Transient triplet differential (TTD) based photoacoustic lifetime (PALT) imaging provides valuable means for background-free molecular imaging and mapping of the oxygen partial pressure (pO2) in deep tissues. However, the broad application of this method is hindered by its long scanning time, poor accuracy, and low stability. This is mainly because most PALT systems execute the three data acquisition sequences separately without automatic control and neglect the long-time fluctuation of the laser output. In this work, we have proposed a novel automatic interleaved data acquisition method for PALT. This new method not only improved the scanning efficiency but also eliminated the long-time fluctuations of laser pulse energy. Results show that this new method can significantly improve the system’s stability and help reduce the scanning time. With this new method, we obtained the 3D background-free TTD images for the first time. We also observed distinct hypoxia inside the tumor due to the high metabolic rate of cancer cells, demonstrating the high reliability of our proposed method. The proposed method in this work can significantly promote the application of PALT imaging in biomedical studies.
Poly (L-lactide) was grafted onto chitosan by ring-opening copolymerization under microwave irradiation in the presence of tin octoate (Sn (Oct)2) as catalyst. The chemical structure and physical properties of the copolymers with different feeding ratios were discussed by FTIR, DTG and X-RD, taking pure chitosan as reference. The results showed that the application of microwave irradiation in the reaction could achieve the copolymer with high grafting percentage in a short time and low temperature. The thermal stability and crystallinity were decreased with the feeding ratio increasing, attributing to the increasing of grafting percentage.
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