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Several different techniques allow a functional assessment of neuronal activations by magnetic resonance imaging (fMRI). The by far most influential fMRI technique is based on a local T2*-sensitive hemodynamic response to neuronal activation, also known as the blood oxygenation level dependent or BOLD effect. Consequently, the term 'fMRI' is often used synonymously with BOLD imaging. Because interpretations of fMRI brain activation maps often appear intuitive and compelling, the reader might be tempted not to critically question the fundamental processes and assumptions. We review some essential processes and assumptions of BOLD fMRI and discuss related confounds and pitfalls in fMRI - from the underlying physiological effect, to data acquisition, data analysis and the interpretation of the results including clinical fMRI. A background framework is provided for the systematic and critical interpretation of fMRI results.

The topic fast and ultrafast MR imaging commonly includes relatively slow gradient-echo techniques with spoiled transverse magnetization (FLASH, FFE-T1, SPGR), gradient-echo techniques with partially refocused transverse magnetization (FISP, FFE, GRASS), gradient-echo techniques with fully refocused transverse magnetization (trueFISP, balanced FFE, FIESTA), the multi-echo spin-echo techniques (RARE, TSE, FSE), a mixture of multi-echo spin-echo and gradient-echo techniques (GRASE, TGSE), and finally single-shot techniques (HASTE, SS-FSE, EPI). This article gives a description of the sequence structures of non-echo-planar fast imaging techniques and a list of potential clinical applications. Recent advances in faster imaging which are not sequence related, such as simultaneous acquisitions of spatial harmonics (SMASH) and sensitivity encoding (SENSE) for fast MRI, are mentioned as well as some novel techniques such as QUEST and BURST. Due to the recent success with gradient-echo techniques with fully refocused transverse magnetization (trueFISP, balanced FFE, FIESTA), this "faster" gradient-echo technique is discussed in more detail followed by multi-echo spin-echo techniques that present the counterpart to the multi-echo gradient-echo (EPI) technique, which is not discussed in this paper. Three major areas appear to be the domain for EPI: diffusion; perfusion; and blood oxygenation level dependent imaging (BOLD, fMRI). For all other applications there is ample room for utilizing other fast and ultrafast imaging techniques, due to some intrinsic problems with EPI.