Biomedical Spectroscopy and Imaging

In view of the global pandemic that started in 2020, caused by COVID-19, the importance of the existence of fast, reliable, cheap diagnostic techniques capable of detecting the virus even in the first days of infection became evident. This review discusses studies involving the use of spectroscopic techniques in the detection of viruses in clinical samples. Techniques based on mid-infrared, near-infrared, Raman, and molecular fluorescence are explained and it was demonstrated how they can be used in conjunction with computational tools of multivariate analysis to build models capable of detecting viruses. Studies that used real clinical samples from 2011 to 2021 were analyzed. The results demonstrate the potential of the techniques in detecting viruses. Spectroscopic techniques, as well as chemometric techniques, were also explained. Viral diagnosis based on spectroscopy has interesting advantages compared to standard techniques such as: fast results, no need for reagents, non-destructiveness for the sample, no need for sample preparation, relatively low cost, among others. Several studies have corroborated the real possibility that, in the near future, we may have spectroscopic tools being successfully applied in viral diagnosis.

When light is illuminated using a broad spectrum and detected without physical contact between source and detector the method is often referred as diffuse reflectance spectroscopy (DRS). Combined with newest computational algorithms, DRS may reach high performance in near future in tissue characterization and pathology. In this study, we show that DRS can be used to automatically differentiate untreated fresh liver tissue from heat-induced and chemically induced tissue denaturation in bovine liver ex vivo. For this, we used a thresholding algorithm that was developed and tested using 10-fold cross validation. Our results indicate that DRS has potential to detect pathological tissue processes that result in tissue injury and ultimately tissue necrosis. The detection of necrosis is important for many medical applications, not least for tissue sampling by biopsy needle, where additional guidance to commonly used ultrasound would be welcome. Furthermore, cancer tissue is prone to necrosis as a result of tissue hypoxia and due to cancer treatments.