The Application Research Of New Contrast Agent In Photoacoustic Tomography

Photoacoustic imaging(PAI) as a promising technique, combines the spectroscopic capability of light with the penetrability of ultrasound can provide high resolution functional information such as hemoglobin and blood oxygenation relevant to physiology and pathology. This method, however, may has a limited detection depth and lack of endogenous contrast. An exogenous contrast agent is often needed to effectively resolve these problems. Such agents are able to greatly enhance the imaging contrast and potentially break through the imaging depth limit. This paper mainly emphasized on the experimental study of Au nanorods(Au NRs) in photoacoustic tomography(PAT).The outline is as follows:1. The basic theory of PAT and PAI were introduced, and the limitations of PAI were discussed. Then the latest research process and progress of photoacoustic contrast agents were briefly described, and illustrated several groundbreaking contrast agents.The characteristics of spherical and non-spherical Au nanoparticles were compared.This article focused on the optical properties and application of Au NRs in PAT.2. The feature of Au NRs was researched in PAT. First of all, the existing PAT system was improved to realize multi-wavelength experiment. Then PAT experiment based on Au NRs injecting in liver or kidney in vitro. With the delay superimposed image reconstruction algorithm, the result demonstrates that photoacoustic images are capable to show the whole distribution of liver or kidney which is in consistent with the real structure under the wavelength of 532 nm. Besides, photoacoustic images are able to display their internal structure which is clearer with Au nanorods under near-infrared wavelength region.3. The changing of cerebral blood flow was studied before and after injection Au NRs in mice brain. The experiment was divided into three groups, including injection Au NRs by the tail vein of mice, injection Au NRs by tail vein + acupuncture Zusanli in the left hind paw, acupuncture Zusanli in the left hind paw. The repetitive experimental data obtained in the experiments was testing by a statistical analysis method called hypothesis testing. The first group of experimental study found that cerebral blood flow changing reached to the absorption peak within 4 min, and losing enhancement effect.after 28 min. Under the stimulation of acupuncture, the cerebral blood flow increasedwith 8 min, and then decreased rapidly to normal level in mice. The combination of Au NRs and acupuncture can prolong the changing time of blood flow, and the enhancement effect of image is the strongest in three groups.