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Abstract: Gradient echo techniques are often hampered by signal dephasing due to macroscopic phase perturbations because of system imperfections (shimming) or object induced perturbations of the magnetic field (hemorrhagic lesions, calcified tissue, air–tissue interfaces). Many techniques have been proposed to reduce the effects of macroscopic phase variations. Among these techniques are tuned pulse sequences, fitting techniques and reconstruction algorithms. These methods, however, suffer from one or more of the following drawbacks: they require longer acquisition times, require additional acquisitions, compensate only locally, can only be applied to multi-gradient echo data or may result in inaccurate results. In this work a generally applicable post-processing technique is presented to evaluate and compensate signal alterations invoked by first and second order macroscopic phase incoherences. In this technique, the derivatives of the signal phase are determined by applying the Fourier derivative theorem on the complex data. As a result, the phase derivatives are obtained without phase unwrapping and without compromising the resolution. The method is validated for single and multi-echo acquisitions by experiments on a co-axial cylinder phantom with known macroscopic field disturbances. The potential of the method is demonstrated on a multi-gradient echo acquisition on the head of a human volunteer. In general a first order correction is shown to be sufficient, however higher order correction is found to be beneficial near sharp transitions of the magnetic field. [Copyright &y& Elsevier]

Explores the utility of selective catheter injection in the context of magnetic resonance-guided endovascular interventions. Prevention of overlapping between vessels in two-dimensional acquisitions; Bolus tracking techniques; Application of test-bolus injections.

Studies the magnetic resonance safety and imaging properties of commonly used vascular stents. Stent screening for magnetic forces and torque; Susceptibility and radio frequency imaging artifacts; Effects of variations in strut geometry on the stents.

Examines the potential of passive magnetic resonance tracking techniques for guiding endovascular interventions. Visualization of paramagnetic trackers; Evaluation of the techniques in patients with stenosed hemodialysis access grafts.