Simulated 50 % radiation dose reduction in coronary CT angiography using adaptive iterative dose reduction in three-dimensions (AIDR3D)

To compare the image quality of coronary CT angiography (CTA) studies between standard filtered back projection (FBP) and adaptive iterative dose reduction in three-dimensions (AIDR3D) reconstruction using CT noise additional software to simulate reduced radiation exposure. Images from 93 consecutive clinical coronary CTA studies were processed utilizing standard FBP, FBP with 50 % simulated dose reduction (FBP50 %), and AIDR3D with simulated 50 % dose reduction (AIDR50 %). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured within 5 regions-of-interest, and image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale. Compared to FBP, the SNR measured from the AIDR50 % images was similar or higher (airway: 38.3 ± 12.7 vs. 38.5 ± 14.5, p = 0.81, fat: 5.5 ± 1.9 vs. 5.4 ± 2.0, p = 0.20, muscle: 3.2 ± 1.2 vs. 3.1 ± 1.3, p = 0.38, aorta: 22.6 ± 9.4 vs. 20.2 ± 9.7, p < 0.0001, liver: 2.7 ± 1.0 vs. 2.3 ± 1.1, p < 0.0001), while the SNR of the FBP50 % images were all lower (p values < 0.0001). The CNR measured from AIDR50 % images was also higher than that from the FBP images for the aorta relative to muscle (20.5 ± 9.0 vs. 18.3 ± 9.2, p < 0.0001). The interobserver agreement in the image quality score was excellent (κ = 0.82). The quality score was significantly higher for the AIDR50 % images compared to the FBP images (3.6 ± 0.6 vs. 3.3 ± 0.7, p = 0.004). Simulated radiation dose reduction applied to clinical coronary CTA images suggests that a 50 % reduction in radiation dose can be achieved with adaptive iterative dose reduction software with image quality that is at least comparable to images acquired at standard radiation exposure and reconstructed with filtered back projection.     

Image quality of Adaptive Iterative Dose Reduction 3D of coronary CT angiography of 640-slice CT: comparison with filtered back-projection

To assess the image quality of coronary CT angiography (CCTA) of 640-slice CT reconstructed by Adaptive Iterative Dose Reduction (AIDR) three-dimensional (3D) in comparison with the conventional filtered back-projection (FBP). CCTA images of 51 patients were scanned at the lowest tube voltage possible on condition that the built-in automatic exposure control system could suggest the optimal tube current. They were, then, reconstructed with FBP and AIDR 3D (standard). Objective measurements including CT density, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were performed. Subjective assessment was done by two radiologists, using a 5-point scale (0:nondiagnostic-4:excellent) based on the 15-coronary segment model which was grouped into three parts as the proximal, mid, and distal segmental classes. Radiation dose was also measured. AIDR images showed lower noise than FBP images (45.0 ± 9.4 vs. 73.4 ± 14.6 HU, p < 0.001) without any significant difference in CT density (665.5 ± 131.7 vs. 668 ± 136.3 HU, p = 0.8). Both SNR (15.0 ± 2.1 vs. 9.2 ± 1.7) and CNR (16.8 ± 2.3 vs. 10.4 ± 1.8) were significantly higher for AIDR than FBP (p < 0.001). Total subjective image quality score was also significantly improved in AIDR compared with FBP (3.1 ± 0.6 vs. 1.6 ± 0.4, p < 0.001), with better interpretability of the mid and distal segmental classes (100 vs. 95 % for the mid, p < 0.001; 100 vs. 90 % for the distal, p < 0.001). Mean effective radiation dose was 2.0 ± 1.0 mSv. The AIDR 3D reconstruction algorithm reduced image noise by 39 % compared with the FBP without affecting CT density, thus improving SNR and CNR for CCTA. Its advantages in interpretability were also confirmed by subjective evaluation by experts.     

The feasibility of sub-millisievert coronary CT angiography with low tube voltage,prospective ECG gating,and a knowledge-based iterative model reconstruction algorithm

We evaluated the feasibility of sub-millisievert (mSv) coronary CT angiography (CCTA) using low tube voltage, prospective ECG gating, and a knowledge-based iterative model reconstruction algorithm. Twenty-four non-obese healthy subjects (M:F 13:11; mean age 50.2 ± 7.8 years) were enrolled. Three sets of CT images were reconstructed using three different reconstruction methods: filtered back projection (FBP), iterative reconstruction (IR), and knowledge-based iterative model reconstruction (IMR). The scanning parameters were as follows: step-and-shoot axial scanning, 80 kVp, and 200 mAs. On the three sets of CT images, the attenuation and image noise values were measured at the aortic root. The signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) were calculated at the proximal right coronary artery and the left main coronary artery. The qualitative image quality of the CCTA with IMR was assessed using a 4-point grading scale (grade 1, poor; grade 4, excellent). The mean radiation dose of the CCTA was 0.89 ± 0.09 mSv. The attenuation values with IMR were not different from those of other reconstruction methods. The image noise with IMR was significantly lower than with IR and FBP. Compared to FBP, the noise reduction rate of IMR was 69 %. The SNR and CNR of CCTA with IMR were significantly higher than with FBP or IR. On the qualitative analysis with IMR, all included segments were diagnostic (grades 2, 3, and 4), and the mean image quality score was 3.6 ± 0.6. In conclusion, CCTA with low tube voltage, prospective ECG gating, and an IMR algorithm might be a feasible method that allows for sub-millisievert radiation doses and good image quality when used with non-obese subjects.     

CT coronary angiography: impact of adapted statistical iterative reconstruction (ASIR) on coronary stenosis and plaque composition analysis

To assess the impact of adaptive statistical iterative reconstruction (ASIR) on coronary plaque volume and composition analysis as well as on stenosis quantification in high definition coronary computed tomography angiography (CCTA). We included 50 plaques in 29 consecutive patients who were referred for the assessment of known or suspected coronary artery disease (CAD) with contrast-enhanced CCTA on a 64-slice high definition CT scanner (Discovery HD 750, GE Healthcare). CCTA scans were reconstructed with standard filtered back projection (FBP) with no ASIR (0 %) or with increasing contributions of ASIR, i.e. 20, 40, 60, 80 and 100 % (no FBP). Plaque analysis (volume, components and stenosis degree) was performed using a previously validated automated software. Mean values for minimal diameter and minimal area as well as degree of stenosis did not change significantly using different ASIR reconstructions. There was virtually no impact of reconstruction algorithms on mean plaque volume or plaque composition (e.g. soft, intermediate and calcified component). However, with increasing ASIR contribution, the percentage of plaque volume component between 401 and 500 HU decreased significantly (p < 0.05). Modern image reconstruction algorithms such as ASIR, which has been developed for noise reduction in latest high resolution CCTA scans, can be used reliably without interfering with the plaque analysis and stenosis severity assessment.     

The effect of iterative image reconstruction algorithms on the feasibility of automated plaque assessment in coronary CT angiography

To evaluate the effect of adaptive statistical (ASIR) and model based (MBIR) iterative reconstruction algorithms on the feasibility of automated plaque assessment in coronary computed tomography angiography (CCTA) compared to filtered back projection reconstruction (FBPR) algorithm. Three ex vivo human donor hearts were imaged by CCTA and reconstructed with FBPR, ASIR and MBIR. Commercial plaque assessment software was applied for the automated delineation of the outer and inner vessel-wall boundaries. Manually corrections were performed where necessary and the percentages were compared between the reconstruction algorithms. In total 2,295 CCTA cross-sections with 0.5 mm increments were assessed (765 co-registered FBPR/ASIR/MBIR triplets). Any boundary corrections were performed in 31.0 % of all cross-sections (N = 712). The percentage of corrected crosssections was lower for MBIR (24.1 %) as compared to ASIR (32.4 %, p = 0.0003) and FBPR (36.6 %, p <0.0001), and marginal between ASIR/FBPR (p = 0.09). The benefit of MBIR over FBPR was associated with the presence of moderate and severe calcification (OR 2.9 and 5.7, p <0.0001; respectively). Using MBIR significantly reduced the need for vessel-wall boundary corrections compared to other reconstruction algorithms, particular at the site of calcifications. Thus, MBIR may improve the feasibility of automated plaque assessment in CCTA and potentially its clinical applicability.     

The impact of a new model-based iterative reconstruction algorithm on prosthetic heart valve related artifacts at reduced radiation dose MDCT

To assess the impact of hybrid iterative reconstruction (IR) and novel model-based iterative reconstruction (IMR) and dose reduction on prosthetic heart valve (PHV) related artifacts and objective image quality. One transcatheter and two mechanical PHVs were embedded in diluted contrast-gel, inserted in an anthropomorphic phantom and imaged stationary with retrospectively ECG-gated computed tomography. Eight acquisitions were obtained of each PHV at 120 kV, 600 mAs (routine), 300 and 150 mAs (reduced dose). Data were reconstructed with filtered back projection (FBP), IR and IMR. Hypodense and hyperdense artifact volumes were quantified using two threshold filters. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated. Artifact volumes differed significantly between reconstruction algorithms for all PHVs (P < 0.005). Compared to FBP, IR decreased overall hypodense and hyperdense artifact volumes; at 150 mAs by 53 and 20 % (IR) and 67 and 23 % (IMR), respectively and significantly increased SNR and CNR at all doses (P < 0.012). Even at reduced dose, IMR resulted in higher image quality than routine dose FBP and IR. Iterative reconstruction and particularly IMR significantly reduce PHV-related artifacts and improve objective image quality in non-pulsatile conditions, even in reduced-dose images. Also, this study suggests that IMR allows for more radiation dose reduction in comparison to hybrid IR while maintaining high image quality.     

新双源CT冠状动脉CTA不同扫描参数与重建算法获得图像质量的体模研究

目的 探讨基于原始数据域的迭代重建(SAFIRE)算法与滤波反投影(FBP)算法冠状动脉CT血管造影(CCTA)图像质量的差异。方法 对置入模拟左、右冠状动脉的仿真体模,采用两组管电压(100 kV、120 kV)行双源CT检查,对冠状动脉原始图像在工作站上分别进行FBP及SAFIRE两种算法的图像重建,对不同管电压及不同管电流组内图像质量指标SNR、CNR、CT值标准差进行t检验;相同管电压不同重建算法,不同管电压相同管电流SAFIRE重建方式的两组SNR、CNR、CT值标准差及CT值采用配对t检验。结果 两组管电压扫描后经SAFIRE重建的冠状动脉图像质量均明显优于FBP重建;两组管电压两种重建算法图像,随着管电流的增加,200~360 mA图像质量呈改善趋势,管电流340 mA及以上图像质量指标趋于稳定;不同管电压相同管电流SAFIRE重建算法成像其图像质量比较,CNR、SNR、CT值标准差差异均有统计学意义(t=5.36、2.49、21.82,P均<0.05)。结论 随着扫描参数(管电流与管电压)的增加,图像质量随之上升,但到达一定值后图像质量趋于稳定;采用SAFIRE在相同扫描条件下可以明显提高图像质量。     

迭代重建在双源CT冠状动脉成像中的应用

目的与滤过反投影法(FBP)对比,评价迭代重建(IR)在双源CT(DSCT)冠状动脉成像中对图像质量的影响。方法对57例患者进行DSCT冠状动脉成像检查,分别采用常规FBP法和IR法对最佳期相图像进行重建。对图像质量进行主观评价,测量两种重建方法所得冠状动脉图像的CT值、噪声、SNR及CNR。结果 57例患者冠状动脉图像质量评分中,IR图像质量为优的血管段比例为83.18%(628/755),高于FBP重建图像(595/755,78.81%,P=0.030)。FBP重建与IR图像强化水平(CT值)分别为(311.49±63.76)HU、(310.57±64.45)HU(P=0.280),图像噪声分别为(19.58±3.47)HU、(13.11±3.06)HU(P<0.001),SNR分别为16.27±3.89、24.48±5.73(P<0.001),CNR分别为20.63±4.24、30.84±7.24(P<0.001)。结论 DSCT冠状动脉成像中应用IR法可在保证冠状动脉腔内强化程度不变的同时明显降低图像噪声,改善图像质量。     

Systematic analysis on the relationship between luminal enhancement, convolution kernel, plaque density, and luminal diameter of coronary artery stenosis: a CT phantom study

To systematically investigate into the relationships between luminal enhancement, convolution kernel, plaque density, and stenosis severity in coronary computed tomography (CT) angiography. A coronary phantom including 63 stenoses (stenosis severity, 10–90 %; plaque densities, ?100 to 1,000 HU) was loaded with increasing solutions of contrast material (luminal enhancement, 0–700 HU) and scanned in an anthropomorphic chest. CT data was acquired with prospective triggering using 64-section dual-source CT; reconstructions were performed with soft-tissue (B26f) and sharp convolution kernels (B46f). Two blinded and independent readers quantitatively assessed luminal diameter and CT number of plaque using electronic calipers. Measurement bias between phantom dimensions and CT measurements were calculated. Multivariate linear regression models identified predictors of bias. Inter- and intra-reader agreements of luminal diameter and CT number measurements were excellent (ICCs > 0.91, p < 0.01, each). Measurement bias of luminal diameter and plaque density was significantly (p < 0.01, each) lower (?12 % and 58 HU, respectively) with B46f as opposed to B26f, especially in plaque densities >200 HU. Measurement bias was significantly (p < 0.01, each) correlated (ρ = 0.37–55 and ρ = ?0.70–85) with the differences between luminal enhancement and plaque density. In multivariate models, bias of luminal diameter assessment with CT was correlated with plaque density (β = 0.09, p < 0.05). Convolution kernel (β = ?0.29 and ?0.38), stenosis severity (β = ?0.45 and ?0.38), and luminal enhancement (β = ?0.11 and ?0.29) represented independent (p < 0.05,each) predictors of measurement bias of luminal diameter and plaque number, respectively. Significant independent relationships exist between luminal enhancement, convolution kernel, plaque density, and luminal diameter, which have to be taken into account when performing, evaluating, and interpreting coronary CT angiography.     

Prognostic value of coronary CT angiography on long-term follow-up of 6.9 years

Long term follow-up of coronary CT angiography (CCTA) is scarce. The aim of the present study was to assess the prognostic value of CCTA over a follow-up period of more than 6 years. 218 Patients were included undergoing 64-slice CCTA. Images were analysed with regard to the presence of nonobstructive (<50 %) or obstructive (50 % stenosis) coronary artery disease (CAD). Major adverse cardiovascular events (MACE) were defined as death, nonfatal myocardial infarction or urgent coronary revascularization. CCTA revealed normal coronaries in 49, nonobstructive lesions in 94, and obstructive CAD in 75 patients. During a median follow-up period of 6.9 years, MACE occurred in 45 patients (21 %). Annual MACE rates were 0.3, 2.7, and 6.0 % (p = 0.001), for patients with normal CCTA, nonobstructive, and obstructive CAD, respectively. Multivariate Cox regression analysis identified the number of segments with plaques [hazard ratio (HR) 1.18, p = 0.002] as well as the presence of obstructive lesions (HR 2.28, p = 0.036) as independent predictors of MACE. The present study extends the predictive value of CCTA over more than 6 years. Patients with normal coronary arteries of CCTA continue to have an excellent cardiac prognosis, while outcome is progressively worse in patients with nonobstructive and obstructive CAD.     

Gender differences in coronary plaque composition and burden detected in symptomatic patients referred for coronary computed tomographic angiography

We assessed gender differences in coronary plaque burden and composition amongst symptomatic patients referred for coronary computed tomographic angiography (CCTA). Over all, 916 symptomatic patients who were referred for a clinically indicated CCTA were included in the study. CCTAs were interpreted on a per-segment basis for plaque composition (non-calcified, calcified, or mixed) and stenosis severity. A stenosis of ≥50 % was considered obstructive coronary artery disease. Among 916 patients, 498 (54.3 %) patients were women. Obstructive stenosis was found in 11 % of women compared to 21 % of men (p < 0.0001). Men had significantly higher plaque prevalence, 67.9 % versus 51.6 % in women (unadjusted OR 1.98; 95 % CI, 1.51–2.60). This remained significant after adjusting for age and potential confounders (adjusted OR 2.96; 95 % CI, 2.01–4.36). A similar relationship existed for all three plaque subtypes. Men were also more likely to have mixed plaque burden (adjusted OR 1.24; 95 % CI, 1.08–1.43) than women without any significant differences in regards to the other plaque sub-types. In conclusion, symptomatic women have a lower prevalence of obstructive coronary artery disease and are less likely to have mixed coronary plaque compared to symptomatic men. Future studies are needed to determine the prognostic implications of these findings.     

Diabetes as an independent predictor of high atherosclerotic burden assessed by coronary computed tomography angiography: the coronary artery disease equivalent revisited

(1) To study the prevalence and severity of coronary artery disease (CAD) in diabetic patients. (2) To provide a detailed characterization of the coronary atherosclerotic burden, including the localization, degree of stenosis and plaque composition by coronary computed tomography angiography (CCTA). Single center prospective registry including a total of 581 consecutive stable patients (April 2011–March 2012) undergoing CCTA (Dual-source CT) for the evaluation of suspected CAD without previous myocardial infarction or revascularization procedures. Different coronary plaque burden indexes and plaque type and distribution patterns were compared between patients with (n = 85) and without diabetes (n = 496). The prevalence of CAD (any plaque; 74.1 vs. 56 %; p = 0.002) and obstructive CAD (≥50 % stenosis; 31.8 vs. 10.3 %; p < 0.001) were significantly higher in diabetic patients. The remaining coronary atherosclerotic burden indexes evaluated (plaque in LM-3v-2v with prox. LAD; SIS; SSS; CT-LeSc) were also significantly higher in diabetic patients. In the per segment analysis, diabetics had a higher percentage of segments with plaque in every vessel (2.6/13.1/7.5/10.5 % for diabetics vs. 1.4/7.1/3.3/4.4 % for nondiabetics for LM, LAD, LCx, RCA respectively; p < 0.001 for all) and of both calcified (19.3 vs. 9.2 %, p < 0.001) and noncalcified or mixed types (14.4 vs. 7.0 %; p < 0.001); the ratio of proximal-to-distal relative plaque distribution (calculated as LM/proximal vs. mid/distal/branches) was lower for diabetics (0.75 vs. 1.04; p = 0.009). Diabetes was an independent predictor of CAD and was also associated with more advanced CAD, evaluated by indexes of coronary atherosclerotic burden. Diabetics had a significantly higher prevalence of plaques in every anatomical subset and for the different plaque composition. In this report, the relative geographic distribution of the plaques within each subgroup, favored a more mid-to-distal localization in the diabetic patients.     

Dose reduction for coronary calcium scoring with hybrid and model-based iterative reconstruction: an ex vivo study

Purpose To determine the influence of dose reduction on coronary calcium scoring using hybrid and model-based iterative reconstruction (IR) techniques. Methods Fifteen ex vivo hearts were scanned in a phantom representing an average adult person at routine dose and three levels of dose reduction; 27, 55 and 82 % reduced-dose, respectively. All images were reconstructed using filtered back-projection (FBP), hybrid IR (iDose⁴, levels 1, 4 and 7) as well as model-based IR iterative model reconstruction (IMR, levels 1, 2 and 3). Agatston, mass and volume scores found with iDose⁴ and IMR were compared to FBP reconstruction (routine dose) as well as objective image quality. Results With FBP calcium scores remained unchanged at 82 % reduced dose. With IR Agatston scores differed significantly at routine dose, using IMR level 3 and iDose⁴ level 7, and at 82 % reduced dose, using IMR levels 1–3 and iDose⁴ level 7. The maximum median difference was 5.3 %. Mass remained unchanged at reduced dose levels while volume was significantly lower at 82 % reduced dose with IMR (maximum median difference 5.0 %). Objective image quality improved with IR, at 82 % reduced dose the CNR of iDose⁴ level 7 was similar to the reference dose CNR, and IMR levels 1–3 resulted in an even higher CNR. Conclusion Calcium scores were not affected by radiation-dose reduction with FBP and low levels of hybrid IR. Objective image quality increased significantly using hybrid and model-based IR. Therefore low level hybrid IR has the potential to reduce radiation-dose of coronary calcium scoring with up to 82 %.     

Image quality and required radiation dose for coronary computed tomography angiography using an automatic tube potential selection technique

To investigate the image quality and the minimum required radiation dose for automatic tube potential selection (ATPS) in dual-source computed tomography (DSCT) coronary computed tomography angiography (CCTA). Three hundred twenty-five consecutive patients (153 men and 172 women) undergoing CCTA were assigned to either the ATPS group (n = 172) or the control group (n = 153); the control group underwent imaging at a constant current of 120 kV. All patients were scanned in either prospectively ECG-triggered high-pitch helical mode or sequential mode. The subjective image quality score, attenuation, image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), volume CT dose index (CTDI_vol), and effective dose (ED) were compared between the two groups with the Student t test or Mann–Whitney U test. The subjective image quality score was not significantly different between the two groups. Imaging noise and attenuation were both significantly higher in the ATPS group than in the control group (imaging noise: 25.6 ± 7.6 versus 15.8 ± 4.0 HU, P < 0.001; attenuation: 559.6 ± 142.0 versus 412.5 ± 64.3 HU, P < 0.001). SNR and CNR were significantly lower in the ATPS group than in the control group (SNR: 23.21 ± 7.40 versus 27.71 ± 8.25, P < 0.001; CNR: 27.81 ± 8.44 versus 33.94 ± 9.69, P < 0.001). ED was significantly lower in the ATPS group than in the control group (ED: 1.25 ± 1.24 versus 2.19 ± 1.77 mSv, P < 0.001). For both groups, ED was significantly lower in the high-pitch mode than in the sequential mode. The use of ATPS for CCTA significantly reduced the radiation dose while maintaining image quality.     

The impact of image resolution on computation of fractional flow reserve: coronary computed tomography angiography versus 3-dimensional quantitative coronary angiography

Calculation of fractional flow reserve (FFR) based on computational fluid dynamics (CFD) requires reconstruction of patient-specific coronary geometry and estimation of hyperemic flow rate. Coronary computed tomography angiography (CCTA) and invasive coronary angiography (ICA) are two dominating imaging modalities used for the geometrical reconstruction. Our aim was to investigate the impact of image resolution as inherently associated with these two imaging modalities on geometrical reconstruction and subsequent FFR calculation. Patients with mild or intermediate coronary stenoses who underwent both CCTA and ICA were included. CCTA images were acquired either by 320-row area detector CT or by 128-slice dual-source CT. Two geometrical models were reconstructed separately from CCTA and ICA, from which FFR_CTA and FFR_QCA were subsequently calculated using CFD simulations, applying the same hyperemic flow rate derived from the ICA images at the inlet boundaries. A total of 57 vessels in 41 patients were analyzed. Average diameter stenosis was 43.4 ± 10.8 % by 3D QCA. Reasonably good correlation between FFR_CTA and FFR_QCA was observed (r = 0.71, p < 0.001). The difference between FFR_CTA and FFR_QCA was correlated with the deviation between minimal lumen areas by CCTA and by ICA (ρ = 0.34, p = 0.01), but not with plaque volume (ρ = ?0.09, p = 0.51) or calcified plaque volume (ρ = 0.01, p = 0.95). Applying the cutoff value of ≤0.8 to both FFR_CTA and FFR_QCA, the agreement between FFR_CTA and FFR_QCA in discriminating functional significant stenoses was moderate (kappa 0.47, p < 0.001). Disagreement was found in 10 (17.5 %) vessels. Acceptable correlation between FFR_CTA and FFR_QCA was observed, while their agreement in distinguishing functional significant stenosis was moderate. Our results suggest that image resolution has a significant impact on FFR computation.     

3.0-T whole-heart coronary magnetic resonance angiography: comparison of gadobenate dimeglumine and gadofosveset trisodium

Gadolinium enhanced coronary magnetic resonance angiography (MRA) at 3 T appears to be superior to non-contrast methods. Gadofosveset is an intravascular contrast agent that may be well suited to this application. The purpose of this study was to perform an intra-individual comparison of gadofosveset and gadobenate for coronary MRA at 3 T. In this prospective randomized study, 22 study subjects [8 (36 %) male; 27.9 ± 6 years; BMI = 22.8 ± 2 kg/m²] underwent two studies using a contrast-enhanced inversion recovery three-dimensional fast low angle shot MRA at 3 T. The order of contrast agent administration was varied randomly, separated by an average of 30 ± 5 days, using either gadobenate dimeglumine (Gd-BOPTA; Bracco, 0.1 mmol/Kg) or gadofosveset trisodium (MS-325; Lantheus Med, 0.03 mmol/Kg). Acquisition time, signal-to-noise ratio (SNR) of coronary vessels and contrast-to-noise ratio (CNR) were evaluated. Of 308 coronary arteries and veins segment analyzed, overall SNR of coronary arteries and veins segments were not different for the two contrast agents (132 ± 79 for gadofosveset vs. 135 ± 78 for gadobenate, p = 0.69). Coronary artery CNR was greater for gadofosveset in comparison to gadobenate (73.5 ± 46.9 vs. 59.3 ± 75.7 respectively, p = 0.03). Gadofosveset-enhanced MRA images displayed better image quality than gadobenate-enhanced MRA images (2.77 ± 0.61 for gadofosveset vs. 2.11 ± 0.51, p < .001). Inter- and intra-reader variability was excellent (ICC > 0.90) for both contrast agents. Gadofosveset trisodium appears to show slightly better performance for coronary MRA at 3 T compared to gadobenate.     

Association of serum total bilirubin levels with the severity, extent and subtypes of coronary atherosclerotic plaques detected by coronary CT angiography

In this study, we aimed to evaluate whether serum total bilirubin was associated with the severity and morphology of coronary atherosclerotic plaques detected by computed tomography angiography (CTA). The study population consisted of 1,115 patients (55.2 % men) who underwent dual-source 64-slice CTA for the assessment of coronary artery disease (CAD). Coronary arteries were evaluated on 16 segment basis and critical coronary plaque was described as luminal narrowing >50 %, whereas plaque morphology was assessed on per segment basis. Serum bilirubin levels were determined using commercially available assay kits. The critical atherosclerotic lesions were detected in 431/1,115 (38.6 %) subjects by CTA. Serum total bilirubin levels were found to be lower in patients with any coronary plaque (0.62 ± 0.21 vs. 0.70 ± 0.25 mg/dL, p = 0.002). Also bilirubin level was lower in patients with critical stenosis compared to non-critical stenosis (0.57 ± 0.18 vs. 0.70 ± 0.24 mg/dL, p < 0.001). Subjects having primarily noncalcified plaque (NCP) and mixed plaque (MP) have lower bilirubin levels compared to calcified plaque (CP) and normal subjects (0.62 ± 0.20 for NCP and 0.60 ± 0.19 for MP, 0.65 ± 0.26 for CP and 0.71 ± 0.25 for normal subjects, p < 0.001). This independent association was remained for NCP after multinominal regression analysis (OR: 0.76; 95 % CI 0.58–0.88; p < 0.001). Our study demonstrated that serum bilirubin level was significantly associated with the presence, severity and the noncalcified morphology of atherosclerotic plaques detected by CTA. Further prospective clinical studies are needed to clarify the exact physiopathologic and prognostic role of bilirubin in CAD.     

A novel method for non-invasive plaque morphology analysis by coronary computed tomography angiography

Coronary computed tomography angiography (CCTA) plaque morphology based on conventional Hounsfield units relies on absolute CT numbers is influenced by imaging and anatomical variables. The project describes and tests a novel alternative method, termed the “labeling method”, which uses relative CT numbers and 3-dimensional plaque structure. Using virtual histology intravascular ultrasound (VH-IVUS) as the reference standard, this study compares the labeling method to a conventional CT-number based method to determine coronary plaque morphology. Thirty-seven high-risk, non-calcified atherosclerotic coronary lesions were prospectively evaluated in 33 consecutive patients who underwent CCTA followed by VH-IVUS (mean interval 8.6 ± 13.3 days). CCTA-derived vessel and minimum lumen areas were compared to VH-IVUS measures. Fibrotic and necrotic core areas were calculated by both the labeling method to the CT-number based method; both were tested for agreement with reference standard VH-IVUS. Inter- and intra-observer correlations were assessed. CCTA significantly underestimated minimum lumen area when compared to VH-IVUS (mean difference ?1.4 ± 0.9 mm², p < 0.0001). Necrotic core and fibrous areas quantified using the labeling method demonstrated superior correlation with VH-IVUS compared to those quantified using the CT-number based method, Pearson’s r = 0.75 versus 0.42 and r = 0.80 and 0.59, respectively. Compared to VH-IVUS, limits of agreement for the labeling method-derived necrotic core (?2.0 to 2.5 mm²) and fibrous areas (0.6–8.0 mm²) were more narrow than those determined using the CT-number based method (?3.7 to 7.3 and ?4.0 to 8.9 mm², respectively). Inter- and intraobserver correlations were excellent for all CCTA derived measures (r = 0.85–0.98). A novel CCTA-based labeling method offers an alternative to conventional CT-number based analyses for plaque morphology. The labeling method demonstrates superior correlation to VH-IVUS for measures of fibrotic and necrotic core areas within non-calcified coronary atherosclerotic plaques.     

Grade-response relationship between blood pressure and severity of coronary atherosclerosis in asymptomatic adults: assessment with coronary CT angiography

Hypertension is known to be a strong risk factor for coronary atherosclerosis. We aimed to investigate the prevalence, severity, and plaque characteristics of coronary atherosclerosis according to grade of blood pressure (BP) using coronary CT angiography (CCTA) in asymptomatic adults. We enrolled 8,238 asymptomatic subjects who underwent coronary artery calcium scoring (CACS) and CCTA for health screening purposes. Subjects were classified according to JNC 7 guidelines (normal, systolic BP/diastolic BP < 120/80; pre-hypertension [PH], 120–139/80–89; hypertension stage 1 [H1], 140–159/90–99; hypertension stage 2 [H2], >160/100). Isolated systolic hypertension (ISH; systolic BP > 140, diastolic BP < 80) was additionally categorized. With CCTA, the presence of plaques, severity of stenosis, and plaque types were assessed. Using multiple logistic regression analysis, the adjusted odds ratios (AORs) for plaque, obstructive coronary artery disease (CAD) (luminal stenosis ≥50 %), non-calcified plaque (NCP), and CACS > 100 were assessed according to BP grade. After adjustment for clinical risk factors, the risk of subclinical atherosclerosis, NCP, and CACS > 100 gradually increased from PH stage (all P values for trend <0.05), while the risk of obstructive CAD increased from the H1 stage (AORs of H1 and H2: 1.70 and 2.33, respectively). In the ISH group, the AOR of subclinical atherosclerosis (1.64) was higher than in the H1 group (1.55), while the AOR of obstructive CAD (2.58) was higher than in the H2 group (2.33). Therefore, our study strongly suggests that coronary atherosclerosis in asymptomatic adults shows a grade-response relationship according to hypertension grade.     

Improved evaluation of calcified segments on coronary CT angiography: a feasibility study of coronary calcium subtraction

We explore the feasibility of coronary calcium subtraction computed tomography angiography (CCTA) in patients with high calcium scores using invasive coronary angiography as the gold standard. Eleven patients with calcium scores of >400 underwent CCTA using a subtraction protocol followed by invasive coronary angiography. In addition to standard reconstructions, subtracted images were obtained using a dedicated subtraction algorithm. A total of 55 calcified segments were evaluated for image quality [using a 4-point scale ranging from 1 (uninterpretable) to 4 (good)] and the presence of significant (≥50 %) luminal stenosis. Conventional and subtracted CCTA were compared using quantitative coronary angiography (QCA) as the gold standard. The average image quality of conventional CCTA was 2.5 ± 0.6 versus 3.1 ± 0.6 on subtraction CCTA (P < 0.001). The percentage of segments with a score 1 or 2 was reduced from 41.8 to 12.7 % after coronary calcium subtraction (P = 0.002). On QCA, significant stenosis was observed in 16 segments. The area under the receiver operating characteristics curve to detect ≥50 % stenosis on QCA increased from 0.741 [95 % confidence interval (CI) 0.598–0.885] for conventional CCTA to 0.905 (95 % CI 0.791–1.000) for subtraction CCTA (P = 0.003). In patients with extensive calcifications undergoing CCTA, coronary calcium subtraction may improve the evaluation of calcified segments.