Characterization of atherosclerotic disease in thoracic aorta: A 3D, multicontrast vessel wall imaging study

ACR Appropriateness Criteria® Thoracoabdominal Aortic Aneurysm or Dissection: Treatment Planning and Follow-Up

As the incidence of thoracoabdominal aortic pathology (aneurysm and dissection) rises and the complexity of endovascular and surgical treatment options increases, imaging follow-up of patients remains crucial. Patients with thoracoabdominal aortic pathology without intervention should be monitored carefully for changes in aortic size or morphology that could portend rupture or other complication. Patients who are post endovascular or open surgical aortic repair should undergo follow-up imaging to evaluate for complications, endoleak, or recurrent pathology. Considering the quality of diagnostic data, CT angiography and MR angiography are the preferred imaging modalities for follow-up of thoracoabdominal aortic pathology for most patients. The extent of thoracoabdominal aortic pathology and its potential complications involve multiple regions of the body requiring imaging of the chest, abdomen, and pelvis in most patients. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Usefulness of rapid MR angiography using two-point Dixon for evaluating carotid and aortic plaques

PURPOSE

Recently, various magnetic resonance imaging (MRI) modalities have been developed to easily detect carotid and aortic plaques, but these techniques are time-consuming and vulnerable to motion artifacts. We investigated the utility of a gradient echo MRI technique known as liver acquisition with volume acceleration flexible (LAVA-Flex) to detect carotid and aortic atherosclerotic plaques.

METHODS

Ten patients who underwent carotid endarterectomy (CEA) were assessed regarding the correspondence between LAVA-Flex findings and the histopathology of excised carotid plaques. In addition, 47 patients with cryptogenic ischemic stroke underwent LAVA-Flex and transesophageal echocardiography (TEE) for detection of embolic sources in the thoracic aorta. We analyzed the relationship between the thickness of the aortic plaque measured by TEE and the presence of high-intensity lesions on LAVA-Flex.

RESULTS

Nine of 10 patients (90.0%) who underwent CEA showed a high-intensity carotid lesion on LAVA-Flex, which corresponded pathologically to plaques containing large lipid cores and hemorrhage. Twenty-four (51.1%) of 47 cryptogenic stroke patients showed a high-intensity lesion in the thoracic aorta on LAVA-Flex; of these, 21 (87.5%) also demonstrated a large plaque (thickness ≥4 mm) on TEE. Twenty-two (95.7%) of 23 patients without a high-intensity lesion on LAVA-Flex demonstrated no large plaque on TEE. LAVA-Flex had a sensitivity of 95.5% and a specificity of 88.0% in patients with large plaques.

CONCLUSION

This study showed that LAVA-Flex successfully detected carotid and aortic plaques. This imaging technique may be useful to rapidly diagnose and evaluate carotid and aortic plaques, which are critical risk factors for aortogenic stroke.

EACVI recommendations on cardiovascular imaging for the detection of embolic sources: endorsed by the Canadian Society of Echocardiography

Cardioaortic embolism to the brain accounts for approximately 15-30% of ischaemic strokes and is often referred to as 'cardioembolic stroke'. One-quarter of patients have more than one cardiac source of embolism and 15% have significant cerebrovascular atherosclerosis. After a careful work-up, up to 30% of ischaemic strokes remain 'cryptogenic', recently redefined as 'embolic strokes of undetermined source'. The diagnosis of cardioembolic stroke remains difficult because a potential cardiac source of embolism does not establish the stroke mechanism. The role of cardiac imaging-transthoracic echocardiography (TTE), transoesophageal echocardiography (TOE), cardiac computed tomography (CT), and magnetic resonance imaging (MRI)-in the diagnosis of potential cardiac sources of embolism, and for therapeutic guidance, is reviewed in these recommendations. Contrast TTE/TOE is highly accurate for detecting left atrial appendage thrombosis in patients with atrial fibrillation, valvular and prosthesis vegetations and thrombosis, aortic arch atheroma, patent foramen ovale, atrial septal defect, and intracardiac tumours. Both CT and MRI are highly accurate for detecting cavity thrombosis, intracardiac tumours, and valvular prosthesis thrombosis. Thus, CT and cardiac magnetic resonance should be considered in addition to TTE and TOE in the detection of a cardiac source of embolism. We propose a diagnostic algorithm where vascular imaging and contrast TTE/TOE are considered the first-line tool in the search for a cardiac source of embolism. CT and MRI are considered as alternative and complementary tools, and their indications are described on a case-by-case approach.

Added value of femoral artery atherosclerosis for determining severity of white matter lesion by carotid atherosclerosis: a magnetic resonance imaging study

BACKGROUND

Previous studies reported that single vascular atherosclerosis was an effective indicator for white matter lesions (WMLs).

PURPOSE

To investigate the added value of femoral atherosclerosis for determining severity of WMLs by carotid atherosclerosis using three-dimensional vessel wall magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Elderly individuals without cardiovascular symptoms within the previous six months were recruited. The plaque features of carotid and femoral arteries were evaluated and compared between individuals with WML score ≤ 3 and those with WML score > 3. Logistic regression and receiver operating characteristic (ROC) analyses were used to determine the value of plaque features in discriminating WMLs with score > 3.

RESULTS

In total, 112 individuals (49 men, mean age 72.0±5.6 years) were included. Participants with a WML score > 3 showed a significantly greater carotid wall area and femoral artery stenosis and higher incidence of carotid calcification and femoral artery calcification and lipid-rich necrotic cores (LRNC) compared to those with a WML score ≤ 3 (all P < 0.05). Carotid artery calcification and femoral artery calcification, LRNC, and stenosis were found to be significantly associated with severe WMLs before and after adjustment for clinical factors (odds ratio 1.51-3.79, all P < 0.05). ROC analysis showed, in discriminating severe WMLs, the area under the curve increased from 0.615 to 0.754 after combining femoral artery LRNC and stenosis with carotid calcification compared to the carotid calcification alone.

CONCLUSION

Characteristics of femoral artery atherosclerosis determined by vessel wall MRI have added value for carotid atherosclerosis in determining the severity of WMLs.

Atherosclerotic plaque detected by transesophageal echocardiography is an independent predictor for all-cause mortality

Atherosclerotic lesions in the great arteries are frequent findings in the elderly. Numerous studies have shown their strong predictive value for cardiovascular disease, embolic events, and mortality. We sought to determine the risk of all-cause mortality depending on the localization of plaques in the thoracic aorta evaluated by transesophageal echocardiography (TEE). A total of 2,054 patients (median age 65 years, interquartile range 52–73; 58% men) who underwent a TEE examination between 01/2007 and 03/2015 were retrospectively analyzed. For each patient, the presence of atherosclerotic lesions in the ascending aorta, the aortic arch, and in the descending aorta, as well as cardiovascular risk factors and survival were documented. Median follow-up period was 48 months (interquartile range 38–58). Multivariate Cox regression analysis indicated plaque in the ascending aorta (HR of 1.36, 95% CI 1.01–1.83, P = 0.046), the aortic arch (HR of 1.78, 95% CI 1.29–2.45, P < 0.001), the descending aorta (HR of 2.01, 95% CI 1.54–2.77, P < 0.001), and plaque in any part of the thoracic aorta (HR of 1.84, 95% CI 1.42–2.4, P < 0.001), as independent predictors for all-cause mortality after adjusting for age, sex, arterial hypertension, hyperlipidemia, smoking, and diabetes. In this study, we could demonstrate that more than mild plaque at any site of the thoracic aorta predicts all-cause mortality. Assessment of atherosclerotic lesions in all segments of the thoracic aorta should be part of every routine TEE examination.

Magnetic resonance multitasking for multidimensional assessment of cardiovascular system: Development and feasibility study on the thoracic aorta

PURPOSE

To develop an MR multitasking-based multidimensional assessment of cardiovascular system (MT-MACS) with electrocardiography-free and navigator-free data acquisition for a comprehensive evaluation of thoracic aortic diseases.

METHODS

The MT-MACS technique adopts a low-rank tensor image model with a cardiac time dimension for phase-resolved cine imaging and a T₂ -prepared inversion-recovery dimension for multicontrast assessment. Twelve healthy subjects and 2 patients with thoracic aortic diseases were recruited for the study at 3 T, and both qualitative (image quality score) and quantitative (contrast-to-noise ratio between lumen and wall, lumen and wall area, and aortic strain index) analyses were performed in all healthy subjects. The overall image quality was scored based on a 4-point scale: 3, excellent; 2, good; 1, fair; and 0, poor. Statistical analysis was used to test the measurement agreement between MT-MACS and its corresponding 2D references.

RESULTS

The MT-MACS images reconstructed from acquisitions as short as 6 minutes demonstrated good or excellent image quality for bright-blood (2.58 ± 0.46), dark-blood (2.58 ± 0.50), and gray-blood (2.17 ± 0.53) contrast weightings, respectively. The contrast-to-noise ratios for the three weightings were 49.2 ± 12.8, 20.0 ± 5.8 and 2.8 ± 1.8, respectively. There were good agreements in the lumen and wall area (intraclass correlation coefficient = 0.993, P < .001 for lumen; intraclass correlation coefficient = 0.969, P < .001 for wall area) and strain (intraclass correlation coefficient = 0.947, P < .001) between MT-MACS and conventional 2D sequences.

CONCLUSION

The MT-MACS technique provides high-quality, multidimensional images for a comprehensive assessment of the thoracic aorta. Technical feasibility was demonstrated in healthy subjects and patients with thoracic aortic diseases. Further clinical validation is warranted.

Understanding Atherosclerosis Through an Osteoarthritis Data Set

Atherosclerotic cardiovascular disease remains a worldwide epidemic and one of the leading causes of death nowadays. Vessel wall imaging can be used to understand the development and progression of atherosclerosis, but it is rarely done because of the high cost. We recently identified the Osteoarthritis Initiative, a large prospective cohort study of knee osteoarthritis, which might serve as a valuable source for atherosclerosis research with its serial knee magnetic resonance imaging data. We have found that these images are suitable for vessel wall image analysis of the lower extremity arteries. Here, we will introduce the Osteoarthritis Initiative data set and explain why it could be used for cardiovascular research purposes. Also, we will briefly comment on peripheral artery atherosclerosis as it is covered in the Osteoarthritis Initiative image data set and review the use of vessel wall imaging for studying atherosclerosis. We think data mining of imaging studies, not originally designed on cardiovascular research, can not only maximize the value of the imaging data set but also boost our understanding of atherosclerosis.

One-Stop MR Neurovascular Vessel Wall Imaging With a 48-Channel Coil System at 3 T

OBJECTIVE

The purpose of this article was to build a radio frequency (RF) coil system to achieve high vessel wall image quality with coverage extending from the aortic arch to the intracranial vessels.

METHODS

A 48-channel coil system was built and characterized at a 3 tesla (T) Magnetic Resonance Imaging (MRI) scanner (uMR 790, Shanghai United Imaging Healthcare, Shanghai, China). The coil's performance was compared with a commercially available 36-channel coil system. By human studies, signal-to-noise ratio (SNR) units were evaluated and g-factors were calculated in the transverse planes of the brain and neck regions.

RESULTS

The SNR was increased by at least 28% in the brain region and up to fourfold in the neck region. The average g-factor with the acceleration factor, R = 3, was lowered by 21% in the transverse plane of the neck region. Intracranial and carotid arterial wall images with an isotropic spatial resolution of 0.63 mm were acquired within 7.7 minutes and thoracic aorta wall images with an isotropic spatial resolution of 1.1 mm were acquired within 2.7 minutes with the 48-channel coil system. The vessel wall can be more clearly visualized with the 48-channel coil system compared with the 36-channel coil system.

CONCLUSION

A 48-channel coil system was developed and demonstrated superior performance for vessel wall imaging at the intracranial and cervical carotid arteries compared with a commercial 36-channel coil.

SIGNIFICANCE

The 48-channel coil system is potentially useful for clinical diagnostics, especially when attempting to diagnose ischemic stroke.

[Possibilities and limitations of three-dimensional transesophageal echocardiography in the diagnosis of thoracic aorta atherosclerosis]

OBJECTIVES

To compare the possibilities and limitations of the two-dimensional (2D) and three-dimensional (3D) multiplane transesophageal echocardiography (TEE) for the diagnosis of the thoracic aorta (TA) atherosclerosis stage, qualitative and quantitative assessment of aortic atheromas and coronary atherosclerosis prediction. Materials and methods. 2D and 3D multiplane TEE of the TA was performed in 180 consecutive CAD patients (104 men, 76 women, mean age 62,4±7,5 years) using Philips IE33 xMatrix system and a X7-2t multiplane probe. Ascending aorta, accessible parts of the arch and descending TA were visualized in 2D mode with standard protocol using Live xPlane mode. 3D study of TA was performed using Live 3D and Full Volume modes. 2D and 3D studies were recorded as video clips series on a system hard drive with subsequent off line processing on a QLab 10.8 (Philips) workstation. Qualitative and quantitative assessment of every atheroma was performed using 2D and 3D modes. The degree of severity and distribution of the TA atheromatosis was evaluated according to the classification of ASE and EACVI (2015): grade 0 - intimal-medial thickness ≤1 mm, 1 - intimal thickness ≤2 mm, 2 - focal or diffuse intimal thickening of 2-3 mm (small atheromas), 3 - atheromas &gt;3-5 mm (no mobile/ulcerated components), 4 - atheromas &gt; 5 mm (no mobile/ulcerated components), 5 - grade 2, 3, or 4 atheromas plus mobile or ulcerated components. After TEE all patients underwent digital coronary angiography. SYNTAX Score was calculated in 122 (67,7%) patients with no coronary stents and bypass grafts. Results. 620 atheromas were analysed: 109 (17,6%) in the ascending part, 8 (1,3%) in the arch and 503 (81,1%) in the descending part. On average 3,4±2,1 atheromas per patient were revealed. Atheromas height in 3D was significantly higher (p&lt;0,001), than in 2D, being 0,38±0,09 cm and 0,26±0,07 cm, respectively.  Averaged atheromas height increase in 3D was 0,12±0,06 cm. In 3D 87,7% of atheromas have shown irregular contours while in 2D only 35,4% of atheromas had rough countors. The mobile component in 6 (66,6%) out of 9 atheromas was revealed only in 3D. In 2D 1-5 stages of TA atheromatosis were revealed in 22 (12,2%), 103 (57,2%), 43 (23,9%), 7 (3,9%) and 4 (2,2%) cases, respectively. In 3D 1-5 stages of TA atheromatosis were revealed in 16 (8,9%), 25 (13,9%), 90 (50%), 38 (21,1%) and 10 (5,5%) cases, respectively. With 3D TEE 130 (72,2%) patients were found to have higher gradation of TA atheromatosis stage. TA atheromatosis was not detected in 1 (0,6%) patient. The direct Spearman's correlation between a stage of TA atheromatosis and SYNTAX Score which has been established for 2D rs =0,32 p&lt;0,001 and 3D rs =0,30, p&lt;0,01, respectively. Conclusion. A comparison between 2D and 3D TEE has shown, that 3D is more precise method of qualitative and quantitative assessment of aortic atheromas and diagnosis of TA atheromatosis stage which allows, ultimately, to change the stage of TA atheromatosis towards a higher gradation. 3D ultrasound stage of TA atheromatosis is a surrogate marker of the severity and prevalence of coronary atherosclerosis.

Quantitative assessment of the intracranial vasculature in an older adult population using iCafe

Comprehensive quantification of intracranial artery features may help us assess and understand variations of blood supply during brain development and aging. We analyzed vasculature features of 163 participants (age 56-85 years, mean of 71) from a community study to investigate if any of the features varied with age. Three-dimensional time-of-flight magnetic resonance angiography images of these participants were processed in IntraCranial artery feature extraction technique (a recently developed technique to obtain quantitative features of arteries) to divide intracranial vasculatures into anatomical segments and generate 8 morphometry and intensity features for each segment. Overall, increase in age was found negatively associated with number of branches and average order of intracranial arteries while positively associated with tortuosity, which remained after adjusting for cardiovascular risk factors. The associations with number of branches and average order were consistently found between 3 main intracranial artery regions, whereas the association with tortuosity appeared to be present only in middle cerebral artery/distal arteries. The combination of time-of-flight magnetic resonance angiography and IntraCranial artery feature extraction technique may provide an effective way to study vascular conditions and changes in the aging brain.

Semiautomatic carotid intraplaque hemorrhage volume measurement using 3D carotid MRI

BACKGROUND

Presence of intraplaque hemorrhage (IPH) is a known risk factor for stroke and plaque progression. Accurate and reproducible measurement of IPH volume are required for further risk stratification.

PURPOSE

To develop a semiautomatic method to measure carotid IPH volume.

STUDY TYPE

Retrospective.

POPULATION

Patients scheduled for carotid endarterectomy and patients with 16-79% asymptomatic carotid stenosis by ultrasound.

FIELD STRENGTH

3T.

SEQUENCE

Simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) MRI.

ASSESSMENT

A semiautomated volumetric measurement of IPH using signal intensity thresholding of 3D SNAP volume was implemented. Fourteen carotid endarterectomy patients were enrolled to determine the signal intensity threshold of IPH using histology. Thirty-three patients with 16-79% asymptomatic stenosis were scanned twice within 1 month to evaluate reproducibility. The normalized SNAP intensity with the highest Youden index for predicting IPH on histology was used for thresholding. Scan-rescan reproducibility of IPH measurement was assessed using the intraclass correlation coefficient (ICC) and coefficient of variation (CV).

STATISTICAL TESTS

Receiver operating characteristic curve, area under the curve, Cohen's kappa, intraclass correlation coefficient, coefficient of variance (CV), and paired t-test.

RESULTS

IPH detection by the algorithm had substantial agreement with manual review (kappa: 0.92; 95% confidence interval [CI]: 0.83, 1.00) and moderate agreement with histology (kappa: 0.55; 95% CI: 0.34, 0.68). IPH volume measurements by the algorithm were strongly correlated with histology (Spearman's rho = 0.76, P = 0.002). IPH measurements were also reproducible, with ICCs of 0.86 (95% CI: 0.57, 0.96), 0.77 (95% CI: 0.32, 0.94), and 0.99 (95% CI: 0.93, 1.00) for maximum/mean normalized intensity and IPH volume, respectively. The corresponding CVs were 10.6%, 5.2%, and 11.8%.

DATA CONCLUSION

IPH volume measurements on SNAP MRI are highly reproducible using semiautomatic measurement. Level of Evidence 2 Technical Efficacy Stage 2 J. Magn. Reson. Imaging 2019;50:1055-1062.

Comparison of two different measurement methods in evaluating basilar atherosclerotic plaque using high-resolution MRI at 3 tesla

Background

To compare the Self-referenced and Referenced measurement methods in assessing basilar artery (BA) atherosclerotic plaque employing dark blood high-resolution MRI at 3 Tesla.

Methods

Forty patients with > 20% stenosis as identified by conventional MRA were recruited and evaluated on a 3 Tesla MRI system. The outer wall, inner wall and lumen areas of maximal lumen narrowing site and the outer wall and lumen areas of sites that were proximal and distal to the maximal lumen narrowing site were manually traced. Plaque area (PA), stenosis rate (SR) and percent plaque burden (PPB) were calculated using the Self-referenced and Referenced measurement methods, respectively. To assess intra-observer reproducibility, BA plaque was measured twice with a 2-week interval in between measurements.

Results

Thirty-seven patients were included in the final analysis. There were no significant differences in PA, SR and PPB measurements between the two methods. The intra-class coefficients and coefficient of variations (CV) ranged from 0.976 to 0.990 and from 3.73 to 5.61% for the Self-referenced method and ranged from 0.928 to 0.971 and from 4.64 to 9.95% for the Referenced method, respectively. Both methods are effective in the evaluation of BA plaque. However, the CVs of the Self-referenced method is lower than the Referenced measurement method. Moreover, Bland-Altman plots showed that the Self-referenced method has a narrower interval than the Referenced measurement method.

Conclusions

The Self-referenced method is better and more convenient for evaluating BA plaque, and it may serve as a promising method for evaluation of basilar atherosclerotic plaque.

Multi-contrast and three-dimensional assessment of the aortic wall using 3T MRI

OBJECTIVES

To develop a 3D-multi-contrast MRI protocol allowing for high resolution imaging of the wall and of atheroma in the thoracic aorta.

METHODS

Eleven healthy volunteers and eleven acute stroke patients with aortic plaques detected by TEE underwent MRI at 3T. The MRI-protocol consisted of a T1w-bright-blood, a T2w- and a PDw-black-blood sequence (spatial resolution=1.15mm³). Image quality was assessed by two blinded investigators using a 3-point score and intra- and inter-rater agreement was tested. In patients, atherosclerotic plaques were graded according to the modified American Heart Association (AHA) classification.

RESULTS

Total examination time was 35:42±7:48min in volunteers and 41:07±3:15min in patients. Image quality was graded with the highest score in 80-94% of T1w, 89-96% of T2w and 79-86% of PDw datasets. Intra- and inter-rater reliability regarding image quality grading was high. Five stroke patients showed AHA type III lesions, three had AHA type VII and two had type VIII plaques. One patient had a vulnerable appearing AHA VI plaque.

CONCLUSIONS

3D-multi-contrast MR-imaging of the aorta was performed with high image quality and in reasonable time. It allows evaluation of atherosclerotic plaque composition throughout the aortic arch and can be used to identify vulnerable plaques in acute stroke patients.