No abstract

Background Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence.Methods ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362.

High-field (!3 T) cardiac MRI is challenged by inhomogeneities of both the static magnetic field (B 0 ) and the transmit radiofrequency field (B 1 1). The inhomogeneous B fields not only demand improved shimming methods but also impede the correct determination of the zero-order terms, i.e., the local resonance frequency f 0 and the radiofrequency power to generate the intended local B 1 1 field. In this work, dual echo time B 0 -map and dual flip angle B 1 1-map acquisition methods are combined to acquire multislice B 0 -and B 1 1-maps simultaneously covering the entire heart in a single breath hold of 18 heartbeats. A previously proposed excitation pulse shape dependent slice profile correction is tested and applied to reduce systematic errors of the multislice B 1 1-map. Localized higher-order shim correction values including the zeroorder terms for frequency f 0 and radiofrequency power can be determined based on the acquired B 0 -and B 1 1-maps. This method has been tested in 7 healthy adult human subjects at 3 T and improved the B 0 field homogeneity (standard deviation) from 60 Hz to 35 Hz and the average B 1 1 field from 77% to 100% of the desired B 1 1 field when compared to more commonly used preparation methods. The increased signal-to-noise ratio at the static magnetic field (B 0 ) of 3 T may improve cardiac MRI and MR spectroscopy applications that are constrained by limited signal-to-noise ratio at 1.5 T (1,2). However, cardiac MR at 3 T is challenged by increased B 0 inhomogeneity due to susceptibility. Noeske et al. (3) reported B 0 field variations over the left ventricle of 6 130 Hz. Furthermore, the overall increased B 0 inhomogeneity makes the determination of the on-resonance frequency f 0 more challenging. The combination of increased B 0 inhomogeneity and potential off-resonance in the heart may lead to image artifacts and distortions, especially when applying balanced steady-state free precession sequences (4) or fat suppression.One way to improve B 0 field homogeneity is to perform localized shimming followed by a frequency scout prescan, in which a series of single-shot images with incremental f 0 are acquired (5). The f 0 that yields best image quality is then visually selected by the operator and used for the subsequent high-resolution scan. Another solution is to determine both localized second-order shim corrections and localized on-resonance frequency f 0 at the same time, based on an acquired B 0 -map (6).In addition to B 0 inhomogeneity, both numerical simulations (7) and measurements (8) have shown that the transmit radiofrequency (RF) field B 1 þ in the heart is more inhomogeneous at 3 T as compared to 1.5 T. Conventional methods to measure B 1 þ-maps, such as the dual angle method (9,10) or the actual flip-angle imaging (AFI) method (11), are rather time consuming and may not easily be used for the heart because of blood flow and cardiac/respiratory motion. Recently, the saturated double-angle method (SDAM) to acquire a B 1 þ-map covering the heart within a single breath hold ...

Endovascular treatment of aortic arch branch origin obstruction is safe and efficacious in experienced hands and can be considered as the preferred treatment, with good mid-term durability. Recurrent symptomatic lesions can be treated safely by renewed endovascular means.