Ingmar Gräßlin

Learn More
PURPOSE To set up a robust and patient-friendly whole-heart protocol based on 32-receive-channel technology that will potentially allow a large part of the patient population to be addressed. MATERIALS AND METHODS Ten volunteers were examined on a clinical 1.5 T scanner equipped with a 32-channel data acquisition system using an experimental 32-element(More)
The specific absorption rate (SAR) is a limiting factor in high-field MR. SAR estimation is typically performed by numerical simulations using generic human body models. However, SAR concepts for single-channel radiofrequency transmission cannot be directly applied to multichannel systems. In this study, a novel and comprehensive SAR prediction concept for(More)
Parallel transmission facilitates a relatively direct control of the RF transmit field. This is usually applied to improve the RF field homogeneity but might also allow a reduction of the specific absorption rate (SAR) to increase freedom in sequence design for high-field MRI. However, predicting the local SAR is challenging as it depends not only on the(More)
The specific absorption rate (SAR) is a limiting constraint in sequence design for high-field MRI. SAR estimation is typically performed by numerical simulations using generic human body models. This entails an intrinsic uncertainty in present SAR prediction. This study first investigates the required detail of human body models in terms of spatial(More)
Introduction With increasing field-strength, the local specific absorption rate (SAR) becomes a limiting factor for MR imaging applications. However, using parallel Tx systems, it becomes possible to tailor the E-fields in the RF pulse design. Certain SAR optimal algorithms have been proposed, e.g. [1], that constrain a specific local region for SAR (e.g.,(More)
Introduction RF safety is a prerequisite for in vivo parallel transmission MRI experiments. In this abstract, a comprehensive RF patient safety concept is proposed to ensure scanning within the SAR limits with multi-channel RF transmit coils. Two paths are pursued. Before the scan, SAR calculations are carried out in (almost) real-time for demand waveforms(More)
Fluorine MRI offers broad potential for specific detection and quantification of molecularly targeted agents in diagnosis and therapy planning or monitoring. Because non-proton MRI applications lack morphological information, accompanying proton images are needed to elucidate the spatial tissue context. Furthermore, low concentrations typical of targeted(More)
Multichannel transmit magnetic resonance imaging (MR) systems have the potential to compensate for signal-intensity variations occurring at higher field strengths due to wave propagation effects in tissue. Methods such as RF shimming and local excitation in combination with parallel transmission can be applied to compensate for these effects. Moreover,(More)
The specific absorption rate (SAR) is an important safety criterion, limiting many MR protocols with respect to the achievable contrast and scan duration. Parallel transmission enables control of the radiofrequency field in space and time and hence allows for SAR management. However, a trade-off exists between radiofrequency pulse performance and SAR(More)
PURPOSE The permanent presence of devices (pacemakers) inside a patient, or the need to use other devices (catheters), for diagnosis and treatment, usually represents a contraindication for a magnetic resonance examination. To help overcome this problem, a novel and noninvasive magnetic resonance system-based concept is proposed to detect potentially unsafe(More)