Coregistration of Angiogenesis Related Hemoglobin and Tissue Density in Breast Tumors Using Real-Time Opto-Acoustic Imaging Combined with Ultrasound.
Authors: Fronheiser M. , Herzog D. , Joy J. , Keane W. , Otto P. , Ermilov S. , Conjusteau A. , Brecht H. , Su R. , Mehta K. , Oraevsky A. 
Published: December 2010

Abstract
BACKGROUNDThis study was performed to provide preliminary clinical feasibility for the characterization of breast tumors using a real-time dual modality laser opto-acoustic and ultrasound system to provide noninvasive characterization and differentiation of breast tumors based on the concentration of blood and its oxygen saturation in the tumor angiogenesis while also showing structure information based on traditional ultrasonic imaging methods. Opto-acoustic imaging uses pulses of laser light in the near-infrared spectral range to illuminate tissues and detects the resulting pressure with arrays of ultrawide-band ultrasonic transducers. After image reconstruction, tumor location, shape and dimensions are determined with a spatial resolution of better than 1 mm.MATERIALS and METHODSLaser illumination at the wavelength of 757 nm provides contrast based mainly on the hypoxic blood of breast carcinomas, while a wavelength of 1064 nm produces contrast dominated by the enhanced water content and normally oxygenated blood in benign fibroadenomas. Detection of the resulting ultrasonic signals with a commercial handheld ultrasound probe preserves quantitative information about the tumor optical absorption. Two opto-acoustic measurements yield solutions for the concentrations of hemoglobin and oxy-hemoglobin in pixels within the field of view. In the same location, ultrasonic images are generated to provide structure information. The optoacoustic information is displayed with the ultrasonic image to provide coregistered images containing structural and functional information.RESULTSInitial studies on 15 patients demonstrated that the combined opto-acoustic/ultrasound imaging system can detect areas of high optical absorption in the region of the tumors, confirmed with ultrasound, across varying tissue densities. Measurement and display of the optoacoustic signal amplitudes showed tumor brightness proportional to the optical absorption. Information obtained at two different wavelengths, one preferentially absorbed by hemoglobin (757 nm) and the other preferentially absorbed by oxyhemoglobin and water (1064 nm) provided noninvasive differentiation of breast carcinomas from benign tumors based upon differences in absorption in the region of the tumor.DISCUSSIONThe combination of optically-induced functional contrast and acoustically generated high resolution imaging in a novel breast cancer imaging modality demonstrated clinical feasibility and the potential for noninvasive diagnostics. Furthermore, coregistered ultrasonic and opto-acoustic images provide complimentary structural and functional images. This new imaging system is envisioned as an adjunct to X-ray mammography by providing ultrasonic imaging enhanced with functional information based on the optoacoustic spectroscopy.
Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5023.