Quantitative Photoacoustic Imaging of Blood Oxygen Saturation in Deep Tissue

Project: Research

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Quantitative imaging of blood oxygen saturation (sO2) with high resolution provides valuableinformation for many preclinical and clinical applications, such as monitoring tumor treatmentoutcome after chemo or radio therapy, assisting cancer diagnosis based on hypermetabolism,mapping the brain activities according to coupling between neuron activities and oxygenconsumption. PA imaging provides optical absorption contrast at high spatial resolution in deepbiological tissue. Because hemoglobin molecules show distinct optical absorption spectra whenbinding or not binding to oxygen, PA imaging can quantify blood sO2with high sensitivity. PA signalmagnitude is proportional to absorbed optical energy within the unit volume, rather than theintrinsic tissue absorption coefficient. The former is the product of the later and the local fluence.Quantitative imaging of absolute sO2requires compensation of the wavelength-dependent localfluence, which has been a long-standing challenge in the quantitative functional PA imaging in deeptissue. Many efforts have been done to compensate or avoid the use of local fluence in quantitativesO2imaging, such as modeling photon transportation in biological tissue, calculating absorptioncoefficient from PA frequency spectrum, using ultrasound modulation to measure and compensatethe optical fluence. Although these methods showed promising results, the problem ofin vivoquantitative imaging of sO2in deep tissue has not been fully solved.Here, we propose a new PA technique for non-invasive imaging of absolute blood sO2in deepbiological tissue. Central to this proposed research is to explore the temperature-dependentproperty of hemoglobin-oxygen binding, utilize a focused ultrasound transducer to modulate thelocal sO2between two different levels, cancel the unknown local fluence between the PA signals atthe two sO2levels, and finally quantify the absolute sO2. A PA imaging system with ultrasoundheating function will be developed to image absolute sO2in deep tissue. The imaging capability andsafety will be validated in both phantoms and small animal disease models. This technical advance inquantitative PA imaging of absolute sO2in deep tissues will provide a new effective tool fordiagnosing, monitoring, or studying many oxygen-metabolism related diseases.We will focus on the following three specific aims: (1) To study the mechanism and validate thesafety of the ultrasound-based sO2modulation in biological tissue; (2) To develop a PA imagingsystem with ultrasound heating function, and optimize the sO2imaging method; (3) To validate thequantitative sO2imaging with tissue phantoms and demonstrate thein vivoimaging of sO2inGlioblastoma tumor model.


Project number9042525
Grant typeGRF
Effective start/end date1/01/18 → …