Xiangxi Meng BME PhD Defense Presentation   Date: June 5, 2019 Time: 21:00 EDT Location: UAW 4235 (GT), Wangkezhen Bldg 907 (PKU)   Committee members: Qiushi Ren, PhD (Advisor) May D. Wang, PhD (Co-Advisor) Weiqiang Chen, PhD Changhui Li, PhD Shuming Nie, PhD   Multiplexed Molecular Imaging in the Second Near-Infrared Window  The second near-infrared window (NIR-II window) is a certain range of near-infrared light with superior ability to penetrate biological tissues. In this research, the basic imaging properties of the NIR-II imaging were first explored. To enable this, equipment for conducting NIR-II imaging were constructed and corresponding fluorescent materials were prepared. A new technique to monitor the NIR-II fluorescence during the synthetic process of the fluorescent material was developed and applied. Liquid phantoms with Intralipid were used as a model system to verify the imaging ability, and the results obtained were verified with a CLARITY experiment. After obtaining such results, new methods to multiplex NIR-II fluorescence imaging and other biomedical procedures were proposed and explored. Taking the advantage of its special penetration ability, NIR-II imaging could be used to investigate the transient process of the first several seconds of the distribution of fluorescent quantum dots administered via tail-vein injection. NIR-II imaging was also used to visualize the intestine structure and bowel movement real-time on nude mice. The NIR-II imaging was conducted to visualize the process of megavolt X-ray beam radiotherapy. The Cherenkov emission can be observed during megavolt X-ray beam therapies, but most of the energy concentrates in the blue to UV range. With the NIR-II imaging system, the NIR-II part of the Cherenkov emission was visualized. The Cherenkov photon energy was also transferred to the NIR-II range using the NIR-II emission quantum dots. Finally, the Cherenkov emission of the radioisotope Cu-64 was studied.