A phantom based laser marking workflow to visually assess geometric image distortion in magnetic resonance guided radiotherapy.

Magnetic resonance (MR)-only workflows require quality assurance due to potential dosimetric impacts of using geometry distorted MR images in radiotherapy planning. MR-visible silicone-based fiducials were arranged in regular 3D structures to cover extended imaging volumes. The scanner's patient marking workflow with a 2-axes movable laser bridge allowed to visually check geometric distortions of each MR reconstructed fiducial against its true position in 3D space.

Closed-form expressions for flip angle variation that maximize total signal in T1-weighted rapid gradient echo MRI.

Purpose: Magnetization-prepared rapid gradient-echo (MPRAGE) sequences are commonly employed for T1-weighted structural brain imaging. Following a contrast preparation radiofrequency (RF) pulse, the data acquisition proceeds under nonequilibrium conditions of the relaxing longitudinal magnetization. Variation of the flip angle can be used to maximize total available signal.

MR-guided placement of a temporary vena cava filter: technique and feasibility.

The purpose of this paper was to investigate the feasibility of MR-guided insertion of a temporary vena cava filter on an open low-field imager. In vivo procedures were performed on four anesthetized pigs using a common nonferromagnetic temporary vena cava filter and a special prototype guidewire developed for vascular interventions guided by low-field MRI. Breath-hold spoiled gradient-echo sequences (fast low-angle shot [FLASH]) with flow compensation were used for position monitoring of the passively visualized intravascular devices.

[Flow contrast behavior in fast MR angiography with an ECG-triggered, slice-selective inversion recovery turbo-FLASH technique].

Purpose: To optimise and evaluate fast "inflow"-based contrast-prepared gradient-echo magnetic resonance angiography (MRA) of blood vessels with pulsatile flow.

Material And Method: We used a standard 2-D Turbo-FLASH sequence with an acquisition time of 0.9 s and a slice-selective hyperbolic secant inversion (SSIR) pulse for contrast preparation.

Optimizing joint imaging: MR imaging techniques.

For optimizing MR imaging of the joints, a sophisticated knowledge of MR system hard- and software conditions and coil technologies, sequence and contrast preparation techniques, and the use of paramagnetic contrast agents is necessary. This review article discusses the basic principles of the appropriate use of surface coils as well as the different conventional and fast imaging sequences, including three-dimensional (3D) MR imaging. In addition, the applications of contrast agents as well as the most important contrast preparation techniques are reviewed.