[Influence of heart rate and cardiac phases on image quality using 320-detector row CT]

To investigate the impact of hart rate (HR) and reconstruction timing on image quality by a 320-detector row dynamic volume CT system (DVCT).

A total of 80 patients were examined by DVCT angiography. There were 43 males and 37 females with a mean age of 64 ± 8 years old. The heart rate (HR) was 47 - 128 beats per minute. The data were reconstructed by 10% steps throughout the R-R interval. And the data sets were evaluated by 2 independent readers for each major coronary vessel, namely right coronary artery, left anterior descending artery and left circumflex artery. The motion score for each vessel was graded from 1 (no motion artifacts) to 4 (severe motion artifacts over an entire vessel). The HR dependency of image quality was determined by an analysis of linear regression. The linear regression between HR and the optimal image quality in diastole or systole was also calculated.

The average HR was 71 ± 15 beats per minute. And the image quality was significantly affected by HR (y = -0.154 + 0.022x, t = 11.0, P < 0.01). According to this equation, images of grades 1 and 2 could be achieved at HR < 98 beats per minute. The proportion of systole was influenced by HR statistically (t = 10.84, P < 0.01). With the increase of HR, the optimal systolic and diastolic reconstruction intervals all shifted to the later phases. The cut-off heart rate at which optimal reconstruction interval turned from diastole to systole was 93 bpm.

Coronary DVCT angiography provides quality diagnostic images within a wide range of heart rates. And the study of optimal reconstruction interval will help to reduce the imaging artifacts and lower the patient absorption dose.