With Europe’s aging population, its high incidence of breast cancer, its tightening health-care budget, and room for improvement in conventional breast imaging modalities, there is a need for a technique that can provide images with high specificity, contrast and spatial resolution. Photoacoustic imaging may turn out to be that technique. In photoacoustics, the contrast is dependent on light absorption in tissue. Since blood, fat and water in tissue absorb light depending on the wavelength used, the method can provide spectroscopic (molecular) specificity to these and other tissue constituents. Blood is of interest as a biomarker since more blood vessels are often present at tumor sites.
PAMMOTH brought together experts from various disciplines to work on a new generation system for imaging the breast using both photoacoustics and ultrasound. Academia, industry and the clinic from 6 different countries were part of the PAMMOTH consortium. The consortium’s objective was to develop, validate and begin exploitation of a dedicated breast imaging device. The proposed device would combine non-invasive 3D photoacoustic imaging with ultrasound imaging to provide full-breast, multimodal images to the radiologist. The device has high through-put, possesses no carcinogenic potential, uses no contrast agent and causes no pain or discomfort to patients.
At the conclusion of the project, we have developed the PAMMOTH imager which can extract two imaging contrasts from tissue, and performed first in human studies. From the study on 10 patients patients, the images do not seem as yet to reveal universal and unmistakable PA imaging biomarkers. Yet it has been possible to visualize specific features at tumor locations which may have diagnostic potential. The presence of the ring pattern of photoacoustic intensity around the tumor, and progressive reduction of photoacoustic intensity inwards into the tumor may turn out to be important signatures of breast disease. The contribution of the sound speed has been helpful to provide context to these blood vessel morphologies, as well as identify tumors from healthy surrounding.
Future work will concentrate on continuing the inclusion of patients, and continuing the analysis of the data. The onus will now lie on extracting the information from the PA data which will depend on improved image reconstruction for retrieving the US reflectivity, blood oxygen saturation in and around tumor vessels as well as on improved image processing, image analysis and visualization.
