The influence of reconstruction algorithm and heart rate on coronary artery image quality and stenosis detection at 64-detector cardiac CT.

Objective: We wanted to evaluate the impact of two reconstruction algorithms(halfscan and multisector) on the image quality and the accuracy of measuringthe severity of coronary stenoses by using a pulsating cardiac phantom with different heart rates (HRs).Materials and Methods: Simulated coronary arteries with different stenoticseverities (25, 50, 75%) and different luminal diameters (3, 4, 5 mm) werescanned with a fixed pitch of 0.16 and a 0.35 second gantry rotation time on a 64-slice multidetector CT. Both reconstruction algorithms (halfscan and multi-sector) were applied to HRs of 40 -120 beats per minute (bpm) at 10 bpm inter-vals. Three experienced radiologists visually assessed the image quality and theymanually measured the stenotic severity. Results: Fewer measurement errors occurred with multisector reconstruction(p = 0.05), a slower HR ( p < 0.001) and a larger luminal diameter ( p = 0.014);measurement errors were not related with the observers or the stenotic severity.There was no significant difference in measurements as for the reconstructionalgorithms below an HR of 70 bpm. More nonassessable segments were visual-ized with halfscan reconstruction ( p = 0.004) and higher HRs ( p < 0.001).Halfscan reconstruction had better quality scores when the HR was below 60bpm, while multisector reconstruction had better quality scores when the HR wasabove 90 bpm. For the HRs between 60 and 90 bpm, both reconstruction modeshad similar quality scores. With excluding the nonassessable segments, bothreconstruction algorithms achieved a similar mean measured stenotic severityand similar standard deviations. Conclusion: At a higher HR (above 90 bpm), multisector reconstruction hadbetter temporal resolution, fewer nonassessable segments, better quality scoresand better accuracy of measuring the stenotic severity in this phantom study.on-invasively evaluating coronary arterial stenoses is a major challengefor multidetector computed tomography (MDCT). There have been rapidadvances of the electrocardiographic (ECG) gated cardiac CT scanningsystems and techniques, including more detector rows and the advanced postprocess-ing software, and CT coronary angiography can now be performed at normal heartrates (HRs) with high sensitivity and specificity for detecting significant coronarystenoses (1-3). The recently introduced 64-detector MDCT allows using a sub-secondgantry rotation speed. The 2 major reconstruction algorithms for CT coronary angiog-raphy are the halfscan algorithm and the multisector algorithm. The multisectorreconstruction algorithm retrospectively reconstructs images from different cardiaccycles (two to five) and this could theoretically reduce the effective temporal resolu-Yi-Ting Wang, MD