Laser optoacoustic imaging for breast cancer diagnostics: Limit of detection and comparison with x-ray and ultrasound imaging

Laser optoacoustic imaging is a promising diagnostic technique for early breast cancer detection. Capability of laser optoacoustic imaging for visualization of small spherical tumor phantoms located within the bulk collagen gels was studied. The experiments were performed with breast phantoms made of optically turbid collagen gel. Optical properties of the phantom resembled the optical properties of human breast at the wavelength of irradiation, 1064 nm (μ_a=0.11 1/cm, μ_s'=2.92 1/cm). Gel spheres with a higher absorption coefficient, μ_v=0.75 1/cm were used to simulate tumors. The experiments demonstrated the capability of laser optoacoustic imaging to detect and localize 2-mm "tumors" at a depth of up to 60 mm within 100-mm thick breast phantoms. Laser optoacoustic images of the phantom tumors were reconstructed from experimentally measured pressure profiles. The optoacoustic images were compared with images obtained with x-ray mammography and ultrasonography. Comparative study revealed experimental conditions and phantom structure for which the laser optoacoustic imaging outperformed both the x-ray mammography and the ultrasonography. The results suggest that the laser optoacoustic imaging may occupy an important niche in breast cancer diagnostics, particularly, for diagnosis of small tumors in radiologically dense and acoustically homogeneous breast tissues.