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Lindner T.,Clinic for Radiology and Neuroradiology | Helle M.,Philips | Jansen O.,Clinic for Radiology and Neuroradiology
Clinical Neuroradiology | Year: 2015

Arterial spin labeling (ASL) is an emerging method for the assessment of perfusion in various diseases of the brain. In ASL, the magnetization of arterial blood water spins is manipulated in a complete non-invasive way before flowing into the tissue of interest. This allows absolute quantification of cerebral blood flow, thereby, presenting an alternative to contrast-enhanced methods based on computed tomography or magnetic resonance imaging. Furthermore, its potential application for flow territory mapping can provide additional information of the individual configuration of intracerebral blood flow. This article gives a brief overview of the basic ASL methodology and its approaches to image individual perfusion territories. Additionally, the utilization of ASL in a variety of cerebrovascular diseases is presented to provide examples of potential applications of (territorial) ASL in clinical routine. © 2015, Springer-Verlag Berlin Heidelberg. Source


Lindner T.,Clinic for Radiology and Neuroradiology | Jensen-Kondering U.,Clinic for Radiology and Neuroradiology | van Osch M.J.P.,Leiden University | Jansen O.,Clinic for Radiology and Neuroradiology | Helle M.,Philips
Magnetic Resonance Imaging | Year: 2015

Angiographic imaging is an important diagnostic tool for the assessment of the intracranial arterial status. Using arterial spin labeling (ASL) techniques, it is possible to visualize the arteries without the administration of exogenous contrast agents. Moreover, modifications of the labeling method allow for the visualization of single arterial trees. In this study, an approach is presented for time-resolved MR angiography based on superselective ASL and keyhole accelerated image acquisition in order to selectively visualize individual cerebral arteries in a clinically acceptable scan time. Keyhole percentage as well as the flip angle of the acquisition sequence was optimized in numerical simulations. Subsequently, the method was validated in healthy volunteers. As a result, image acquisition in 5 minutes with a temporal resolution of 100 ms and spatial resolution below 1 mm was achieved. © 2015 Elsevier Inc. Source


Roubin G.S.,Cardiovascular Assoc. of the Southeast | Jansen O.,Clinic for Radiology and Neuroradiology | Hendrikse J.,University Utrecht | Halliday A.,John Radcliffe Hospital | And 11 more authors.
The Lancet | Year: 2016

Background Age was reported to be an effect-modifier in four randomised controlled trials comparing carotid artery stenting (CAS) and carotid endarterectomy (CEA), with better CEA outcomes than CAS outcomes noted in the more elderly patients. We aimed to describe the association of age with treatment differences in symptomatic patients and provide age-specific estimates of the risk of stroke and death within narrow (5 year) age groups. Methods In this meta-analysis, we analysed individual patient-level data from four randomised controlled trials within the Carotid Stenosis Trialists' Collaboration (CSTC) involving patients with symptomatic carotid stenosis. We included only trials that randomly assigned patients to CAS or CEA and only patients with symptomatic stenosis. We assessed rates of stroke or death in 5-year age groups in the periprocedural period (between randomisation and 120 days) and ipsilateral stroke during long-term follow-up for patients assigned to CAS or CEA. We also assessed differences between CAS and CEA. All analyses were done on an intention-to-treat basis. Findings Collectively, 4754 patients were randomly assigned to either CEA or CAS treatment in the four studies. 433 events occurred over a median follow-up of 2·7 years. For patients assigned to CAS, the periprocedural hazard ratio (HR) for stroke and death in patients aged 65-69 years compared with patients younger than 60 years was 2·16 (95% CI 1·13-4·13), with HRs of roughly 4·0 for patients aged 70 years or older. We noted no evidence of an increased periprocedural risk by age group in the CEA group (p=0·34). These changes underpinned a CAS-versus CEA periprocedural HR of 1·61 (95% CI 0·90-2·88) for patients aged 65-69 years and an HR of 2·09 (1·32-3·32) for patients aged 70-74 years. Age was not associated with the postprocedural stroke risk either within treatment group (p≥0·09 for CAS and 0·83 for CEA), or between treatment groups (p=0·84). Interpretation In these RCTs, CEA was clearly superior to CAS in patients aged 70-74 years and older. The difference in older patients was almost wholly attributable to increasing periprocedural stroke risk in patients treated with CAS. Age had little effect on CEA periprocedural risk or on postprocedural risk after either procedure. Funding None. © 2016 Elsevier Ltd. Source


Dommaschk M.,University of Kiel | Peters M.,University of Kiel | Gutzeit F.,University of Kiel | Schutt C.,University of Kiel | And 6 more authors.
Journal of the American Chemical Society | Year: 2015

We present a fully reversible and highly efficient on-off photoswitching of magnetic resonance imaging (MRI) contrast with green (500 nm) and violet-blue (435 nm) light. The contrast change is based on intramolecular light-driven coordination-induced spin state switch (LD-CISSS), performed with azopyridine-substituted Ni-porphyrins. The relaxation time of the solvent protons in 3 mM solutions of the azoporphyrins in DMSO was switched between 3.5 and 1.7 s. The relaxivity of the contrast agent changes by a factor of 6.7. No fatigue or side reaction was observed, even after >100 000 switching cycles in air at room temperature. Electron-donating substituents at the pyridine improve the LD-CISSS in two ways: better photostationary states are achieved, and intramolecular binding is enhanced. © 2015 American Chemical Society. Source

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