ABSTRACT
Objective To establish chronic coronary stenosis model for fractional flow reserve derived from coronary CT angiography (FFRcT) in Bama miniature pig,and to evaluate its reliability.Methods Sixteen Bama miniature pigs were used to establish chronic coronary stenosis models through placing Ameroid constrictor into proximal or middle segments of left anterior descending arteries (LAD).In the 2nd week after modeling,the degrees of stenosis were monitored with coronary CTA.Invasive coronary angiography was used to verify stenosis degrees and measure fractional flow reserve (FFR) within 2 days of last coronary CTA examination.Computational fluid dynamics model was constructed and FFRcT was calculated by the specialized laboratory based on coronary CTA data respectively.Simulated FFRcT and FFR values were compared to verify this model.Results Models were successfully established in 10 pigs with a total of 24 coronary CT examinations,of which image quality met the diagnostic requirements.All models were with LAD stenosis＜25 ％ in the 2nd week after operation.LAD stenosis ＞50％ was found in the 3rd week in 9 pigs,and the other one was found with LAD stenosis ＞50％ in the 4th week.The results of coronary CTA corresponded to those of coronary angiography.There was no significant difference between simulated FFRcT and FFR value (t =-1.13,P =0.29).Conclusion Through placing Ameroid constrictor into LAD of Bama miniature pig and monitoring the degree of stenosis with coronary CTA,model of chronic coronary stenosis could be successfully established,which are suitable for noninvasive simulating hemodynamics study based on coronary CTA.
ABSTRACT
Objective To assess the image quality (IQ) of an iterative reconstruction (IR) technique (iDose4) from prospective electrocardiography (ECG)-triggered coronary CTA on a 256 MSCT scanner and determine the optimal dose reduction using IR that can provide IQ comparable to filtered back projection (FBP).Methods Prospectively ECG gated CCTA were performed on 120 patients [76 men,44 women; age:(53 ± 10)y] using a 256-slice MSCT (Brilliance iCT,Philips Healthcare).The control group (Group A,n =30) were scanned using the conventional tube output (120 kVp,210 mAs) and reconstructed using FBP.The other 3 groups were scanned with the same kVp but successively reduced tube output as follows:B (n =30):105 mAs,C (n =30):84 mAs:D (n =30):65 mAs and reconstructed using IR levels of L4 to L6,respectively.All images were reconstructed using the same kernel (XCB).Two radiologists graded IQ in a blinded fashion on a 4-point scale (4-excellent,3-good,2-fair and 1-poor).Quantitative measurements of CT values,image noise,Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were obtained in each group.Analysis of variance (ANOVA) was used for comparisons of objective evaluation indices (noise,CNR) and radiation dose (CTDIvol,DLP,ED) between the four groups.The Kruskal-Wallis test was used for comparisons of demographic data and for detection of differences in subjective evaluation of IQ among groups.A level of P ＜ 0.05 was considered statistically significant.A ROC analysis was performed to determine a radiation reduction threshold up to which excellent IQ was maintained.Results There was no significant differences in objective noise among Groups A (37.4 ±7.9) HU,B(33.2±7.1) HU,C(35.7±9.8) HU,and D(36.0±6.8) HU (F=1.48,P=0.22).There was no significant differences in CNR among Groups A(15.0 ±2.3),B(16.5 ±3.6),C(16.3 ±3.5),and D(15.3±2.8) (F=1.70,P =0.17).Group B and C had good and excellent scores of the subjective IQ (≥3),and there was no significant differences in the scores of the subjective IQ between Group A,and Groups B,C (P =0.30-1.00).Significant differences in image sharpness and study acceptability were observed between groups A and D (P ＜ 0.01).Using the criterion of excellent IQ (score 4),the ROC curve of dose levels and IQ acceptability established a reduction of 60％ of tube output (Group C) as optimum cutoff point (AUC:0.76,95％ CI:0.65-0.87).The effective dose (ED) of Group C was 61％ lower than that of Group A,(1.2 ± 0.1) mSv vs.(3.1 ± 0.6) mSv.Conclusion Iterative reconstruction techniques can provide 61％ ED reduction in prospectively-triggered coronary CTA using 256-slice MSCT while maintaining excellent image quality.