| Part 1Low-concentration contrast material and low dose technique: for prospective electrocardiogram-triggered dual-source computed tomography coronary angiography by a combination of iterative reconstructionBackground Coronary computed tomography angiography has become an effective noninvasive screening method for coronary coronar y atherosclerosis heart disease(CAD), had a very good imaging effect and high diagnostic accuracy. In retrospectively electrocardiogram(ECG)- gated spiral data acquisition mode, high radiation exposure has been widely given attention. Prospectively ECG-triggered C TCA can greatly reduce the effective radiation compared with traditional retrospective ECG-gated CCTA. In addition, associated CIN risks have raised concern with the widely application of the CCTA. Choosing a low iodine concentration contrast media will be a way to lower the iodine burden of patients,but the lower the iodine concentration, the lower the density will bewithin the region of interest. The use of a low-tube-voltage results in higher CT values. However, lowering k V might involve degraded image quality because of increased image noise. However, recently introduced iterative reconstruction(IR) techniques are less susceptible to image noise and artefacts. They can markedly effectively increase signal-to-noise ratio(SNR) and contrast-to-noise ratio(CNR), and achieve a better image quality compared to filtered back projection(FBP) reconstruction algorithms. That is, reduction in radiation dose when achieve an equivalent image quality.Objective The purpose of this study is to assess the impact of low concentration contrast media on the degree of vascular enhancement, image quality and radiation dose in coronary CT angiography(c CTA) studies when using a combination of iterative reconstruction and 80 k V or 100 k V.Methods 128-slice dual-source CT prospective EC G-triggered coronary angiography was performed in 100 patients randomize to a low or high contrast medium concentration. The patients in group A received iopromide 370 were scanned using the conventional tube output(100 k V and 300 m As in BMI<23 kg/m2, 120 k V and 300 m As in BMI≥23 kg/m2), and images were reconstructed using filtered back projection(FBP). The patients in group B received iodixanol 270 were scanned using the low tube output(80 k V and 300 m As in BMI<23 kg/m2, 100 k V and 300 m As in BMI≥23 kg/m2), and images were reconstructed using iterative reconstruction technique(SAFIRE, Siemens Healthcare). CT attenuation was measured in the coronary arteries, great arteries, interventricular septum and left ventricular cavity. Noise, subjective image quality scores and effective radiation dose were compared between the two groups.Results There was no significant difference in the mean CT attenuation achieved at each anatomic site between iomeprol 270 groups and iopromide 370 groups. At the proximal segments of coronary arteries, the mean CT attenuation were 585.63±101.00 Hu or 385.16±60.71 Hu in low or high weigh subgroups after Iodixanol 270, and 576.63±110.04 Hu or Hu 396.04±65.88 in low or high weigh subgroups after iopromide 370, respectively, and they did not differ(P= 0.414 in BMI<23 kg/m2 and P=0.185 in BMI≥23kg/m2). Similar ?ndings were noted for the mean attenuation in the ascendingaorta, pulmonary trunk, interventricular septum and left ventricular cavity. There were no significant differences in mean image noise and mean image quality score using Iodixanol 270 with SAFIRE than Iopromide 370 with FBP in coronary arteries and the other same evaluated anatomical regions. The effective radiation dose were 0.44±0.25 m Sv and 0.94±0.42 m Sv for iomeprol 270 and iopromide 370 in low weight subgroups, and1.17±0.30 m Sv and 2.37±0.66 m Sv in high weight subgroups, respectively, reflecting dose savings of 53.2%(P<0.001) and 50.6%(P<0.001), respectively.Conclusion The results demonstrate that with a combination of iterative reconstruction and a tube voltage of 80 k V or 100 k V, a low iodine concentration of 270 mg I/ml still improves the contrast enhancement witho ut impairing image quality, as well as significantly lowers effective radiation dose.Part 2Low-concentration contrast material and low dose for High-pitch dual-source computed tomography coronary angiography by a combination of iterative reconstruction prospective electrocardiogram-triggeredBackground Pitch is also an important parameter of CCTA. Recently, the second generation of dual-source CT systems was introduced, providing high detector coverage with the use of two 128-section detectors. This dual-source CT system also allows CCTA examinations to be performed at high pitch(HP) values of up to 3.4. A high pitch, prospectively ECG-triggered spiral protocol can further reduce radiation dose allowing depiction of the entire heart within a single heart beat. In this mode, on the basis of the first part of the experiment, data acquisition is also prospectively trigge red with the ECGof the patient. The radiation dose may be greatly reduced.Objective The purpose of this study is to assess the impact of low concentration contrast media on the degree of vascular enhancement, image quality and radiation dose in CCTA studies by using prospectively EC G-triggered high-pitch spiral acquisition with 80 k V combination with iterative reconstruction.Methods 128-slice dual-source C T prospective EC G-triggered high-pitch spiral acquisition coronary angiography was performed in 120 patients randomize to a low or high contrast medium concentration. The patients in group A received iodixanol 270 were scanned using the low tube output(80 k V and 300 m As), and images were reconstructed using iterative reconstruction technique(SAFIRE, Siemens Hea lthcare). The patients in group B received iopromide 370 were scanned using the conventional tube output(100 k V and 300 m As), and images were reconstructed using filtered back projection(FBP). CT attenuation was measured in coronary artery and other anatomical regions. Image quality score, noise, SNR, CNR and radiation dose were compared between the two groups. Results There was significant difference in the mean CT attenuation achieved at each anatomic site between iodixanol 270 group and iopromide 370 group. There were no significant differences in image noise SNR, CNR.The effective radiation dose were 0.25±0.05 m Sv and 0.55±0.11 m Sv for iodixanol 270 and iopromide 370 groups,(p<0.001),reflecting dose savings of 54.5%.Conclusions The results demonstrate that with high-pitch spiral acquisition mode combination of iterative reconstruction and a tube voltage of 80 k V, a low iodine concentration of 270 mg I/ml still improves the contrast enhancement without impairing image quality, as well as significantly lowers effective radiation dose. |
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