Association of carotid atherosclerotic plaque features with acute ischemic stroke: A magnetic resonance imaging study

Background and purpose

It remains unclear whether direct vessel wall imaging can identify carotid high-risk lesions in symptomatic subjects and whether carotid plaque characteristics are more effective indicators for cerebral infarct severity than stenosis. This study sought to determine the associations of carotid plaque characteristics by MR imaging with stenosis and acute cerebral infarct (ACI) sizes on diffusion weighted imaging (DWI).

Materials and methods

One hundred and fourteen symptomatic patients underwent carotid and brain MRI. ACI volume was determined from symptomatic internal carotid artery territory on DWI images. Ipsilateral carotid plaque morphological and compositional characteristics, and stenosis were also determined. The relationships between carotid plaque characteristics, stenosis and ACIs size were then evaluated.

Results

In carotid arteries with 30–49% stenosis, 86.7% and 26.7% were found to have lipid-rich necrotic core (LRNC) and intraplaque hemorrhage, respectively. Furthermore, 45.8% of carotid arteries with 0–29% stenosis developed LRNCs. Carotid morphological measurements, such as % wall volume, and the LRNC size were significantly associated with ipsilateral ACIs volume before and after adjustment for significant demographic factors (age and LDL) or stenosis in patients with carotid plaque (all p < 0.05).

Conclusions

A substantial number of high-risk plaques characterized by vessel wall imaging exist in carotid arteries with lower grade stenosis. In addition, carotid plaque characteristics, particularly the % wall volume and LRNC size, are independently associated with cerebral infarction as measured by DWI lesions. Our findings indicate that characterizing atherosclerotic plaque by MR vessel wall imaging might be useful for stratification of plaque risk and infarction severity.     

Agreement between multi-detector-row CT angiography and US-ECD in quantification of carotid artery stenosis and plaque characterization

Purpose

The purpose of this work was to evaluate the agreement between ultra-sound echo-color Doppler (US-ECD) and multi-detector-row CT angiography (MDCTA) in the quantification of carotid artery stenosis as well as plaque characterization.

Materials and methods

From January 2012 to January 2013 forty-five patients who underwent both MDCTA and US-ECD for the study of carotid arteries, were evaluated (33 males, 12 females; age range 43–70 years; mean age of 59.6 years). For all subjects the following parameters were analyzed: stenosis degree by using the NASCET method, plaque morphology (regular versus irregular), type of the plaque (fatty, mixed and calcified) and presence of ulcerations. Statistical analysis was performed to calculate concordance between the two techniques employed.

Results

The agreement observed in the quantification of carotid artery stenosis was 94.4% with a kappa value of 0.9306 (95% confidence interval of 0.8612–1.0). In the definition of the type of plaque, the observed agreements were 91.1% and the kappa value was 0.8815 (95% confidence interval: 0.7920–0.9709). In the definition of plaque ulceration, the observed agreements were 88.4% but the kappa value was only 0.325 (95% confidence interval: 0.201–0.449). Agreement observed in the evaluation of plaque morphology was 78.3% with a kappa value of 0.513 (95% confidence interval: 0.452–0.574).

Conclusion

We observed a good agreement between US-ECD and MDCTA in the quantification of carotid artery stenosis and the assessment of plaque type. There was, however, a poor agreement in the evaluation of plaque ulceration. The use of US-ECD and MDCTA provides different results in the evaluation of plaque. Our results suggest that information derived from US-ECD should be always critically compared with other diagnostic techniques.     

Diagnostic performance of three-dimensional MR maximum intensity projection for the assessment of synovitis of the hand and wrist in rheumatoid arthritis: A pilot study

Purpose

To evaluate the diagnostic performance of three-dimensional (3D) MR maximum intensity projection (MIP) in the assessment of synovitis of the hand and wrist in rheumatoid arthritis (RA) compared to 3D contrast-enhanced magnetic resonance imaging (CE-MRI).

Materials and methods

Twenty-five patients with RA underwent MR examinations. 3D MR MIP images were derived from the enhanced images. MR images were reviewed by two radiologists for the presence and location of synovitis of the hand and wrist. The diagnostic sensitivity, specificity and accuracy of 3D MIP were, respectively, calculated with the reference standard 3D CE-MRI.

Results

In all subjects, 3D MIP images yielded directly and clearly the presence and location of synovitis with just one image. Synovitis demonstrated high signal intensity on MIP images. The k-values for the detection of articular synovitis indicated excellent interobserver agreements using 3D MIP images (k = 0.87) and CE-MR images (k = 0.91), respectively. 3D MIP demonstrated a sensitivity, specificity and accuracy of 91.07%, 98.57% and 96.0%, respectively, for the detection of synonitis.

Conclusion

3D MIP can provide a whole overview of lesion locations and a reliable diagnostic performance in the assessment of articular synovitis of the hand and wrist in patients with RA, which has potential value of clinical practice.     

How should we estimate carotid stenosis using magnetic resonance angiography?

Our purpose was to assess the reproducibility of and differences between the most commonly used methods for assessing carotid artery stenosis using magnetic resonance angiography (MRA). We studied 55 patients who underwent axial three-dimensional time-of-flight MRA (1.5 T). Quantitative caliper measurements were performed from maximum intensity projection (MIP) and multiple planar reconstruction (MPR) images, according to the criteria of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST). The measurements were compared to each other and to visual interpretation, using conventional angiography as the reference. The measured percentage stenoses were higher on MRA than on digital subtraction angiography (DSA) using both NASCET (mean difference 1.9–3.0%) and ECST (6.3–6.7%) criteria. The kappa coefficients for the agreement between DSA and MRA were higher using the NAS-CET (0.61–0.76) than the ECST criteria (0.52–0.65). No statistically significant differences were found between measurements from MIP and MPR images. The ECST measurement criteria gave significantly higher percentage stenoses than the NASCET criteria (P<0.001), this difference being more prominent on MRA (mean difference in diameter stenosis percentage 14.3–16.4%) than on DSA (7.6–11.2%) and most important with mild stenoses. The difference between visual interpretation and quantitative measurements on MRA was significant (P=0.01–0.001). There were no statistically significant interobserver differences in the MRA film readings, either in visually estimated degrees of stenosis or stenosis measurements. Thus, the different criteria of the two multicentre trials led to significantly different results, especially in the assessment of mild stenosis, and these differences are more important with MRA than with aging modalities or the reconstruction programs seem less important.     

Evaluation of carotid vessel wall enhancement with image subtraction after gadobenate dimeglumine-enhanced MR angiography

Objectives

This study was aimed at testing the value of image subtraction for evaluating carotid vessel wall enhancement in contrast-enhanced MR angiography (MRA).

Materials and methods

IRB approval was obtained. The scans of 81 consecutive patients who underwent carotid MRA with 0.1 mmol/kg of gadobenate dimeglumine were reviewed. Axial carotid 3D T1-weighted fast low-angle shot sequence before and 3 min after contrast injection were acquired and subtracted (enhanced minus unenhanced). Vessel wall enhancement was assigned a four-point score using native or subtracted images from 0 (no enhancement) to 3 (strong enhancement). Stenosis degree was graded according to NASCET.

Results

With native images, vessel wall enhancement was detected in 20/81 patients (25%) and in 20/161 carotids (12%), and scored 2.0 ± 0.6 (mean ± standard deviation); with subtracted images, in 21/81 (26%) and 22/161 (14%), and scored 2.5 ± 0.6, respectively (P < 0.001, Sign test). The overall stenosis degree distribution was: mild, 41/161 (25%); moderate, 77/161 (48%); severe, 43/161 (27%). Carotids with moderate stenosis showed vessel wall enhancement with a frequency (17/77, 22%) significantly higher than that observed in carotids with mild stenosis (1/41, 2%) (P = 0.005, Fisher exact test) and higher, even though with borderline significance (P = 0.078, Fisher exact test), than that observed in carotids with severe stenosis (4/43, 9%).

Conclusion

Roughly a quarter of patients undergoing carotid MRA showed vessel wall enhancement. Image subtraction improved vessel wall enhancement conspicuity. Vessel wall enhancement seems to be an event relatively independent from the degree of stenosis. Further studies are warranted to define the relation between vessel wall enhancement and histopathology, inflammatory status, and instability.     

Interobserver agreement of semi-automated and manual measurements of functional MRI metrics of treatment response in hepatocellular carcinoma

Purpose

To assess the interobserver agreement in 50 patients with hepatocellular carcinoma (HCC) before and 1 month after intra-arterial therapy (IAT) using two semi-automated methods and a manual approach for the following functional, volumetric and morphologic parameters: (1) apparent diffusion coefficient (ADC), (2) arterial phase enhancement (AE), (3) portal venous phase enhancement (VE), (4) tumor volume, and assessment according to (5) the Response Evaluation Criteria in Solid Tumors (RECIST), and (6) the European Association for the Study of the Liver (EASL).

Materials and methods

This HIPAA-compliant retrospective study had institutional review board approval. The requirement for patient informed consent was waived. Tumor ADC, AE, VE, volume, RECIST, and EASL in 50 index lesions was measured by three observers. Interobserver reproducibility was evaluated using intraclass correlation coefficients (ICC). P < 0.05 was considered to indicate a significant difference.

Results

Semi-automated volumetric measurements of functional parameters (ADC, AE, and VE) before and after IAT as well as change in tumor ADC, AE, or VE had better interobserver agreement (ICC = 0.830–0.974) compared with manual ROI-based axial measurements (ICC = 0.157–0.799). Semi-automated measurements of tumor volume and size in the axial plane before and after IAT had better interobserver agreement (ICC = 0.854–0.996) compared with manual size measurements (ICC = 0.543–0.596), and interobserver agreement for change in tumor RECIST size was also higher using semi-automated measurements (ICC = 0.655) compared with manual measurements (ICC = 0.169). EASL measurements of tumor enhancement in the axial plane before and after IAT ((ICC = 0.758–0.809), and changes in EASL after IAT (ICC = 0.653) had good interobserver agreement.

Conclusion

Semi-automated measurements of functional changes assessed by ADC and VE based on whole-lesion segmentation demonstrated better reproducibility than ROI-based axial measurements, or RECIST or EASL measurements.     

Internal carotid artery stenosis measurements from 3D reconstructed multi-directional views using phantom data set on MRA image sequence

Purpose

To evaluate the inter-observer variability of stenosis measurements by using multi-directional 3D reconstructed projection view of internal carotid artery (ICA) that simulate the pre-determined stenosis degree on magnetic resonance angiography (MRA) image sequence of phantom data set and to compare the difference in measured percentages of maximum ICA stenosis between projection and axial images.

Materials and methods

By using adaptive region growing and circumscribed quadrangle on the clinical data set, the cylinder shape of a mathematical phantom was modeled and implemented. The maximum ICA stenosis was categorized as mild (30%), moderate (50%), and severe (70%) stenosis those simulated on the tomographic image sequence of ICA only and synthesized phantom. The 36 maximum intensity projection (MIP) images were radially projected at 10° increments that were rotated about the long axis of the body by using the simulated stenosis degree on the tomographic image sequence of phantom data sets. The six different projection image data sets were used to measure the minimum residual lumen and reference diameter by three blinded observers. The percentage of maximum ICA stenosis was calculated as the following. The ICA stenosis grading was [1 − (minimum residual lumen/averaged reference diameter)] × 100%.

Results

The percentage of maximum ICA stenosis degree measured on projection image was underestimated on ICA only phantom and overestimated on synthesized phantom compared to the simulated ICA stenosis degree on the axial image. In addition, the synthesized phantom provided the less projection image for stenosis measurement than ICA only phantom. These results attributed to the nature of MIP algorithm and the overlapping effects of surrounded anatomic structures such as other ICA, pair of external carotid artery (ECA), pair of VA, and background tissues. Furthermore, the inter-observer variability was also introduced by manual measurement.

Conclusion

The automated scheme is recommended to measure the ICA stenosis by using axial image. This technique is not only accurate as possible but also robust, simple to handle, and less time consuming compared with manual measurements. A computerized ICA stenosis measuring method, which applied the image processing technique on the axial image, is necessary to overcome the drawbacks introduced by using the projection image and manual measurement.     

Carotid artery stenosis: performance of advanced vessel analysis software in evaluating CTA

Objectives

The aim of this study was to evaluate time efficiency and diagnostic reproducibility of an advanced vessel analysis software for diagnosis of carotid artery stenosis.

Material and methods

40 patients with suspected carotid artery stenosis received head and neck DE-CTA as part of their pre-interventional workup. Acquired data were evaluated by 2 independent radiologists. Stenosis grading was performed by MPR eyeballing with freely adjustable MPRs and with a preliminary prototype of the meanwhile available client-server and advanced visualization software syngo.via CT Vascular (Siemens Healthcare, Erlangen, Germany). Stenoses were graded according to the following 5 categories: I: 0%, II: 1–50%, III: 51–69%, IV: 70–99% and V: total occlusion. Furthermore, time to diagnosis for each carotid artery was recorded.

Results

Both readers achieved very good specificity values and good respectively very good sensitivity values without significant differences between both reading methods. Furthermore, there was a very good correlation between both readers for both reading methods without significant differences (kappa value: standard image interpretation k = 0.809; advanced vessel analysis software k = 0.863). Using advanced vessel analysis software resulted in a significant time saving (p < 0.0001) for both readers. Time to diagnosis could be decreased by approximately 55%.

Conclusions

Advanced vessel analysis application CT Vascular of the new imaging software syngo.via (Siemens Healthcare, Forchheim, Germany) provides a high rate of reproducibility in assessment of carotid artery stenosis. Furthermore a significant time saving in comparison to standard image interpretation is achievable.     

A comparison between NASCET and ECST methods in the study of carotids: Evaluation using Multi-Detector-Row CT angiography

Purpose

NASCET and ECST systems to quantify carotid artery stenosis use percent diameter ratios from conventional angiography. With the use of Multi-Detector-Row CT scanners it is possible to easily measure plaque area and residual lumen in order to calculate carotid stenosis degree. Our purpose was to compare NASCET and ECST techniques in the measurement of carotid stenosis degree by using MDCTA.

Methods and material

From February 2007 to October 2007, 83 non-consecutive patients (68 males; 15 females) were studied using Multi-Detector-Row CT. Each patient was assessed by two experienced radiologists for stenosis degree by using both NASCET and ECST methods. Statistic analysis was performed to determine the entity of correlation (method of Pearson) between NASCET and ECST. The Cohen kappa test and Bland-Altman analysis were applied to assess the level of inter- and intra-observer agreement.

Results

The correlation Pearson coefficient between NASCET and ECST was 0.962 (p < 0.01). Intra-observer agreement in the NASCET evaluation, by using Cohen statistic was 0.844 and 0.825. Intra-observer agreement in the ECST evaluation was 0.871 and 0.836. Inter-observer agreement in the NASCET and ECTS were 0.822 and 0.834, respectively. Agreement analysis by using Bland-Altman plots showed a good intra-\inter-observer agreement for the NASCET and an optimal intra-\inter-observer agreement for the ECST.

Conclusions

Results of our study suggest that NASCET and ECST methods show a strength correlation according to quadratic regression. Intra-observer agreement results high for both NASCET and ECST.     

Hepatic artery stenosis in liver transplantation: imaging and interventional treatment

Introduction

Main purpose of our study is to demonstrate the spectral and color Doppler ultrasonography (DUS) findings that would indicate hepatic artery stenosis (HAS) after liver transplantation and to report our single center results. Moreover we want to establish role and limits of the different imaging techniques in detecting HAS, proposing a non invasive diagnostic approach and to depict indications and feasibility of endovascular treatment in the single patient.

Materials and methods

Our study consisted of 222 patients who underwent liver transplantation between January 1999 and December 2009. DUS findings were correlated with multidetector computed tomography angiography (MDCTA) and angiographic results.

Results

HAS occurred in 21 cases (9.5%). In all cases diagnosis was performed by DUS. MDCTA quantified stenosis and showed an overall picture of splanchnic vascularization. Based on DUS and MDCTA data integration, in 9 cases we adopted the “wait and see” strategy. Moreover in 12 cases treatment was considered necessary. For hepatic artery stenosis, use of DUS criteria resulted in a sensitivity of 100% (20/20), a specificity of 99.5% (201/202), a positive predictive value (PPV) of 95% (20/21), and negative predictive value (NPV) of 100% (201/201), and an overall accuracy of 99.5% (221/222).

Conclusion

Our study underline the role of DUS in early diagnosis of HAS: repeated evaluation of both direct and indirect signs increases NPV and sensitivity of DUS.     

High field carotid vessel wall imaging: A study on reproducibility

Purpose

Currently, a multi-contrast protocol, including a combination of five MR-sequences is used as reference standard for morphologic imaging and quantitative measurements of the carotid artery vessel wall. The purpose of this study is to investigate the scan–rescan reproducibility together with intra- and inter-observer reproducibility of each of the five MR-sequences.

Methods

Twenty healthy volunteers (55% male, mean age = 26 years) underwent repeated MR-examinations (3T-Philips-MRI) of the left carotid artery vessel wall with five sequences; T1-TFE, T2-TSE, PD-TSE, T1-TSE and 3D TOF. A standard phased-array coil with two flexible elements of 14 cm × 17 cm was used to obtain nine transverse imaging sections of the left carotid artery with identical in-plane resolution (0.46 mm × 0.46 mm). Reproducibility analysis was performed in 3 slices of the common carotid artery for all sequences.

Results

For, scan–rescan reproducibility, intra class correlation coefficients (ICC) were excellent for all sequences and ranged from 0.79 to 0.95. The intra-observer ICC ranged from 0.89 to 0.98 and the inter-observer ICC ranged from 0.84 to 0.96, for both lumen and vessel wall assessment.

Conclusions

By high field MR imaging, vessel wall and lumen area of the carotid artery can be assessed with excellent scan–rescan, intra- and inter-observer reproducibility for all five sequences.     

Volumetric response classification in metastatic solid tumors on MSCT: Initial results in a whole-body setting

Purpose

To examine technical parameters of measurement accuracy and differences in tumor response classification using RECIST 1.1 and volumetric assessment in three common metastasis types (lung nodules, liver lesions, lymph node metastasis) simultaneously.

Materials and methods

56 consecutive patients (32 female) aged 41–82 years with a wide range of metastatic solid tumors were examined with MSCT for baseline and follow up. Images were evaluated by three experienced radiologists using manual measurements and semi-automatic lesion segmentation. Institutional ethics review was obtained and all patients gave written informed consent. Data analysis comprised interobserver variability operationalized as coefficient of variation and categorical response classification according to RECIST 1.1 for both manual and volumetric measures. Continuous data were assessed for statistical significance with Wilcoxon signed-rank test and categorical data with Fleiss kappa.

Results

Interobserver variability was 6.3% (IQR 4.6%) for manual and 4.1% (IQR 4.4%) for volumetrically obtained sum of relevant diameters (p < 0.05, corrected). 4–8 patients’ response to therapy was classified differently across observers by using volumetry compared to standard manual measurements. Fleiss kappa revealed no significant difference in categorical agreement of response classification between manual (0.7558) and volumetric (0.7623) measurements.

Conclusion

Under standard RECIST thresholds there was no advantage of volumetric compared to manual response evaluation. However volumetric assessment yielded significantly lower interobserver variability. This may allow narrower thresholds for volumetric response classification in the future.     

Correlation between US-PSV and MDCTA in the quantification of carotid artery stenosis

Purpose

Stroke is a major cause of death and serious long-lasting neurological disability and the severity of carotid artery stenosis is one of the most important determinants of cerebrovascular events. The purpose of this paper is to evaluate the correlation between multi-detector-row CT angiography (MDCTA) and ultra-sound peak-systolic-velocity (US-PSV) in the quantification of carotid artery stenosis.

Methods and material

52 patients were retrospectively studied by using four-detector row CT and ultra-sound. Each patient was assessed for stenosis degree by using NASCET method when studied by using MDCT and by using PSV when studied by using US. Statistic analysis was performed to determine the entity of correlation (method of Pearson) between MDCTA and US-PSV. The Bland-Altman analysis was applied to assess the level of inter-technique agreement.

Results

Sonographic PSV measurements ranged from 70 to 589 cm/s. Distal ICA velocities ranged from 29 to 238 cm/s. Linear regression analysis showed a good correlation (r² = 0.613) between MDCTA-NASCET linear percentage stenosis and PSV and measured. PSV value that corresponded to a NASCET linear percentage stenosis of 70% was 283 cm/s and with this values sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 75%, 88.6%, 90.7% and 70.5%, respectively.

Conclusions

Results of our study suggest that NASCET stenosis measured in MDCTA and PSV values have a good correlation. The use of a threshold of 283 cm/s allows obtaining good value of sensitivity and specificity.     

Functional MRI using Fourier decomposition of lung signal: Reproducibility of ventilation- and perfusion-weighted imaging in healthy volunteers

Purpose

To assess the reproducibility of Fourier decomposition (FD) based ventilation- and perfusion-weighted lung MRI.

Methods

Sixteen healthy volunteers were examined on a 1.5 T whole-body MR-scanner with 4–6 sets of coronal slices over the chest volume with a non-contrast enhanced steady-state free precession sequence. The identical protocol was repeated after 24 h. Reconstructed perfusion- and ventilation-weighted images were obtained through non-rigid registration and FD post-processing of images. Analysis of signal in segmented regions of interest was performed for both native and post-processed data. Two blinded chest radiologists rated image quality of perfusion- and ventilation-weighted images using a 3-point scale.

Results

Reproducibility of signal between the two time points was very good with intra-class correlation coefficients of 0.98, 0.94 and 0.86 for native, perfusion- and ventilation-weighted images, respectively. Perfusion- and ventilation-weighted images were of overall good quality with proportions of diagnostic images of 87–95% and 69–75%, respectively. Lung signal decreased from posterior to anterior slices with image quality of ventilation-weighted images in anterior areas rated worse than in posterior or perfusion-weighted images. Inter- and intra-observer agreement of image quality was good for perfusion and ventilation.

Conclusions

The study demonstrates high reproducibility of ventilation- and perfusion-weighted FD lung MRI.     

Diagnostic accuracy of image postprocessing methods for the detection of coronary artery stenoses by using multidetector CT

PURPOSE: To retrospectively evaluate the diagnostic accuracy of multidetector computed tomography (CT) coronary angiography for detection of hemodynamically significant (>or=50%) stenoses by using various image postprocessing methods, with conventional coronary angiography as the reference standard. MATERIALS AND METHODS: The analysis used data from previous studies, use of which had been approved by the Institutional Review Board. Sixteen-section multidetector CT data sets for 40 patients (30 men, 10 women; mean age 56 years +/- 8; mean heart rate, 61 beats per minute +/- 6) were evaluated. Six independent investigators evaluated the data sets for the presence of stenoses with diameter reduction of 50% or more, by using either exclusively transverse images, free oblique multiplanar reconstructions (MPRs), free oblique maximum intensity projections (MIPs, 5 mm thick), prerendered curved MPRs, prerendered curved MIPs, or prerendered three-dimensional volume rendered reconstructions (VRTs). Evaluation results were compared with conventional coronary angiography for each artery in a blinded fashion (chi(2) test). RESULTS: Overall, 35 coronary artery stenoses were present. Percentage of evaluable arteries and accuracy for detecting stenosis (percentages of accurately classified arteries were, respectively, 99% and 88% for transverse, 99% and 91% for oblique MPR, 94% and 86% for oblique MIP, 94% and 83% for curved MIP, 93% and 81% for curved MPR, and 91% and 73% for VRT). Accuracy was significantly higher for oblique MPR than for curved MPR (P=.01), curved MIP (P=.03), and VRT (P<.001). CONCLUSION: The evaluation of multidetector CT coronary angiography with interactive image display methods, especially interactive oblique MPRs, permits higher diagnostic accuracy than evaluation of prerendered images (curved MPR, curved MIP, or VRT images).     

Evaluation of failing hemodialysis fistulas with multidetector CT angiography: comparison of different 3D planes

Purpose

To evaluate failing hemodialysis fistula complications using 16-detector MDCTA, and to assess the accuracies of different 3D planes.

Materials and methods

Thirty patients (16 men, 14 women, aged 27–79 years) were referred for hemodialysis access dysfunction. Thirty-one MDCTA exams were done prior to fistulography. For MDCTA, contrast was administered (2 mL/kg at 5 mL/s) via a peripheral vein in the contralateral arm. Axial MIP, coronal MIP, and VRT images were constructed. Venous complications were evaluated on axial source images, on each 3D plane, and on all-planes together. Results were analyzed using McNemar test.

Results

Axial MIP, VRT and all-planes evaluations were most sensitive for fistula site detection (93%). Coronal MIP had the highest sensitivity, specificity and accuracy (35%, 96%, and 85%, respectively) for detecting venous stenosis. VRT and all-planes had the highest sensitivity and accuracy for detecting aneurysms (100%). All-planes and axial MIP were most sensitive for detecting venous occlusion (61% and 54%). Comparisons of detection frequencies for each venous pathology between the five categories of MDCTA revealed no significant differences (P > 0.05). MDCTA additionally showed 3 partially thrombosed aneurysms, 4 anastomosis site stenosis and 12 arterial complications.

Conclusion

MDCTA overall gives low sensitivity for detection of central vein stenosis and moderate sensitivity for occlusion. For most pathology, all-planes evaluation of MDCTA gives highest sensitivity and accuracy rates when compared to other planes. For venous stenosis and occlusion, MDCTA should be considered when ultrasonography and fistulography are inconclusive. MDCTA is helpful in identifying aneurysms, collaterals, partial venous thromboses and additional arterial, anastomosis site pathologies.     

Reproducibility of real-time shear wave elastography in the evaluation of liver elasticity

Objective

To evaluate the reproducibility of real-time shear wave elastography in assessing liver elasticity in healthy volunteers.

Methods

Forty-two volunteers were studied in day 1. Shear wave elastography studies were performed by using the ultrasound system Aixplorer™ (SuperSonic Imagine S.A., Aix-en-Provence, France) with a convex broadband probe. Measurements were carried by two operators, an expert (operator 1) and a novice (operator 2). Examinations were performed on the right lobe of the liver. Each operator performed 10 consecutive measurements in each volunteer. In a subset of volunteers (n = 18) measurements were performed twice on two different days (day 1 and day 2). Intraobserver and interobserver agreement were assessed by intraclass correlation coefficient.

Results

Intraobserver agreement between measurements performed in the same subject in the same day (day 1 or day 2) showed intraclass correlation coefficient values of 0.95 (95% confidence interval, 0.93–0.98) and 0.93 (95% confidence interval, 0.90–0.96) for operator 1 and operator 2, respectively. Intraobserver agreement between measurements performed in the same subject in different days showed intraclass correlation coefficient values of 0.84 (95% confidence interval, 0.69–0.98) and 0.65 (95% confidence interval, 0.39–0.91) for operator 1 and operator 2, respectively. Interobserver agreement was 0.88 (95% confidence interval, 0.82–0.94).

Conclusions

The results of this study show that shear wave elastography is a reliable and reproducible noninvasive method for the assessment of liver elasticity. Expert operator had higher reproducibility of measurements over time than novice operator.     

Reproducibility of high-resolution MRI for the middle cerebral artery plaque at 3 T

Purpose

To assess the reproducibility of HR-MRI for the identification of MCA atherosclerotic plaque components and quantification of stenosis.

Materials and methods

Seventy-three consecutive subjects who initially had ischemic stroke or asymptomatic MCA stenosis (>50%) were enrolled in the study. All subjects were scanned using 3.0 T MRI. Two independent readers reviewed all images and one reader reevaluated all images four weeks later. The tissue components of plaques were analyzed qualitatively and the vessels were quantitative measured.

Results

HR-MRI displayed the artery wall and lumen clearly. The intra-observer reproducibility was excellent for the identification of plaques (kappa [κ] = 0.96; 95% CI: 0.83–1.04) and contrast enhancement (κ = 0.89; 0.78–0.95); it was substantial for intra-plaque hemorrhage (κ = 0.79; 0.57–0.96) and the fibrous cap (κ = 0.65; 0.42–0.86). The inter-observer reproducibility was excellent for plaques (κ = 0.92; 0.73–1.06), substantial for contrast enhancement (κ = 0.80; 0.65–0.93), intra-plaque hemorrhage (κ = 0.68; 0.47–0.92) and moderate for the fibrous cap (κ = 0.58; 0.44–0.79). Both intra-observer and inter-observer reproducibility were excellent for quantitative vessel, lumen and wall measurements with intraclass correlation coefficients ranging from 0.91 to 0.97 and 0.87 to 0.96, respectively. However, vessel and wall areas and the intervals defined by the Bland–Altman plots were wide in comparison to the mean.

Conclusions

The identification of MCA atherosclerotic plaque components and the quantification of vessel and lumen measurements are reproducible. The reproducibility is overall acceptable. HR-MRI may provide a useful tool for clinical risk evaluation in MCA atherosclerosis.     

CT angiographic analysis of carotid artery stenosis: comparison of manual assessment, semiautomatic vessel analysis, and digital subtraction angiography

BACKGROUND AND PURPOSE: To compare multisection CT angiography (CTA) analyzed with source/maximum intensity projection (MIP) images as well as semiautomated vessel analysis software with intra-arterial digital subtraction angiography (DSA) in detection and grading of carotid artery bifurcation stenosis. METHODS: Consecutive patients with sonography evidence of a marked internal carotid artery stenosis underwent both carotid CTA and DSA (37 patients, 73 vessels). In CTA, the grade of stenosis was determined using axial source and MIP images as well as vessel analysis. The scans were blind-analyzed by 2 neuroradiologists using the NASCET criteria. RESULTS: Correlation of CTA source/MIP images versus DSA estimates of stenosis (R = 0.95) was higher than for the vessel analysis method versus DSA (R = 0.89). Compared with DSA, CTA source/MIP images underestimated high (78.2% versus 86.4%, P < .05) and moderate grades of stenosis (57.3% versus 63.1%, P < .05) to a lesser extent than the vessel analysis method (68.5% versus 83.5% and 51.8% versus 63.1%, P < .05). For a high-grade stenosis, sensitivity and specificity of source/MIP image CTA were 75% and 96%, respectively, whereas for the vessel analysis method, they were 47% and 96%, respectively. For moderate stenosis, the source/MIP image CTA sensitivity and specificity were 88% and 82%, respectively, and for vessel analysis method, 62% and 82%, respectively. CTA detected all 4 occlusions. CONCLUSION: In evaluation of carotid stenosis, CTA provides an adequate, less invasive alternative with a high correlation to conventional DSA, though it tends to underestimate clinically relevant grades of stenosis. Its accuracy is not improved by semiautomated analysis. The data support the use of CTA in confirming carotid occlusion.     

CT coronary angiography: Coronary CT-flow quantification supplements morphological stenosis analysis

Background

Our rationale was to evaluate whether a 64-slice CT scanner allows accurate measurement of computed tomographic (CT) changes in coronary artery flow profiles and whether CT flow measurements are suitable for classifying the significance and hemodynamic relevance of a stenosis and thereby supplement as a functional parameter for morphological stenosis analysis.

Methods

A total of 50 patients prospectively underwent computed tomography coronary angiography (coronary CTA) in a multidetector CT scanner (Brilliance 64, Philips) ± 1 day before or after invasive coronary angiography (ICA). Immediately thereafter, 2 radiologists reviewed the imaging data to detect any vessel segments with morphology poorly evaluable by coronary CTA. A locally constant cyclical measurement was acquired in these coronary arteries in breath-hold technique during the passage of a 50 ml bolus of contrast media. For analysis, time–density curves of the bolus passage were registered in the coronary artery and the aorta (internal reference), the up-slopes were determined and correlated with each other. The results were compared with the ICA findings.

Results

47 of 50 CT flow measurements were evaluable. A good correlation was found between the degrees of stenosis and slope ratios in aorta and coronary artery (R² = 0.92). The threshold corridor was 0.55–0.77 for distinguishing hemodynamically (≥70%) from non-hemodynamically relevant stenoses.

Conclusions

CT-based coronary artery flow measurements (CTFM) correlate well with the angiographically determined degree of stenosis and can elevate by non-invasive means the diagnostic accuracy of coronary CTA. From both a clinically diagnostic and scientific standpoint, CTFM proves a suitable method for quantifying coronary blood flow.