Korean J Radiol.  2009 Jun;10(3):227-234. 10.3348/kjr.2009.10.3.227.

The Influence of Reconstruction Algorithm and Heart Rate on Coronary Artery Image Quality and Stenosis Detection at 64-Detector Cardiac CT

• Wang YT
• Yang CY
• Hsiao JK
• Liu HM
• Lee WJ
• Shen Y

• KMID: 1779449
• DOI: http://doi.org/10.3348/kjr.2009.10.3.227

Abstract

OBJECTIVE
We wanted to evaluate the impact of two reconstruction algorithms (halfscan and multisector) on the image quality and the accuracy of measuring the severity of coronary stenoses by using a pulsating cardiac phantom with different heart rates (HRs). MATERIALS AND METHODS: Simulated coronary arteries with different stenotic severities (25, 50, 75%) and different luminal diameters (3, 4, 5 mm) were scanned 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 multisector) were applied to HRs of 40-120 beats per minute (bpm) at 10 bpm intervals. Three experienced radiologists visually assessed the image quality and they manually 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 reconstruction algorithms below an HR of 70 bpm. More nonassessable segments were visualized with halfscan reconstruction (p = 0.004) and higher HRs (p < 0.001). Halfscan reconstruction had better quality scores when the HR was below 60 bpm, while multisector reconstruction had better quality scores when the HR was above 90 bpm. For the HRs between 60 and 90 bpm, both reconstruction modes had similar quality scores. With excluding the nonassessable segments, both reconstruction algorithms achieved a similar mean measured stenotic severity and similar standard deviations. CONCLUSION: At a higher HR (above 90 bpm), multisector reconstruction had better temporal resolution, fewer nonassessable segments, better quality scores and better accuracy of measuring the stenotic severity in this phantom study.

Keyword

Computed tomography (CT); Reconstruction; Algorithm; Phantom; Coronary artery angiography

MeSH Terms

*Algorithms
Artifacts
Computer Simulation
Coronary Angiography/*methods
Coronary Stenosis/*radiography
Electrocardiography
*Heart Rate
Image Processing, Computer-Assisted/*methods
Models, Cardiovascular
Observer Variation
Phantoms, Imaging
Reproducibility of Results
Severity of Illness Index
Tomography, Spiral Computed/*methods

Figure

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  Fig. 1 Cardiac phantom and simulated coronary artery stenosis. A. Simulated coronary artery with different degrees of stenoses is slung on surface of pulsating cardiac phantom. B, C. CT images of cardiac phantom and simulated coronary artery scanned at static status.

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  Fig. 2 Image quality score. A. Grade 1 equals good quality without artifacts. B. Grade 2 equals acceptable quality with mild motion artifacts. C. Grade 3 equals nondiagnostic quality with significant motion artifacts.

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  Fig. 3 Temporal window shows waveform improvement with heart rate above 60 bpm and it ranges between 127 and 227 msec in multisector reconstruction algorithm, but it does not change in halfscan reconstruction.

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  Fig. 4 Image quality score is average of scores given by three radiologists. At heart rate between 60 and 90 bpm, both reconstruction algorithms achieved similar quality scores. At other rates, halfscan reconstruction scored better at lower heart rates and multisector reconstruction scored better at high heart rates. Paradoxical reversal was noted at heart rate of 90 bpm.

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  Fig. 5 Summation of nonassessable segments by heart rate. Multisector reconstruction results in fewer nonassessable segments, and especially at higher heart rates. This trend is most obvious above heart rate of 80 bpm.

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  Fig. 6 Excluding nonassessable segments, there is no significant difference between reconstruction algorithms for mean measured stenotic severity and standard deviation.

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  Fig. 7 Relative errors of both assessable and nonassessable segments were analyzed. At heart rates from 40 to 70 bpm, there are similar small measurement errors with using both reconstruction algorithms. Multisector reconstruction achieved better performance at heart rate above 80 bpm, except at heart rate of 90 bpm.

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  Fig. 8 Upper images: volume rendering images of halfscan reconstruction at heart rates of 40, 80 and 120 bpm (left to right). Lower images: volume rendering images of multisector reconstruction at heart rates of 40, 80 and 120 bpm (left to right). There is fewer cardiac motion related banding artifacts noted on multisector reconstruction, and especially at higher heart rates.

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