Purpose: To compare 128 slice coronary CT angiography (CCTA, Definition AS+, Siemens Medical Solution) with ECG based tube current modulation (mindose) with echocardiography for the determination of LVEF and left ventricular volumes (LV) in subjects with chest pain and assess coronary artery image quality and patient radiation dose in a group of patients who underwent 128 slice CCTA with mindose. Material and Methods: 30 patients (20 men, 10 women; mean age 57.9 짹 11.4 years, mean heart rate 56.1 짹 9.6) referred for 128 slice CCTA with mindose for evaluation of chest pain (22 patients in atypical chest pain, 8 patients in typical chest pain). Coronary artery segment subjective image quality (1, excellent; 4, poor) and patients radiation dose were recorded with two observers by consensus. All patients underwent echocardiography at the same day. Multiphase axial CT images were analysed with a semiautomatic region growing algorithms (Syngo Circulation; Siemens Medical Solutions) by two independent blinded observers and inter-observer variability were assessed. EF, end-diastolic volume (EDV), End-systolic volume (ESV), and stroke volume (SV) were determined for both modalities, and correlation coefficient were assessed. Results: The mean LVEFs calculated by CCTA with mindose (64.92짹9.60%) and echocardiography (65.77짹8.68%) were not statistically different (p=0.535). Comparison of LVEFs from CCTA and echocardiography yielded correlation coefficients of 0.903 (p<0.01). The mean EDV calculated with echocardiography (71.26짹24.41ml) was significantly lower than CCTA with mindose (122.22짹22.01ml) (p<0.00). The mean ESV calculated with echocardiography (27.85 짹 20.03ml) was also significantly lower than CCTA with mindose (43.88짹20.45ml) (p<0.00). Comparison of EDV from echocardiography and CCTA with mindose yielded a correlation coefficient of 0.644 (p<0.01). The correlation of ESV between echocardiography and CCTA with mindose showed a correlation coefficient of 0.819 (p<0.01). All coronary artery segment could be evaluated in CCTA with mindose except less than 1.5 mm sized segment or anatomical variant. Average image quality score of coronary artery segment was 1.10 and Mean patient radiation dose was 4.85짹 1.21. Conclusion: The LVEF, EDV, and ESV calculated by CCTA with mindose correlated significantly with those of estimated with echocardiography. In addition, there were no statistical differences of LVEF. However in terms of LV, EDV and ESV from CCTA were statistically significantly higher than those of echocardiography. Clinical application: The CCTA using 128 slice MDCT with mindose could present information with regard to coronary artery disease and LVEF, LV at low patient radiation dose.