Application Of The Optimal Scanning Protocol On 128-slice Dual-source CT In Children With Tetralogy Of Fallot

PART IApplication of the Optimal Contrast Medium Injection Protocol on 128-slice dual-source CT in children with Tetralogy of FallotObjectiveTo explore the clinical value of the optimal contrast medium injection protocol on 128-slice dual-source CT (DSCT) in children with Tetralogy of Fallot (TOF).Materials and MethodsSixty patients with TOF were randomly divided into group A, group B and group C, twenty patients in each group, underwent 128-slice DSCT angiography with sequential mode according to the contrast injection protocol:the volume of contrast medium was 1.5ml/kg,1.2ml/kg and 1.2ml/kg and the injection time was 15s,12s and 10s respectively. The contrast medium was followed by a saline bolus for 10s. Enhancement and noise of ascending aorta, the main pulmonary artery, descending aorta and left ventricle was quantified. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), dose-length product (DLP), volume CT dose index (CTDIvol) and effective dose (ED) were calculated. The absolute valve of the difference of left and right ventricular attenuation was calculated to represent the image uniformity. Subjective image quality was assessed by two radiologists in consensus. One-Way ANOVA was performed to analyze the differences between the three groups regarding patient demographics, image attenuation, SNR, CNR and the image uniformity. The image quality scores among groups were compared by using the Kruskal-Wallis test and scores between the two groups were compared by using the Mann-Whitney test.ResultsNo significant difference was found in the attenuation, SNR, CNR between the three groups in the same evaluated anatomic regions. No significant difference was found in the image quality of heart chamber and great vessels. The image uniformity and the subjective image quality of the artifacts of the superior vena cava were significantly better in group B than that in group A and C (P<0.05).ConclusionIt is feasible that the contrast medium injection protocol,1.2ml/kg volume contrast medium injected in 12s, can increase image quality on 128-slice dual-source CT in children with Tetralogy of Fallot.Part IIApplication of low tube voltage and low volum contrast medium protocol on 128-slice dual-source CT in children with Tetralogy of FallotObjectiveTo investigate the effectiveness and feasibility of cardiovascular Computed Tomography Angiography (CTA) with low tube voltage and low dosage contrast media in children with Tetralogy of Fallot (TOF).Materials and MethodsForty patients with TOF were randomly divided into group A and group B, twenty patients in each group, underwent 128-slice DSCT angiography with sequential mode according to the scanning and contrast injection protocol:patients in group A received a conventional scan with 80kVp and contrast media of 1.2ml/kg. Patients in group B, 70kVp and contrast media of 1.0ml/kg were used. The injection time of the two groups were both fixed for 12s. CT attenuation, image noise and signal-to-noise ratio (SNR) of ascending aorta, the main pulmonary artery, left ventricle and right ventricle were quantified. Radiation dose and volume of the contrast medium were recorded. Subjective image quality was assessed by two radiologists in consensus. The Student’s t-test was performed to analyse the differences between the two groups regarding CT attenuation, image noise, SNR, radiation dose and volume of the contrast medium. The image quality scores between the two groups were compared by using the Mann-Whitney U test.ResultsNo significant difference was found in the attenuation, noise, SNR between the two groups in the same evaluated anatomic regions and no significant difference was found in the image quality. Effective dose (ED) was 0.17±0.05 mSv,0.13±0.04mSv respectively, there was significantly reduction in group B than that in group A (t=2.48, P=0.019). The consumed iodine amount was 10.00±1.84ml,8.29±1.45ml respectively, there was significantly reduction between the two groups (t=2.89, P=0.007). Conclusions In children with Tetralogy of Fallot, the cardiovascular Computed Tomography Angiography (CTA) with diagnostic quality can be adequately acquired with low tube voltage (70kVp) and low concentration contrast media (1.0ml/kg), there was significantly reduction in radiation dose and contrast medium amount.