Real-time optoacoustic imaging of breast cancer using an interleaved two laser imaging system coregistered with ultrasound

We present results from a clinical case study on imaging breast cancer using a real-time interleaved two laser optoacoustic imaging system co-registered with ultrasound. The present version of Laser Optoacoustic Ultrasonic Imaging System (LOUIS) utilizes a commercial linear ultrasonic transducer array, which has been modified to include two parallel rectangular optical bundles, to operate in both ultrasonic (US) and optoacoustic (OA) modes. In OA mode, the images from two optical wavelengths (755 nm and 1064 nm) that provide opposite contrasts for optical absorption of oxygenated vs deoxygenated blood can be displayed simultaneously at a maximum rate of 20 Hz. The real-time aspect of the system permits probe manipulations that can assist in the detection of the lesion. The results show the ability of LOUIS to co-register regions of high absorption seen in OA images with US images collected at the same location with the dual modality probe. The dual wavelength results demonstrate that LOUIS can potentially provide breast cancer diagnostics based on different intensities of OA images of the lesion obtained at 755 nm and 1064 nm. We also present new data processing based on deconvolution of the LOUIS impulse response that helps recover original optoacoustic pressure profiles. Finally, we demonstrate the image analysis tool that provides automatic detection of the tumor boundary and quantitative metrics of the optoacoustic image quality. Using a blood vessel phantom submerged in a tissue-like milky background solution we show that the image contrast is minimally affected by the phantom distance from the LOUIS probe until about 60-65 mm. We suggest using the image contrast for quantitative assessment of an OA image of a breast lesion, as a part of the breast cancer diagnostics procedure.