Quantitative Photoacoustic Imaging Evaluation Of The Structure And Function Of Ischemic Stroke And Liver Fibrosis

Photoacoustic imaging(PAI)is a novel noninvasive imaging modality that uses the differences in optical absorption of oxyhemoglobin and deoxyhemoglobin and may be performed in a dynamic fashion to provide structural and functional information of ischemic stroke(IS)image the indocyanine green pharmacokinetics in the liver.For mouse ischemic stroke model,we adopted dynamic contrast enhanced photoacoustic imaging to assess the stereoscopic and comprehensive pathophysiological status of IS at an early stage.Non-invasive PAI of the IS model in mouse provided structural information of the brain lesion,achieving early disease identification(5 min after the onset of disease).Moreover,it was able to dynamically reflect disease progression.In terms of functional imaging,significant differences in oxygen saturation(sO2)levels between infarcted and normal areas could be observed by PACT,permitting effective functional parameters for the diagnosis of IS.For mouse liver fibrosis model,at the 1st,4th and 8th week of modeling,the changes of liver structure were monitored dynamically by photoacoustic technique.The maximum peak time(Tmax)and the half-life(T1/2)of indocyanine green were calculated in different pathological stages.Corresponding results of liver histopathology and blood biochemical data were obtained.Spearman’s rank correlation was used to evaluate the relationship between the DCE-PAI results and histology scores.The photoacoustic liver function curve showed that the Tmax varied between groups(normal group,9±1.8 seconds(s);1-week,51±4.4 s;4-weeks,73±5.3 s;8-weeks,104±6.6 s,P<.001)and T1/2(normal group,28±6.5 s;1-week,201 ± 12.4 s;4-weeks,285±11s;8-weeks,318 ± 30.5 s,P<.001).There was a positive correlation between the dynamic parameters(Tmax and T1/2)and the histopathological scores;Sirius-red/α smooth muscle actin(αSMA)positive area vs Tmax had Spearman’s rho values=0.93/0.94,both P<.001 and Sirius-red/αSMA positive area vs T1/2 had Spearman’s rho values=0.87/0.89,both P<.001.Our results indicated that PAI can be used to quantitatively evaluate the structure and function of mice with ischemic stroke and liver fibrosis.Photoacoustic technology can be used as a basic tool for the basic research of related disease models.With the improvement of laser technology and the further development of PA technology,it is very hopeful to complete the corresponding clinical transformation and apply it to patients in the future.