Inflammatory skin disorder, eczema, is usually assessed by subjective disease scoring systems such as SCORAD and EASI. These scoring systems are based on clinical observations and questionnaires and hence it is subjected to inter and intra-assessor variability. Here, for the first time, we used optoacoustic imaging to image the structural and morphological changes of the skin in a non-invasive manner. Through a clinical study, we computed specific metrics such as epidermis thickness, total blood volume, vessel diameter in the dermis, ratio of low and high frequency signals. We trained a linear kernel-based support vector machine model for eczema classification using these metrics. We could achieve an accuracy of 86.6% and high sensitivity and specificity of 96.2% and 82.1% respectively. We also formulated a novel Eczema Vascular and Structural Index (EVSI) to objectively assess the severity of eczema.
A flexible membrane based Surface-Enhanced Raman Spectroscopy (SERS) sensor was developed as a viable point-of-care platform to monitor changes of these surrogate indicators of healing status in chronic wounds, such as tumor necrosis factor alpha (TNFα) and matrix metalloproteinase (MMPs). In terms of performance, SERS approach is superior to enzyme-based assays, which are resource intensive. We demonstrated the efficiency of this flexible SERS platform for the sensitive detection of TNFα and MMP9 in the nM to pM range. These substrates may be incorporated into wound dressings to permit routine monitoring of wound status.
Blood flow measurement in deep tissue is important because the circulatory system transports oxygen and nutrition to the tissue and removes carbon dioxide out from the tissue. Several non-invasive optical methods were developed for blood flow measurement in deep tissue, such as diffuse correlation spectroscopy (DCS) and diffuse speckle contrast analysis (DSCA). In this paper we will introduce a new speckle-based method for fast blood flow measurement in deep tissue: diffuse speckle pulsatile flowmetry (DSPF). By using a multi-mode fiber for speckle pattern detection, DSPF achieves high blood flow measurement rate of 300 Hz. It has one of the fastest measurement rates of blood flow among non-invasive modalities.
Significance: Noninvasive in vivo fast pulsatile blood flow measurement in deep tissue is important because the blood flow waveform is correlated with physiological parameters, such as blood pressure and elasticity of blood vessels. Compromised blood flow may cause diseases, such as stroke, foot ulcer, and myocardial ischemia. There is great clinical demand for a portable and cost-effective device for noninvasive pulsatile blood flow measurement.
Aim: A diffuse-optics-based method, diffuse speckle pulsatile flowmetry (DSPF), was developed for fast measurement (∼300 Hz) of deep tissue blood flow noninvasively. To validate its performance, both a phantom experiment and in vivo demonstration were conducted.
Approach: Over the past two decades, single-mode fibers have been used as detection fibers in most diffuse-optics-based deep tissue blood flow measurement modalities. We used a multimode (MM) detection fiber with a core size of 200 μm for diffused speckle pattern detection. A background intensity correction algorithm was implemented for speckle contrast calculation. The MM detection fiber helped to achieve a level of deep tissue blood flow measurement similar to that of conventional modalities, such as diffuse correlation spectroscopy and diffuse speckle contrast analysis, but it increases the measurement rate of blood flow to 300 Hz.
Results: The design and implementation of the DSPF system were introduced. The theory of the background intensity correction for the diffused speckle pattern detected by the MM fiber was explained. A flow phantom was built for validation of the performance of the DSPF system. An in vivo cuff-induced occlusion experiment was performed to demonstrate the capability of the proposed DSPF system.
Conclusions: An MM detection fiber can help to achieve fast (∼300 Hz) pulsatile blood flow measurement in the proposed DSPF method. The cost-effective device and the fiber-based flexible probe increase the usability of the DSPF system significantly.