Ultrasonic Cavitation Blocking Normal Liver Blood Promote The Temperature Of Ultrasound Thermotherapy

BackgroundCancer treatment is known as a difficult and hot research in the medical field. For the treatment of inoperable tumors, local high temperature thermotherapy is one of the primary means of treating the liver cancer. As the tumor cells are more sensitive to heat, at the same temperature, normal tissue can be free of or less of injury or damage, which makes thermotherapy an important method of cancer treatment. Now, the common ways of enhancing the effects of thermotherapy are as follows: First, improve the radiation energy, which is achieved by increasing the transmission power and extending irradiation time. But the over high energy may also cause damage towards the sound transmission path and the surrounding tissues. Second, change the acoustic properties of the target tissues and enhance acoustic impedance to improve the effect of energy deposition in the target area. Third, reduction of tissue blood perfusion, increase the heat energy in the local area. But by now, a way of blocking the blood supply towards the tumor area has not been found yet.During the thermotherapy, the thermal distribution is the key to the successful treatment, and the control of temperature is an important determinant of the thermal distribution. For the commonly used laser for microwave frequency generation in clinic, the needle distance and the effective range of each needle is not easy to control precisely, so that it can not guarantee that the tumor be heated in a balanced way. Because of heat loss by blood circulation,heating effect out contral .Therefore, the scope of thermotherapy, the process of heating, the control of the maximum temperature and other issues are still to be studied.Previous study found that cavitation ultrasonic caused by micro-bubble can separate the mechanical damage from the small blood vessels wall in normal rabbit liver , to cause bleeding, hematoma and thrombosis and therefore to block the blood flow temporary. During this experiment, maybe a new non-invasive embolism was used to block the local blood supply. This method can be free of the influence of the blood circulation, which can remove heat to cause the temperature increase. And then, through the Thermotherapy, study whether blocking blood flow can strengthen the effect of ultrasonic Thermotherapy.ObjectiveThis study is based on micro-bubble caused ultrasound cavitation blocking normal rabbit liver blood flow. The purpose of the study is to discuss the effect of the temporary blocking of liver blood perfusion on the liver ultrasound thermotherapy, and to analyze the possible damage towards liver.Materials and Methods1.Principal instruments and reagents1. Experimental instruments:The small, pulsed, focused ultrasonic cavitation treatment apparatus developed by Xinqiao Hospital of the Third Military Medical University, with a treatment probe frequency of 831KHz, an emission duty of 0.5%, a peak negative pressure of 4.6 MPa, a mean sound intensity of (ISPTA)0.89 W/cm2. Logic 9 color Doppler ultrasonic machine with ultrasonic contrasting mode (GE). Ultrasonic therapeutic apparatus of Australia Metron (Meikang Corporation) Thermodetector of Guangzhou Shenggao Observe and Control Technology Co. Ltd.2.Experimental reagents:"Zhifuxian", a kind of lipid microbubbles in milky suspension developed by Xinqiao Hospital of the Third Military Medical University, with perfluoropropane as core gas at approximately(4-9)×109 microbubbles/ml. 98% microbubbles <8μm (mean, 2μm) in diameter.3.Methods40 healthy New Zealand rabbits were randomly divided into 4 groups, each for ultrasound and microbubble with thermotherapy (USC + MB + UST), a simple micro-bubble with thermotherapy (MB + UST), saline with thermotherapy (NS + UST),and a simple micro-bubble + sham thermotherapy control group (MB + Sham). 10 in each group. Open the abdomen to explore the left middle liver, then each group was treated ultrasonic Cavitation and thermotherapy as follows:(1) Ultrasonic Cavitation1) USC + MB + UST Group: inject lipid microbubbles contrast medium via ear vein with 5 minutes of pulse ultrasonic irradiation towards the liver.2) MB + UST Group: inject lipid microbubbles contrast medium via ear vein with no pulse ultrasonic irradiation3) NS + UST group: inject physiological saline via ear vein with no pulse ultrasonic irradiation4) MB + Sham group: inject lipid microbubbles contrast medium via ear vein with no pulse ultrasonic irradiation(2) ThermotherapyAfter the treatment of Ultrasonic Cavitation, each group uses part of the liver where blood flow has been blocked through thermotherapy of ultrasound therapy apparatus. Them insert the temperature electrode,Every 10 seconds, write down the temperature by using thermodetector. After the temperature reaches 42℃, it continued to hyperthermia for 10 minutes, all for about 20 minutes; MB + Sham groups according to the implementation of ultrasound hyperthermia leave (not fired ultrasound hyperthermia energy), temperature measurement time about 20 minutes also .(3) Contrast Enhanced Ultrasound Liver function tests and PathologyAs for the Group 1, 2 and 4, observe the change of the liver blood flow before the block, after the block and after the thermotherapy by Contrast Enhanced Ultrasound. But group 3 having CEUS only after the thermotherapy.Take the venous blood of each group before the block, after the block and after the thermotherapy to observe the liver enzymes. After the operation, take the treated liver tissue as HE staining, observe the liver cells and sinusoids under the light microscopy.(4) Analyses1) Visual density analysis: The dynamic ultrasonic contrasting images of the target area were recorded at various time points in each group. The digital images of points of interest were imported in the JPG format, and then were subjected to quantitative grayscale analysis using the histogram feature of Adobe Photoshop CS3 software. The cross-section of large or medium vessels should be avoided during sampling. The mean grayscale value in the sampling window was calculated automatically by the software. 2) Record the temperature change, calculate the final temperature range, depict temperature variation curve, and pathologically examine the change of liver blood vessels and cells.Results1.Visual densityBefore treatment, in USC + MB + UST group, the mean grayscale value and ROI contrast mean grayscale value 116.42±6.18~119.52±4.14differed insignificantly between the 1.2.4groups at various time points. in the three groups; 0min after the cavitation treatment, in the USC + MB + UST group, the peak gray value of ROI was significantly reduced by 0.42±0.29 ~ 2.18±0.68 after thermotherapy, while for MB + UST group, NS + UST group and the MB + Sham group, whenever the time is, the average gray value is within 112.98±7.73~118.30±3.87, there was statistical difference in the groupitself.2.Temperature changeIn USC + MB + UST group, the temperature rose steadily after thermotherapy, eventually the maximum temperature rise (mean, same below) up by 17.81±2.41℃, which means the most obvious effect of Thermotherapy. It took 7.43±1.49min (minutes) to reach 42℃, there was no significant difference with the MB + UST group, which took 7.00±5.17min (P>0.05), the temperature curve was most fitted with the equation, regression coefficient, linear equation R = 0.909 the quadratic curve equation R = 0.924; MB + UST group's final temperature rise up by 13.23±5.89℃, compared with the USC + MB + UST group P = 0.159, temperature curve was not well fitted with equation, regression coefficient, linear equation R = 0.259 the quadratic curve equation R = 0.277; NS + UST group's final temperature rose up by 7.11±2.78℃, and many groups failed to reach 42℃, the temperature change curve was poor to fit with the equation, regression coefficient, linear equation R = 0.632 the quadratic curve equation R = 0.639; MB + Sham group's final temperature rise by-0.68±0.88℃, and can not be up to 42℃, temperature curve was the worst to fit with the equation, regression coefficient, linear equation R = 0.115 the quadratic curve equation R = 0.119. At the same time, each groups recorded the temperature of the non treated liver, in the first three groups, the temperature increased slightly than the one before Thermotherapy (3.15±1.36~3.88±2.13), the range of change was far less than treated parts (P <0.01), there was no significant difference among the three groups; MB + Sham group's temperature reduced by 0.94℃on their own, there was no significant difference (P>0.05).3.Liver function testsLiver enzymes increased, and there was difference among the groups (P <0.05 , mainly caused by the time factor, the experimental treatment group was also a factor; no significant differences had been found in the coagulation (P>0.05).4.Pathological changesUSC + MB + UST Group: Thermotherapy portal area had tissue hyperemia, hemorrhage and thrombosis, and the wall of Sucquet's canal was injured, there was massive haemorrhage in sinus hepaticus. The liver cells were opaque and tumorous, there were some vacuoles distributed in some tissues. MB + UST group: Thermotherapy portal area had tissue hyperemia, less hemorrhage in some parts; the wall of Sucquet's canal was relatively complete; there was less hyperemia in sinus hepaticus, and the liver cells were opaque and tumorous, there were some vacuoles distributed in some tissues. NS + UST Group: there were light - moderate hyperemia in some lumens, no bleeding, and some liver cells were less opaque and tumorous. There was no vacuole found. MB + Sham group: there was no hyperemia or hemorrhage in the lumens of the portal area. Sinus hepaticus saw a small amount of scattered red blood cells. There was no significant change in the liver cells.ConclusionsThe cavitation effect resulting from the use of microbubbles and a pulsed ultrasonic cavitation treatment apparatus can block normal liver microcirculation temporarily, Thermotherapy had achieved more significant temperature rise under the foundation than no-cycling blocked . Simply the existence of micro-bubble has a certain temperature to promote the role of ultrasound hyperthermiaTemperature also. After the whole block of the blood flow, the side effect of the treatment was the increase of liver enzymes. There was no significant change in the coagulation index.