Photoacoustic breast tomography prototypes with reported human applications.

OBJECTIVES: Photoacoustic breast tomography could provide optical molecular imaging with near-infrared light at sonographic image resolution by utilizing the photoacoustic effect. This review summarizes reports about current prototypes that were applied in vivo in humans.
METHODS: Four databases were searched for reports about prototypes of photoacoustic breast tomography that were tested in vivo in humans. Data extracted from the reports comprised details about system design, phantom studies, and clinical studies.
RESULTS: Five prototypes were included. System designs comprised planar, hemicylindrical and hemispherical geometries. In total, 52 of 61 breast cancers (85 %) were detected by three of the prototypes, showing image details such as ring-pattern of the haemoglobin-rich tumour vasculature. A refined prototype provided submillimetre resolution at a good contrast-to-noise ratio up to a depth of about 5 cm in a cup-shaped breast configuration. Another novel prototype demonstrated that in the mammographic imaging geometry, the total imaging depth approximately duplicates with bilateral laser illumination. Most prototypes focused on detecting elevated haemoglobin content related to tumours, but proof-of-principle was also given for multispectral optoacoustic tomography by additional imaging of tissue oxygenation.
CONCLUSIONS: Photoacoustic breast tomography can detect breast cancer. This radiation-free molecular imaging technology should be further refined and studied for clinical applications. KEY POINTS: • Photoacoustics combines optical imaging with sonographic signal detection. • Photoacoustic tomography could provide molecular imaging at high image resolution. • Prototypes have been designed for human breast cancer imaging. • Preliminary evaluation studies show that photoacoustic tomography detects breast cancer. • This radiation-free method should be further improved and studied for clinical applications.