also by visualisation to assist with biopsy.


During surgery, the Sentimag probe detects the tracer trapped in the lymph nodes and guides the surgeon to remove them for biopsy. Sentimag uses a visual reading and sounds of different pitches to indicate how close the surgeon is to the magnetic tracer. The nodes often appear dark brown or black in colour, which also helps identification.

Care pathway


A sentinel lymph node biopsy helps to stage cancer that has spread to the lymph nodes and is followed by a surgical procedure to remove 1 or more of the nodes. NICE's guideline on early and locally advanced breast cancer recommends sentinel lymph node biopsy as the preferred technique to stage the axilla for people with invasive breast cancer and no evidence of lymph involvement on ultrasound or a negative ultrasound-guided needle biopsy. The guideline also recommends that sentinel lymph node biopsy should be offered to people who are having a mastectomy for ductal carcinoma in-situ breast cancer and people with a preoperative diagnosis of ductal carcinoma in-situ who are considered to be at high risk of invasive disease.


The recommended treatment option for locating sentinel lymph nodes during biopsy is a dual technique combination of a tracer containing a radioactive isotope, and blue dye. When the radioactive isotope is not available, some centres report using blue dye on its own, but this can reduce the detection rate of sentinel lymph nodes.

Innovative aspects


The key innovative feature of the Magtrace and Sentimag system is its magnetic mechanism of action. This means that unlike the dual technique, the system can be used without the need for nuclear medicine safety procedures and facilities. Magtrace can also be injected up to 30 days before surgery, whereas the radioactive tracers can be given no more than 24 hours before the sentinel lymph node biopsy procedure.

Intended use


Magtrace and Sentimag are intended to help locate sentinel lymph nodes during biopsy procedures for cancer staging. Magtrace can be injected by a nurse or surgeon up to 30 days before a biopsy or in the operating theatre 20 minutes before surgery. Sentimag is then used by the surgeon during the biopsy procedure to detect the tracer trapped in the lymph nodes.



Known contraindications to Magtrace include people with known hypersensitivity to iron oxide or dextran compounds, people with iron overload disease and people with a metal implant in the axilla or in the chest. Sentimag is contraindicated for use within 15 mm of a working pacemaker.



Magtrace costs £226 per unit (excluding VAT). The Sentimag probe costs £24,900 to purchase. However, NHS trusts entering a consumable commitment of 100 to 120 units per annum receive the Sentimag system free of charge.

For more details, see the webpage for Magtrace and Sentimag at the Endomag UK website.

  • National Institute for Health and Care Excellence (NICE)