The Preliminary Study On Real-time Monitoring By Ultrasound Image During Pulsed High Intensity Focused Ultrasound Irradiation

BACKGROUND AND OBJECTIVESome previous research found that the strong echo of target area onultrasonographic after HIFU irradiation immediately relate to cavitationeffect and bubble behavior in the process of HIFU treatment. Previousultrasound real-time monitoring process is also based on this principle,through the ultrasonographic changes after treatment immediately and grayvalue changes to determine the reliability of the coagulation necrosis andjudge the accuracy of target area, Although received good results, but not inthe true sense of real-time monitoring, its target gray value changes duringthe treatment can not be effectively monitored, and if the deviation fromtarget during treatment, showed focal area target location after treatment,now can’t recover. Therefore, in the treatment process of this technology tothe real-time monitoring is very important.The purpose of this paper is to through research the real-timemonitoring during PHIFU rradiation, discuss the feasibility of B ultrasonicmonitoring in the process of PHIFU irradiation, and the gray value changesand histological changes of target under the pulse parameters of PHIFU irradiation, providing a new method to real-time monitoring during HIFUirradiation and reliable experiment basis.MATERIALS&METHODS1. The observation B-Mode Ultrasound Image after PHIFU irradiationimmediately and the biological effect experiment1.1Experiment Equipment:（1）MRIgHIFU treatment system，fromthe Chongqing Haifu Technology Co．， Ltd． jointly developed andSIEMENS．Treatment of head parameters：diameter200mill，focal length150mm，frequency1．0MHz．（2）High intensity focused ultrasoundtreatment system, from the Chongqing Haifu Technology Co．，Ltd．Treatment of head and parameter system with MRJgHWU．1.2Experiment Object： The samples of bovine liver tissue invitro(within6hours of slaughter)，immersed in0.9%saline，select theconnective tissue and blood vessels less office cleaning，cut into10cm×10cm×8cm size，30min spare conventional degassing．1.3Experimental Method：（1）Select12fresh in vitro bovine livertissue, adopts fixed point and point way irradiation, set the irradiation poweris300w, depth of the irradiation is20mm, experimental group（PHIFU）according to the duty cycle for1~5groups, duty ratio and accordinglyirradiation time, respectively are5%、120s；10%、60s；20%、30s；50%、12s；75%、8s；control group（CHIFU）Irradiation time is set to6s.Monitoring the targer temperature by MRI during irradiation.（2）The above test are repeated on high intensity focused ultrasound treatment system,Irradiation parameters as above, record ultrasonogram by ultrasound beforeand after irradiation. Observe the temperature changes in irradiation focus,ultrasonogram gray level difference after irradiation immediately,and thevolume of necrosis.2. The experiment of real-time monitoring by ultrasound image duringPHIFU2.1Experiment Equipment:（1）High intensity focused ultrasoundtreatment system, from the Chongqing Haifu Technology Co．，Ltd．Treatment of head parameters：frequency0.93MHz,diameter220mill，focal length140mm．（2）Gray processing software: GrayAnalyse, from theChongqing Haifu Technology Co．，Ltd．（3）video processing software:Photron FASTCAM Viewer3.0,from US Photron company.2.2Experiment Object：With the first part.2.3Experimental Method：（1）Depth of the irradiation is20mm,Irradiation time is5s, pulse repetition frequency is10Hz. The duty ratio ofpower group is10%, power respectively are150W，250W，350W，450W，550W.The power of duty ratio group is600W, duty ratio respectively are2%，4%，6%，8%，10%.Repeated for each parameter experiment10times.Using ultrasound to observe the target gray level changes during the wholeprocess of irradiation, the ultrasound image of before irradiation, irradiationprocess (1s,2s,3s,4S,5s) and immediately after irradiation were selected respectively, calculation of the target gray difference of ultrasound image,and to compare the probability of the irradiation process of Kn (n=1,2,3,4,5)and immediately after irradiation (Kj) gray difference is greater than athreshold10.RESULT1. In the first part of the experiment, the maximal temperatures amongcontrol group,3～5group respectively were （95.60±11.50℃）、（89.60±12.60℃）、（89.90±12.10℃）、（94.10±9.70℃）, there was nostatistical difference among all groups （P＞0.05）, target area organizationwere coagulation necrosis. the maximal temperatures of group5%and10%respectively were（53.30±3.90℃）（、56.70±4.10℃）, there was no statisticaldifference between the two groups（P＞0.05）, target area organization werehole shaped damage. There was no statistical difference among all group intarget area necrosis volume（P＞0.05）. After hematoxylin-eosin staining,the cells’ structures were destroyed, nucleus pycnosis, and there are amountof vacuoles in the cytoplasm under the microscope in1、2group. the cells’structures were destroyed, part of the nucleolus were disappeared and thecytoplasms were homogeneous under the microscope in3～5group.Observe ultrasound image after irradiation immediately，the target grayscaleimages of1,2group didn ‘t change significantly,even appeared low echoarea; The images of control group and3～5group all were high echo area.2. In the second part of the experiment, During PHIFU irradiation,target gray value increased with the increase of power, duty cycle and time,butimmediately after irradiation target gray value abate or disappear, K2, K3,K4, K5greater than Kj (P <0.05). Target area organization were holeshaped damage. The edges of hole is obviously different from normaltissue,the cells’ structures were destroyed, nucleus pycnosis, and there areamount of vacuoles in the cytoplasm under the microscope.CONCLUSION1.CHIFU and long duty cycle of PHIFU are easy to form heating effect,lead to target tissue coagulation necrosis, the B-Mode ultrasound Images oftarget can create high echo area; Target area organization were hole shapeddamage by the short duty cycle of PHIFU through non-thermal effects, theB-Mode ultrasound Images of target weren’t changed obviously, so theultrasonogram after irradiation immediately cannot fully reflect the situationof the tissue damage; The length of duty cycle does not influencesignificantly the necrosis volume of tissue.2.During PHIFU irradiation process, target gray value would beincreased with the power increasing, duty cycle and time, but abated ordisappeared immediately after irradiation.3.The way of real-time monitoring by ultrasound image during PHIFUirradiation is more effective than post-irradiation.