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Objective: To evaluate the correlation between image quality and thoracic diameters, anteroposterior diameter (AP) and right-left diameter (RL) for the optimization of reducing radiation dose in coronary artery imaging with Dual-source CT., Methods: 118 patients underwent CT coronary artery imaging (CTCA) were divided into two groups (A and B) according to body mass index (BMI). There were 58 patients in group A with BMI values > or = 25 kg/m2 and < 30 kg/m2; and 60 patients in group B with BMI values < 25 kg/m2. Scan parameters: collimation 64 X 0.6 mm, reconstruction slice thickness 0.75 mm, reconstructin interval 0.7 mm, FOV 150-180 mm, the pitch adjusted according to heart rate automatically. CT imagings were obtained with tube voltage 100 kV, tube current 330 mAs (group A) and 100 kV, tube current 220 mAs (group B). The contrast-noise ratio (CNR), signal to noise ratio (SNR), as well as blind correlation test score values were calculated to establish the relationship among BMI, AP, RL and CNR, SNR., Results: RL of five levels in groups of A, B were correlated to CNRa (P < 0.05). In group A and B (except iii, iv level of Group A), AP were associated with CNRa (P < 0.05). In addition to ii, iv level of group A, v level of group B, BMI were associated with CNRa (P < 0.05). The correlation coefficient of CNRa and RL of group A except ii level was greater than that of CNRa and AP. The correlation coefficient of CNRa, SNRa and RL of group B was greater than that of CNRa, SNRa and AP. Except iii level, the correlation coefficient of CNRa, SNRa and AP of group A was greater than that of CNRa, SNRa and BMI. Except ii level, the correlation coefficient of CNRa and AP of group B was greater than that of CNRa and BMI., Conclusion: Thoracic diameter of RL can be used as a guider to select the appropriate scan protocol in the coronary imaging acqusition with dual-source CT.

Objective: To evaluate the clinical value of low-dose chest pain protocol for cardiac and chest vascular imaging using dual-source computed tomography., Methods: 102 patients with requests for examinations of cardiac and thoracic blood vessels, were scanned in chest pain protocol for angiography. With heart electrical impulses dose control techniques, maximum tube current within the R-R interval was set up by different heart rate. Patients with a heart rate less than or equal to 75 beats/min were divided into two groups: regular-dose group (A) 28 patients; low-dose group (B) 25 patients. Patient with a heart rate of 76-120 beats/min were also divided into two groups: regular-dose group (C) 24 patients; low-dose group (D) 25 patients. The image quality of pulmonary artery, coronary artery and aortic were blind evaluated. The effective dose for each patient was calculated and group comparisons were made., Results: Every radiation dose gained satisfactory images. No differences in image quality were found between Group A and Group B, and between Group C and Group D (P > 0.05). The effective doses of Group A (7.09 +/- 0.95) mSv were significantly higher than those of Group B (5.01 +/- 0.34) mSv. The effective doses of Group C (4.79 +/- 0.91) mSv were significantly higher than those of Group D (2.48 +/- 0.43) mSv. CONCLUSION; For patients with acute chest pain and relatively stable heart rate, their cardiac and thoracic vessels can be shown clearly in images of low-dose chest pain protocol, which provides a rapid and clear diagnostic instrument.