Finger-Mounted Optical Probe Improves Breast Cancer Removal

Researchers have developed a wearable probe that enhances the sense of touch by imaging and quantifying the stiffness and elasticity of biological tissue in order to improve the surgical removal of breast cancer.

The finger-mounted probe uses a technique called quantitative micro-elastography (QME) to translate the sense of touch into high-resolution images. QME uses measurements from optical coherence tomography (OCT), an optical imaging technique that generates high-resolution, depth-resolved images of tissue structure by measuring the reflections, or “echoes,” of light.

The University of Western Australia researchers created the device that incorporates a fiber probe into a wearable thimble to make breast cancer removal more precise.

During breast-conserving surgery, the most common surgical treatment for breast cancer, surgeons touch and compress tissue to confirm that the stiffer cancerous tissue has been removed. Histopathological testing is performed days later to ensure that the whole tumor has been removed. Today, 20 to 30 percent of patients undergoing this type of surgery require another procedure because the testing shows that cancerous cells remain.

Researchers from the University of Western Australia have developed a wearable probe that enhances the sense of touch.

“Our new probe aims to enhance the surgeon’s subjective sense of touch through quantified, high-resolution imaging of tissue stiffness,” said Rowan W. Sanderson, first author of the paper published in The Optical Society of America’s Biomedical Optics Express.

“This could make it easier to detect and remove all the cancerous tissue during the first breast-conserving surgery, which would reduce the physical and psychological burden and cost that accompanies re-excision,” Sanderson said.

The device is used by pressing the finger-mounted probe perpendicularly into the tissue while OCT images are recorded.

“By preserving the sense of touch, we aim to conserve the existing clinical workflow and increase the likelihood that this technology would be adopted for wider clinical use,” Sanderson said.

For accurate elasticity measurements, the researchers developed new signal-processing methods with custom algorithms to deal with inconsistent motion and pressure during scanning. 3D printing helped them to quickly produce prototypes of the probe’s outer casing in a simple and cost-effective manner.

“Our finger-mounted probe can accurately detect microscale changes in stiffness, which are indicative of disease,” Sanderson explained. “The small size makes it ideal for imaging in confined spaces such as a surgical cavity.”

Testing of the probe began on materials known as silicone phantoms that are designed to mimic healthy and diseased tissues in the breast. These tests showed that the finger-mounted probe had an 87 percent accuracy rate, which was slightly lower than a conventional benchtop QME system, but still sufficiently high for potential clinical use.

Researchers then used the probe to measure the change in stiffness caused by heating a sample of kangaroo muscle. This experiment showed that the muscle sample underwent a sixfold increase in stiffness following the heating process. A preliminary 2D image was obtained by scanning the probe laterally across a silicone phantom containing a stiff inclusion. Although it showed lower accuracy than the experiment performed without scanning, the researchers said that the prospect for imaging by swiping the operator’s finger is very encouraging.

“The contrast between sample features was still evident, which indicates that 2D scanning holds a lot of promise going forward,” Sanderson said.

The researchers are now working to embed the optical components of the probe into a surgical glove that would preserve the touch sensitivity and dexterity of manual palpation. They are also improving the accuracy of the 2D scanning.

The technology might also be useful for brain and liver surgery and other types of cancer.