Multidetector row computed tomography may accurately estimate plaque vulnerability: does MDCT accurately estimate plaque vulnerability? (Pro)

Detection of positively remodeled coronary artery lesions by multislice CT and its impact on cardiovascular future events

Background

Positive arterial remodeling may be a characteristic of early proliferative lesions. The study was done to identify the different morphological characteristics of the positively remodeled coronary lesions, and causing non-significant arterial stenosis, as detected by multislice computed tomography coronary angiography (MSCT CA) and its predictors of cardiovascular clinical events at 90-day follow-up. The study included 55 patients who were candidate for MSCT CA and found to have a single-vessel disease with less than 70% stenosis positively remodeled lesions. The most expansive or solitary lesion was selected for each patient. Positive remodeling defined as remodeling index (RI) > 1.05. We followed the patients clinically for 90 days.

Results

Twenty-four patients had a history of acute coronary syndrome at initial presentation with normal LV systolic function for all studied patients. Dyslipidemia was found in 37 patients (67.3%) while diabetes was found in 29 patients (52.7%). The majority of the lesions were found in the proximal LAD (43.6%). The mean calculated remodeling index was 1.41 ± 0.25. At the end of 90 days, 25 patients had clinical events in the form of unstable coronary syndromes, coronary interventions, or coronary angiography related to the index lesion. The predictors of clinical events were duration of DM, higher degree of luminal narrowing, calculated wall/lumen area percentage, plaque burden, plaque-specific calcification, and total calcium score at remodeling site as well as a lower percentage of low-attenuation plaque area. The mean calculated wall/lumen area percentage was 263.72 ± 122.71%. A cut-off value of > 226% was found a predictor for clinical events. The mean plaque burden percentage was 69.72 ± 9.71%, a value of > 69% was found a predictor for clinical events. Both values had a sensitivity of 68% and specificity of 86.6% and PPV of 81%. Positively remodeled lesions with a high RI > 1.4 were correlated with patients who had acute coronary syndrome on their initial presentation.

Conclusion

Different morphological characteristics of positively remodeled non-occlusive atherosclerotic plaques as detected by multislice CT coronary angiography may be good potential predictors of future cardiovascular events.

Carotid artery plaque characterization with a wide-detector computed tomography using a dedicated post-processing 3D analysis: comparison with histology

PURPOSE

The characterization of atherosclerotic carotid plaque plays a key role in the identification of patients at risk. The aim of our work was to evaluate the potentialities of carotid computed tomography angiography (CCTA) in assessing composition of atherosclerotic plaque.

MATERIALS AND METHODS

We retrospectively evaluated 29 patients (7 women and 22 men, age range 54-81; mean age 69) who underwent carotid endarterectomy. All patients underwent pre-surgical CCTA using a 320-slice scanner. Post-processing reconstructions and analysis were performed using a specific software. Percentage of three different components of the atherosclerotic plaque (adipose, fibrotic and calcific) were classified based on Hounsfield unit values. Post-processing results were compared with histological analysis. Vessel and plaque parameters were compared using the Pearson correlation coefficient (r). Bland-Altman plots with 95% confidence intervals were calculated for correlation. McNemar's test was used for comparison of dichotomous variables.

RESULTS

A significant correlation between histology and CCTA was found with respect to the areas corresponding to adipose, fibrotic and calcified plaques. The existence of proportional bias was observed between the two quantifying methods with lower discrepancies found for the adipose and fibrotic plaque areas. The Bland-Altman analyses showed a mean bias of 3.2%, 2.5% and 0.6% between histology and CCTA, for adipose, fibrotic and calcified plaque areas, respectively.

CONCLUSIONS

Multi-detector CT angiography represents a valuable technique to assess quantitatively the composition of atherosclerotic plaques, with particular reference to the prevalence of fibrotic tissue, and is a useful diagnostic tool to improve risk stratification of patients for cerebral stroke.

Does the Tube Voltage Affect the Characterization of Coronary Plaques on 100- and 120-kVp Computed Tomography Scans

OBJECTIVE

The aim of this study was to compare the diagnostic performance of 100- and 120-kVp coronary computed tomography (CT) angiography (CCTA) scans for the identification of coronary plaque components.

METHODS

We included 116 patients with coronary plaques who underwent CCTA and integrated backscatter intravascular ultrasound studies. On 100-kVp scans, we observed 24 fibrous and 24 fatty/fibrofatty plaques; on 120-kVp scans, we noted 27 fibrous and 41 fatty/fibrofatty plaques. We compared the fibrous and the fatty/fibrofatty plaques, the CT number of the coronary lumen, and the radiation dose on scans obtained at 100 and 120 kVp. We also compared the area under the receiver operating characteristic (ROC) curve of the coronary plaques on 100- and 120-kVp scans with their ROC curves on integrated backscatter intravascular ultrasound images.

RESULTS

The mean CT numbers of fatty and fatty/fibrofatty plaques were 5.71 ± 36.5 and 76.6 ± 33.7 Hounsfield units (HU), respectively, on 100-kVp scans; on 120-kVp scans, they were 13.9 ± 29.4 and 54.5 ± 22.3 HU, respectively. The CT number of the coronary lumen was 323.1 ± 81.2 HU, and the radiation dose was 563.7 ± 81.2 mGy-cm on 100-kVp scans; these values were 279.3 ± 61.8 HU and 819.1 ± 115.1 mGy-cm on 120-kVp scans. The results of ROC curve analysis identified 30.5 HU as the optimal diagnostic cutoff value for 100-kVp scans (area under the curve = 0.93, 95% confidence interval = 0.87-0.99, sensitivity = 95.8%, specificity = 78.9%); for 120-kVp plaque images, the optimal cutoff was 37.4 HU (area under the curve = 0.87, 95% confidence interval = 0.79-0.96, sensitivity = 82.1%, specificity = 85.7%).

CONCLUSIONS

For the discrimination of coronary plaque components, the diagnostic performance of 100- and 120-kVp CCTA scans is comparable.

Prediction of carotid artery in-stent restenosis by quantitative assessment of vulnerable plaque using computed tomography

BACKGROUND AND PURPOSE

To assess the relationship between plaque volume evaluated by multidetector computed tomographic angiography (MDCT) and in-stent restenosis (ISR) after carotid artery stenting (CAS).

MATERIALS AND METHODS

From a retrospectively maintained database, data were collected for 52patients with carotid artery stenosis treated with CAS between 2007 and 2012. We defined ISR of≥50% as a peak systolic velocity≥200cm/s on echo-duplex scan. Carotid plaques were subdivided into four components according to radiodensity in Hounsfield units (HU) as follows: <0, 0-60, 60-130, and>600HU. Risk factors that influenced ISR were compared using univariate and multivariate Cox regression analyses.

RESULTS

During a median follow-up period of 36months, ISR of≥50% was detected in five patients (9.6%). In the univariate Cox proportional hazard regression analysis, renal insufficiency, coronary artery disease, total plaque volume, and plaque volumes with radiodensities<0 and≥600HU increased the risk for ISR (P<0.10). When the significant risk factors determined from the univariate analysis were subjected to a multivariate analysis, only the volumes of the plaque components with radiodensities<0 HU independently predicted the development of ISR (hazard ratio: 1.041; 95% confidence interval: 1.006-1.078; P=0.021).

CONCLUSION

Our data suggest that the high volume of the plaque components with radiodensities<0HU was independently associated with the increased risk of ISR after CAS. Quantitative and qualitative tissue characterizations of carotid plaques using MDCT might be a useful predictive tool of the development of ISR.

Imaging quality evaluation of low tube voltage coronary CT angiography using low concentration contrast medium

PURPOSE

To compare the image quality of prospectively ECG-gated low voltage coronary computed tomography angiography (CTA) with an administration of low concentration contrast medium.

METHOD AND MATERIALS

A total of 101 patients, each with a heart rate below 65 beats per minute (BPM), underwent a prospectively ECG-gated axial scan in CT coronary angiography on a 64-slice CT scanner. All patients were allocated in three groups (group A: n=31, 80 kVp, 300 mgI/ml; group B: n=34, 100 kVp, 300 mgI/ml; group C: n=36, 120 kVp, 370 mgI/ml). The CT attenuation values of aortic root (AR), left main coronary artery (LMA), right main coronary artery (RMA) and chest subcutaneous fat tissue were measured. The contrast-to-noise ratio (CNR) of AR, LMA and RMA were calculated according to the formulas below. The values of computed tomography dose index (CTDI) and dose-length product (DLP) were recorded. Image quality was assessed on a 5-point scale. The results were compared using the one-way ANOVA and rank sum tests.

RESULTS

The values of CNR and SNR for vessels in group A and group B were not significantly different from group C (each p > 0.05). The effective radiation dose in group A (1.51 ± 0.70 mSv) and group B (2.59 ± 1.24 mSv) were both lower than group C (4.92 ± 2.82 mSv) (each p < 0.05). There was no significant difference among the image quality scores of group A (4.10 ± 0.41), group B (3.90 ± 0.48) and group C (4.04 ± 0.36) (each P > 0.05).

CONCLUSION

Low tube voltage coronary CT angiography using low concentration contrast medium does not affect the imaging quality for assessing the coronary arteries compared with high voltage coronary CT angiography using high concentration contrast medium. Meanwhile low concentration contrast medium allowed 47-69% of radiation dose reduction.

Quantitative analysis of coronary vessels with optimized intracoronary CT number

Background

Variability in intracoronary computed tomography (CT) number may influence vessel quantification. We confirmed the feasibility of a novel method for measuring vessel diameter and area using coronary CT angiography (CCTA) with an optimized intracoronary CT number, 350 HU.

Methods

We performed intravascular ultrasound (IVUS) imaging in 52 patients with significant stenosis detected by coronary CT angiography targeting 350 HU using a CT number-controlling system. We measured 0-to-0 HU distances in the cross-sectional coronary images of 32 patients. We analyzed the ratio of 0-to-0 HU distances in CT images to media-to-media distances in IVUS images (C:I ratio). The area of ≥0 HU for 103 representative points in the remaining 20 patients was compared to the area of the traced external elastic membrane (EEM) in IVUS images.

Results

There was a strong correlation between 0-to-0 HU distance in CT images and media-to-media diameter in IVUS images (r = 0.97, p<0.001). The C:I ratio was 1.1. EEM area was estimated by dividing the area of ≥0 HU by the square of C:I. There was also a strong correlation between the estimated EEM area and the EEM area in IVUS images (r = 0.95, p<0.001).

Conclusions

Media-to-media diameter and EEM area can be estimated by CCTA targeting the optimized intracoronary CT number when blood vessel borders are defined at 0 HU.

The effect of iterative reconstruction on quantitative computed tomography assessment of coronary plaque composition

To compare coronary plaque size and composition as well as degree of coronary artery stenosis on coronary Computed Tomography angiography (CCTA) using three levels of iterative reconstruction (IR) with standard filtered back projection (FBP). In 63 consecutive patients with a clinical indication for CCTA 55 coronary plaques were analysed. Raw data were reconstructed using standard FBP and levels 2, 4 and 6 of a commercially available IR algorithm (iDose(4)). CT attenuation and noise were measured in the aorta and two coronary arteries. Both signal-to-noise-ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The amount of lipid, fibrous and calcified plaque components and mean cross-sectional luminal area were analysed using dedicated software. Image noise was reduced by 41.6% (p < 0.0001) and SNR and CNR in the aorta were improved by 73.4% (p < 0.0001) and 72.9% (p < 0.0001) at IR level 6, respectively. IR improved objective image quality measures more in the aorta than in the coronary arteries. Furthermore, IR had no significant effect on measurements of plaque volume and cross-sectional luminal area. The application of IR significantly improves objective image quality, and does not alter quantitative analysis of coronary plaque volume, composition and luminal area.

CT number-controlling system for reproducibility of intracoronary CT number on follow-up coronary CT angiography

BACKGROUND

Coronary computed tomography angiography (CCTA) may be useful for noninvasive follow-up; however, evaluation of coronary stenosis and CT number of plaque may be inaccurate under different vessel enhancement of contrast media. We examined the reproducibility of the CT number of repeat CCTA using our original CT number-controlling system (CTN-CS), which selects contrast level by a multiple regression equation using body surface area and peak CT number and peak time on timing bolus and during CCTA.

METHODS AND RESULTS

One hundred seventy-two patients who underwent serial CCTA were prospectively and randomly assigned to 3 groups. In the first group, Group A, the amount of contrast for the second CCTA was determined by CTN-CS to match the intracoronary CT number of the first CCTA. In Group B, each patient received the same amount of intravenous contrast in both CCTA examinations. In Group C, 0.7 mL/mg body weight (BW) of contrast medium (350 mgI/mL) was used for baseline and follow-up CCTAs. The regression of repeated CCTAs was the best in Group A (r=0.85, p<0.001) vs. Group B (r=0.52, p<0.001), and Group C (r=0.61, p<0.001). The absolute difference between intracoronary CT numbers of the second and first CCTA was the lowest in Group A (24.8 ± 21.8HU), followed by Group B (37.6 ± 26.2 HU; p<0.05) and Group C (46.5 ± 34.4HU; p<0.001).

CONCLUSIONS

Using CTN-CS, the difference of intracoronary CT numbers of the second and first CCTA was the smallest when compared to CCTAs using the same contrast volumes or constant volumes per body weight.

Coronary computed tomography angiography using ultra-low-dose contrast media: radiation dose and image quality

To analyze the invasiveness and image quality of coronary CT angiography (CCTA) with 80 kV. We enrolled 181 patients with low body weight and low calcium level. Of these, 154 patients were randomly assigned to 1 of 3 groups: 280 HU/80 kV (n = 51); 350 HU/80 kV (n = 51); or 350 HU/120 kV (n = 52). The amount of contrast media (CM) was decided with a CT number-controlling system. Twenty-seven patients were excluded because of an invalid time density curve by timing bolus. The predicted amount of CM, volume CT dose index, dose-length product, effective dose, image noise, and 5-point image quality were measured. The amounts of CM for the 80 kV/280 HU, 80 kV/350 HU, and 120 kV/350 HU groups were 10 ± 4 mL, 15 ± 7 mL, and 30 ± 6 mL, respectively. Although image noise was greater at 80 than 120 kV, there was no significant difference in image quality between 80 kV/350 HU and 120 kV/350 HU (p = 0.390). There was no significant difference in image quality between 80 kV/280 HU and 80 kV/350 HU (4.4 ± 0.7 vs. 4.7 ± 0.4, p = 0.056). The amount of CM and effective dose was lower for 80 kV CCTA than for 120 kV CCTA. CCTA at 80 kV/280 HU may decrease the amount of CM and radiation dose necessary while maintaining image quality.

Controlling intracoronary CT number for coronary CT angiography

BACKGROUND

Controlling intracoronary computed tomography (CT) number for coronary CT angiography (CCTA) has been difficult.

OBJECTIVE

The study assessed whether intracoronary CT number of CCTA could be estimated.

METHODS

One hundred twenty six patients were randomly assigned to either CCTA with 30 mL of contrast media (CM) following 5 mL of CM at timing bolus or CCTA with 50 mL of CM following 10 mL of CM at timing bolus. The relationships between intracoronary CT number and patients' characteristics and peak time and peak CT number at timing bolus in patients who showed valid time-density curve were analyzed in both groups. Then, the multiple regression equation best described was made. The prediction system was validated by 112 patients randomly targeted between 250 HU and 430 HU of CT number.

RESULTS

In group 5/30, intracoronary CT number was positively correlated with peak CT number at timing bolus (correlation coefficient, 1.42, p<0.001), negatively correlated with body surface area (-109.19, p<0.001) and peak time (-6.93, p<0.001). Whereas, intracoronary CT number was positively correlated with only peak CT number at timing bolus (1.33, p<0.001) in group 10/50. Then, CT number-controlling system using the simple equation best described CT number was established for CCTA following 5 mL of CM at timing bolus. Of 112 patients, there was good correlation between target CT number and measured CT number (r=0.85, p<0.0001) in 96 patients (85.7%), having valid time-density curve at timing bolus.

CONCLUSIONS

Controlling CT number may be enabled by CT number-controlling system following 5 mL of CM at timing bolus.

Comparison between integrated backscatter intravascular ultrasound and 64-slice multi-detector row computed tomography for tissue characterization and volumetric assessment of coronary plaques

Background

The purpose of this study was to determine the cut-off values of Hounsfield units (HU) for the discrimination of plaque components and to evaluate the feasibility of measurement of the volume of plaque components using multi-detector row computed tomography (MDCT).

Methods

Coronary lesions (125 lesions in 125 patients) were visualized by both integrated backscatter intravascular ultrasound (IB-IVUS) and 64-slice MDCT at the same site. The IB values were used as a gold standard to determine the cut off values of HU for the discrimination of plaque components.

Results

Plaques were classified as lipid pool (n =50), fibrosis (n =65) or calcification (n =35) by IB-IVUS. The HU of lipid pool, fibrosis and calcification were 18 ± 18 HU (−19 to 58 HU), 95 ± 24 HU (46 to 154 HU) and 378 ± 99 HU (188 to 605 HU), respectively. Using receiver operating characteristic curve analysis, a threshold of 50 HU was the optimal cutoff values to discriminate lipid pool from fibrosis. Lipid volume measured by MDCT was correlated with that measured by IB-IVUS (r =0.66, p <0.001), whereas fibrous volume was not (r =0.21, p =0.059).

Conclusion

Lipid volume measured by MDCT was moderately correlated with that measured by IB-IVUS. MDCT may be useful for volumetric assessment of the lipid volume of coronary plaques, whereas the assessment of fibrosis volume was unstable.

Prevalence of noncalcified coronary plaque in patients with calcium score of 0: the silent enemy

Noncalcified coronary artery plaques (NCAPs) are susceptible to rupture, resulting in coronary artery thrombosis. Using computer tomography coronary angiography (CTCA), we evaluated the prevalence and degree of stenosis caused by NCAP in patients without coronary artery calcification (CAC). A retrospective analysis of 447 symptomatic patients with 0 CAC score revealed negative CTCA in 400 (89.5%). Noncalcified coronary artery plaques were demonstrated in 47 (10.5%), with 4 presenting stenosis >50%. Patients with positive CTCA, compared to those with normal CTCA, had significantly higher mean age (56.2 years vs 50.6 years, P < .004) and higher pretest coronary artery disease (CAD) probability (26% vs 34%, P < .0001). Noncalcified coronary artery plaque was predominantly developed in the proximal segment of the left anterior descending artery. Noncalcified coronary artery plaque is present in up to 10% of patients with a CAC score of 0. Computer tomography coronary angiography could be of diagnostic value in symptomatic patients with multiple risk factors for CAD, even in the absence of CAC.

Assessment of cardiac computed tomography-myocardial perfusion imaging - promise and challenges -

Cardiac computed tomography (CT) has evolved rapidly over the last decade into a reliable imaging modality for the non-invasive assessment of coronary artery disease. With the advancement in multi-detector CT technology, there has developed an increasing body of evidence that suggests that the role of cardiac CT can be extended to include functional assessment of the myocardium not only at rest but also during stress. Simultaneous anatomical and functional assessment approaches will have a number of advantages such as evaluation of the transmural extent of myocardial perfusion defects (including small subendocardial perfusion defects), reduced risk associated with multiple sources of radiation, and short image acquisition time. Although initial results hold some promise, CT myocardial perfusion imaging is a modality in the early stages of development and further work and studies are required to define, validate, and optimize this technique. This review will provide an overview of this novel perfusion imaging method, its underlying principles, evolution, limitations and future directions.

Assessment of coronary vasoreactivity by multidetector computed tomography: feasibility study with rubidium-82 cardiac positron emission tomography

BACKGROUND

Positron emission tomography (PET) during the cold pressor test (CPT) has been used to assess endothelium-dependent coronary vasoreactivity, a surrogate marker of cardiovascular events. However, its use remains limited by cardiac PET availability. As multidetector computed tomography (MDCT) is more widely available, we aimed to develop a measurement of endothelium-dependent coronary vasoreactivity with MDCT and similar radiation burden as with PET.

METHODS AND RESULTS

A study group of 18 participants without known cardiovascular risk factor (9F/9M; age 60±6 years) underwent cardiac PET with (82)Rb and unenhanced ECG-gated MDCT within 4h, each time at rest and during CPT. The relation between absolute myocardial blood flow (MBF) response to CPT by PET (ml·min(-1)·g(1)) and relative changes in MDCT-measured coronary artery surface were assessed using linear regression analysis and Spearman's correlation. MDCT and PET/CT were analyzed in all participants. Hemodynamic conditions during CPT at MDCT and PET were similar (P>0.3). Relative changes in coronary artery surface because of CPT (2.0-21.2%) correlated to changes in MBF (-0.10-0.52ml·min(-1)·g(1)) (ρ=0.68, P=0.02). Effective dose was 1.3±0.2mSv for MDCT and 3.1mSv for PET/CT.

CONCLUSIONS

Assessment of endothelium-dependent coronary vasoreactivity using MDCT CPT appears feasible. Because of its wider availability, shorter examination time and similar radiation burden, MDCT could be attractive in clinical research for coronary status assessment.