Carotid artery stenosis: reproducibility of automated 3D CT angiography analysis method

The aim of this study was to assess the reproducibility and anatomical accuracy of automated 3D CT angiography analysis software in the evaluation of carotid artery stenosis with reference to rotational DSA (rDSA). Seventy-two vessels in 36 patients with symptomatic carotid stenosis were evaluated by 3D CT angiography and conventional DSA (cDSA). Thirty-one patients also underwent rotational 3D DSA (rDSA). Multislice CT was performed with bolus tracking and slice thickness of 1.5 mm (1-mm collimation, table feed 5 mm/s) and reconstruction interval of 1.0 mm. Two observers independently performed the stenosis measurements on 3D CTA and on MPR rDSA according to the NASCET criteria. The first measurements on CTA utilized an analysis program with automatic stenosis recognition and quantitation. In the subsequent measurements, manual corrections were applied when necessary. Interfering factors for stenosis quantitation, such as calcifications, ulcerations, and adjacent vessels, were registered. Intraobserver and interobserver correlation for CTA were 0.89 and 0.90, respectively. (p<0.001). The interobserver correlation between two observers for MPR rDSA was 0.90 (p<0.001). The intertechnique correlation between CTA and rDSA was 0.69 (p<0.001) using automated measurements but increased to 0.81 (p<0.001) with the manually corrected measurements. Automated stenosis recognition achieved a markedly poorer correlation with MPR rDSA in carotids with interfering factors than those in cases where there were no such factors. Automated 3D CT angiography analysis methods are highly reproducible. Manually corrected measurements facilitated avoidance of the interfering factors, such as ulcerations, calcifications, and adjacent vessels, and thus increased anatomical accuracy of arterial delineation by automated CT angiography with reference to MPR rDSA.     

Diagnostic accuracy of colour Doppler ultrasonography, CT angiography and blood-pool-enhanced MR angiography in assessing carotid stenosis: a comparative study with DSA in 170 patients

Purpose

This study was undertaken to prospectively evaluate the diagnostic performance of colour Doppler ultrasonography (CDUS), first-pass (FP) and steady-state (SS) contrast-enhanced magnetic resonance angiography (MRA) and computed tomography angiography (CTA) of the carotid arteries using digital subtraction angiography (DSA) as the reference standard.

Materials and methods

A total of 170 patients with previous cerebrovascular events and suspected carotid artery stenoses underwent CDUS, blood-pool MRA, CTA and DSA. Accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for CDUS, FP MRA, SS MRA and CTA. The McNemar and Wilcoxon tests and receiver operating characteristic (ROC) curve analysis were used to determine significant differences (p<0.05) between the diagnostic performances of the four modalities, and the degree of stenosis was compared using linear regression.

Results

A total of 336 carotid bifurcations were studied. The area under the curve (AUC) for degree of stenosis was: CDUS 0.85±0.02, FP MRA 0.982±0.005, SS MRA 0.994±0.002 and CTA 0.997±0.001. AUC analysis showed no statistically significant difference between CTA and MRA (p=0.0174) and a statistically significant difference between CDUS and the other techniques (p<0.001). Plaque morphology analysis showed no significant difference between CTA and SS MRA; a significant difference was seen between CTA and SS MRA versus FP MRA (p=0.04) and CDUS (p=0.038). Plaque ulceration analysis showed a statistically significant difference between MRA and CTA (0.04< p<0.046) versus CDUS (p=0.019).

Conclusions

CTA is the most accurate technique for evaluating carotid stenoses, with a slightly better performance than MRA (97% vs. 95% for SS MRA and 92% for FP MRA) and a greater accuracy than CDUS (97% vs. 76%). Blood-pool contrast-enhanced SS sequences offer improved evaluation of degree of stenosis and plaque morphology with accuracy substantially identical to CTA.     

Calcification remodeling index assessed by cardiac CT predicts severe coronary stenosis in lesions with moderate to severe calcification

ObjectivesTo assess the diagnostic performance of the calcification remodeling index (RI) as assessed by coronary computed tomography angiography (coronary CTA) to predict the presence of severe coronary stenosis in atherosclerotic coronary lesions with moderate to severe calcification.MethodsPatients who underwent coronary CTA and invasive coronary angiography (ICA) within one month and had moderately to severely calcified lesions as revealed by coronary CTA, were retrospectively included. The calcification RI was calculated as the ratio of the cross-sectional lumen area (with inclusion of calcium area) of the most severely calcified site to the proximal reference lumen area. Other parameters, such as the calcium volume, regional Agatston score, calcification length, involved calcium arc quadrants and CTA-assessed diameter stenosis, were also recorded. A multivariate model was used to identify the variables that predict the presence of severe coronary stenosis (diameter stenosis ≧ 70%) as determined by ICA.Results422 patients with 629 lesions were finally included in the study. Lesions with severe stenoses as determined by ICA tended to have larger calcium volumes, regional Agatston scores, CTA-assessed diameter stenoses, longer calcium length, more involved calcium arc quadrants and a significantly smaller calcification remodeling index. ROC curve analysis determined the best cutoff value of the calcification RI as 0.94 (AUC = 0.816, p < 0.001), which yielded highest diagnostic accuracy (83.3%, 524/629) to identify severe coronary stenosis. Among all parameters, calcification RI ≦0.94 is the strongest independent predictor (odds ratio: 17.5, p < 0.001) of severe coronary stenosis.ConclusionsWith an optimalcut-off value of 0.94, calcification RI is the strongest independent predictor of severe coronary stenosis in calcified coronary atherosclerotic lesions.     

Validation of a new cardiac image fusion software for three-dimensional integration of myocardial perfusion SPECT and stand-alone 64-slice CT angiography

Purpose Combining the functional information of SPECT myocardial perfusion imaging (SPECT-MPI) and the morphological information of coronary CT angiography (CTA) may allow easier evaluation of the spatial relationship between coronary stenoses and perfusion defects. The aim of the present study was the validation of a novel software solution for three-dimensional (3D) image fusion of SPECT-MPI and CTA. Methods SPECT-MPI with adenosine stress/rest ^99mTc-tetrofosmin was fused with 64-slice CTA in 15 consecutive patients with a single perfusion defect and a single significant coronary artery stenosis (≥50% diameter stenosis). 3D fused SPECT/CT images were analysed by two independent observers with regard to superposition of the stenosed vessel onto the myocardial perfusion defect. Interobserver variability was assessed by recording the X, Y, Z coordinates for the origin of the stenosed coronary artery and the centre of the perfusion defect and measuring the distance between the two landmarks. Results SPECT-MPI revealed a fixed defect in seven patients, a reversible defect in five patients and a mixed defect in three patients and CTA documented a significant stenosis in the respective subtending coronary artery. 3D fused SPECT/CT images showed a match of coronary lesion and perfusion defect in each patient and the fusion process took less than 15 min. Interobserver variability was excellent for landmark detection (r = 1.00 and r = 0.99, p < 0.0001) and very good for the 3D distance between the two landmarks (r = 0.94, p < 0.001). Conclusion 3D SPECT/CT image fusion is feasible, reproducible and allows correct superposition of SPECT segments onto cardiac CT anatomy.     

Multislice spiral CT angiography in peripheral arterial occlusive disease: a valuable tool in detecting significant arterial lumen narrowing?

The aim of this study was to evaluate the potential of multislice CT angiography (CTA) in detecting hemodynamically significant (70%) lesions of lower extremity inflow and runoff arteries. Fifty patients (42 men, 8 women; mean age 68 years) with peripheral arterial occlusive disease underwent multislice spiral CTA and digital subtraction angiography (DSA) from the infrarenal aorta to the supramalleolar region. CT parameters were 4×2.5-mm collimation, 15-mm table increment/rotation (pitch 6), and 1.25-mm reconstruction increment. Semitransparent volume rendering technique (STVR) images with semitransparent display of the arterial lumen (opacity: 50%) and vascular calcifications (opacity: 20%), as well as maximum intensity projection (MIP), and MIP together with axial CT studies were independently reviewed for hemodynamically significant lesions (70% cross-sectional area reduction). DSA was the standard of reference. In 46 patients, 260 lesions were found (95 stenoses, 165 occlusions). For detecting 70% lesions in all vessel regions, sensitivity and specificity were 84% and 78% (STVR), 89% and 74% (MIP), and 92% and 83% (MIP+axial CT), respectively, with a significantly lower sensitivity of STVR (p<0.05) and a significantly lower specificity of MIP studies (p<0.01). Sensitivity and specificity were, respectively, 81% and 93% (STVR), 88% and 75% (MIP). and 92% and 95% (MIP+axial CT) at aortoiliac arteries, 92% and 73% (STVR), 95% and 70% (MIP) and 98% and 70% (MIP+axial CT) at femoropopliteal arteries, as well as 82% and 64% (STVR), 86% and 74% (MIP), and 90% and 74% (MIP+axial CT) at infrapopliteal arteries. Specificity of MIP-CTA was significantly lower in the aortoiliac region (p<0.01), whereas STVR revealed significantly lower specificity at infrapopliteal arteries (p<0.05). In the infrapopliteal region, the particular CTA imaging modalities led to misinterpretation regarding stenoses and occlusions in 39–45 cases, whereas only 0–6 significant aortoiliac and femoropopliteal lesions were misinterpreted. Multislice CTA is helpful in detecting hemodynamically significant lesions in peripheral arterial occlusive disease. Since axial CT studies yielded the most correct results, they should always be reviewed additionally. In the infrapopliteal region, exact lesion assessment remains problematic due to small vessel diameters.     

Peripheral artery stent visualization and in-stent stenosis analysis in 16-row computed tomography: an in-vitro evaluation

The accuracy of 16-row multidetector CT in the visualization of different peripheral artery stents and in the appraisal of in-stent stenosis was assessed. Nine different stent types (nitinol and stainless steel) with three diameters (6, 8 and 10 mm) were used; altogether 27 stents were analyzed in a barrel-shaped vascular model. Low-grade (<40%) and high-grade (>60%) in-stent stenoses were simulated by polyurethane sticks (70 HU) of differing diameters (2–6 mm). Imaging was performed with 16×0.75-mm detector collimation, 130 mAs, 120 kV, 12-mm table feed/rotation, 1.0-mm slice thickness and 0.5-mm increment. The stent diameter, strut thickness, in-stent attenuation values, degree and degree of in-stent stenosis were evaluated. Nitinol stents showed significantly (P<10–6) less stent lumen narrowing, artificial strut thickening and overestimation of the degree of in-stent stenoses than stainless steel stents. In-stent attenuation values and artificial strut thickening were significantly (P<10–6) lower in 10- and 8-mm stents than in 6-mm stents. Stent lumen narrowing was significantly less in 10-mm stents than in 8-mm (P<10–4) or 6-mm (P<10–6) stents. In-stent stenoses were significantly overestimated, irrespective of the stent diameter. In 6-mm stents overestimation was significantly higher than in 8-mm (P<0.01) or 10-mm stents (P<10–6). Under in-vitro conditions 16-row MDCT allowed an accurate identification of in-stent stenosis, but significantly overestimated the effective degree of the stenosis.     

Quantitative coronary CT angiography: absolute lumen sizing rather than %stenosis predicts hemodynamically relevant stenosis

Objective

To identify the most accurate quantitative coronary stenosis parameter by CTA for prediction of functional significant coronary stenosis resulting in coronary revascularization.

Methods

160 consecutive patients were prospectively examined with CTA. Proximal coronary stenosis was quantified by minimal lumen area (MLA) and minimal lumen diameter (MLD), %area and %diameter stenosis. Lesion length (LL) was measured. The reference standard was invasive coronary angiography (ICA) (>70 % stenosis, FFR <0.8).

Results

210 coronary segments were included (59 % positive). MLA of ≤1.8 mm² was identified as the optimal cut-off (c?=?0.97, p?<?0.001; 95 % CI 0.94–0.99) (sensitivity 90.9 %, specificity 89.3 %) for prediction of functional-relevant stenosis (for MLA >2.1 mm² sensitivity was 100 %). The optimal cut-off for MLD was 1.2 mm (c?=?0.92; p?<?0.001; 95 % CI 0.88–95) (sensitivity 90.9, specificity 85.2) while %area and %diameter stenosis were less accurate (c?=?0.89; 95 % CI 0.84–93, c?=?0.87; 95 % CI 0.82–92, respectively, with thresholds at 73 % and 61 % stenosis). Accuracy for LL was c?=?0.74 (95 % CI 0.67–81), and for LL/MLA and LL/MLD ratio c?=?0.90 and c?=?0.84.

Conclusions

MLA ≤1.8 mm² and MLD ≤1.2 mm are the most accurate cut-offs for prediction of haemodynamically significant stenosis by ICA, with a higher accuracy than relative % stenosis.

Key Points

? Quantitative coronary CT-angiography is accurate for prediction of functional relevant stenosis. ? Absolute lumen area and diameter rather than %stenosis predict functional relevance. ? Lumen area <1.8 mm ² and diameter <1.2 mm are the most accurate cut-offs. ? Quantitative parameters are helpful for decision-making in terms of patient management.

     

Screening and detection of blunt vertebral artery injury in patients with upper cervical fractures: The role of cervical CT and CT angiography

Objective

To evaluate the clinical utility of nonenhanced CT (NECT)-based screening criteria and CTA in detection of blunt vertebral artery injury (BVAI) in trauma patients with C1 and/or C2 fractures.

Methods

We retrospectively reviewed the clinical records of all blunt trauma patients with C1 and/or C2 fractures between 8/2006 and 9/2011. Cervical CTA was prompted by cervical fractures involving/adjacent to a transverse foramen, and/or subluxation on NECT. Two neuroradiologists independently reviewed the CTA studies, and graded the BVAI.

Results

210 patients were included; of these, 124 underwent CTA (21/124 with digital subtraction angiography, DSA), and 2 underwent DSA only. Overall, 30/126 suffered BVAI. Among 21 patients who underwent both CTA and DSA, there was 1 false negative and 1 false positive (both grade 1). There was strong interobserver agreement regarding CTA-based BVAI detection (kappa = 0.93, p < 0.001) and grading (kappa = 0.90, p < 0001). Only 3/30 BVAI patients suffered a posterior circulation stroke; none of the patients who had a negative CTA or were not selected for CTA, based on NECT screening criteria, suffered symptomatic stroke. While C1/C2 comminuted fracture was more common in patients with high grade BVAI (p = 0.039), simultaneous C3–C7 comminuted fracture increased the overall BVAI risk (p = 0.011).

Conclusion

CTA reliably detects symptomatic BVAI in patients with upper cervical fractures. Utilization of NECT-based screening criteria such as transverse foraminal involvement or subluxation may be adequate in deciding whether to perform CTA, as no patients who were not selected for CTA suffered a symptomatic stroke. However, CTA may miss lower grade, asymptomatic BVAI.     

Advanced computed tomographic anatomical and morphometric plaque analysis for prediction of fractional flow reserve in intermediate coronary lesions

Objective

To determine the application of advanced coronary computed tomography angiography (CCTA) plaque analysis for predicting invasive fractional flow reserve (FFR) in intermediate coronary lesions.

Methods

Sixty-one patients with 71 single intermediate coronary lesions (≥50–80% stenosis) on CCTA prospectively underwent coronary angiography and FFR. Advanced anatomical and morphometric plaque analysis was performed based on CCTA data set to determine optimal criteria for significant flow impairment. A significant stenosis was defined as FFR ≤ 0.80.

Results

FFR averaged 0.85 ± 0.09, and 19 lesions (27%) were functionally significant. FFR correlated with minimum lumen area (MLA) (r = 0.456, p < 0.001), minimum lumen diameter (MLD) (r = 0.326, p = 0.006), reference lumen diameter (RLD) (r = 0.245, p = 0.039), plaque burden (r = −0.313, p = 0.008), lumen area stenosis (r = −0.305, p = 0.01), lesion length (r = −0.692, p < 0.001), and plaque volume (r = −0.668, p < 0.001). There was no relationship between FFR and CCTA morphometric plaque parameters. By multivariate analysis the independent predictors of FFR were lesion length (beta = −0.581, p < 0.001), MLA (beta = 0.360, p = 0.041), and RLD (beta = −0.255, p = 0.036). The optimal cutoffs for lesion length, MLA, MLD, RLD, and lumen area stenosis were >18.5 mm, ≤3.0 mm², ≤2.1 mm, ≤3.2 mm, and >69%, respectively (max. sensitivity: 100% for MLA, max. specificity: 79% for lumen area stenosis).

Conclusions

CCTA predictors for FFR support the mathematical relationship between stenosis pressure drop and coronary flow. CCTA could prove to be a useful rule-out test for significant hemodynamic effects of intermediate coronary stenoses.     

Clinical usefulness of novel cardiac MDCT/SPECT fusion image

Background  We evaluated the relationship between computed tomography angiography (CTA) and SPECT, and assessed to determine the clinical usefulness of the fusion image using CTA and myocardial perfusion imaging (MPI). Methods  Forty-one consecutive patients [after coronary artery bypass operation (n = 13) and suspected stenosis (n = 28)] underwent MPI and CTA. SPECT/CTA fused images were generated. Results  In total, 687 segments including bypass graft in 164 coronary arteries were analyzed. Myocardial ischemia on MPI was observed in 11 patients among 28 with CTA abnormalities, one had both ischemia and infarction, and 7 had only infarction. Segment-based analysis showed that ischemia was found in 14 segments (24%) among 59 stenoses on CTA. Forty stenotic segments (69%) were not associated with perfusion abnormality. The rest 5 stenotic segments were considered equivocal (8%). A fusion image made it possible to associate perfusion defects with its corresponding coronary artery in 4 out of 5 equivocal lesions on side-by-side analysis. Patients with incremental diagnostic information on SPECT/CTA fusion (n = 4) had significant smaller coronary diameter than that of not-improved coronary vessels (2.0 ± 0.4 vs. 3.9 ± 0.4 mm, p = 0.001). Conclusion  Cardiac fusion imaging accurately diagnosed functionally relevant coronary stenosis. SPECT/CTA fusion images in coronary artery disease may provide added diagnostic information on functional relevance of coronary artery disease.     

Failing Hemodialysis Arteriovenous Fistula and Percutaneous Treatment: Imaging with CT, MRI and Digital Subtraction Angiography

Purpose: To evaluate failing hemodialysis arteriovenous fistulas with helical CT angiography (CTA), MR angiography (MRA), and digital subtraction angiography (DSA), and to compare the efficacy of the three techniques in detecting the number, location, grade, and extent of stenoses and in assessing the technical results of percutaneous transluminal angioplasty (PTA) and stenting. Methods: Thirteen patients with Brescia-Cimino arteriovenous fistula malfunction underwent MRA and CTA of the fistula and, within 1 week, DSA. A total of 11 PTAs were performed; in three cases an MR-compatible stent was placed. DSA served as the gold standard for comparison in all patients. The presence, site, and number of stenoses or occlusions and the technical results of percutaneous procedures were assessed with DSA, CTA, and MRA. Results: MRA underestimated a single stenosis in one patient; CTA and MRA did not overestimate any stenosis. Significant artifacts related to stent geometry and/or underlying metal were seen in MRA sequences in two cases. Conclusions: CT and MRI can provide information regarding the degree of vascular impairment, helping to stratify patients into those who can have PTA (single or multiple stenoses) versus those who require an operative procedure (occlusion). Conventional angiography can be reserved for candidates for percutaneous intervention.     

Preliminary experience with MRA in evaluating the degree of carotid stenosis and plaque morphology using high-resolution sequences after gadofosveset trisodium (Vasovist) administration: comparison with CTA and DSA

Purpose

The authors performed a preliminary study with blood-pool contrast-enhanced magnetic resonance angiography (MRA) in evaluating the degree of carotid artery stenosis and plaque morphology, comparing the diagnostic performance of first-pass (FP) and steady-state (SS) acquisitions with 64-slice computed tomography angiography (CTA) and using digital subtraction angiography (DSA) as the reference standard.

Materials and methods

Twenty patients with ≥50% carotid artery stenosis at Doppler sonography underwent blood-pool contrast-enhanced MRA, CTA and DSA. Two independent radiologists evaluated MRA and CTA examinations to assess the degree of stenosis and characterise plaque morphology. Accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for FP, SS and CTA. The McNemar and Wilcoxon tests were used to determine significant differences (p<0.05) between the diagnostic performance of the three modalities.

Results

Forty carotid bifurcations were studied. For stenosis grading, accuracy, sensitivity, specificity, PPV and NPV were 90%, 89%, 90%, 89% and 90%, respectively, at FP; 95%, 95%, 95%, 95% and 95%, respectively, at SS; and 97.5%, 95%, 100%, 100% and 95%, respectively, at CTA. SS and CTA were superior to FP for evaluating the degree of stenosis (p<0.05). For evaluating plaque morphology, accuracy, sensitivity, specificity, PPV and NPV were 87.5%, 89%, 86%, 85% and 90%, respectively, at FP; 97.5%, 100%, 95%, 95% and 100%, respectively, at SS; and 100%, 100%, 100%, 100% and 100%, respectively, at CTA. There were no significant differences between FP, SS and CTA for plaque assessment (p>0.05).

Conclusions

Blood-pool contrast-enhanced MRA with SS sequences allow improved diagnostic evaluation of the degree of carotid stenosis and plaque morphology compared with FP and is substantially equal to CTA and DSA.     

Carotid bifurcation calcium and correlation with percent stenosis of the internal carotid artery on CT angiography

The aim of this paper was to determine the correlation between calcium burden (expressed as a volume) and extent of stenosis of the origin of the internal carotid artery (ICA) by CT angiography (CTA). Previous studies have shown that calcification in the coronary arteries correlates with significant vessel stenosis, and severe calcification (measured by CT) in the carotid siphon correlates with significant (greater than 50% stenosis) as determined angiographically. Sixty-one patients (age range 50–85 years) underwent CT of the neck with intravenous administration of iodinated contrast for a variety of conditions. Images were obtained with a helical multidetector array CT scanner and reviewed on a three-dimensional workstation. A single observer manipulated window and level to segment calcified plaque from vascular enhancement in order to quantify vascular calcium volume (cc) in the region of the bifurcation of the common carotid artery/ICA origin, and to measure the extent of ICA stenosis near the origin. A total of 117 common carotid artery bifurcations were reviewed. A significant stenosis was defined arbitrarily as >40% (to detect lesions before they become hemodynamically significant) of luminal diameter on CTA using NASCET-like criteria. All significant stenoses (21 out of 117 carotid bifurcations) had measurable calcium. We found a relatively strong correlation between percent stenosis and the calcium volume (Pearsons r = 0.65, P<0.0001). We also found that there was an even stronger correlation between the square root of the calcium volume and the percent stenosis as measured by CTA (r= 0.77, P<0.0001). Calcium volumes of 0.01, 0.03, 0.06, 0.09 and 0.12 cc were used as thresholds to evaluate for a significant stenosis. A receiver operating characteristic (ROC) curve demonstrated that thresholds of 0.06 cc (sensitivity 88%, specificity 87%) and 0.03 cc (sensitivity 94%, specificity 76%) generated the best combinations of sensitivity and specificity. Hence, this preliminary study demonstrates a relatively strong relationship between volume of calcium at the carotid bifurcation in the neck (measured by CT) and percent stenosis of the ICA below the skull base (as measured by CTA). Use of calcium volume measurements as a threshold may be both sensitive and specific for the detection of significant ICA stenosis. The significance of the correlation between calcium volume and ICA stenosis is that potentially a score can be obtained that will identify those at risk for high grade carotid stenosis.Presented at the 41st Annual Meeting of the American Society of Neuroradiology, Washington D.C., 2003. Sean Casey, MD and Charles Truwit, MD are members of the Medical Advisory Board of Vital Images (Plymouth, Minnesota), the company that developed the Vitrea 2 software.     

Difference of coronary stenosis severity between systolic and diastolic phases in quantitative CT angiography

Background

To compare the difference of coronary diameter stenosis by quantitative analysis of CT angiography (QCT) in the systolic (QCT-S) and diastolic phase (QCT-D) of the cardiac cycle, with invasive catheter angiography (QCA) as reference standard.

Dual-energy CT head bone and hard plaque removal for quantification of calcified carotid stenosis: utility and comparison with digital subtraction angiography

We evaluated quantification of calcified carotid stenosis by dual-energy (DE) CTA and dual-energy head bone and hard plaque removal (DE hard plaque removal) and compared the results to those of digital subtraction angiography (DSA). Eighteen vessels (13 patients) with densely calcified carotid stenosis were examined by dual-source CT in the dual-energy mode (tube voltages 140 kV and 80 kV). Head bone and hard plaques were removed from the dual-energy images by using commercial software. Carotid stenosis was quantified according to NASCET criteria on MIP images and DSA images at the same plane. Correlation between DE CTA and DSA was determined by cross tabulation. Accuracies for stenosis detection and grading were calculated. Stenosis could be evaluated in all vessels by DE CTA after applying DE hard plaque removal. In contrast, conventional CTA failed to show stenosis in 13 out of 18 vessels due to overlapping hard plaque. Good correlation between DE plaque removal images and DSA images was observed (r ² = 0.9504) for stenosis grading. Sensitivity and specificity to detect hemodynamically relevant (>70%) stenosis was 100% and 92%, respectively. Dual-energy head bone and hard plaque removal is a promising tool for the evaluation of densely calcified carotid stenosis.     

Quantitative assessment of stenosis severity and atherosclerotic plaque composition using 256-slice computed tomography

Objective

To quantitatively estimate lumen narrowing and to assess the volume and composition of atherosclerotic plaque with 256-slice computed tomography angiography (CTA), using conventional quantitative coronary angiography (QCA) as the gold standard.

Methods

Twenty-seven consecutive patients with suspected coronary artery disease (CAD) underwent 256-slice CTA and subsequent coronary angiography within 4 weeks. Quantification of lumen narrowing was performed on curved multiplanar reformatted CTA images, in identical projections to those used for QCA. Atherosclerotic plaque volume and composition were assessed by using commercially available software.

Results

The overall correlation between the stenosis severity by QCA compared with CTA was high (r ²?=?0.79, p?<?0.001). For the detection of ≥50% and ≥75% diameter lesions, CTA yielded high sensitivity, specificity and accuracy (86%, 95% and 90%; and 89%, 100% and 96%, respectively), using QCA as the standard reference. Furthermore, assessment of atherosclerotic plaque yielded highly reproducible results (inter-observer and intra-variability of 13% and 9%, respectively, for the assessment of plaque volume, and high agreement between observers (κ?=?0.86) for the differentiation between non-calcified, mixed and calcified plaque).

Conclusions

Clinically indicated 256-slice CT angiography in symptomatic patients can aid both quantification of lumen narrowing and evaluation of atherosclerotic plaque, with high reproducibility.     

Impact of advanced modeled iterative reconstruction on interreader agreement in coronary artery measurements

ObjectivesTo evaluate the influence of advanced modeled iterative reconstruction (ADMIRE) on coronary artery computed tomography angiography (cCTA) measurements in comparison to filtered back projection (FBP).Material and methodsPhantom scans and coronary CTA studies of 27 patients were acquired with a third generation dual-source CT scanner. Images were reconstructed using FBP and ADMIRE. Phantom measurements were used as reference standard. In patient studies, representative axial slices of each coronary artery segment without (n = 308) and with coronary plaques (n = 40) were assessed in identical positions for comparison of FBP and ADMIRE reconstructions. Image analyses included quality assessment, phantom and coronary artery measurements, plaque analysis, and interreader agreement of two independent and blinded readers.ResultsMean image noise was lower on ADMIRE reconstructions with 31.3 ± 9.9 HU compared to 55.9 ± 15.7 HU on FBP reconstructions (p < 0.001). Measurement precision and interreader agreement of both observers were assessed satisfactorily on phantom images in comparison to the full width half maximum method. In patients, correlation of lumen diameters of both observers improved using ADMIRE with a Pearson’s r = 0.987 (95% confidence interval [CI], 0.983–0.989; p < 0.001) compared to FBP images with r = 0.939 (95% CI, 0.924–0.951; p < 0.001). Applying ADMIRE, agreement of both observers for lumen diameter measurements significantly increased (p < 0.001). This was also observed for the degree of stenosis (p < 0.001) with r = 0.560 using FBP (95% CI, 0.301–0.742) and with r = 0.818 using ADMIRE (95% CI, 0.680–0.900). Plaque density measurements correlated closely with a Pearson’s r of 0.951 in FBP (95% CI, 0.909–0.974) and 0.967 in ADMIRE (95% CI, 0.939–0.983).ConclusionsAdvanced modeled iterative reconstruction significantly improves coronary artery assessment in coronary CTA in comparison to FBP by improved image quality due to image noise removal. This renders improved interobserver agreement for coronary lumen diameter and degree of stenosis measurements without influencing mean plaque attenuation.     

Relationship of the Duke jeopardy score combined with minimal lumen diameter as assessed by computed tomography angiography to the hemodynamic relevance of coronary artery stenosis

ObjectivesTo study the diagnostic performance of the ratio between the Duke jeopardy score (DJS) and the minimal lumen diameter (MLD) (DJS/MLDCT ratio) as assessed by coronary computed tomographic angiography (CTA) for differentiating functionally significant from non-significant coronary artery stenoses, with reference to invasive fractional flow reserve (FFR).MethodsPatients who underwent both coronary CTA and FFR measurement during invasive coronary angiography (ICA) within 2 weeks were retrospectively included in the study. Invasive FFR measurement was performed in patients with intermediate to severe coronary stenoseis. DJS/MLDCT ratio and anatomical parameters were recorded. Lesions with FFR ≤0.80 were considered to be functionally significant.ResultsOne hundred and sixty-one patients with 175 lesions were included into the analysis. Diameter stenosis in CT, area stenosis, plaque burden, lesion length (LL), ICA-based stenosis degree, DJS, LL/MLD⁴ ratio, DJS/MLA ratio as well as DJS/MLD ratio were all significantly different between hemodynamically significant and non-significant lesions (p<0.05 for all). ROC curve analysis determined the optimal cut-off value for DJS/MLD_CT ratio to be 1.96 (area under curve = 0.863, 95 % confidence interval = 0.803–0.910), yielding a high diagnostic accuracy (86.9%, 152/175).ConclusionsIn coronary artery stenoses detected by coronary CTA, the DJS/MLD ratio is able to predict hemodynamic relevance.     

Subtraction CT angiography for the diagnosis of iliac arterial steno-occlusive disease

Purpose

Accurate evaluation of stenosis in severely calcified arteries is a major challenge in conventional CT angiography (CTA) for peripheral arterial disease (PAD). The aim of this study was to evaluate the efficacy of subtraction CTA compared with conventional CTA and conventional angiography.

Materials and methods

175 arterial segments of 31 consecutive patients with PAD who underwent CTA and subsequent digital subtraction angiography (DSA) were evaluated. The percentage stenosis of diseased arteries was measured in iliac arteries with caliper methods on conventional CTA and subtraction CTA, and the concordance of each CTA method with DSA in the identification of >50 % stenosis was evaluated. Interpretation of CTA was always based only on maximum intensity projection (MIP).

Results

174 (99 %) segments were interpretable on subtraction CTA and showed a good correlation with DSA (R ² = 0.844), although 55 (31 %) segments were not evaluable on conventional CTA due to severe calcification. On subtraction CTA, the segmental accuracy, sensitivity, and specificity were 90.5, 78.9, and 80.0 %, respectively.

Conclusion

Subtraction CTA is an accurate diagnostic tool for the evaluation of PAD. It may be easier to interpret stenosis in the presence of calcifications using subtraction CTA rather than with the conventional CTA approach. Also, subtraction CTA using only MIP presented a similar accuracy to DSA.

     

Detection of Carotid Artery Stenosis: A Comparison between 2 Unenhanced MRAs and Dual-Source CTA

BACKGROUND AND PURPOSE:Dual-source CTA and black-blood MRA are recently developed techniques for evaluating carotid stenosis. The purpose of this study was to compare dual-source CTA with black-blood MRA and conventional TOF MRA in both detecting carotid stenosis by using DSA as a reference standard and demonstrating plaque morphology.MATERIALS AND METHODS:Thirty patients with suspected carotid artery stenosis underwent unenhanced MRA by using black-blood and TOF MRA and dual-source CTA. Source images from unenhanced MRAs and dual-source CTA were reconstructed with MIP or curved planar reconstruction. The degree of carotid artery stenosis was measured, and plaque surface morphology at the stenosis was analyzed and compared among different techniques.RESULTS:Good correlation was observed for measuring the degree of carotid stenosis among dual-source CTA, black-blood MRA, TOF MRA, and DSA. Sensitivity and specificity for detecting severe stenosis were 100% and 97% with dual-source CTA, 100% and 95% with black-blood MRA, and 79% and 95% with TOF MRA. None of the 3 technologies resulted in stenosis of <50% being overestimated. Plaque surface irregularity or ulceration was more frequently detected with dual-source CTA and black-blood MRA than with TOF MRA and DSA.CONCLUSIONS:This preliminary study shows that black-blood MRA is a promising technique, comparable with dual-source CTA and DSA, but better than TOF MRA, in the evaluation of carotid stenosis. Unlike dual-source CTA, black-blood MRA requires no intravenous contrast or radiation.

Carotid artery atherosclerosis is a major cause of ischemic cerebrovascular disease.^1,2 Measurement of carotid stenosis and demonstration of plaque morphology are critical for the management of patients with carotid atherosclerosis. DSA is the current reference standard for evaluating carotid artery stenosis. The diagnostic role of DSA has largely been replaced, however, by noninvasive techniques such as sonography, CTA, and MRA.Sonography has been the most commonly performed technique but may be restricted by its operator dependence and limited coverage. CTA is another widely used technique for the evaluation of carotid artery stenosis with high accuracy.³ Dual-source CTA (DSCTA) uses 2 x-ray sources and 2 detectors at the same time. With this technique, 2 images can be simultaneously acquired with different tube voltages; this feature has been shown to be an advantage for the evaluation of densely calcified carotid stenosis.^4,5 Contrast-enhanced MRA has been established as an alternative for carotid imaging with a diagnostic accuracy similar to that of CTA.^6,7 Both CTA and contrast-enhanced MRA use contrast media and are restricted in patients with impaired renal function, and CTA also requires ionizing radiation. As a result, unenhanced MRA without gadolinium is a desirable alternative, especially in patients with renal failure. Conventional TOF MRA has been widely used in clinical practice for carotid visualization, but it is limited by local reduction of signal intensity related to slow and turbulent flow and also prolonged imaging time.⁸ T2-weighted black-blood MRA (BB MRA) is a newly developed technique showing potential in the evaluation of both the lumen and the wall of the carotid artery after optimal suppression of the signal from flowing blood.^9,10 Few studies, to our knowledge however, have compared DSCTA with BB MRA and conventional TOF MRA in evaluating carotid stenosis.The aim of this study was to prospectively and intraindividually compare these 2 unenhanced MRA methods with DSCTA in detecting carotid artery stenosis by using DSA as the standard of reference and in demonstrating plaque morphology.