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Objective To explore the feasibility of a modified two breath-hold method with radiation dose reduction technique using lower voltage of 100 kV in subtraction coronary CT angiography (CCTA) for patients with limited breath-hold (<15 s).Methods A total of 17 patients with Agatston score >400,and body mass index less than 25 kg/m2 were enrolled in this study.The pre-contrast and post-contrast volume data was acquired during two breath-holds with the same time window period in 65%-80% of the R-R interval. A 4-point scale was used for the evaluation of subjective image quality.Results A total of 53 calcified coronary segments were evaluated.There was an improvement in the image quality from 2.51±0.95 with conventional CCTA to 3.36±0.92 with subtraction CCTA (P<0.01).The non-diagnostic segments significantly reduced from 23(43.4%) to 6 (11.3%) using subtraction CCTA (P=0.02). The average total effective radiation dose was (2.80±0.64) mSv.Conclusions This preliminary study has shown that our modified method in subtraction CCTA could significantly reduce the non-assessable segments and improve the accessibility of severe calcified segments by reducing or eliminating artifacts.Using 100 kV tube voltage,the total radiation dose was distinctly reduced with maintained image quality in BMI＜25 kg/m2 patients. [ABSTRACT FROM AUTHOR]