| Part one.Evaluating the Image Quality of CT Angiography of the Superior Mesenteric Artery by use of the Iterative Model Reconstruction combined with Low Tube Voltage TechniqueObjective: To assess the feasibility of iterative model reconstruction(IMR)combined with low tube voltage for superior mesenteric artery CT angiography(CTA).Materials and Methods: 60 cases of abdominal and pelvic enhancement CT scans were randomly divided into standard dose group and low dose group.Standard dose group was assigned to group A(n=30,120 k V and i Dose4 reconstruction)and group B(n=30,120 k V and IMR reconstruction).Low dose group was regarded as group C(n=30,80 k V and IMR reconstruction).The other parameters kept consistent.The volume rendering(VR)subjective score of superior mesenteric artery(SMA)and enhancement CT value,image noise(SD),signal noise ratio(SNR),contrast noise ratio(CNR)were compared among these groups.Results:(1).The enhancement CT value of SMA of group C was significantly higher than group A and B(P <0.01).There was no significant difference between group A and B(P >0.05).(2).The SD of SMA of group A was significantly higher than group C and B(P <0.01).And that of group C was significantly higher than group B(P <0.01).(3).The SNR and CNR of group B and C were significantly higher than group A(P <0.05).There was no significant difference between group B and C(P >0.05).(4).ED of standard dose group and low dose group were 2.3±0.5m Sv,7.2±1.6m Sv.There was significant difference between the two groups(P <0.01).(5).The subjective scores of SMA VR reconstruction in group A、B and C were 2.4±0.4、3.0±0.3 and 3.6±0.3 respectively,there was significant diffrernce among three groups(P <0.01).Conclusion: Low tube voltage combined with IMR technique used in SMA-CTA can decrease effective radiation dose,improve the imaging quality by increasing enhancement CT value and reducing image noise.Part two.Effect of Different Iterative Model Reconstruction Algorithms and Matrixs on Image Quality of Superior Mesenteric Artery CT angiographyObjective: To investigate the effect of different IMR reconstruction algorithms and matrixs on image quality of SMA-CTA.Materials and Methods: 30 cases of abdominal and pelvic enhancement CT scans were included in this study.At first,primitive arterial phase images were reconstructed as three groups according to different IMR reconstruction algorithms,group A1(n=30,Sharp Plus and 512×512 reconstruction),group A2(n=30,Routine and 512×512 reconstruction),group A3(n=30,Soft and 512×512 reconstruction).Then these on IMR routine reconstruction algorithm were reconstructed as another three groups according to different matrixs,group B1(n=30,1024×1024 matrix),group B2(n=30,768×768 matrix),group B3(n=30,512×512 matrix).And the reconstruncting times were recorded.The VR subjective score of SMA,enhancement CT value,SD,SNR,CNR and reconstruction speed were compared among these groups.Results:(1).There was no significant difference in enhancement CT value of SMA among different patterns and matrixs of IMR(P>0.05).(2).The SD of SMA in group A1 was significantly higher than group A2 and A3(P<0.05).And SD in group A2 was significantly higher than group A3(P<0.05).SD in group B1 and B2 were significantly higher than group B3(P<0.05).There was no significant difference between group B1 and B2(P>0.05).(3).SNR and CNR in group A3 was significantly higher than group A2 and A1(P<0.05).SNR and CNR in group A2 was significantly higher than group A1(P<0.05).SNR and CNR in group B3 was significantly higher than group B1 and B2(P<0.05).There was no significant difference between group B1 and B2(P>0.05).(4).The subjective scores of SMA in group A1,A2 and A3 were 3.5±0.2,2.8±0.2,2.4±0.2 respectively,there was significant difference among three groups(P<0.05).The subjective scores of SMA in group B1,B2 and B3 were 3.1±0.2,3.1±0.2,2.8±0.2 respectively,there was no significant difference between group B1 and B2(P>0.05),and significant difference existed in the rest groups(P<0.05).(5)The reconstruction speed in group A3 was significantly faster than group A1 and A2(P<0.05).There was no significant difference between group A1 and A2(P>0.05).The reconstruction speed in group B3 was significantly faster than group B2 and B1(P<0.05).And that in group B2 was significantly faster than group B1(P<0.05).Conclusion: Different patterns and matrixs of IMR had different effects on SMA VR.IMR Sharp Plus reconstruction algorithm can obtain higher spatial resolution and better VR image quality of SMA,but have higher SD and more slower reconstruction speed.It is reasonable to use 768×768 matrix for SMA-CTA,which has the same image quality as 1024×1024 matrix,but reconstruction speed faster than the latter.Part Three.Clinical Study of Superior Mesenteric Artery Dilated by use of NitroglycerinObjective: To investigate the effect of nitroglycerin on SMA and its influence on image quality of SMA-CTA.Materials and Methods: 60 cases of abdominal and pelvic enhancement CT scans were randomly divided into medication group(n=30,taken 0.25 mg nitroglycerin under the tongue before 3 to5 minutes of arterial phase scan),and control group(n=30,which hadn’t taken nitroglycerin),while the other parameters kept consistent.The diameter of the lumen was measured at the beginning of SMA.Subjective scores of SMA,lumen diameter and enhancement CT value,SD,SNR,CNR were compared between the two groups.Results:(1).The enhancement CT value in medication group was highter than control group,but there was no significant difference between them(P>0.05).(2).The SD、SNR and CNR between the two groups had no significant difference(P>0.05).(3).The lumen diameter of SMA in medication group and control group were 7.5±0.9mm,7.0±1.0mm.There was significant difference between the two groups(P<0.05).(4).Subjective scores of SMA of medication group and control group were 3.4±0.2,3.0±0.2.There was significant difference between the two groups(P<0.05).Conclusion: Nitroglycerin can dilate the lumen of SMA and improve the imaging quality of SMA VR. |
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