Influence of Heart Rate and Innovative Motion-Correction Algorithm on Coronary Artery Image Quality and Measurement Accuracy Using 256-Detector Row Computed Tomography Scanner: Phantom Study

OBJECTIVE: To investigate the efficacy of motion-correction algorithm (MCA) in improving coronary artery image quality and measurement accuracy using an anthropomorphic dynamic heart phantom and 256-detector row computed tomography (CT) scanner. MATERIALS AND METHODS: An anthropomorphic dynamic heart phantom was scanned under a static condition and under heart rate (HR) simulation of 50–120 beats per minute (bpm), and the obtained images were reconstructed using conventional algorithm (CA) and MCA. We compared the subjective image quality of coronary arteries using a four-point scale (1, excellent; 2, good; 3, fair; 4, poor) and measurement accuracy using measurement errors of the minimal luminal diameter (MLD) and minimal luminal area (MLA). RESULTS: Compared with CA, MCA significantly improved the subjective image quality at HRs of 110 bpm (1.3 ± 0.3 vs. 1.9 ± 0.8, p = 0.003) and 120 bpm (1.7 ± 0.7 vs. 2.3 ± 0.6, p = 0.006). The measurement error of MLD significantly decreased on using MCA at 110 bpm (11.7 ± 5.9% vs. 18.4 ± 9.4%, p = 0.013) and 120 bpm (10.0 ± 7.3% vs. 25.0 ± 16.5%, p = 0.013). The measurement error of the MLA was also reduced using MCA at 110 bpm (19.2 ± 28.1% vs. 26.4 ± 21.6%, p = 0.028) and 120 bpm (17.9 ± 17.7% vs. 34.8 ± 19.6%, p = 0.018). CONCLUSION: Motion-correction algorithm can improve the coronary artery image quality and measurement accuracy at a high HR using an anthropomorphic dynamic heart phantom and 256-detector row CT scanner.

Effect of a Novel Intracycle Motion Correction Algorithm on Dual-Energy Spectral Coronary CT Angiography: A Study with Pulsating Coronary Artery Phantom at High Heart Rates

OBJECTIVE: Using a pulsating coronary artery phantom at high heart rate settings, we investigated the efficacy of a motion correction algorithm (MCA) to improve the image quality in dual-energy spectral coronary CT angiography (CCTA). MATERIALS AND METHODS: Coronary flow phantoms were scanned at heart rates of 60–100 beats/min at 10-beats/min increments, using dual-energy spectral CT mode. Virtual monochromatic images were reconstructed from 50 to 90 keV at 10-keV increments. Two blinded observers assessed image quality using a 4-point Likert Scale (1 = non-diagnostic, 4 = excellent) and the fraction of interpretable segments using MCA versus conventional algorithm (CA). Comparison of variables was performed with the Wilcoxon rank sum test and McNemar test. RESULTS: At heart rates of 70, 80, 90, and 100 beats/min, images with MCA were rated as higher image scores compared to those with CA on monochromatic levels of 50, 60, and 70 keV (each p < 0.05). Meanwhile, at a heart rate of 90 beats/min, image interpretability was improved by MCA at a monochromatic level of 60 keV (p < 0.05) and 70 keV (p < 0.05). At a heart rate of 100 beats/min, image interpretability was improved by MCA at monochromatic levels of 50 keV (from 69.4% to 86.1%, p < 0.05), 60 keV (from 55.6% to 83.3%, p < 0.05) and 70 keV (from 33.3% to 69.3%, p < 0.05). CONCLUSION: Low-keV monochromatic images combined with MCA improves image quality and image interpretability in CCTAs at high heart rates.

Correction Algorithm of Pseudothrombocytopenia due to Platelet Clumping / 대한진단검사의학회지

BACKGROUND: Pseudothrombocytopenia is a phenomenon that automated hematology analyzers calculate platelets at a spuriously low count. The most common cause of this phenomenon is platelet clumping. Several methods such as vortex mixing, changing anticoagulant to sodium citrate or heparin, and adding amikacin to ethylenediaminetetraacetic acid (EDTA) have been routinely used for managing pseudothrombocytopenia. The purposes of this study were to compare the efficacy of these four methods and to propose a cost-effective algorithm for managing pseudothrombocytopenia in clinical laboratories. METHODS: Ten patients (six males and four females) having pseudothrombocytopenia were evaluated. In these patients, platelet clumpings had been detected on more than three occasions by Coulter STKS (Beckman-Coulter, USA) and by microscopic examination on peripheral blood smear (PBS). We recollected blood samples from each patient in four tubes coated with EDTA, sodium citrate, heparin, or EDTA with amikacin. CBC of the blood samples in each tube was performed within one hour of collection; the samples in EDTA-coated tube were retested after vortex mixing. RESULTS: Platelet counts were increased in all cases (100%) by EDTA with amikacin as an anticoagulant, 80% (8/10) by vortex mixing or heparin, and in 90% (9/10) by sodium citrate. However, platelet counts were decreased in 20% (2/10) of heparin coated samples. `Clinically meaningful increase' was achieved in 60% (6/10) by heparin and EDTA with amikacin, in 50% (5/10) by sodium citrate, and in 40% (4/10) by vortex mixing. But `clinically meaningful decrease' was found in 10% (1/10) by heparin. CONCLUSIONS: When pseudothrombocytopenia due to platelet clumpings is detected, vortex mixing is recommended first. If platelet count does not increase after the vortex mixing, changing anticoagulant to sodium-citrate or adding amikacin to EDTA is recommended for managing pseudothrombocytopenia.