| Objective: To investigate the influence of ASi R-V variations(from 0% to 70%)on the stability of CAC score-values in the coronary artery calcium scanning with a phantom Using 256-slice Revolution CT.and follows with a clinical study to validate the association between FBP(ASi R-V 0%)algorithm and hybrid iterative reconstruction(ASi R-V50%)algorithm in the stability of CAC scoring.And to analyze the imagine quality and radiation dose.Methods:This research was comprised of a phantom test and a clinical trial.The phantom test was performed using an anthropomorphic cardiac CT thorax phantom represent small patient size(cardiology,QRM,M?hrendorf,Germany)in which a calcium insert was placed.The cylindrical calcium insert included 9 very calcifications with sizes of 1–3 mm and density of 200–800 mg HA(D9 insert,QRM,M?hrendorf,Germany)—the diameter of 3 small calcifications were 1mm with densities of 800 mg HA/cm3,400 mg HA/cm3,,200 mg HA/cm3 respectively.the diameter of 3 moderate calcifications were 3mm with densities of 800 mg HA/cm3,400 mg HA/cm3,200 mg HA/cm3 respectively.the diameter of 3 large calcifications were 5mm with densities of 800 mg HA/cm3,400 mg HA/cm3,200 mg HA/cm3 respectively.The densities of 800 mg HA/cm3,400 mg HA/cm3,200 mg HA/cm3 represented respectively high,intermediate and low density calcifications.The thorax phantom was scanned with a 256-slice Revolution CT(Revolution CT,GE Healthcare,Waukesha,WI,USA).Data were acquired according to the folowing set of parameters: Squential acquisition with prospective ECG-triggering,tube voltage of 140 k V,120 k V,100 k V,80 k V and 70 k V;pre-noise-index ranging from 14 HU to 24 HU with the interval of 4HU,tube current using smart m A technique.Pre-ASi R-V of multi-model iterative algorithm were set with 0%,10%,20%,30%,40%,50%,60% and 70% respectively.The levers of ASi R-V this data reconstructed are according with their pre-ASi R-V.All reconstructed data were send to the commercially available workstation(Advantage AW 4.6 GE Healthcare).We used semiautomatic software(Smart Score,GE Healthcare) to calculate Agatston scores(AS),Volume scores(VS)and Mass scores in this data.Kendall's ?b and independent-samples-median test were used to determine trends and differences in calcium scores.The clinical trial was enrolled 98 individuals to undergo CACS scanning with both full dose and low dose scanning protocols.All subjects provided informed consent for participation and this study was approved by our university institutional review board.Every participation enrolled in this trial was required to undergo a full dose CAC scanning(ASi R-V 0%)and following a low dose CAC scanning(ASi R-V50%)in a same week.CT protocol: image acquisition was performed on a 256 detector row CT platform(Revolution CT,GE Healthcare)and using prospective ECG triggering.Scanning parameters were: 120 k V,automatic exposure control(Smart m A),Noise index of 20 HU,gantry rotation 0.28 s,160mm coverage and 25 cm field of view.The full dose scan was done by setting the level of pre-ASi R-V to 0%.Similarly,low dose CAC scan CT was performed by setting the level of pre-ASi R-V to 50%.Kappa coefficient was used to test the calcium scores agreement between full and low protocols.Effective radiation dose and noise were assessed using Paired t-test.Agatston,calcium mass and volume scores in full and low dose CAC scanning CT were assessed using Wilcoxon signed rank test.For all statistical analyses,p of 0.05 was considered to indicate a significant difference.Bland-Altman analysis and Pearson correlation coefficient were used to determine agreement and correlation of AS,VS and MS between low and full dose CT.Results:The phantom study:It was about 120 scans combined with different levels of tuber-voltages,noise-indexs and ASi R-Vs.The range AS,VS,and MS of the small clacifications were form 0 to 3.The overall detectability of the small and high density calcification was 72.5%(87/120).According with the ASi R-V levels From 0% to 70%,the detectabilities of the small and high density calcification were 93%(14/15),93%(14/15),93%(14/15),100%(15/15),93%(14/15),87%(13/15),20%(3/15).The detectabilities remained stable for increasing levels of ASi R-V from 0% to 50%(?b = 0.026,P = 0.766),and decreased for increasing levels of ASi R-V from 50% to 70%(?b =-0.529,P<0.001).The overall detectability of small and moderate density calcification was very low 2.5%(3/120).The overall detectability of small and low density calcification was 0(0/120).The AS,and MS of moderate and large size califications increased for Redution the levels of tuber voltage(the range of F values from 54.741 to 1660.363,all P<0.001)),but remained stable with different ASi R-V levels and noise-index levels(the range of F values from 0.01 to 2.066,the range of P values from 0.133 to 1).Additional,The VS of large size calcifications with moderate and high density were stable with Variety levels of tuber voltage,the values of P were 0.971,0.581 respectively.The clinical trial: the effective radiation in full dose CACS CT was significantly higher than with the low dose protocol,(2.60 ± 1.08 vs.1.80 ±0.97 m Sv,P<0.05).Image SNR was significantly different in full and low dose CACS CT(2.66 ± 0.62 vs.2.92 ± 0.53,P<0.05).AS,MS and VS in full and low dose CT were similar: 150.36 ± 424.82 vs.148.86 ± 403.77(P=0.77),25.87 ± 88.34 vs.27.11 ± 96.90(P=0.211),and 53.40 ± 124.04 vs.52.09 ± 121.32(P=0.38).Bland-Altman plot analysis of AS,MS,and VS produced by full dose(ASi R-V 0%)and low dose(ASi R-V50%)CT showed excellent agreement without a systematic bias.The correlation between scores was high: AS(r = 0.994),MS(r = 0.999)and VS(r = 0.993),respectively.The agreement of the rise classification between two scan were excellent(k = 0.94,P<0.05).Conclusion: 1.Different levels of ASi R-V from 0% to 50% scanning and reconstruction parameters showed overall good stable in the detectability and calcium scores.2.The detectability of the calcification were influenced when the levels of ASi R-V over 50%.3.The stability of calcium scores values were influenced by the variety of tuber voltages,but remained stable within range of ASi R-V(0%-50%)and noise index(14-28HU)4.Compared with FBP,Revolution CT with ASi R-V50% can provide a higher quality and reduce the radiation dose. |
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