Spontaneous preterm birth (sPTB) occurs in about one in ten infants born in the United States and is leading to almost 1 million neonatal deaths worldwide [1]. Diagnostic imaging of cervix is mostly limited to using ultrasound (US) to measure cervical length and has shown a low specificity to determine the risk of sPTB [2-7]. Quantitative functional imaging modalities such as elastography (EL) and photoacoustic (PA) imaging, are commonly used in conjunction with US imaging to provide additional information on tissue compositions and function. We propose using an endocavity probe to acquire US, PA, and EL information of the cervical tissue. Specifically, spectroscopic PA (sPA) is proposed to provide information on cervical tissue such as total hemoglobin (blood perfusion), tissue oxygenation level, and more importantly the collagen-to-water ratio in tissue. Shear wave elastography (SWE) measurements of cervical tissue indicates the correlation between cervical ripening and lower tissue elasticity. Our custom-designed imaging system consists of an endovaginal US transducer (ATL C9-5) capable of performing high frame rate US and acoustic radiation force shear wave imaging, and an optimized fiber-optic light delivery system’s for PA imaging. Our experimental results indicate the system’s ability to measure the presence of different concentrations of hemoglobin in tissue-mimicking phantoms as well as accurate measurement of hemoglobin oxygen saturation (SO2). In another set of experiments, we demonstrated the feasibility of monitoring collagen-to-water ratio in tissues through monitoring changes in sPA signature between 1100 and 1650 nm. Monitoring the variations of collagen in cervical tissue can help to predict sPTB.
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