Diamond-based sensor advances detection of metastasized breast cancer

University of Warwick researchers have built a new diamond-based magnetic field sensor that could be used to better find tumors through tracing magnetic fluid injected in the body.

A cancer diagnosis is most problematic when cells from the tumor have metastasized (spread) to other organs. This most often occurs through the lymph nodes and the lymphatic draining system. Tests to find whether cancer cells are lodged in the lymph nodes are the gold standard for detecting metastasis and directing the course of treatment.

Published in Physical Review Applied, Warwick researchers report they have built a new non-toxic and non-radioactive device that uses the unique properties of diamonds to diagnose metastasized breast cancer. This device is ultra-sensitive, handheld and works at long ranges, providing an upgraded solution to a regular challenge that cancer surgeons must cope with.

First author Alex Newman, PhD student in the Physics Department at the University of Warwick commented: "There is a real demand for versatile non-toxic means of finding cancer. For this new diamond-based sensor, we managed to get the size of the sensor head down to just 10 mm, which means it is the first diamond sensor to be able to detect magnetic tracer fluid while being small enough for endoscopic use and keyhole surgery.

"It is also very sensitive, capable of detecting one hundredth of the typical full clinical dose of magnetic tracer fluid."

The diamond sensor works by detecting magnetic tracer fluid (iron oxide nanoparticles) that is introduced into the patient during or before breast cancer surgery. The tracer fluid is injected into the tumor and then travels to the lymph nodes alongside metastasized cancer cells. A magnetic field sensor based on a diamond can then locate the tracer fluid and pinpoint the lymph nodes to be surgically removed to stop the cancer spread.

Its compact design is achieved by using a tiny diamond (0.5 mm³) and a small permanent magnet that is attached to the probe head. This eliminates the need for bulky electronics allowing for a handheld versatile tool.

Senior author and group leader, Professor Gavin Morley, Department of Physics, University of Warwick said: "Diamonds can sense magnetic fields thanks to colour centres in the diamond, called nitrogen vacancy centres. They allow the diamond to detect very small changes in magnetic field and give the diamonds a lovely pink colour.

"We hope to use these magnetic field sensors not just for medical applications, but for spacecraft and fusion power too."

Tracing cancer is not new, but the traditional methods used in hospitals use radioactive tracers or simple blue dyes. Radioactive tracers are not available in all hospitals due to the extra precautions required when handling radioactive materials. Blue dye causes an allergic reaction in one out of a hundred people, which is an unwanted complication when the patient is under a general anaesthetic.

Detecting a magnetic tracer with a small sensitive sensor like the diamond-based one could be a game changer, and this technology has been built with clinician support.

Stuart Robertson, Consultant Breast Cancer Surgeon at University Hospitals Coventry and Warwickshire (UHCW) NHS Trust added: "I now regularly utilise magnetic localisation in my breast cancer work, for impalpable breast lesions and detecting lymph nodes, as it offers advantages over more traditional techniques. It's great to collaborate with the University of Warwick, exploring ways to optimise magnetic technology further."  

The use of magnetic tracer fluids is becoming more widespread, however, this new diamond sensor could provide a smaller, more sensitive detector, particularly as further quantum technology techniques are implemented. The applications to other cancers such as lung, liver, colorectal and oesophageal could provide even more benefits to patients.