Endometriosis is a condition in which the endometrium grows outside of the uterus. One of its severe effects is that it may cause infertility. Investigating only the symptoms of the disease is insufficient for the diagnosis. The correct and the exact diagnosis can be done by laparoscopy. During the disease the amount of molecules such as lipids, proteins and some antigens (i.e. CA125) in the blood serum changes. Raman spectroscopy is a vibrational spectroscopy technique which can analyze specific spectral patterns, substances and molecular changes with high specificity. In this study, Raman spectroscopy has been used as a tool for detecting the changes in blood serum contents for diagnosis of endometriosis.
In our study, the Raman spectra of blood sera of 49 patients with 45 healthy women have been compared. Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) methods are used in the analysis. The results indicated that 1003 cm-1 Raman band (phenylalanine) decreased for the women with endometriosis. In addition, a decrease in 1448 cm-1 band shows that the total amount of proteins decreased. The changes in the bands at 1155 and 1521 cm-1 imply that the amount of carotenoids diminished during the disease which is an expected effect of endometriosis.
According to the analysis results, the sensitivity and the specificity of the Raman spectroscopy analysis were found to be 98.8% and 91.0% respectively for the detection of endometriosis. As a complementary method to laparoscopy, Raman spectroscopy can be used for diagnosis of endometriosis.
Sensing photoacoustic waves brings a lot of loss since the detector distance is in the order of millimeters which also leads to noise in the measured signal. To solve this problem, we used an optically trapped silica particle as a transducer in this study. We used two laser sources, one for optical tweezers (976 nm, CW) and a fiber laser for photoacoustic imaging (SHG output: 532 nm, pulsed). The fiber laser was produced in our laboratory whose pulse duration is 8 ns, pulse energy is 10 µJ, and pulse repetition frequency is 65 kHz. The separation between them in the sample plane is 8 µm. The green laser excited several absorbing mediums such as trypan blue, horse hair, black ink and gold thin film. We tracked the position of trapped silica particle (5µm diameter) when the green laser is on and off. We observed dramatic difference between two states. We have validated that this effect is fully photoacoustic by changing the frequency of the green laser with a chopper which led to the exact same frequency when we calculated the Fourier transform of the position distribution of the trapped silica particle. Also, when we change the power of the green laser, the amplitude of the Fourier transformation of the position distribution of the trapped silica particle changes in the same way.
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