| Part one:The stability of compression of left iliac vein on CT venographyObjective: This study aimed to evaluate the longitudinal stability of compression of left iliac vein on different times by contrast-enhanced CT in the same patient.Methods: 124 patients without signs of lower extremity venous diseases who underwent contrast-enhanced CT of the pelvic cavity twice within two years were included in this study.We calculated the degree of compression of left iliac vein and compared in two examinations.There were 67 males and 57 females,with an average age of 59.24±11.71 years,with an average interval of 7.84±5.64 months.Results: 1.The compression degree of the LCIV range is 5-73%.On the first time,CT scan images showed the left iliac venous compression rate averaged41.03%±17.74%.On the second examination,the rate averaged42.11%±19.25%,no obvious difference of LCIV compression rate was seen during twice check(t = 0.957,P = 0.340),left iliac venous compression rate of124 patients were stable.2.According to the gender group,there was no significant change in the left iliac vein compression rate in patients with different gender(male group :t=-1.327,P=0.189,P>0.05;female group :t=0.005,P=0.096,P>0.05).3.The patients were divided into two groups according to the pressure rate.the LCIV compression rate of 88 patients were <50%,and the compression rate of this group was not significantly changed in the two examinations(t=-1.369,P=0.180,P>0.05).There were 36 patients with a pressure ratio of 50% or more,and the compression rate was not significantly changed in two examinations(t=-0.549,P=0.585,P>0.05).4.The age and compression rate of left iliac vein in different age groups were analyzed.: 36 cases of patients under 50 years of age had no significant correlation between age and compression rate(r=0.152,P=0.376).There was no significant correlation between age and compression rate(r=-0.214,P=0.056)in 88 patients older than 50 years old.Conclusion: The compression degree of the LCIV was almost stable in the short term.The enhanced CT scan for single time can accurately display and diagnose the degree of compression of the left iliac vein.Part two:Image quality and radiation dose of CT venography with differents pitch combined with low voltage and SAFIREObjective: The aim of this study was to investigate the image quality and radiation dose of lower limb CT by effects of appropriate pitch,lower tube voltage,iterative reconstruction algorithm and lower dose contrast agent.Methods: There were 45 patients who were suspected deep vein thrombosis admitted to our hospital from June 2017 to December 2017,and were randomly divided into three groups: A,B and C,each with 15 cases.The setting of group A was 1.0 standard pitch,group B was medium pitch 1.55,group C was 2.0 pitch。Three sets adopted lower tube voltage 80 kv,iterative reconstruction algorithm,and lower non-ionic contrast agent(90 ml).The scanning range from the third lumbar vertebra to ankle joint.Effective dose was estimated using the computed tomography dose index(CTDI)and dose-length product(DLP).Background noise(BN),contrast to noise ratio(CNR),vascular enhancement of the inferior vena cava(IVC),iliac vein,femoral vein,and popliteal vein in three groups were analyzed.Two radiologists,who were blinded to the image protocol,assessed image quality score independently.The feasibility of reducing the radiation dose of CTV with appropriate pitch,lower voltage,iterative reconstruction algorithm was analyzed.Results: 1.The image noise of the three groups gradually increased.The noise of group B(15.01 + 4.43)was significantly higher than that of group A(9.91 + + 2.32),and the image noise of group C(16.76 + 5.43)was higher than that of group B.2.The mean CT values of the Inferior Vena Cava(I V C),Iliac vein(IV),Femoral vein(FV)and Popliteal vein(PV)were respectively: 171.51±83.08 HU,159.23± 74.95 HU,145.83 ±97.08 HU,152 ± 54.63 HU in Group A;138.33 ±86.91 HU,142.55±66.52 HU,149.72±61.78 HU,132.52±65.05 HU in Group B;135.03 ± 83.08 HU,140.07± 74.95 HU,145.83 ± 97.08 HU,136.94±65.63 HU in Group C.Therefore,the CT values of the inferior vena cava and iliac vein in group A were higher than that of group B and C,and the CT values of the femoral vein and popliteal vein had no significant different between the three groups.3.The CNR of the three groups was: 6.86 ±3.54 in group A,4.72 ±3.34 in group B,3.74± 4.33 in group C,so the CNR of group A was higher than that of B and C,and there was no significant difference in CNR between group B and group C.4.The image quality scores of the three groups gradually decreased,but the images of both groups A and B met the diagnostic requirements.5.The radiation dose of group B was significantly lower than that of group A,and decreased by about 70.18%.The radiation dose of C pitch group was lower than that of group B,and decreased by about 21.11%.Conclusion: Lower extremity CTV with 1.0 pitch,low voltage,iterative reconstruction,less contrast agents was suitable for the initial inspection,the image can comprehensive evaluate abdominal,pelvic as well as lower extremity lesions.For follow-up examinations,1.55 pitch with low radiation protocol can reduce the radiation dose with accept-able image quality at the same time. |
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