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Fighting cancer using terahertz and gigahertz radiation

A case study by Harry Penketh^a, Lauren Barr^a, Euan Hendry^a?and Chris Lawrence^b 

^aUniversity of Exeter,?^bQinetiQ 

The challenge

Breast cancer is the most commonly diagnosed cancer in women worldwide, with around 2.3 million new cases and 670,000 related deaths each year.

Surgical removal of the tumour remains a cornerstone of breast cancer treatment, during which, surgeons remove the tumour together with a surrounding margin of apparently healthy tissue.  The width of this margin is critical for reducing the risk of local cancer recurrence. However, accurately assessing surgical margins during the operation remains challenging. As a result, postoperative analysis can reveal that cancer cells extend to, or lie too close to, the edge of the excised tissue. In many cases, this requires the patient to undergo additional surgery to remove further tissue, resulting in increased healthcare costs and additional physical and emotional burden for patients.

Our solution

Researchers at Exeter's Centre for Metamaterial Research and Innovation (CMRI) are developing new techniques for cancer detection and surgical margin assessment. The work forms part of the EPSRC-funded Terabotics project, a collaboration between the Universities of Exeter, Warwick, and Leeds, which aims to integrate cutting-edge terahertz (THz) sensors with robotic probes for improved cancer detection and guided surgery.

Our strategy is to use terahertz (THz) and gigahertz (GHz) radiation to measure the thickness of the tissue margin surrounding a tumour immediately after it has been removed. This technique exploits the ability of THz and GHz waves to penetrate healthy fatty tissue while remaining highly sensitive to the elevated water content commonly found in breast tumours. By providing rapid feedback on margin thickness, surgeons could remove additional tissue during the same procedure when required, reducing the need for repeat operations. To do this, we have developed a way to quickly and conveniently collect high-resolution THz and GHz images of a tumour using a dynamic metamaterial. 

Our GHz wave imaging system has been tested using breast tissue mimicking materials and has demonstrated the ability to measure margin thickness as deep as the clinical target of 2 mm.  

Why use a metamaterial?

To obtain sufficient resolution, we need to record the THz and GHz radiation very close to the cancerous tissue, placing the excised tumour on top of our dynamic metamaterial (modulator).? This geometry allows a form of super-resolution imaging, where image detail can break the diffraction limit by orders of magnitude, and allows us to measure sub-mm features in inhomogeneous tissues. 

This means that arrays of detectors (like those found in digital cameras) are not suitable. Instead we use a single detector along with a silicon wafer to make a dynamic metamaterial mask, where shining light on the silicon makes it behave like a metal. Patterning the light by using a reconfigurable array of small mirrors (a digital micro-mirror device) means that we can create regions of the silicon that are metallic and regions that are not. This dynamic metamaterial allows us to record many pixels simultaneously, increasing the signal by orders of magnitude and allowing us to collect clearer images much faster than with conventional raster scanning.  

Selected publications