David J. Bowden

Utility of high resolution MR imaging to assess carotid plaque morphology: A comparison of acute symptomatic, recently symptomatic and asymptomatic patients with carotid artery disease

OBJECTIVES Compare carotid plaque morphology of acute symptomatic, recently symptomatic and asymptomatic patients (groups 1, 2 and 3 respectively) with carotid artery disease using high resolution magnetic resonance imaging (MRI), to identify high-risk plaque characteristics best associated with risk of recurrent thrombo-embolic events. METHODS 60 patients underwent multi-contrast imaging of their internal carotid arteries. Different plaque components were manually delineated on acquired axial images to assess the difference in prevalence of plaque hemorrhage, fibrous cap (FC) rupture and FC thickness among the three groups. RESULTS 55% acute symptomatic patients had plaque hemorrhage vs. 35% for recently symptomatic group and 5% for asymptomatic group (p-value: group 1 vs. 3: 0.001, group 2 vs. 3: 0.04). Type 1 hemorrhage was more common in acute symptomatic patients than recently symptomatic patients (40% vs. 5%, p=0.01). Type 2 hemorrhage was more common in recently symptomatic vs. acute symptomatic patients (15% vs. 30%). FC rupture was observed in 50% of patients in group 1 vs. 35% of group 2 patients (p=0.02) but none in group 3. The mean minimum FC thickness was same in acute and recently symptomatic groups (600+/-200microm), compared to 800+/-200microm for asymptomatic patients (p-value: 0.03 and 0.007 respectively). Good correlation was present among the three MR readers (intra-class correlation coefficient=0.71). CONCLUSION High resolution MRI can differentiate plaque components associated with increased risk of thrombo-embolic events.

Characterisation of carotid atheroma in symptomatic and asymptomatic patients using high resolution MRI

Background and purpose: To prospectively evaluate differences in carotid plaque characteristics in symptomatic and asymptomatic patients using high resolution MRI. Methods: 20 symptomatic and 20 asymptomatic patients, with at least 50% carotid stenosis as determined by Doppler ultrasound, underwent preoperative in vivo multispectral MRI of the carotid arteries. Studies were analysed both qualitatively and quantitatively in a randomised manner by two experienced readers in consensus, blinded to clinical status, and plaques were classified according to the modified American Heart Association (AHA) criteria. Results: After exclusion of poor quality images, 109 MRI sections in 18 symptomatic and 19 asymptomatic patients were available for analysis. There were no significant differences in mean luminal stenosis severity (72.9% vs 67.6%; p = 0.09) or plaque burden (median plaque areas 50 mm2 vs 50 mm2; p = 0.858) between the symptomatic and asymptomatic groups. However, symptomatic lesions had a higher incidence of ruptured fibrous caps (36.5% vs 8.7%; p = 0.004), haemorrhage or thrombus (46.5% vs 14.0%; p<0.001), large necrotic lipid cores (63.8% vs 28.0%; p = 0.002) and complicated type VI AHA lesions (61.5% vs 28.1%; p = 0.001) compared with asymptomatic lesions. The MRI findings of plaque haemorrhage or thrombus had an odds ratio of 5.25 (95% CI 2.08 to 13.24) while thin or ruptured fibrous cap (as opposed to a thick fibrous cap) had an odds ratio of 7.94 (95% CI 2.93 to 21.51) for prediction of symptomatic clinical status. Conclusions: There are significant differences in plaque characteristics between symptomatic and asymptomatic carotid atheroma and these can be detected in vivo by high resolution MRI.

Association Between Aneurysm Shoulder Stress and Abdominal Aortic Aneurysm Expansion A Longitudinal Follow-Up Study

Background— Aneurysm expansion rate is an important indicator of the potential risk of abdominal aortic aneurysm (AAA) rupture. Stress within the AAA wall is also thought to be a trigger for its rupture. However, the association between aneurysm wall stresses and expansion of AAA is unclear. Methods and Results— Forty-four patients with AAAs were included in this longitudinal follow-up study. They were assessed by serial abdominal ultrasonography and computed tomography scans if a critical size was reached or a rapid expansion occurred. Patient-specific 3-dimensional AAA geometries were reconstructed from the follow-up computed tomography images. Structural analysis was performed to calculate the wall stresses of the AAA models at both baseline and final visit. A nonlinear large-strain finite element method was used to compute the wall-stress distribution. The relationship between wall stresses and expansion rate was investigated. Slowly and rapidly expanding aneurysms had comparable baseline maximum diameters (median, 4.35 cm [interquartile range, 4.12 to 5.0 cm] versus 4.6 cm [interquartile range, 4.2 to 5.0 cm]; P=0.32). Rapidly expanding AAAs had significantly higher shoulder stresses than slowly expanding AAAs (median, 300 kPa [interquartile range, 280 to 320 kPa] versus 225 kPa [interquartile range, 211 to 249 kPa]; P=0.0001). A good correlation between shoulder stress at baseline and expansion rate was found (r=0.71; P=0.0001). Conclusion— A higher shoulder stress was found to have an association with a rapidly expanding AAA. Therefore, it may be useful for estimating the expansion of AAAs and improve risk stratification of patients with AAAs.

Magnetic resonance elastography: Feasibility of liver stiffness measurements in healthy volunteers at 3 T

AIM To demonstrate the feasibility of obtaining liver stiffness measurements with magnetic resonance elastography (MRE) at 3T in normal healthy volunteers using the same technique that has been successfully applied at 1.5 T. METHODS AND MATERIALS The study was approved by the local ethics committee and written informed consent was obtained from all volunteers. Eleven volunteers (mean age 35 ± 9 years) with no history of gastrointestinal, hepatobiliary, or cardiovascular disease were recruited. The magnetic resonance imaging (MRI) protocol included a gradient echo-based MRE sequence using a 60 Hz pneumatic excitation. The MRE images were processed using a local frequency estimation inversion algorithm to provide quantitative stiffness maps. Adequate image quality was assessed subjectively by demonstrating the presence of visible propagating waves within the liver parenchyma underlying the driver location. Liver stiffness values were obtained using manually placed regions of interest (ROI) outlining the liver margins on the gradient echo wave images, which were then mapped onto the corresponding stiffness image. The mean stiffness values from two adjacent sections were recorded. RESULTS Eleven volunteers underwent MRE. The quality of the MRE images was adequate in all the volunteers. The mean liver stiffness for the group was 2.3 ± 0.38 kPa (ranging from 1.7-2.8 kPa). CONCLUSIONS This preliminary work using MRE at 3T in healthy volunteers demonstrates the feasibility of liver stiffness evaluation at 3T without modification of the approach used at 1.5 T. Adequate image quality and normal MRE values were obtained in all volunteers. The obtained stiffness values were in the range of those reported for healthy volunteers in previous studies at 1.5 T. There was good interobserver reproducibility in the stiffness measurements.

Cost-Effectiveness Analysis of Endovascular versus Open Surgical Repair of Acute Abdominal Aortic Aneurysms Based on Worldwide Experience:

Purpose: To present an economic evaluation of endovascular versus open surgical repair of ruptured abdominal aortic aneurysms (AAA). Methods: Endovascular aneurysm repair (EVAR) is currently being appraised by the National Institute for Clinical Excellence. To aid in this appraisal, a health economic model developed to demonstrate the cost-effectiveness of EVAR for elective treatment of nonruptured AAAs versus OSR was used for an analysis in the emergency setting. The base case data on 730 patients undergoing EVAR was extracted from our recently published 22- study meta-analysis of 7040 patients presenting with acute AAA (ruptured or symptomatic) treated with either emergency EVAR or OSR. These data reflected a patient population with an average age of 70 years. The base case model, which assumed a time horizon of 30 years and applied all-cause mortality rates, was subjected to a number of 1-way sensitivity analyses. A multivariate analysis was undertaken using 10,000 Monte-Carlo simulations. Results: EVAR dominated OSR in the base case analysis, with a mean cumulative cost/patient of £17,422 (

Angiogenesis Imaging in Neoplasia

26,133) for EVAR and £18,930 (

Quantitative BOLD imaging at 3T: Temporal changes in hepatocellular carcinoma and fibrosis following oxygen challenge

28,395) for OSR [-£1508 (

Mycotic pseudoaneurysm of the superficial femoral artery in a patient with Cushing disease: case report and literature review.

2262) difference]. The mean quality-adjusted life years (QALYs)/patient was 3.09 for EVAR versus 2.49 for OSR (0.64 difference). EVAR was cost-effective compared with OSR at a threshold value of £20,000 to £30,000 (

Carotid endarterectomy performed in the morning is associated with increased cerebral microembolization

30,000-

Response to Letter Regarding Article, “Association Between Aneurysm Shoulder Stress and Abdominal Aortic Aneurysm Expansion: A Longitudinal Follow-Up Study”

45,000)/QALY. In no single combination tested did open surgical repair provide the patient with more QALYs than EVAR. Sensitivity analyses demonstrated that the results were most sensitive to length of hospital and intensive care stays, use of blood products, and the cost of the EVAR device, which were the main cost drivers. Conclusion: While the UKs National Institute for Clinical Excellence does not set an absolute limit at which treatments would not be funded, £30,000 (