| Objective: According to the checked body mass index(BMI), to study the feasibility of the image quality and radiation dose of high-pitch CT renal angiography(CTRA) in iterative reconstruction combined with low tube voltage.Methods:40 consecutive patients who had suspected secondary hypertension caused by renal artery stenosis underwent high-pitch spiral CTRA, with normal BMI(< 25kg/m2)40 patients, random divided into groupⅠand Ⅱ, over BMI(≥ 25kg/m2)40 patients,random divided into group Ⅲ and Ⅳ.GroupⅠand Ⅱ respectively with group Ⅲ and Ⅳof age sex and BMI to match. Using 2nd generation dual-source CT system of high-pitch spiral scan mode. 80 k V for groupⅠ, 100 k V for group Ⅱand Ⅲ, 120 k V for group Ⅳ. IR(I26f) for groupⅠ and Ⅲ, IR(I26f) and filtered back projection(FBP) for group Ⅱ and Ⅳ; the other parameters of CT scan: 0.32 As per rotation tube current time product, 280 ms gantry rotation time, 3.4 pitch, reconstruction of temporal resolution0.075 s, detector collimation 0.6 × 64 × 2 mm, a slice thickness of 0.75 mm, increment of 0.7 mm. Before the examination giving all the tested patients a vein remaining needlleiv in antecubital vein, during the examination 70 ml of iodinated contrast material and 50 ml of saline was injected at the speed of 5.5ml/s by using a dual-syringe injector.Renal artery CT vale, the image noise, signal-to-noise ratio(SNR) and contrast-to-noise ratio between IR and FBP reconstruction were compared respectively in group Ⅱ or Ⅳ.According to BMI, renal artery CT vale, the image noise, SNR, contrast-to-noise ratio,image quality and radiation dose were compared respectively in each matched groups(Ⅰ IR CTRA and Ⅱ FBP CTRA; Ⅲ IR CTRA and Ⅳ FBP CTRA).Results:(1) In group Ⅱ or Ⅳ, the image noise with IR was significantly lower than that with FBP(25.32 ± 2.28 HU vs. 31.72 ± 2.01 HU, P<0.01; 23.24 ± 1.90 HU vs. 28.95 ±1.68 HU, P<0.01), the former SNR(15.47 ± 3.13 vs. 12.27 ± 2.20, P<0.01; 13.90 ± 2.12vs. 11.12 ± 1.58, P<0.01) and contrast-to-noise ratio(13.36 ± 3.00 vs. 10.60 ± 2.15, P<0.01; 11.80 ± 1.90 vs. 9.44 ± 1.43, P<0.01) were significantly higher than the latter.(2)The CT vale of renal artery(589.96 ± 95.68 HU vs. 386.10 ± 55.05 HU, P<0.01) and the image noise(47.48 ± 5.64 HU vs. 31.72 ± 2.01 HU, P<0.01) were significantly higher in group Ⅰ with IR high-pitch CTRA and group Ⅱ with FBP high-pitch CTRA, no significant differences in SNR(12.78 ± 2.47 vs. 12.27 ± 2.20, P>0.05), contrast-to-noise ratio(11.58 ± 2.50 vs. 10.60 ± 2.15, P>0.05) and image quality scores(4.00 ± 0.62 vs.4.10 ± 0.63, P>0.05) were seen between Ⅰand Ⅱ group, the effective radiation dose of group Ⅰ(0.48 ± 0.02 m Sv) was 46.67% lower than that of group Ⅱ(0.90 ± 0.07 m Sv).(3) The CT vale of renal artery was significantly higher in group Ⅲ with IR high-pitch CTRA and group Ⅳ with FBP high-pitch CTRA(389.70 ± 56.68 HU vs. 320.33 ± 35.80 HU, P<0.01), the image noise(30.04 ± 1.97 HU vs. 28.95 ± 1.68 HU, P>0.05) and image quality scores(4.17 ± 0.54 vs. 4.11 ± 0.50, P>0.05) were no significant differences between two groups, the SNR and contrast-to-noise ratio were significantly higher in group Ⅲ than in group Ⅳ(13.03 ± 2.11 vs. 11.12 ± 1.60, P<0.01;11.34 ± 2.03 vs. 9.44 ± 1.43, P<0.01), the effective radiation dose of group Ⅲ(0.89 ± 0.07 m Sv) was37.32% lower than that of group Ⅳ( 1.42 ± 0.08 m Sv).Conclusion:(1) In normal BMI, compared with CTRA using high-pitch with FBP reconstruction and 100 k V tube voltage, CTRA using high-pitch with IR and 80 k V tube voltage can decreased approximately 47% of the radiation dose(average 0.48 m Sv)with the same image quality.(2) In over BMI, compared with CTRA using high-pitch with FBP reconstruction and 120 k V tube voltage, CTRA using high-pitch with IR and100 k V tube voltage can decreased approximately 37% of the radiation dose(average0.89 m Sv) with the same image quality. In conclusion, it is feasibility using iterative reconstruction combined with low tube voltage in high-pitch CTRA. |
PDF Full Text Request