| Objective:(a) To compare image quality between iterative reconstruction (IR) andfiltered back projection (FBP) algorithm in high-pitch spiral scan of coronary CTangiography (CTA).(b) To assess the image quality and radiation dose of high-pitchspiral scan of coronary CTA using100kVp and IR, in comparison with CT using120kVp and FBP reconstruction.Methods:65consecutive patients who had suspected coronary artery disease underwentcoronary CTA according to body mass index (BMI):(a)100kVp and300mAs for BMI<25kg/m2(group A1,30subjects),(b)100kVp and360mAs for BMI≥25kg/m2(group B1,35subjects). For comparison, the two sex-age-and BMI-matched groupswere selected:(a)120kVp and300mAs for BMI <25kg/m2(group A2,30subjects),(b)120kVp and360mAs for BMI≥25kg/m2(group B2,35subjects). Coronary CTAusing prospective-ECG triggered high-pitch spiral scan mode was performed on a2ndgeneration dual source CT system. Acquisition parameters were as follows:2×64×0.6mm detector collimation,280ms gantry rotation time and3.4pitch. High-pitch spiralscan was prospectively triggered at60%of the R-R interval. Images were reconstructedwith FBP and IR algorithm. Parameters for image reconstruction include a slicethickness of0.75mm, increment of0.7mm, and a medium soft convolution kernel(I26f for IR and B26f for FBP). Contrast medium enhancement was achieved byinjecting50-60ml of iodinated contrast material and injected at5-6ml/s through an18-G intravenous antecubital catheter by using a dual-syringe injector. The image noise,signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were comparedrespectively between IR and FBP reconstruction in each group. The image noise, SNR,CNR, image quality and radiation dose were compared respectively in each matched groups (A1and A2; B1and B2).Results:(a) In the each group, there was no significant difference in CT attenuation ofascending aorta between two reconstruction algorithms (P>0.05). The image noise wassignificantly lower with IR than with FBP (P <0.01), and the SNR and CNR weresignificantly higher with IR than with FBP (P <0.01).(b) In patients with a BMI <25kg/m2, the CT attenuation of ascending aorta was significantly higher with100kVp andIR (group A1) than with120kVp and FBP (group A2)(448.95±79.10HU vs.338.36±53.84HU, P <0.01). The image noise was similar between two groups (17.48±3.24HU vs.17.35±2.11HU, P>0.05). The SNR and CNR were significantly higher ingroup A1than in group A2(26.24±5.36vs.19.64±3.32,17.48±3.90vs.11.81±3.07,P <0.01). There were no significant differences in image quality scores between twogroups (1.21±0.45vs.1.23±0.49, P>0.05). The effective radiation dose of group A1was37.60%lower than that of group A2(0.78±0.10mSv vs.1.25±0.11mSv, P <0.01).(c) In patients with a BMI≥25kg/m2, the CT attenuation of ascending aorta wassignificantly higher with100kVp and IR (group B1) than with120kVp and FBP (groupB2)(417.21±82.41HU vs.349.10±46.56HU, P <0.01). The image noise was similarbetween two groups (16.96±3.17HU vs.17.73±2.59HU, P>0.05). The SNR andCNR were significantly higher in group B1than in group B2(25.13±5.84vs.20.20±4.47,16.16±5.22vs.12.39±3.45, P <0.01). There were no significant differences inimage quality scores between two groups (1.22±0.48vs.1.24±0.51, P>0.05). Theeffective radiation dose of group B1was40.52%lower than that of group B2(0.91±0.09mSv vs.1.53±0.14mSv, P <0.01).Conclusion:(a) Compared with FBP reconstruction, IR can reduce image noise andimprove image quality on prospective-ECG triggered high-pitch spiral scan of coronaryCTA.(b) Prospective-ECG triggered high-pitch spiral scan of coronary CTA using100kVp and IR can provide equivalent coronary quality, compared with CT using120kVpand FBP reconstruction, that decreased approximately40%of the radiation dose. |
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