Application Of Low Tube Voltage Combined With Full Model Iterative Algorithm In Lower Limb CTA

Part ⅠFeasibility study of low tube voltage combined with iterative model reconstruction in lower extremity CT angiographyObjective:To investigate the feasibility of lower extremity CT angiography using low tube voltage combined with iterative model reconstruction(IMR)algorithm.Methods:Lower extremity CT angiography scans were acquired for 82 patients:41 patients were scanned with routine dose(RD)protocol(120kVp,100ml contrast medium),and 41 patients were scanned with low dose(LD)protocol(80kVp,80ml contrast medium).Automatic tube current modulation(ATCM,DoseRight,Philips Healthcare)was used in both protocols with a quality reference index of 12 for RD group and 1 for LD group.Images from RD group and LD group were reconstructed with filtered back projection(FBP)and IMR algorithms respectively.CT attenuation,image noise,SNR and CNR of 5 positions including aortic bifurcation,iliac bifurcation,proximal femoral artery,middle femoral artery,proximal popliteal artery were calculated.Subjective image quality of lower extremity arteries were assessed on a 4-point scale.Radiation dose of the two groups were compared.Results:Higher mean intravascular attenuation,SNR,CNR and lower image noise were obtained in LD group compared to RD group(all P<0.05).Better score of leg segment was found in LD group compared to RD group(P<0.05)while no difference was found in aortoiliac and femoral popliteal segment(both P>0.05).Radiation dose was reduced 72.97%(0.50±0.08 mSv;1.85±0.45 mSv,P<0.05)and contrast medium volume was reduced 20.00%in LD group compared to RD group.Conclusion:By using of IMR,lower extremity CTA with both radiationPart ⅡA comparative study of low dose CT angiography and DSA in lower extremity arterial occlusive diseasesObjective:To evaluate the clinical value of low dose CT angiography(CTA)in diagnosing the peripheral arterial occlusive disease(PAOD),compared with digital subtraction angiography(DSA)as a reference standard.Methods:34 patients with PAOD were enrolled in this tetrospective study and underwent CTA and DSA.CT scan parameters included 80 kVp,automatic tube current modulation(ATCM,DoseRight,Philips Healthcare)with a quality reference index 1 for LD group.Images were reconstructed with iterative model reconstruction(IMR)algorithms.To evaluate the efficacy of CTA in diagnosing significant POAD(>50%stenosis),compared with DSA as a reference standard.Radiation dose was recorded.Results:540 segments of 34 patients were examined.24 segments could not be visualized by DSA,while only 13 segments that could not be visualized by CTA.For arterial segments with significant disease(>50%stenosis),the diagnostic accuracy,sensitivity,specificity,positive and negative predictive values of CTA in arterial segments above the knee were 90.57%、93.70%、92.78%、85.71%and 95.97%,respectively.While in arterial segments below the knee were 85.19%、90.23%、87.80%、89.03%and 86.74%,respectively.Effective dose were 0.66±0.13 mSv.Conclusion:Low dose CTA was found to have good diagnostic performance and better visualized of distal arteries compared to DSA for the assessment of patients with PAOD.It may provide accurate basis for preoperative evaluation.dose and contrast medium volume reduction allows better or similar image quality.