Introduction

In previous chapters we have seen how the image appearance can be manipulated by altering the sequence parameters such as TR, TE, TI and flip angle to give T1-weighted or T2-weighted contrast. We have examined the practical aspects of image acquisition: choosing the matrix size, field of view and slice thickness, the relationship between resolution and signal-to-noise ratio, and how, in practice, to avoid artefacts. Hopefully by now, you have got your head round spatial frequencies and spatial encoding. You will also have noticed by now that there are literally hundreds of pulse sequences. Every year at MR conferences around the world scores of new pulse sequences are launched and, in the tradition of the MR scientific community, all sporting stylish acronyms.

The trouble with acronyms is that despite sounding memorable and snappy (e.g. FLASH, HASTE, DRESS, SLIT-DRESS, DIET, PEPSI, etc.) it's virtually impossible to remember what they stand for, and therefore what they do. Moreover, MR manufacturers have the annoying tendency to use different names for the same things (a manufacturer conversion chart is given at the end of the chapter). Whilst the end-point of an acquisition can be expressed in terms of T1 or T2 weighting, there are numerous ways of achieving this — few destinations but many routes.