Porcine Liver Photothermal Therapy Evaluated By Shear Wave Elastography:An Experimental Study

ObjectivePLGA-PDPA nanoparticles was used as photothermal conversion materials,and shear wave elastography was used to monitor photothermal ablation treatment of liver tissue,in order to explore new real-time monitoring methods for photothermal ablation treatment of liver.MethodPLGA microspheres were produced by the emulsification method.Under basic conditions,dopamine was self-aggregated on the surface of PLGA microspheres to form PLGA-PDPA nanoparticles with a polydopamine shell.The morphology of the nanoparticles was observed under a light microscope and a transmission electron microscope,and the average particle diameter and potential value were measured by Malvern particle size analyzer.808 nm laser was used to irradiate 1 ml of a PLGAPDPA solution at a concentration of 0.5 mg/ml,1.0 mg/ml,2.0 mg/ml,4.0 mg/ml,and 8.0 mg/ml for 10 minutes,respectively,and the temperature of the solution was measured every minute.Porcine liver was heated by water bath method,SWE used to detect the tissue stiffness liver tissue from 35°C to 85°C,and the change of the tissue stiffness of liver before and after maintaining a certain temperature value of 10 min,obtain the relationship between the stiffness value of liver and the temperature,A comparative analysis was carried out with pathological histology to explore the possible causes of changes in liver stiffness values.SWE was used to monitor the stiffness of liver tissue and display the stiffness distribution of liver tissue in real time with SWE images: the Porcine liver with PLGA-PDPA NPs was injected and with near-infrared laser irradiation,the temperature value of liver tissue in the treatment group by measuring tissue stiffness was estimated to stop photothermal treatment when it reached about 55°C,60°C and 70°C,respectively.The only PLGAPDPA injected group and the only NIR irradiated 10 min group.After treatment was completed,observe the liver tissue of each group by general specimen,and with pathological histology.ResultsThe average particle size value of the made PLGA-PDPA nanoparticles is 209.0 to 7.7nm,and the average potential value is?? The solution was black,with a concentration of 0.5 mg/ ml,1.0 mg/ml,2.0 mg/ ml,4.0 mg/ml,8.0 mg/ml of PLGA-PDPA solution,which rose rapidly to a maximum of about 35°C,42°C,51°C,60°C,67°C,respectively,with NIR.In liver tissue continuous heating test and the time accumulation experiment,temperature values were compared in each group.From 55? to 80?,the stiffness value of liver increased with temperature increasing(P <0.05),The average liver stiffness values at 55?,60?,65?,70?,75? and 80? were 10.72±0.76 kPa,14.40±1.49 kPa,23.20±2.35 kPa,37.46±3.16 kPa,82.14±4.05 kPa,93.06±3.08 kPa,respectively,and stiffness values did not change after 10 min temperature suspended(P>0.05).The pathological tissue observations speculated that the swelling of the intact liver cells and the narrowing of the sinusoids may be the cause of this phenomenon.In the photothermal treatment experiment,the average tissue stiffness of the treatment area measured at 6 min,7 min,and 9 min in the treatment group were 10.9kPa,21.8kPa,and 34.4kPa,respectively.It is speculated that the temperature of the liver tissue has reached 55 °C,60 °C and 70 °C,the liver tissue was found to be whitened to varying degrees after the incision of the liver tissue,and the pathological tissue was observed to have more obvious cell swelling and narrowing of the hepatic sinus.However,the only PLGA-PDPA injection group and only NIR-irradiated group`s specimens and pathological tissues showed no significant changes.ConclusionPLGA-PDPA nanoparticles were successfully produced.The nanoparticles have uniform particle size,good dispersibility,and good photothermal conversion performance,and can be used for liver photothermal ablation treatment.During the temperature rise of liver tissue,when the temperature is 55°C ~ 80°C,the temperature could be inferred by the tissue stiffness value.Using SWE to monitor the liver tissue stiffness value and distribution can estimate the liver tissue temperature and treatment range,so SWE can be used to monitors photothermal ablation of liver.