| Research background and purpose:Lower limb angiopathy is mainly caused by diabetes,vascular occlusion and vascular trauma,and the incidence rate is increasing year by year.Early detection,early diagnosis and early treatment are important channels to prevent further aggravation of the disease and improve the prognosis and quality of life of patients.at present,there is a need for a rapid,simple and instructive imaging examination technique for clinical diagnosis and treatment.With the upgrading of computed tomography equipment,ultrahigh-end multi-slice spiral CT has a faster scanning speed in recent years,the radiation dose of lower extremity arterial and venous angiography continues to decrease,and the image quality continues to improve.At present,there are two methods of CT lower limb arteriovenous imaging:(1)indirect CTA scanning of lower extremity arteries has different selection of areas of interest and scanning threshold and scanning speed.In the past,the main monitoring areas of interest were at the lower end of abdominal aorta and popliteal arteries,and the threshold value was 100～200 HU.The scanning time was more than 10 seconds and the image quality was unstable.The deficiency of indirect venous CTV lies in poor visualization of small diameter arteries and veins and their lesions,poor display of distal arteries and veins of lower extremities,and poor circulation of lower extremities,which is difficult to ensure image quality and has a certain distortion rate.Conventional arteriovenous imaging,scanning secondary scanning radiation dose and contrast agent dosage are relatively large.(2)as a new examination method,direct CTV of lower extremity vein is rarely reported in foreign literature.the domestic research report is only carried out in a few large and medium-sized hospitals in some areas,and the technology is not yet proficient.The previous examination only completed CT imaging of lower limb arteries or veins,and there was no one-stop imaging report.The study of lower limb arteriovenous imaging with RevolutionCT is divided into two parts:(1)the feasibility of rapid CTA scanning of both lower extremity arteries;(2)the feasibility and application value of indirect combined with direct imaging(CTV)of lower extremity veins.Materials and Methods:According to the inclusion and exclusion criteria,219 patients with suspected vascular lesions of lower extremities in the second people’s Hospital of Yibin City,Sichuan Province from April 2018 to August 2022 were selected.Among them,124 patients mainly received lower limb CTA examination and 95 patients mainly received lower limb CTV examination.1.Exploring the pre-experiment of artery scanning time:dynamic scanning of thigh root or ankle artery was performed in 45 patients(all patients with enhanced disease examination in the pelvis and feet,and informed consent).dynamic scanning of thigh root was performed in 21 cases(group A)and ankle in 24 cases(group B)by Revolution CT.Time-density curves were obtained.2.Exploring the experiment of artery scanning time:another 79 patients suspected of lower extremity arterial disease were randomly divided into group C(slow scanning group,n=40)and group D(rapid scanning group,n=39).The bilateral external iliac arteries were monitored by automatic threshold injection trigger scanning technique,and the starting threshold was set to 250 HU.The time-density curves of external iliac arteries in groups A and B were analyzed,and the appropriate combination of delay+total scanning time in group C and D was selected.The vascular CT value,signal-to-noise ratio,contrast signal-to-noise ratio,volume CT dose index and dose length product were compared between the two groups,and the effective dose was calculated.The image quality of the two groups was subjectively evaluated by two experienced imaging diagnostic doctors.3.Exploring the pre-experiment of vein scanning time:dynamic scanning of thigh root vein(group E),30 patients completed lower limb artery imaging first.After 120 seconds delay from elbow vein injection,10%diluted contrast medium(iohexol 350 mgI/ml)100ml was directly injected through bilateral foot vein to complete dynamic scanning of thigh root vein(30 cases in each group).The CT values of external iliac vein,great saphenous vein and femoral vein were measured in each group.Draw its timedensity curve and find its peak time t.4.Exploring the experiment of vein scanning time:sixty-five patients with arteriovenous imaging of lower extremities were randomly divided into group F(n=32)and group G(n=33).The dilution concentration and injection method of contrast medium in group F were the same as those in group E,and the fastest time for Revolution CT to complete venous scanning of lower extremities was about 5s.Group F completed rapid scanning of both lower extremities after the total delay time of intravenous injection of contrast medium T=120+t s.Group G underwent routine indirect lower limb vein scanning.The vascular CT value,signal-to-noise ratio,contrast signal-to-noise ratio and effective dose were compared between the two groups.The image quality of the two groups was subjectively evaluated by two experienced imaging diagnostic doctors.Result:1.The dynamic scanning time-density curves of thigh root and ankle arteries were analyzed.The time difference between group An and B in ascending to 200 HU was 20.8±2.2 s,and the average time difference to 250 HU was 19.3±2.1 s.The difference in peak time between the two groups was 18.8±3.5 s and the shortest duration of 250 HU in group A was 21.9±5.3 s.In group A,the shortest duration of 250 HU was 12.0 s.2.The difference of artery ascending to 250 HU and peak time between group An and group B was close to 19.0 s,and the average duration of 250 HU in group A was less than 21.9s±5.3 s,so 19.0 s was chosen as the total delay+scanning time of group C and D.In group C(slow scanning group),the delay time(about 2.5 s)was the physical preparation time(moving bed and tube preparation time),and the scanning time was 19.02.5=16.5 s.The shortest duration of 250 HU in group A was 12.0 s,which was selected as the delay time of group D(fast scanning group),and the scanning time was 7.0 s.In group C and D,bilateral external iliac arteries were used as the monitoring target and 250 HU as the threshold to scan the arteries of both lower extremities.3.There was no significant difference in the CT value of thigh artery between group C and D(P>0.05),but the CT value of knee artery,calf artery and ankle artery in group D was higher than that in group C(P<0.05).The SNR and CNR of thigh artery,knee artery,leg artery and ankle artery in group D were lower than those in group C(P<0.05).There was no significant difference in subjective score of image quality between the two groups.The dose of radiation in group D was lower than that in group C(P<0.05).4.The results of dynamic scanning of thigh root vein in group E showed that the peak value of CT fluctuated greatly.The time density curve of great saphenous vein is ascending type,descending type,platform type and fast rising type,while the time density curve of femoral vein is fast rising type and flat type,and its peak time is difficult to determine.The time-density curves of the external iliac vein showed the type of rapid rise and fall,and the peak time was relatively stable.The external iliac vein was selected as the analysis of interest vessels,and the average peak time was t=44.5±5.6 s.5.The CT values of lower extremity vessels in group F were higher than those in group G(P<0.05).There was no significant difference in SNR,CNR and radiation dose between the two groups.The subjective scores of lower limb vein in group F were higher than those in group G(P<0.05).Conclusion:1.Revolution CT double lower extremity artery imaging,with the external iliac artery as the monitoring target,using automatic threshold injection trigger scanning technology,250 HU as the starting threshold,its rapid scanning scheme has good image quality,clear and reliable display of lesions,and low scanning radiation dose.2.After Revolution CT scanning the arteries of both lower extremities,the total delay is about 165.0 s to start the direct rapid scanning of the veins of both lower extremities.The image quality of the veins of the lower extremities is good and the radiation dose is low,which is beneficial to the clinical analysis of venous lesions of the lower limbs.3.CT rapid scanning indirect CTA of bilateral lower extremity arteries and direct one-stop CTV imaging of bilateral lower extremity veins can significantly reduce the radiation dose.One examination can be used to analyze the arteriovenous lesions of both lower extremities,which is feasible. |
PDF Full Text Request