Participants
The adult patients aged 18–88 years who received CCTA examination in Hunan Provincial People’s Hospital (The First Affiliated Hospital of Hunan Normal University) from June 2021 to December 2021 were included in the research. The inclusion criteria were as follows: (1) patients had not undergone cardiac pacemaker implantations or other cardiac surgeries; (2) patients had a favorable vascular condition and were capable of tolerating the flow rate (4–5 mL/s) of conventional contrast agents; (3) patients were able to hold their breaths for at least 6 s in the training before examination. The exclusion criteria were listed as follows: (1) patients had excellent breath-holding training outcomes before examination and poor breath-holding outcomes during examination; (2) patients had poor-quality images (poor display of superior vena cava, right atrium, right ventricle, or main pulmonary artery structure). A total of 200 cases of eligible patients were chosen to undergo modified saline test injection before CTA examination (the case group) and 200 cases of patients in the same period were randomly selected to receive conventional saline test injection before CTA examination (the control group). Among them, 6 cases were excluded for poor breath-holding results during examination despite excellent breath-holding training outcomes before examination, and 8 cases were excluded for the poor-quality image. Finally, this research included 187 cases in the case group and 199 cases in the control group, a total of 386 patients (Fig. 
Inclusion and exclusion criteria