Research On Ultrasound Images Applied To Evaluate Tissue Injury Caused By Pulsed High Intensity Focued Ultrasound

Background:As an emerging non-invasive tumor treatment, HIFU (high intensityfocused ultrasound) has been widely used in the clinical treatment of avariety of benign and malignant solid tumors in recent years. It is becauseHIFU is a non-invasive treatment method, how to accurate monitoring of thetreatment process and evaluation of treatment effect become an importantissues in HIFU treatment. There are three ways it can be used to monitor theHIFU treatment: US(ultra-sonography)、 MRI （Magnetic ResonanceImaging） and CT （computed tomography）. Although CT has highimage-contrast and tissue-resolution, because of its ionizing radiation hasgreat impact on human health, it is less used in clinical treatment. MRIimages have sharp contrast, high spatial resolution, non-ionizing radiation,and does not affect the HIFU sound field, however, its imaging inflexible,not easy to achieve real-time monitoring, to some extent limited its clinicalapplication.Compare with this two methods, US imaging flexible, real-time,low-cost, non-ionizing radiation and compatible with ablation device. Itbecomes the most widely used and highly potential method of monitoringand evaluation method.There are still some limitations in US-guided HIFU. Currently, gray-change evaluation is the commonly used method of evaluation of tissuecoagulation necrosis, that is, stop irradiation when strong echo appears onthe ultrasound image. But it is usually can not see grayscale change whencoagulation necrosis occurred during continuous wave HIFU irradiation. Sowe must extend irradiation time and increase doses, it made the rate ofcomplication increase and reducing the security of the HIFU treatment. InPHIFU irradiation, Ai Huijian studies have shown that irradiation underhigh power (500W), low duty cycle (1%-4%) the sonogram gray not onlydoes not increase, but lower than before. Then, we use pulse wave HIFUirradiation, can gray-changes of sonographic reflect tissue damageaccurately? This study was to explore effective ways of PHIFU monitoringthrough compare the grayscale change of sonogram and correlation functionanalysis two ultrasound monitoring methods. Provide the basis for researchand clinical application of PHIFU.Objective:(1) To explore the accuracy of sonographic gray and correlationfunction analysis these two methods on determine coagulation necrosis. Toimprove the sensitivity of ultrasonography determine tissue necrosis madeby PHIFU treatment.(2)To explore the accuracy and stability of sonographic gray andcorrelation function analysis these two methods on determine coagulationnecrosis, between perfusion and non-perfusion isolated porcine live afterPHIFU irradiation use isolated porcine live perfusion model. To improve thesensitivity of ultrasonography determine tissue necrosis made by PHIFUtreatment.Materials and Methods:(1) Fresh bovine liver in vitro, degassing and soaked in0.9%NS, with HIFU. According to the different therapeutic dose, the treatment weredivided into2groups: group A(2000J)and group B(1440J).Because of thedifferent duty cycle，group A and group B were divided again into groupA1(power100w,duty cycle100%, Irradiate20s), group A2(power100w,duty cycle50%, Irradiate40s), group A3(power100w,duty cycle40%,Irradiate50s), group B1(power120w,duty cycle100%, Irradiate12s), groupB2(power100w,duty cycle50%, Irradiate24s)and group B3(power100w,duty cycle40%, Irradiate30s).Were observed by ultrasonic imagechange after irradiating, and calculate correlation function of the imagebefore and after irradiation, pathological findings as the Standard, comparethe accuracy of the two methods correlation function and gray-scale change.(2) Establish isolated porcine live perfusion model, dot-exposed inisolated porcine live perfusion model. Therapeutic dose were set for640J,system output power80w, cycle/frequency set10ms/100Hz. The treatmentdivided into group A and group B. Group A receive irradiation at perfusionconditions and group B receive irradiation after stop perfusion5minites,rest of the conditions was same to group A. Each group were divided3groups again. Group A1and group B1: continuous wave HIFU irradiate8s,groupA2and group B2: pulse wave HIFU of duty cycle50%irradiate16s,groupA3and group B3: pulse wave HIFU of duty cycle40%irradiate20s.Were observed by ultrasonic image change after irradiating, and calculatecorrelation function of the image before and after irradiation, pathologicalfindings as the Standard, compare the accuracy and Stability of the twomethods correlation function and gray-scale change.Results:(1)It contains25points in A1, A2, A3, B1, B2, B3each group, totally 150irradiated points. Explicit coagulation necrosis occurred in all the150points. The grayscale significant change was group A172%and group B192%after continuous wave HIFU irradiation，and this data in each pulsewave HIFU groups were about50%. The gray-scale changes do not follow anormal distribution, the median of gray-scale changes in group A1is47（89-25），in group B1is66（87-41）. In pulsewaveHIFU groups medianof gray-scale changes is22.5（46-9）, and6cases in it difference of grayvalue is negative. Compared the gray-scale changes of the two groups, thedifference was significant(Z=-5.361，p=0.000). It can be seen that theaccuracy of sonographic gray scale used to judge coagulation necrosiscaused by PHIFU was low. The probability of correct judgment ofcorrelation function method to judge the tissue damage caused bycontinuous wave HIFU was group A192%and group B188%. And this datain each pulse wave HIFU groups were up to80%. Based on the above twosets of data, the probability of correct judgment of the correlation functionmethod (90%) was slightly higher than that of sonographic gray change(84%) under continuous wave HIFU irradiation. But the probability ofcorrect judgment of correlation function method(85%) was significantlyhigher than that of sonographic ray change(51%) under pulse wave HIFUirradiation(χ~2=26.422，P=0.000), although the dose and duty cycle weredifferent. That is to say, the accuracy of correlation function method wassignificantly higher than that of sonographic ray change when judge theinjury caused by PHIFU.(2)In groupA1the number of necrosis is21， not-necrosis is9；Ingroup A2the number of necrosis is25，not-necrosis is5；In group A3the number of necrosis is26，not-necrosis is4；In group B1the number ofnecrosis is23，not-necrosis is7，In group B2the number of necrosis is26，not-necrosis is4；In group B3the number of necrosis is28，not-necrosis is2. In the case of perfusion, the probability of correct judgment of correlationfunction method can reach80%, whether it is to determine the tissue damagecaused by the continuous wave or pulse wave HIFU. It means that accuracyand sensitivity of correlation function method higher than that ofsonographic ray change (p<0.05). Then compare the probability of correctjudgment of correlation function method in perfusion and non-perfusionisolated porcine live, there is no statistically significant difference betweenthem (p>0.05), the accuracy of correlation function method do not beaffected by the perfusion flow signals. That is, determine tissue damagecaused by PHIFU use correlation function analysis, not only have highaccuracy and sensitivity, but also less susceptible to the impact of blood flowsignals, has a strong stability.Conclusion:Monitoring PHIFU radiation damage, can not only depend onSonographic gray change, Judge tissue damage caused by PHIFU thecorrelation function method can be more accurate and sensitive. Underinfusion conditions, the accuracy and sensitivity of correlation functionmethod was still higher than sonographic gray change, and its accuracy is notreduced due to the impact of the flow signal, can reflect the tissue injurycaused by PHIFU steady and accurately.