The state of the art in breast imaging using the Twente Photoacoustic Mammoscope: results from 31 measurements on malignancies.

Objectives: Photoacoustic mammography is potentially an ideal technique, however, the amount of patient data is limited. To further our understanding of the in vivo performance of the method and to guide further research and development, we imaged 33 breast malignancies using the research system - the Twente Photoacoustic Mammoscope (PAM).
Methods: Thirty-one patients participated in this retrospective, observational study. The study and informed consent procedure were approved by the local ethics committee. PAM uses 1,064 nm light for excitation with a planar, 588-element, 1-MHz ultrasound array for detection. Photoacoustic lesion visibility and appearance were compared with conventional imaging (x-ray mammography and ultrasonography) findings, histopathology and patient demographics.
Results: Of 33 malignancies 32 were visualized with high contrast and good co-localization with conventional imaging. The contrast of the detected malignancies was independent of radiographic breast density, and size estimation was reasonably good with an average 28 % deviation from histology. However, the presence of contrast areas outside the malignant region is suggestive for low specificity of the current system. Statistical analyses did not reveal any further relationship between PAM results and patient demographics nor lesion characteristics.
Conclusions: The results confirm the high potential of photoacoustic mammography in future breast care.
Key Points: • Photoacoustic breast imaging visualizes malignancies with high imaging contrast. • Photoacoustic lesion contrast is independent of the mammographically estimated breast density. • No clear relationship exists between photoacoustic characteristics and lesion type, grade, etc. • Photoacoustic specificity to breast cancer from some cases is not yet optimal.