Multislice parallel imaging involves the simultaneous sampling of multiple parallel slices which are subsequently separated using parallel imaging reconstruction. The CAIPIRINHA technique improves this reconstruction by manipulating the phase of the RF excitation pulses to shift the aliasing pattern such that there is less aliasing energy to be reconstructed. In this work, it is shown that combining the phase manipulation used in CAIPIRINHA with a non‐Cartesian (radial) sampling scheme further decreases the aliasing energy for the parallel imaging algorithm to reconstruct, thereby further increasing the degree to which a multi‐channel receiver array can be utilized for parallel imaging acceleration. In radial CAIPIRINHA, individual bands (slices) in a multislice excitation are modulated with view‐dependent phase, causing a destructive interference of entire slices. This destructive interference leads to a reduction in aliasing compared to the coherent shifts one observes when using this same technique with a Cartesian trajectory. Recovery of each individual slice is possible because the applied phase pattern is known, and a conjugate‐gradient reconstruction algorithm minimizes the contributions from other slices. Results are presented with a standard 12‐channel head coil with acceleration factors up to 14, where radial CAIPIRINHA produces an improved reconstruction when compared with Cartesian CAIPIRINHA. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.

Purpose Diffusion Spectrum Imaging (DSI) has been shown to be an effective tool for non-invasively depicting the anatomical details of brain microstructure. Existing implementations of DSI sample the diffusion encoding space using a rectangular grid. Here we present a different implementation of DSI whereby a radially symmetric q-space sampling scheme for DSI (RDSI) is used to improve the angular resolution and accuracy of the reconstructed Orientation Distribution Functions (ODF). Methods Q-space is sampled by acquiring several q-space samples along a number of radial lines. Each of these radial lines in q-space is analytically connected to a value of the ODF at the same angular location by the Fourier slice theorem. Results Computer simulations and in vivo brain results demonstrate that RDSI correctly estimates the ODF when moderately high b-values (4000 s/mm2) and number of q-space samples (236) are used. Conclusion The nominal angular resolution of RDSI depends on the number of radial lines used in the sampling scheme, and only weakly on the maximum b-value. In addition, the radial analytical reconstruction reduces truncation artifacts which affect Cartesian reconstructions. Hence, a radial acquisition of q-space can be favorable for DSI.

The use of MRI for intervention and real-time imaging has seen many changes since its inception in the late 1980s. Initial interventional MRI researchers made great strides in building this new specialty, creating devices, sequences, and applications to push the field forward. More recently, researchers have gained more access to the systems themselves, and have taken advantage of this situation to create truly interactive interventional systems. Techniques such as fully interactive scan adjustments and device tracking can be accomplished in real time due to increased transparency between vendors and researchers. Additionally, pulse sequences have undergone an evolution as well, with the constant emergence of novel acquisition schemes to generate image contrast quickly, increase temporal resolution and cover k-space with nonrectilinear trajectories. We will look at both emerging system interface concepts and novel pulse sequences that we believe will continue to push innovation in the field of interventional MRI.