An Application Research On The Low Radiation Dose And Low Contrast Material Dose Of AIDR 3D In Hepatic Enhanced CT Scan

Part 1 water phantom studyPurpose:To evaluate the image noise reduction capability in water phantom using Adaptive Iterative Dose Reduction 3D(AIDR 3D). To evaluate the influence of image noise with different tube voltage.Materials and methods:A CT water phantom(diameter 25cm) was scanned at 120KV/FBP, 120KV/AIDR 3D, 100KV/ AIDR 3D and 80KV/ AIDR 3D with different noise index respectively, the noise index was varying from 5 to 11, interval 0.5. Image noise was evaluated and compared between four groups.Results:The image noise used 120KV+AIDR 3D was lower than that used 120KV+FBP, there had statistical difference between them(q=7.131,P < 0.001). The image noise used 100KV+AIDR 3D was lower than that used 120KV+FBP, there had statistical difference between them(q=6.064,P<0.001). The image noise used 80KV+AIDR 3D was higher than that used 100KV+ AIDR 3D, there had statistical difference between them(q=3.888,P<0.05).Conclusion:① Compared with FBP, AIDR 3D reconstruction can reduce image noise obviously.② When tube voltage varied from 120 KV and 100 kv to 80 kv, the image noise increased obviously.Part 2 Clinical studyPurpose:0bjective to investigate the application value of AIDR 3D(Adaptive Iterative Dose Reduction 3D) reconstruction technique with automatic tube current modulation and low tube voltage combined with automatic tube current modulation technique in hepatic enhanced CT with low dose contrast material.Materials and methods:150 patients treated with hepatic enhanced CT were randomly divided into 3 groups(A,B, C) Prospectively. 50 cases in each group, Patients in group A were reconstructed with filtered back projection(FBP) and conventional dose contrast material(1.5ml/Kg), patients in group B were reconstructed with AIDR 3D and low dose contrast material( 1.0ml/Kg) with 120 KV tube voltage; while patients in group C were reconstructed with AIDR 3D and low dose contrast material(1.0ml/Kg)with 100 KV tube voltage. CT dose index-volume(CTDIvol) and dose length product(DLP) were recorded, and the effective dose of 3 groups(Effective Dose, ED), mean CT value, image noise, signal-to-noise ratio(SNR), contrast to noise ratio(CNR) were calculated. Qualitative ranking of noise and image quality were graded(scale :1(worse)-4(best)).Measurement data were analyzed using completely randomized design analysis of variance and rank-sum test, Count data was analyzed using completely randomized design Kruskal-Wallis test.Results:The effective dose in group B and group C is lower than that in group A.(A, B, C groups were 2.98 ± 1.33, 2.23 ± 0.75, 2.54 ± 0.55 respectively),there had statistical difference between group A and group B(F=8.10,T=4.004,P=0.000, <0.01),there also had statistical difference between group A and group C(F=8.10,t=2.348,P=0.020, <0.05); there was no statistical difference between group B and group C(p>0.05). The image noise of liver, aorta and portal vein was highest in group A, while group C was the lowest, there had statistical difference between the three groups(liver: F=216.06,aorta:F=150.83,portal vein: F=150.61,p=0.000,<0.01). The CT value of liver, aorta and portal vein had no statistical difference between group A and group C(p>0.05). The CT value of group B was the lowest, there had statistical difference compared with group A and group C(liver: F=38.79,aorta:F=52.78,portal vein: F=56.19,P<0.01). The CNR of group B had no statistical difference with group A(p>0.05); The CNR of group C was higher than that of group A and group B(A VS C: F=37.62,t=7.010,P=0.000, <0.01;B VS C: F=37.62,t=7.937,P=0.000, <0.01). The SNR of group A was the highest, while group A was the lowest, there had statistical differences between the 3 groups(A VS B: F=162.36,t=3.096,P=0.000, <0.01;A VS C: F=162.36,t=16.936,P=0.000, <0.01;B VS C: F=162.36,t=13.84,P=0.000, <0.01). In the Subjective assessment of image quality, the score of group B and group C was higher than that of group A(A VS B: H=-5.288,P=0.000, <0.01;A VS C: H=-5.688,P=0.000, <0.01); there had no statistical difference between group B and group C(p>0.05).Conclusion:① AIDR 3D reconstruction combined with low dose of contrast material could get similar or even better image quality in abdominal enhanced CT compared with that of FBP reconstruction combined with routine dose of contrast material;② Low tube voltage combined with automatic tube current modulation technique could get better image quality in hepatic enhanced CT with low dose contrast material compared with that of simple automatic tube current modulation.