The metabolic rate of oxygen consumption (MRO₂) quantifies tissue metabolism, which is important for diagnosis of many diseases. For a single vessel model, the MRO₂ can be estimated in terms of the mean flow velocity, vessel crosssectional area, total concentration of hemoglobin (CHB), and the difference between the oxygen saturation (sO₂) of blood flowing into and out of the tissue region. In this work, we would like to show the feasibility to estimate MRO₂ with our combined photoacoustic and high-frequency ultrasound imaging system. This system uses a swept-scan 25-MHz ultrasound transducer with confocal dark-field laser illumination optics. A pulse-sequencer enables ultrasonic and laser pulses to be interlaced so that photoacoustic and Doppler ultrasound images are co-registered. Since the mean flow velocity can be measured by color Doppler ultrasound, the vessel cross-sectional area can be measured by power Doppler or photoacoustic imaging, and multi-wavelength photoacoustic methods can be used to estimate sO₂ and C_HB, all of these parameters necessary for MRO₂ estimation can be provided by our system. Experiments have been performed on flow phantoms to generate co-registered color Doppler and photoacoustic images. To verify the sO₂ estimation, two ink samples (red and blue) were mixed in various concentration ratios to mimic different levels of sO₂, and the result shows a good match between the calculated concentration ratios and actual values.

Date Published: 22 February 2011
PDF: 6 pages
Proc. SPIE 7899, Photons Plus Ultrasound: Imaging and Sensing 2011, 789942 (22 February 2011); doi: 10.1117/12.875786

Published in SPIE Proceedings Vol. 7899:
Photons Plus Ultrasound: Imaging and Sensing 2011
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)