How to choose the right MR sequence for your research question at 7 T and above?

Abstract

The choice of a pulse sequence at ultra-high field can be influenced by a number of considerations and constraints that are not always the same as those at lower fields. Foremost amongst these is of course the information required and the time available, but considerations of static main field- and transmit field- inhomogeneities as well as power deposition can also play an important role.In this review we first briefly examine the characteristics of high field MRI, and then describe the performance and constraints relevant to the major imaging readouts, and their implementation with parallel imaging techniques.In the main body of the text we review the main current applications of neuro imaging at 7T: functional brain imaging; diffusion weighted imaging; structural imaging; and conclude with a brief summary of time of flight angiography.FMRI is explored in the context both of whole brain coverage, and for high resolution imaging of cortical layers and columns.The major pulse sequences considered include 3D and 2D EPI multi-echo EPI and spin echo EPI. Diffusion weighted single shot EPI is the sequence of choice with segmented approaches having some niche applications.In structural imaging a distinction is made between qualitative and quantitative approaches, with both T1 and T2*-based approaches considered. The application of these techniques to important brain pathologies is shown, in addition to their capability for high resolution imaging of cortical and sub-cortical anatomy. The advantages of 7T for time of flight angiography at 7T are elucidated and exemplary applications given.