PII: S0720-048X(07)00592-X

Abstract

Magnetic resonance imaging at 3 T has come a long way from initial experimental studies in the early 1990s to a reliable, high-utility clinical modality. Initial attempts aimed at simply transferring established imaging algorithms from 1.5 T into the 3 T environment. This was followed by stepwise optimization of the implemented techniques at 3 T and, at the same time, the development of strategies to reduce artifacts. This included new radiofrequency (rf) pulses, methods for reducing the specific absorption rate as well as improved techniques for signal transmission and reception. The third step, which we are now witnessing for the last few years, includes the further optimization and extension of these protocols using e.g. new coil and scanner designs, thereby outperforming the results known from 1.5 T.Although the gain in signal-to-noise ratio at 3 T is nearly twofold compared to 1.5 T, one should not solely aim at increasing spatial resolution. It is known from physics that simply reducing the slice thickness in one dimension to half already uses up the entire gain in signal-to-noise ratio when migrating from 1.5 to 3 T. Instead, it has turned out that a weighted combination of higher resolution and faster imaging improves clinical protocols and work flow. Here methods for parallel acquisition techniques are greatly advantageous particularly at higher field strengths, thereby allowing to reduce measurement times of minutes to a single breath hold. The introduction of parallel imaging has to go along with improved coil designs of dedicated multi-channel coil systems. With the advent of multi-channel scanners with more than 16 independent receiver channels, these concepts can now be applied for the entire body.This special issue gives a comprehensive view on the current state-of-the-art status for imaging at 3 T and the underlying fundamental physical principles as well as on cutting-edge research developments. In the first part, three review articles cover strengths and limitations of MRI at higher field strengths, as well as their exploitation for clinical protocols. In the second part of this special issue, original research articles present a large spectrum of current morphologic and functional imaging developments from head to toe.View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT) Magnetic resonance imaging at 3 T has come a long way from initial experimental studies in the early 1990s to a reliable, high-utility clinical modality. Initial attempts aimed at simply transferring established imaging algorithms from 1.5 T into the 3 T environment. This was followed by stepwise optimization of the implemented techniques at 3 T and, at the same time, the development of strategies to reduce artifacts. This included new radiofrequency (rf) pulses, methods for reducing the specific absorption rate as well as improved techniques for signal transmission and reception. The third step, which we are now witnessing for the last few years, includes the further optimization and extension of these protocols using e.g. new coil and scanner designs, thereby outperforming the results known from 1.5 T. Although the gain in signal-to-noise ratio at 3 T is nearly twofold compared to 1.5 T, one should not solely aim at increasing spatial resolution. It is known from physics that simply reducing the slice thickness in one dimension to half already uses up the entire gain in signal-to-noise ratio when migrating from 1.5 to 3 T. Instead, it has turned out that a weighted combination of higher resolution and faster imaging improves clinical protocols and work flow. Here methods for parallel acquisition techniques are greatly advantageous particularly at higher field strengths, thereby allowing to reduce measurement times of minutes to a single breath hold. The introduction of parallel imaging has to go along with improved coil designs of dedicated multi-channel coil systems. With the advent of multi-channel scanners with more than 16 independent receiver channels, these concepts can now be applied for the entire body. This special issue gives a comprehensive view on the current state-of-the-art status for imaging at 3 T and the underlying fundamental physical principles as well as on cutting-edge research developments. In the first part, three review articles cover strengths and limitations of MRI at higher field strengths, as well as their exploitation for clinical protocols. In the second part of this special issue, original research articles present a large spectrum of current morphologic and functional imaging developments from head to toe.