Feasibility of 16-slice spiral CT "double low mode" combined iterative reconstruction technique in cranial CTA examination
Objective To analyze the feasibility of 16-slice spiral CT "double low mode" combined iterative reconstruction technique in cranial CT angiography (CTA) examination. Methods 120 patients who underwent cranial CTA were selected as study subjects and retrospectively divided into group A (tube voltage of 100 kV,contrast concentration of 370 mg I/ml),group B (tube voltage of 100 kV,contrast concentration of 320 mg I/ml),group C (tube voltage of 100 kV,contrast concentration of 270 mg I/ml),group D (after turning on Care kV,the reference tube voltage was set to 80 kV and the contrast concentration to 270 mg I/ml),with 30 cases in each group. The original data obtained from the scans of the four groups were subjected to image reconstruction using the filtered backprojection (FBP) and adaptive statistical iterative reconstruction (ASIR). 8 subgroups of A1/A2,B1/B2,C1/C2,D1/D2 were obtained according to the different reconstruction techniques (1 was the FBP image reconstruction subgroup and 2 was the ASIR image reconstruction subgroup). The mean vascular CT values,contrast-to-noise ratios (CNR),signal-to-noise ratios (SNR),BHA,and subjective image quality scores of the two subgroups within the four groups were compared;the mean vascular CT values,CNR,SNR,BHA,and subjective image quality scores of the four groups were compared;and the volumetric CT dose indices,and dose-length product were compared between the four groups. Results The mean CT values,CNR,SNR and subjective image quality scores of group A2,group B2,group C2 and group D2 were higher than those of group A1,group B1,group C1 and group D1 (P<0.05). There was no difference in the comparison of mean vascular CT value,CNR,SNR,BHA and subjective image quality scores in group A,group B,group C and group D (P>0.05). The volumetric CT dose index and dose length product were (13.32±1.46) mGy and (863.67±95.17) mGy·cm in group A,(11.63±1.40) mGy and (734.62±90.43) mGy·cm in group B,(9.45±1.34) mGy and (642.49±87.12) mGy·cm in group C,and (8.52±1.23) mGy and (558.25±80.52) mGy·cm in group D. There was a decreasing trend in the volumetric CT dose index and dose-length product in group A,group B,group C,and group D,respectively (F=11.563,95.736;P=0.000,0.000<0.05). Conclusion 16-slice spiral CT "double low mode" combined iterative reconstruction technique can improve the image quality of cranial CTA,reduce radiation dose,and can be used for the examination of cranial vascular related diseases.
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