Two-photon microscopy traditionally suffers from slow frame rates due to the necessity of raster scanning the laser excitation spot over the field of view (FOV). We have developed a miniaturized elliptical beam shaper (MEBS) which is compatible with the state-of-the-art open-source two-photon miniscopes for imaging neural activity in freely moving mice. The MEBS enables an elliptical two-photon excitation pattern with a long axis of 5-10 µm, which greatly reduces the number of scanning rows required while maintaining cellular resolution in imaging. As a result, the overall frame rate is increased compared to the diffraction-limited-point scanning method. We demonstrate this high-speed miniaturized two-photon microscope in fluorescence imaging and show a significant frame rate improvement while maintaining cellular resolution across a 400 µm diameter FOV.
Noninvasive measurement of fetal oxygen saturation can provide clinicians with critical information about fetal health, and potentially contribute to improved management of childbirth. We recently proposed a novel transabdominal fetal pulse oximetry through frequency-modulated continuous-wave near-infrared spectroscopy. Here, we report our experimental results which validate one of the most important steps of our method. By shining near-infrared light on the pregnant sheep abdomen and measuring the time-resolved reflectance, we have successfully extracted the fetal heartbeat signal originating from deep tissue. This result sets up the foundation to further improve our transabdominal fetal oxygen saturation measurement method.
We propose a novel non-invasive approach to transabdominally measure fetal oxygen saturation via time-domain near-infrared spectroscopy. We employ the frequency-modulated continuous-wave technique to measure the time-resolved reflectance of near-infrared light shining on the maternal abdomen. The time-of-flight reflectance reveals path-lengths of different photons traveling through the tissue, facilitating the separation of signal from the shallow maternal layer and the deep fetal layer. Using two optical wavelengths, oxygen saturation of the fetus can be measured. This technique has the potential to improve labor outcomes by providing an important assessment of fetal health intrapartum.
We propose a new non-invasive approach to transabdominally measure fetal oxygen saturation based on time-domain interferometric near-infrared spectroscopy. We use the frequency-modulated continuous-wave technique to measure the time resolved reflectance of near-infrared light shining on the maternal abdomen. By modeling the maternal abdomen as two-layered media (i.e. maternal and fetal tissue) through diffusion equations, the optical properties of both the maternal and fetal tissue can be deduced. Using two optical wavelengths, oxygen saturation can be measured for both the mother and fetus. This technique could provide an important assessment of intrapartum fetal health during labor in the delivery room.
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