Application Of Low Radiation Dose CT In Coronary Arterial Disease Of Infants And Children

Objective:To prospectively evaluate the application of low dose CT coronary angiography in the diagnosis of children with coronary arterial lesions due to Kawasaki disease (KD) in comparison with transthoracic echocardiography (TTE).Materials and Methods:Forty-seven children with suspected coronary arterial lesions due to Kawasaki disease were prospectively enrolled, and a total of45patients could be included in this study. All patients underwent low-dose CT coronary arterial angiography and TTE with interval about1-9days. There were28males and17females, mean age11months (age range2months to63months), mean body weight12.8kg (range from5.8kg to28kg), mean heart rates112bpm (range from87bpm to146bpm), mean fever time38days (range from13days to196days). Persistent and unexplained fever was found in all cases, bilateral non-suppurative conjunctivitis, inflammation of the mucosa in the lip and mouth were found in all cases, strawberry-tone were founded in15cases, changes in the extremities appeared in20cases. All of the patients meet the diagnostic standard of KD.The visualization capability of coronary arteries was graded for13arterial segments.Subjective image quality was independently assessed by2radiologists with several years of experience in reading coronary artery angiographic images. Overall image quality was assessed using a5-point grading scale(1=no motion artifact;2=minimal motion artifact, one stair-step artifact;3=moderate motion artifact,≥2stair-step artifacts or minimal blurring of a vessel;4=severe artifact, assessment was limited by blurring of vessel;5=the vessel was not recognisable). The risk-level category (risk level Ⅰ-Ⅴ) was evaluated by the statement about diagnosis, treatment and long-term management of KD from American Heart Association (AHA) in2004. Inter-observer agreement in subjective image quality grading and CT measurements was assessed by Cohen’s k-test. Bland-Altman analysis was used to evaluate the agreement on measurements of aneurysms between CT angiographic images and TTE. The average radiation dose parameters (CTDIvol, DLP, effective dose) were calculated for all children.Results:All low dose CT angiography and TTE examinations were performed successfully, and the image quality was sufficient for data analysis in all cases. The diagnostic coronary arterial segments ratio was90.94%(532/585)for CT angiography, and29.91%(175/585)for TTE.1.Low dose CT coronary artery angiographic findingsThe mean score of2observers for coronary artery segments was2.12±0.7and2.07±0.5,respectively. And mean score of the2observers was2.10±0.8.The inter-observer agreement for subjective image quality was excellent (kappa=0.85). Diagnostic image quality was present in90.94%(532/585)of the segments.The CT measurements showed excellent inter-observer agreements (diameter:k=0.83;length: k=0.87).Twenty-nine cases out of45patients were diagnosed with Kawasaki disease by CT angiography.A total of10dilations,98aneurysms and17arterial ectasias were detected by low dose CT angiography. Twenty-eight cases were classified as risk level IV and1case was classified as risk level V by low dose CT. Thrombosis was found in10aneurysms and4ectasias;Calcification was founded in2cases; and stenosis was detected in one patient by DSCTCA.2.Echocardiography findingsTwenty-nine cases out of45patients were diagnosed with Kawasaki disease by TTE. A total of4dilations,52aneurysms and11arterial ectasias were found by TTE. Thrombosis was found in8aneurysms and4ectasias. Calcification was founded in2cases; and no stenosis was detected by TTE.26cases were classified as risk level IV and3cases were classified as level Ⅲby TTE.3.Assessment of Agreement between Low dose CT and TTEFor all the4dilations,52aneurysms and11ectasias detected by both low dose CT and TTE, the described location and size were consistent with each other. Mean aneurysms diameter with CT was (0.74±0.32) cm and with TTE was (0.74±0.29) cm. Comparison the mean diameters between DSCTCA and TTE yielded a bias of2.3%, a lower limit of agreement of-27.5%, and an upper limit of agreement of33.8%. Mean aneurysms length with CT was (2.07±1.31)cm and with TTE was (2.01±1.31)cm. Comparison the mean lengths between CT and TTE yielded a bias of-2.0%, a lower limit of agreement of-21.6%, and an upper limit of agreement of25.3%.The Bland-Altman plot for agreement between low dose CT and TTE showed good correlation in the diameter and length measurements.4. Radiation Dose EstimatesThe mean CTDIvol, DLP and effective dose of all45patients was (0.95±0.22) mGy,(10.0±2.72) mGy*cm and (0.59±0.23)mSv (range from0.36to1.17mSv), respectively.Conclusions:Low dose CT with excellent image quality and low radiation exposure has been proved useful in diagnosis and risk stratification for infants and children with coronary artery lesions due to Kawasaki disease, especially for the distal segments. Purpose:To prospectively compare pediatric CT coronary angiography performed at a low tube voltage of70kV and reduced dose of contrast agent(1.0ml/kg) with standard tube voltage of80kV, standard contrast agent dose(1.5ml/kg) CT angiography in patients with coronary arterial diseases.Materials and methods:The study has institutional review board approval; written informed consent was obtained.In this prospective study,81consecutive infants or children suspected with coronary arterial diseases (coronary arterial lesions due to Kawasaki diseases or coronary arterial deformities accompanied with congenital heart diseases) were evaluated. All infants and children underwent prospective ECG-triggering DSCT coronary arterial angiography using128-slice DSCT. Patients were divided into3groups by different scanning protocols. Group A (n=26):80kV and1.5ml/kg contrast agent, tube current was tailored by patients’weight:<5kg,50-69mAs;5-10kg,70-89mAs;10-15kg,90-109mAs;15-20kg,110-129mAs;>20kg,130-160mAs; Group B (n=26):70kV and1.5ml/kg contrast agent, tube current was tailored by patients’weight, at the same weight group, the tube current was20mAs more than the group A; Group C (n=26):70kV and1.0ml/kg contrast agent, tube current setting is the same as group B. The patients’age, weight, sex, heart rates, scanning time and scanning range were compared with each group. Two-independent radiologists were invited to evaluate the subjective image quality by4-point grading scale (3=excellent,2=good,1=mediate,0=poor). Vessel enhancement (CT attenuation), image noise (IN), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated for each protocol. Radiation dose (CTDIvol, DLP) was recorded and effective dose was calculated. Compared with conventional cardiac angiography (CCA) or surgical findings, the diagnostic efficiency was evaluated. Results:All low-dose CT angiography were performed successfully, and the image quality was sufficient for data analysis in all cases.There were no significant differences in patients’characteristics (age, weight, sex and heart rates) and scanning time, scanning range.In group A, the diagnoses at CTA were coronary-cameral fistula (n=3), left coronary artery from the pulmonary artery (ALCAPA, n=2), anomalies of coronary artery (n=3),coronary arterial lesions due to Kawasaki disease (n=8), coronary-pulmonary fistula (n=2), single coronary artery (n=2), no coronary arterial disease (n=6). In group B, the diagnoses at CTA were coronary-cameral fistula (n=2), left coronary artery from the pulmonary artery (ALCAPA, n=2), coronary arterial lesions due to Kawasaki disease (n=8), coronary-pulmonary fistula (n=1),single coronary artery (n=1),anomalies of coronary artery (n=3), no coronary arterial disease (n=9).In group C, the diagnoses at CTA were coronary-cameral fistula (n=3), coronary-pulmonary fistula(n=1),left coronary artery from the pulmonary artery (ALCAPA, n=3),anomalies of coronary artery (n=2), single coronary artery (n=1), coronary arterial lesions due to Kawasaki disease (n=10), no coronary arterial disease (n=6). Compared with surgical/conventional coronary angiographic findings, all of the coronary arterial diseases were confirmed, and the accuracy of CTA with different protocol was100%.The mean score of subjective image quality was2.2±0.6,2.1±0.5and2.4±0.4, respectively. There was no significant difference in visual scores for subjective image quality among3protocols and within groups (all p>0.05).The CTDIvol of80kV-and70kV-protocol was (0.98±0.23)mGy,(0.57±0.16) mGy,there was significant differences among protocols (t=7.55, p=0.00), the DLP of80kV-and70kV-protocol was(10.3±2.76) mGy*cm,(6.21±1.93)mGy*cm, there was significant differences among protocols (t=5.31,p=0.00), the effective dose of80kV-and70kV-protocol was (0.60±0.24) mSv,(0.39±0.10) mSv, there was significant differences among protocols (t=3.40,p=0.005;-35.0%). Conclusion:At a low tube voltage and a reduced dose of contrast agent, the protocol of70-kV and1ml/kg contrast agent is a feasible and accurate option for128-slice DSCT coronary angiography in pediatric patients with coronary arterial diseases.