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Unlabelled: Transient ischemic dilation (TID) in the setting of abnormal stress-rest cardiac SPECT myocardial perfusion imaging (MPI) has been linked with increased cardiovascular risk. However, the significance of TID in the setting of an otherwise normal SPECT MPI study has not been clearly established. In this study, cardiac CT was used to evaluate the prevalence of atherosclerotic lesions and the severity of coronary artery stenosis in patients with TID of the left ventricle with or without associated myocardial perfusion defects on SPECT MPI., Methods: The study population consisted of 1,553 consecutive patients who had undergone both cardiac CT and SPECT MPI within 1 mo between January 1, 2006, and September 1, 2011. Patients included in the study group had a pathologic TID value defined as ≥1.18 for men and ≥1.22 for women. Coronary CT angiography was used to evaluate each coronary segment for the presence and composition of atherosclerotic plaque and the degree of coronary stenosis. TID-positive patients were compared with a 2:1 risk-factor-matched-pair control cohort without TID., Results: TID was identified in 30 patients who were compared with TID-negative risk-factor-matched controls (n = 60). When compared with the TID-negative control cohort, TID-positive patients had no significant differences in the presence and extent of atherosclerosis, the degree of coronary artery stenosis, or the calcium score at cardiac CT. Similarly, there were no significant differences in these CT measures in TID-positive patients with a normal perfusion study (n = 20) when compared with TID-negative patients with a normal perfusion study (n = 48). In addition, there was no significant difference in the incidence of major adverse cardiac events when comparing both the TID-positive patients and the TID-negative control cohort and when comparing patients who were TID-positive with normal perfusion with patients who were TID-negative with normal perfusion., Conclusion: The presence of TID with an otherwise normal SPECT MPI study does not translate into a greater extent of coronary artery disease as assessed by cardiac CT or increased risk for future major adverse cardiac events., (© 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc.)

Rationale and Objectives: To investigate the impact of iterative reconstruction in image space (IRIS) on image noise, image quality (IQ), and postprocessing at coronary computed tomography angiography (cCTA) compared to traditional filtered back-projection (FBP)., Materials and Methods: The cCTA results of 50 patients (26 men; 58 ± 15 years, body mass index 31.5 ± 6.7 kg/m²) were investigated using a second-generation dual-source computed tomography system. Scan data were reconstructed with the use of IRIS and FBP algorithms. Two radiologists independently evaluated the reconstructions using automated coronary tree analysis software. Image noise was measured and IQ was rated on a 5-point Likert scale. The number of manual corrections after automated vessel segmentation, the time required to complete segmentation, and the number of missed segments were assessed in both IRIS and FBP reconstructions. Results were compared using paired t-test., Results: IRIS significantly reduced image noise compared to FBP (23.3 ± 8.8 vs. 33.5 ± 13.5 Hounsfield units, P < .001). Subjective IQ improved with IRIS (IRIS 3.2 ± 1.0 vs. FBP 3.0 ± 1.0, P < .05). IRIS decreased the time needed for coronary segmentation from 111.9 ± 40.5 seconds to 95.2 ± 38.2 seconds with FBP (P < .01) and required fewer manual corrections (5.7 ± 3.0 vs. 6.8 ± 3.6, P < .01). The number of missed vessel segments was not significantly different (3.6 ± 1.8 vs. 3.8 ± 1.9, P > .05) between IRIS and FBP, respectively., Conclusions: During cCTA postprocessing, IRIS significantly decreases the time and the number of manual corrections for a complete coronary segmentation compared to FBP. This effect is likely attributable to suppression of image noise by IRIS, which improves the performance of automated vessel segmentation and positively impacts cCTA analysis., (Copyright © 2014 AUR. Published by Elsevier Inc. All rights reserved.)

Objectives: To evaluate image quality (IQ) of low-radiation-dose paediatric cardiovascular CT angiography (CTA), comparing iterative reconstruction in image space (IRIS) and sinogram-affirmed iterative reconstruction (SAFIRE) with filtered back-projection (FBP) and estimate the potential for further dose reductions., Methods: Forty neonates and children underwent low radiation CTA with or without ECG synchronisation. Data were reconstructed with FBP, IRIS and SAFIRE. For ECG-synchronised studies, half-dose image acquisitions were simulated. Signal noise was measured and IQ graded. Effective dose (ED) was estimated., Results: Mean absolute and relative image noise with IRIS and full-dose SAFIRE was lower than with FBP (P < 0.001), while SNR and CNR were higher (P < 0.001). Image noise was also lower and SNR and CNR higher in half-dose SAFIRE studies compared with full-and half-dose FBP studies (P < 0.001). IQ scores were higher for IRIS, full-dose SAFIRE and half-dose SAFIRE than for full-dose FBP and higher for half-dose SAFIRE than for half-dose FBP (P < 0.05). Median weight-specific ED was 0.3 mSv without and 1.36 mSv with ECG synchronisation. The estimated ED of half-dose SAFIRE studies was 0.68 mSv., Conclusions: IR improves image noise, SNR, CNR and subjective IQ compared with FBP in low-radiation-dose paediatric CTA and allows further dose reductions without compromising diagnostic IQ., Key Points: • Iterative reconstruction techniques significantly improve non-invasive cardiovascular CT in children. • Using half traditional radiation dose image quality is higher with iterative reconstruction. • Iterative reconstruction techniques may allow further radiation reductions in paediatric cardiovascular CT.

Objectives: Performance evaluation of a fully automated system for calculating computed tomography (CT) coronary artery calcium scores from contrast medium-enhanced coronary CT angiography (cCTA) studies., Methods: One hundred and twenty-seven patients (58 ± 11 years, 71 men) who had undergone cCTA as well as an unenhanced CT calcium scoring study where included. Calcium scores were computed from cCTA by an automated image processing algorithm and compared with calcium scores obtained by standard manual assessment of unenhanced CT calcium scoring studies. Results were compared vis-a-vis (1) absolute calcium score values, (2) age-, gender- and race-dependent percentiles, and (3) commonly used calcium score risk classification categories., Results: One hundred and nineteen out of 127 (93.7%) studies were successfully processed. Mean Agatston calcium score values obtained by traditional non-contrast CT calcium scoring studies and derived from contrast medium-enhanced cCTA did not significantly differ (235.6 ± 430.5 vs 262.0 ± 499.5; P > 0.05). Calcium score risk categories and Multi-Ethnic Study of Atherosclerosis (MESA) percentiles showed very high correlation (Spearman rank correlation coefficient = 0.97, P < 0.0001/0.95, P < 0.0001) between the two approaches., Conclusions: Calcium score values automatically computed from cCTA are highly correlated with standard unenhanced CT calcium scoring studies. These results suggest a radiation dose- and time-saving potential when deriving calcium scores from cCTA studies without a preceding unenhanced CT calcium scoring study.

Objectives: Comparison of coronary artery stent assessment with cardiac CT angiography (cCTA) using traditional filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE), in both full- and half-radiation dose image data., Methods: Dual-source cCTA studies of 37 implanted stents were reconstructed at full- and half-radiation dose with FBP and SAFIRE. Half-dose data were based on projections from one DSCT detector. In-stent noise, signal-to-noise ratio (SNR), and stent-lumen attenuation increase ratio (SAIR) were measured and image quality graded. Stent volumes were measured to gauge severity of beam hardening artefacts., Results: Full-dose SAFIRE reconstructions were superior to full-dose FBP vis-à-vis in-stent noise (21.2 ± 6.6 vs. 35.7 ± 17.5; P < 0.05), SNR (22.1 ± 8.6 vs. 14.3 ± 6.7; P < 0.05), SAIR (19.6 ± 17.6 vs. 33.4 ± 20.4%; P < 0.05), and image quality (4.2 ± 0.86 vs. 3.5 ± 1.0; P < 0.05). Stent volumes were lower measured with SAFIRE (119.9 ± 53.7 vs. 129.8 ± 65.0 mm(3); P > 0.05). Comparing half-dose SAFIRE with full-dose FBP, in-stent noise (26.7 ± 13.0 vs. 35.7 ± 17.5; P < 0.05) and SNR (18.2 ± 6.9 vs. 14.3 ± 6.7; P < 0.05) improved significantly. SAIR (31.6 ± 24.3 vs. 33.4 ± 20.4%; P > 0.05), stent volume (129.6 ± 57.3 vs. 129.8 ± 65.0 mm(3); P > 0.05), and image quality (3.5 ± 1.0 vs. 3.7 ± 1.1; P > 0.05) did not differ. Radiation dose decreased from 8.7 ± 5.2 to 4.3 ± 2.6 mSv., Conclusions: Iterative reconstruction significantly improves imaging of coronary artery stents by CT compared with FBP, even with half-radiation-dose data.

Objective: The objective of our study was to evaluate radiation dose and quantitative image quality parameters at high-pitch CT angiography (CTA) of the aorta compared with conventional CTA., Materials and Methods: We studied the examinations of 110 patients (65 men and 45 women; mean age ± SD, 64 ± 15 years) who had undergone CTA of the entire aorta on a second-generation dual-source CT system; 50 examinations were performed in high-pitch mode. The mean arterial attenuation, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and figure of merit (FOM) were calculated for the high-pitch CTA and conventional CTA groups. Radiation exposures were compared., Results: All studies were considered of diagnostic quality. At high-pitch CTA, the mean tube voltage and tube current-exposure time product were 118 ± 7 kV (SD) and 197 ± 78 mAs compared with 120 ± 1 kV and 258 ± 78 mAs, respectively, at conventional CTA (p < 0.05). The mean volume CT dose index, dose-length product, and effective dose were 8.1 ± 2.4 mGy, 561.1 ± 178.6 mGy × cm, and 9.6 ± 3.0 mSv at high-pitch CTA and 18.3 ± 7.7 mGy, 1162.6 ± 480.1 mGy × cm, and 19.8 ± 8.2 mSv at conventional CTA (p < 0.001). Attenuation was similar for both protocols, whereas significantly less contrast medium was injected for high-pitch CTA than for standard-pitch CTA (87.3 ± 16 mL vs 97.9 ± 16 mL, respectively; p < 0.01). The SNR and CNR were significantly lower in the high-pitch CTA examinations (p < 0.01), whereas the FOM was nonsignificantly higher. Twenty patients underwent both high-pitch CTA and conventional CTA, with a 45% reduction in radiation dose (p < 0.001)., Conclusion: High-pitch CTA of the aorta yields 45-50% reduction of radiation exposure as well as contrast medium savings with maintained vessel attenuation.

Background: The performance of dual-energy CT (DECT) for the detection of myocardial blood volume deficits has not systematically been compared with single-energy CT (SCT) spectra., Objective: We evaluated the accuracy for detection of myocardial blood volume deficits in DECT and SCT compared with 99m-Tc-Sestamibi-SPECT (single-photon emission CT) during rest and stress., Methods: 47 patients underwent rest/stress SPECT myocardial perfusion imaging and cardiac DECT on a dual-source CT scanner. The A- and B-tubes were operated with 140 kV and 80 kV/100 kV, respectively. DECT raw data were reconstructed by (1) only using high-energy (140 kV) CT spectra, (2) only using low-energy (80 kV/100 kV) CT spectra, (3) merging data (30% low- and 70% high-energy CT spectra), and (4) DECT-based iodine maps. Two independent, blinded observers analyzed all CT data according to each of the 4 reconstruction strategies for myocardial blood volume deficits., Results: Specificity and positive predictive values were relatively similar between the 4 reconstruction strategies, with highest specificity (98%) of SCT datasets based on 140 kV for mixed perfusion deficits seen on SPECT. DECT iodine maps showed highest sensitivity, negative predictive value, and accuracy of 91%, 97%, and 93%, respectively, for mixed perfusion deficits. Analysis with receiver operating characteristics showed highest area under the curve values (0.84-0.93) with the use of DECT iodine maps in the detection of purely fixed and mixed perfusion deficits., Conclusion: DECT iodine maps show superior performance for the detection of fixed and mixed perfusion deficits compared with SCT spectra., (Copyright © 2011 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.)

The use of coronary computed tomography angiography (cCTA) is growing rapidly, in large part because of fast-paced technical innovations that have increased diagnostic accuracy while providing new opportunities for radiation dose reduction. cCTA using recent generation CT scanners has been repeatedly shown to have excellent negative predictive value for ruling out significant coronary stenosis in comparison with invasive coronary angiography (ICA) and is now accepted for this use in selected populations. Current work is increasingly focused on evaluating and optimising radiation dose reduction techniques, the cost-effectiveness of cCTA implementation, and the impact of cCTA on patient management and outcomes. In addition, the potential value of emerging applications, such as atherosclerotic plaque characterisation and myocardial perfusion and viability assessment, are undergoing intense investigation., (© 2011 Blackwell Publishing Ltd.)

Three-dimensional reconstruction of the coronary tree from a conventional cineangiographic study is limited, in part, by the small number of available cineangiographic views. The potential utility of a maximum entropy iterative algorithm (MENT) for reconstruction of myocardial planes perpendicular to the axis of cineangiographic rotation from a small number (n = 6-18) of cineangiographic views was tested in vitro. The coronary arteries of postmortem human, canine, and calf hearts were filled with a silicone/thorium oxide mold to simulate in vivo angiographic contrast. Thirty-five-millimeter cineradiographs of each heart were obtained at 10 degrees intervals over 180 degrees about a myocardial central axis of rotation under exposure conditions which simulated the clinical setting. Projection data were derived from cinedensitometric scans across the entire myocardial shadow, perpendicular to the axis of rotation in each view, after 512 X 512 digitization with a vidicon camera/digitizer interfaced to a VAX computer. Comparison of MENT-reconstructed images with corresponding anatomic myocardial cross sections indicate that as few as 6 to 12 views can be used to reconstruct the cross sections of the multiple coronary branches (n = 6-11) within a plane of reconstruction.