Laser optoacoustic imaging of breast cancer in vivo

A clinical prototype of the laser optoacoustic imaging system (LOIS) was employed for breast cancer detection and localization in patients with confirmed breast cancer and scheduled for radical mastectomy. The prototype LOIS used a single optical fiber for delivery of laser pulses, an arc shaped 32-element PVDF transducer array for ultrawide-band piezoelectric detection of optoacoustic signals and a single-channel data acquisition card for signal processing. The resonance ultrasound frequency of the 110 μm PVDF film was outside detectable range of ultrasound. Spatial resolution of the transducer array was slightly better than 1mm in radial direction and slightly worse than 1 mm in lateral direction. The system was optimized for contrast and sensitivity. Data acquisition, signal conditioning and image processing were significantly improved and optimized resulting in reduced image frame rate of 2 seconds employing 700 MHz Aphlon processor. The computer code for digital signal processing employed band-pass hyper-Gaussian filtering and denoising. An automatic recognition of the optoacoustic signal detected from the irradiated surface was implemented in order to visualize the breast surface and improve the accuracy of tumor localization. Radial back-projection algorithm was employed adopting combination of integration along spherical wavefronts and integration along planar wavefronts (as in Radon transform) for image reconstruction. The system performance was evaluated initially in breast tissue-like phantoms with embedded blood vessels. Clinical studies in breast cancer patients scheduled for surgical mastectomy were performed and compared with x-ray radiography, ultrasound and pathology reports.