Lower Extremity Arterial Diseases:investigation And Clinical Application Of Multislice Spiral CT

Abstract: bjective: To discuss the effect of MSCT scanning methods of64-slice spiral CT angiography of lower extremity arterial angiography onradiation dose and image quality,such as: pitch, table speed, machine speed ofrotation,and discuss the image quality of different reconstruction parametersand reconstruction thickness,to analyse the image quality of the same scanparameters, different concentration contrast agent.To evaluate the value in thediagnosis of lower extremity arterial disease in clinical applications.Methods:60cases with lower extremity arterial disease were scanned in different pitchusing GE light speed VCT, and were randomly divided into three groups(groupA1.375:1,group B0.984:1, group C0.516:1). The other60patients wererandomly divided into three groups(group D0.6s/week, group E0.8s/week,group F1.0s/week), the other scanning parameters is same. Injecting90ml ofnon-ionic contrast agent Ultravist (370mgI/m1) or povidone-iodine alcohol(320mgI/m1) by using high-pressure syringe, by flow rate of4.2m/s. Vascularenhancement of the large arteries was measured every10cm along the z-axisfrom the upper abdomen to the toe.Bolus tracking was used to monitor the enh-ancement of the artery in order to determine the best delay time. Radiation doseparameters,such as CT dose index（CTDIvol）,DLP,the efficiency of X-raywere obtained from the automatic recorded information after scanning. Thebasic data were reconstructed through different slice thickness and reconstructi- on parameters, and then transfer to ADW4.3workstation.Qualitative assessmentof bolus timing was performed independently by two radiologists.The lowerextremity arterial trees were divided into27segments. Radiologists observedand analyzed the MSCTA combined source image together. The stenosissegments were measured on the ADW4.3work station and classed on thedegree of stenosis. MSCTA measurements in the stenosis and the normal profileof upstream of stenosis were performed respectively. The degree of stenosis=(normal profile of upstream of stenosis－stenosis)/normal profile ofupstream of stenosis×100%. The degree of stenosis were classed into4grade:I slight stenosis(0-49%); II medium stenosis(50%-74%)； III severestenosis(75%-99%)； IV occlusion(100%). The obliterative segments weremeasured. Regarded DSA and operation as gold standard, to evaluate theaccuracy of MSCTA in lower extremity arterial occlusive disease, and analyzethe MSCTA characteristics in the different lower extremity arterial occlusivediseases. Results:1.The radiation dose level of A group[CTDIvol:14.94mGy,DLP:1698.75±74.78mGy/cm]was lower than B group[CTDIvol:20.87mGy,DLP:2331.87±62.62mGy/cm]by28.4%，and was more lower than C group[CTDIvol:39.83mG,DLP:4485.69±205.00mGy/cm] by62.5%, differencebetween the three groups was statistically significant. The difference of imagenoise in four levels between A group（3.55±0.40）and B group(3.67±0.28)andC group(32.78±1.49) was no significant (P>0.05).2. The radiation dose levelof D group [CTDIvol:14.94mGy, DLP:1698.75±74.78mGy/cm]was lower than E group[CTDIvol:19.92mGy, DLP:2117.02±111.14mGy/cm]by19.77%，and was more lower than F Group[CTDIvol:24.90mGy, DLP:2651.38±107.86mGy/cm] by56.08%, difference between the three groups wasstatistically significant. The difference of image noise in four levels between Dgroup（3.63±0.32）and E group(3.58±0.38)and F group(3.7±0.40) was nosignificant (P>0.05).3.It is better of lung reconstruction to observe thecollateral circulation, and will showed the most luxuriant branches of smallvessels.It is better of shown the muscle tissue, vascular, soft tissue and muscledefinition. There is inferior of details reconstruction, bone parametersreconstruction and standard reconstruction. There is worst of soft tissuereconstruction,it showed the least blood vessels, and vessel edge sharpness.4.There was no significant differences of1.25mm thickness and0.625mmthickness reconstruction of small branches of rate, blood vessel sharpness andcontrast with the surrounding tissue.There was significant differences of2.5mmthickness and0.625mm thickness reconstruction about it.5.There was nosignificant differences of CT values of lumen and image quality of contrastagent concentration370mgI/ml and320mgI/ml （p﹥0.05）.6.16out of120patients underwent conventional digital subtraction angiography or operationafter three dimensional contrast-enhanced magnetic resonance angiography intwo weeks. Based on DSA and operation as standard,149arterial segmentswere evaluated. There are overestimated of II grade3stenosis and III grade4stenosis of MSCTA. The mean of occlusion measured on MSCTA was（60± 31.6）mm and on DSA or operation was （61.8±30.0）mm, respectively. Basedon Paired-Samples t Test, there was no significant difference between MSCTAand DSA or operation（t=0.132, p＝0.054﹥0.05）.Conclusion: l, The scanparameters of pitch1.375has lowest radiation dose and high image quality.2,The scan parameters of rotation time0.6s/week has lowest radiation dose andhigh image quality.3, It is better of lung reconstruction to observe the collateralcirculation, and it will showed the most luxuriant branches of small vessels, themuscle tissue, vascular, soft tissue and muscle definition.4, It is，feasible touse slice thickness reconstruction of1.25mm.5, It is，feasible to use low dosecontrast agent of320mgI/ml in low extremity，at the same time it reducedpatient economical burden and the dosage of contrast agent.6,Comparing withDSA,CTA has the same effect in demonstrating the position and the degree ofperipheral arterial stenosis．7,As a non-invasive，high accurate，fast acquisition，high-resolution technique for vascular imaging,CTA can replace DSA to acertain extent.