SOLUS Project aims for more accurate breast cancer diagnosis

21 Mar 2017

European system will combine ultrasound, elastography and diffuse optical tomography.

Differentiating between benign and malignant lesions when diagnosing breast cancer is a significant clinical challenge, and ways to reduce the number of false positives recorded during examination are highly desirable.

A European research project coordinated by Politecnico di Milano is aiming to develop a platform that could help. The instrument envisaged by the SOLUS Project - from Smart OpticaL and UltraSound diagnostics of breast cancer - will combine optical methods based on diffuse optical tomography (DOT) with both conventional ultrasound imaging and advanced quantitative elastography.

Such a platform could provide a valuable multi-modal imaging system able to classify breast lesions detected during mammography screening in a non-invasive manner, and significantly improve the ability to identify malignancies.

Each of the three modalities used in SOLUS is known to be effective to some extent in breast cancer discrimination, but they have yet to fully realize their potential for clinical diagnosis. The principle behind SOLUS is that when used in concert in one platform, they can offer a major advantage over separate applications of the techniques.

Compact systems
"B-mode, or two-dimensional, ultrasound scanning is routinely used in clinics, while quantitative shear wave elastography is available on some commercial instruments, although typically is not yet used in routine clinical examinations," commented Paola Taroni of Politecnico di Milano, one of the nine partners in the SOLUS consortium. "However, few academic and commercial systems for DOT are available, and the technique is still mostly in the research phase."

Taroni's group at Politecnico di Milano specializes in diffuse optical techniques operating in the time domain, the approach currently believed to deliver the most useful information about the photons collected during the examination and the heterogeneous areas revealed within the tissues of interest.

"Time-domain DOT is now taking advantage of recent developments enabling higher performance and more compact devices, offering ways to overcome the limitations of previous devices in terms of both sensitivity and penetration depth into tissues," she said. "Systems have previously been table-top size, but the possibility of squeezing them down to a few cubic centimeters is clearly changing the potential for their use outside the lab, and for their effective integration into multimodal instruments."

To deliver that size reduction the project is developing an innovative smart optode, a small and low-cost device for optical tomography said by SOLUS to be the first multi-wavelength time-gated time-domain module for diffuse optics within a small-footprint device. Integrating several of these smart optodes directly into the ultrasound probe should lead to improved light harvesting and ultimately to real-time DOT acquisition, allowing a chemical and structural analysis of the suspect lesion.

Other cancers, and other applications
DOT and optical mammography in general have been under development for some time and promising results have been achieved, but the techniques have as yet made limited translation into wide clinical application. The use of widely different protocols and instruments during clinical studies may have played a part in this inertia, so development of the SOLUS optode is in part intended to promote greater standardization in performance assessment and study protocols.

"Specifically, SOLUS can make a step forward in the use of ultrasound information to guide DOT reconstruction," noted Taroni. "It would for the first time combine in a multi-parametric analysis the information on tissue composition and physiological parameters provided by DOT with the data on tissue stiffness provided by elastography, alongside morphological information from ultrasound imaging," .

The microelectronic architecture of the optode has been designed to allow straightforward large-scale manufacture, potentially opening up opportunities to employ it in both multi-optode clinical applications, and single-optode consumer appliances outside of medicine.

"The multi-modal SOLUS instrument can find application in the diagnosis of cancers other than breast cancer, but will also allow development of wearable devices for reliable and quantitative monitoring of physiological parameters during medical rehabilitation or sports training," commented Taroni. "Its small size and low cost will make it attractive for applications in different fields - for example, the non-destructive assessment of fruit quality, just to mention a field our research group is already familiar with."

• The SOLUS project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No. 731877 and is an initiative of the Photonics Public Private Partnership.