[High-resolution functional cardiac MR imaging using density-weighted real-time acquisition and a combination of compressed sensing and parallel imaging for image reconstruction]. / Hochaufgelöste funktionelle Herz-MR Bildgebung mithilfe dichtegewichteter Echtzeit-Datenaufnahme und einer Kombination von Compressed Sensing und paralleler Bildgebung in der Rekonstruktion.

PURPOSE: The aim of this study was to perform high-resolution functional MR imaging using accelerated density-weighted real-time acquisition (DE) and a combination of compressed sensing (CO) and parallel imaging for image reconstruction. MATERIALS AND METHODS: Measurements were performed on a 3 T whole-body system equipped with a dedicated 32-channel body array coil. A one-dimensional density-weighted spin warp technique was used, i. e. non-equidistant phase encoding steps were acquired. The two acceleration techniques, compressed sensing and parallel imaging, were performed subsequently. From a complete Cartesian k-space, a four-fold uniformly undersampled k-space was created. In addition, each undersampled time frame was further undersampled by an additional acceleration factor of 2.1 using an individual density-weighted undersampling pattern for each time frame. Simulations were performed using data of a conventional human in-vivo cine examination and in-vivo measurements of the human heart were carried out employing an adapted real-time sequence. RESULTS: High-quality DECO real-time images using parallel acquisition of the function of the human heart could be acquired. An acceleration factor of 8.4 could be achieved making it possible to maintain the high spatial and temporal resolution without significant noise enhancement. CONCLUSION: DECO parallel imaging facilitates high acceleration factors, which allows real-time MR acquisition of the heart dynamics and function with an image quality comparable to that conventionally achieved with clinically established triggered cine imaging.

[Oxygen-enhanced functional MR lung imaging]. / Sauerstoffverstärkte funktionelle MR-Lungenbildgebung.

Current diagnostic tools for the assessment of lung function are limited by global measurements or the need for radioactive tracers. Ideally, these tools should allow quantitative, regional distinct analyses without exposure to radiation. The current paper presents oxygen-enhanced functional MRI for assessment of lung ventilation. First applied in humans in 1996, a considerable amount of experience is now available on 1.5T scanners. The generation of quantitative T1-maps shows a high clinical potential. Low-field MR scanners, which are mostly open-designed, are especially interesting for functional lung imaging. The open design has advantages in respect to patient comfort by lower noise production and easy access to the patients and the costs are lower (no need for helium cooling). Lower signal-to-noise ratios can be overcome by changing the relaxation times. New navigator techniques allow further compensations. This article focuses on the presentation of low-field scanners and the application of T1 and T2(*) maps is described for healthy volunteers and first patients.