Concept of minimal heart rate for each pitch value to avoid interpolation artifact when using dual-source CT: a phantom study.

Interpolation artifact is known to occur when the heart rate is decreased lower than the critical value for the specific pitch. The purpose of our study is to determine the minimum heart rate (minHR) for the specific pitch that provides images without interpolation artifact when using dual-source computed tomography (DSCT). We scanned the 'thin slice thickness block' of the CT performance phantom provided by the American Association of Physicists in Medicine using DSCT for variable pitches. Change in heart rate was simulated through ECG editing by changing R-R interval. Axial, sagittal, and coronal image sets were reconstructed and assessed for the presence and extent of interpolation artifact. MinHR at which no interpolation artifact was detected for each pitch value was determined. Length of interpolation artifact (LOA) on sagittal view was also measured when the heart rate was simulated at 10 bpm lower than the minHR on each pitch setting. MinHRs for each pitch value were 9-10 bpm from the estimated heart rate. However, minHR for the lowest pitch value 0.2, estimated heart value 40 bpm was 37 bpm. LOA was larger in the low heart rate condition. Measured values of minHR were correlated exactly with the calculated values. MinHRs that provide images without interpolation artifact for each pitch value when using DSCT were determined. The concept of minHR is important for obtaining high quality images of cardiac CT angiography when using DSCT.