The Studying Of The Clinical Value Of Dual-energy Computed Tomography Angiography In Lower Extremity

Objectives：(1) Used to generate dual energy automatically bone-subtracted images as well as boneand plaque-subtracted images and standard auto bone subtraction images, Residual bone wasremoved manually. Operator time for bone removal and presence of vessel erosions wasmeasured. Stenosis grading in plaque subtracted and unsubtracted images was assessed andcorrelated. To study the clinical value of dual-energy bone and calcium removal in lowerextremity computed tomography angiography.(2) To study the accuracy of dual-energy computed tomographic angiography (DE-CTA)for the assessment of symptomatic peripheral arterial occlusive disease of the lower extremityby various post-processing images obtained by the DECTA compared with DSA images；Respectively, by using the dual-energy bone removal technique and a standard auto boneremoval tool obtained after dual-energy and after the traditional auto boneless MIP imagescompared with DSA images, Operator time for bone removal was measured, to study theclinical value of the dual-energy lower extremity maximum intensity projection CTA imagein lower extremity arterial occlusive disease.(3) Follow the prinliple of ALARA (as low as reasonably achievable), Changing mAsvalue according to patient BMI in the dual-energy CTA of lower extremity arterialexamination, we study that if reducing mAs value can achieve not only reduces the patientsreceived radiation doses but also to ensure image quality, to meet the requirements of thepurpose of diagnosis.Materials and Methods:(1)43patients (86lower limb) being doubt of lower limb artery diseases were scannedby dual energy CT, the following scan range from aorta below renal to the foot, Transmit theoriginal axial images to Siemens workstation (syngo2008C), using three-dimensionalmaximum intensity projection (MIP), curved planar reformation (CPR), volume rendering (VR) techniques for image reconstruction, used to generate automatically bone-subtractedimages as well as bone and plaque subtracted images and standard auto bone subtractionimages. Residual bone was removed manually. Operator time for bone removal and presenceof vessel erosions was measured. Stenosis grading in plaque subtracted and unsubtractedimages was assessed and correlated.(2)36patients(72lower limb)being doubt of lower limb artery diseases were scanned bydual energy CT，and had DSA examination (examination of which underwent bilateral lowerextremity in16cases and20cases of unilateral examination, a total of52lower limbs).DECTA and DSA findings were compared in two ways:1, CTA data using dual energyautomatically bone-subtracted method and compared with DSA results, all comparisons arenot with the original axial images and other post-processing methods were not bonelessimage；2. CTA data were postprocessed with two different modes: conventional bone removaland dual-energy bone removal. All data were reconstructed and evaluated as maximumintensity projections. Operator time for bone removal was measured， two methods，timeafter the removal of residual bone are also included. All data are used only MIP images wereevaluated. The vessels in every cases segements wese divided into7segements, The accuracyof CTA and conventional digital subtraction angiography was compared.(3)60patients being doubt of lower limb artery diseases were scanned by dual energyCT，All patients were divided into two groups based on BMI index similar principles, Agroup of30patients, regardless of height, weight and other factors, all in accordance with theoriginal scan data provided by the manufacturer to scan (tube voltage140kV, tube current47mAs and tube voltage80kV, tube current199mAs tube dual dual energy scanning), Anothergroup of patients (B group) is based on BMI index appropriate to reduce the mAs value of thetube. Two groups of patients were recorded abdominal aorta, iliac artery on one side and theside of the femoral artery at the noise index values and image quality of patients wereevaluated, the scores were recorded, the machine automatically records of each patientCTDIvol Value were recorded too.Results：(1)43patients were successfully DECTA check, lower extremity arterial images canmeet the diagnostic requirements. Residual bone fragments were only observed with automatically bone-subtracted images. The time of dual energy automatically bone-subtracted(1.86±0.28min) was significantly lower than the duration of standard auto bone subtraction(2.00±0.24min, P<0.01,t=-4.382). A total of822arteries were analyzed, compromisingvessel erosions were observed less frequently in dual energy automatically bone-subtractedimages than in standard auto bone subtraction images, especially in the lower extremityarteries（P<0.01）.(2) In the first part，a total of364vascular segments were analyzed，CTA and DSA fordiagnosis of lower extremity arterial stenosis is very good consistency, K value is0.948, thesensitivity, specificity, and accuracy was98.64%、95.80%and97.53%. In the second part，atotal of363vascular segments were analyzed. Compared with digital subtraction angiography,sensitivity, specificity, and accuracy, respectively, of CTA was90%by the dual-energy boneremoval technique, whereas the conventional bone removal technique showed a substantialdecrease of sensitivity, specificity, and accuracy.In whole lower extremity arterial, whenstenosis was over50%,the sensitivity, specificity, and accuracy was96.1%and93.4%,83.3%and68.8%,92.2%and86.1%by the dual-energy bone removal techniqueand theconventional bone removal tool. In the small leg arteries，the sensitivity, specificity, andaccuracy was94.2%and91.9%,77.5%and59.0%,88.9%and81.6%.(3) A, B two groups of patients，excellent image quality were96.7%and93.3%, imagequality scores were3.833±0.461and3.733±0.583, P>0.05, the two are not statisticallysignificant. A, B two groups of patients，abdominal aorta, iliac artery and femoral artery at thenoise index were18.183±3.058(abdominal aorta),14.633±3.212(iliac artery),13.907±3.037(femoral artery) and22.713±3.566(abdominal aorta),18.863±3.801(iliac artery),18±3.757(femoral artery), P <0.01, B group were higher than the A group, with statisticalsignificance; Two groups of patients with BMI values were22.14±2.61and22.33±2.61, P>0.05, the two are not statistically significant. CTDIvol of the two groups were respectively8.461±0.332and4.823±1.197, P <0.01, statistically significant, B group of patientsreceived radiation doses significantly lower than group A, decreased about40%.Conclusions:(1) DE CTA has substantial advantages over conventional CTA. Dual energy automaticbone subtraction is more time efficient and reliable, especially in the lower extremity arteries. Automatic plaque subtraction can improve the accuration of the diagnose.(2) Dual-energy CTA can be more accurate、wide range show lower extremity arterialocclusive disease in patients with lower extremity arterial disease. Combination of CTAimages obtained afte various post-processing method, compared with the gold standard DSAhas a very high accuracy. There is an excellent agreement in detecting peripheral arterialobstructive disease for MIP image of DE-CTA and DSA, especially in the calf blood vessels,than MIP image obtained from the conventional bone removal technique more reliable.DECTA is a feasible and accurate diagnostic method in the assessment of symptomaticperipheral arterial occlusive disease.(3) In dual-energy CTA examination of lower extremity arteries, the use of individualscans, which according to the different body mass index in patients with different mAs values,can not affect the image quality to meet the diagnostic requirements of the premise,significantly lower radiation dose received by patients, reduce patient radiation damage, it isproposed to use in clinical work.