CEUS In The Assessment Of Artery Stenosis Of Rabbits And Application To Artery Stenosis After Balloon Injuries In Different Degrees

The phyisical examinations of vascular disease include Doppler ultrasonography, CT angiography(CYA),magnetic resonance angiography(MRA),digital substract angiography(DSA),and intravascular ultrasonography.CTA and MRA obtain images by reconstruction,so the image definition is bad and the stenosis rate measured by them are not well related with DSA and pathology.Although DSA is the golden standard, few people choose it only when have they had to accept intervention.Doppler ultrasonography has been adopted widely because of its convenience and low-cost,but the quality of image depends on appropriate modulation of the machine,condition of patients and technique of doctors.People are looking forward to a new method with non-invasion,low-cost and high accuracy to observe the severity of lesion,follow up the entire process,and assess revasculization theraphy.With the developement of intravascular intervention,the incidence of restenosis is higher than before.Due to the limitation of ultrasound condition,the assessment of restenosis is difficult.DSA is regarded as golden standard in a lot of studies on restenosis,but it is high-cost and difficult to practice on animals which can not tolerate again and again within a short period.So,DSA is not suitable to follow up.Contrast-enhanced ultrasonography (CEUS) can distinguish artery lumen by means of enhancing scatter intensity by injection of contrast agent.In my study,I compared the accuracy and reproducibility of CEUS and common ultrasonography(US) in assessment of artery stenosis in different degrees,and recorded the changes of color Doppler and pulse wave Doppler after injection of contrast agent.I also observed the process of abdominal aortic stenosis after different balloon injuries in rabbits and compared the value of CEUS and US in following-up process. Materials and methodsTirty rabbits underwent US,CEUS and DSA by two observers after abdominal aorta was ligated in 3 different degrees(We ligated different diameter needles with abdominal aorta parallelly and then took off the needles).We measured diameter stenosis rate by 2-dimesion,color Doppler flow imaging(CDFI) and CEUS,and some dynamic parameters,such as peak of systolic velocity(PSV),pulse index(PI),resistance index(N),and calculated ratio of systolic velocity(SVR).We compared the accuracy and reproducibility of 4 ultrasonic methods and calculated the concordance coefficient between observers.We also recorded changes of CDFI and parameters on pulse wave Doppler(PW) curve.Tirty rabbit's abdominal aortas were injured by different balloons in order to establish stenosis in different degrees.The light injury group was dealt with a common 3.0mm balloon and the severe injury group was injuried by a special balloon which enveloped with slender wire.They underwent CEUS and US on the 3^rd,7^th,14^th and 28^th days.We measured diameter stenosis rate(R) by CEUS and US,compared them with stenosis index measured by pathology on the 28^th day.At last,we measured peak of intensity(I_P),time to peak(T_P),halving time(T_1/2) and area under curve(AUC) on time-intensity curve of contrast agent.Results1,The order of accuracy of stenosis rate from top to bottom was CEUS,PW,CDFI and 2-dimesion.In comparision with DSA,the kappa value of four ultrasonic methods was 0.933,0.866,0.783 and 0.548,respectively.The kappa value between observers of CEUS is higher than other ultrasonic methods.2,PSV and PI increased after we injected contrast media,but RI and SVR did not change.There was no difference in accuracy rate of SVR before and after we injected contrast media.The sign of blooming was found in moderate and serious stenosis group after we injected contrast media.3,In light injury group,there was no difference of diameter between lesion and normal segement and color was well-distributed on the 3^rd,7^th,14^th days.The decrease of diameter on the lesion was detected by common US on the 28^th day and stenosis rate was 25.28%.SVR was lower than 2 in the entire process.Color Doppler CEUS displayed slight turbulence on the 3^rd and 7^th days,the festoon color on the 14^th and 28^th days.CEUS detected slight decrease of diameter on the lesion on the 14^th day.This detection was earlier than common US.The stenosis rate was 33.92%on the 28^th day.4,In severe injury group,thickening of intima and decrease of diameter were detected by common US on the 14^th day.The stenosis rate was 29.31%on the 14^th day, and slight turbulence was detected by CDFI and PSV increased at the same time.On the 28th day,the serious decrease of diameter and festoon color code were observed by common US and PSV increased more than 150cm/s,SVR was higher than 2,so it was confirmed that stenosis rate was higher than 50%.Color Doppler CEUS showed the reverse of color on the lesion on the 3^rd day,festoon color on the 7^th day,and blooming on the 14th and the 28^th days.The stenosis rates measured by CEUS on the 7^th,14^th and 28^th days were 31.78%,50.39%and 63.25%,respectively.5,The comparision of T_P,I_P,AUC and T_1/2 on the 3^rd day indicated that there was no statistical difference between lesion and normal segement in light injury group.In severe injury group,T_P and T_1/2 of the lesion were longer than normal segement and also longer than parameters of the lesion in light injured group.Ip and AUC of the lesion were higher than normal segement but were similar with the lesion in light injured group.Conclusion1,CEUS displayed flow tract more clearly than other ultrasonic methods and made it easy to distinguish the border of intima,so its accuracy and reproducbility were the highest.2,Color Doppler CEUS amplified the turbulance and expressed "blooming" in sever stenosis.PSV and PI increased after contrast agent was injected to rabbits,but SVR,and RI didn't change.3,Injury by a common balloon didn't induce stenosis with dynamic change,and injury by the balloon enveloped with wire produced stenosis at the rate of more than 50%.4,In follow-up process of artery stenosis after balloon injury,CEUS detected slight decrease of diameter earlier than common US,and the accuracy of CEUS was higher than common US.Color Doppler CEUS displayed turbulence more clearly and could locate position of injury in the early stage when no difference occurred in diameter and hemodynamics.5,The parameters on time-intensity curve of lesion indirectly implied the degree of injury and should be helpful to adjust stenosis degree.