A hazy memory of a strange metallic taste

This is essentially a dictionary of MRI (magnetic resonance imaging) rather than a textbook. It comprises an alphabetically ordered set of short entries, typically two or three sentences, about terms of relevance to the understanding of MRI in medicine. It is of small paperback size and reasonably priced. It claims to be aimed at the medical professional users of MRI so they can look up a term with which they are unfamiliar and could well be used as an aid when reading journal papers.

There are relatively few illustration, and the book contains few equations or references to the literature. But is it helpful?

I looked up DWI - diffusion-weighted imaging. The entry correctly references DTI, diffusion tensor imaging, with a short description of what a diffusion tensor is. But it does not indicate why it might be of clinical interest. Reference is also made to tractography (looking for neural connections in the brain) and also fractional anisotropy (FA), which contains an equation showing how FA can be derived from the eigenvalues of the diffusion tensor. I am afraid that if you did not already know these things, they would probably still be largely incomprehensible.

Another example is the term "navigator echo", which is defined in a single (unhelpful) sentence. However, there are a number of interesting entries for less technical terms, one example being "metallic taste" or the phenomenon of observing an unpleasant taste, anecdotally noted at high magnetic field strengths. Another is "mag lag" or the "urban myth" of memory loss caused by exposure to high magnetic fields. By and large, the definitions are accurate and up to date. A surprising omission concerns the current arguments about safety as related to recent European directives. As a general medical physicist, I found the book quite helpful but fear that it falls between stools by being too technical for the clinician and not detailed enough for the specialist. It is of little value to the public, including patients undergoing MRI.

Perhaps the worst failure of the book is that it is rather dull and would certainly have been improved by greater use of illustrations and images and the inclusion of more (relevant) clinical material.

Andrew Todd-Pokropek is professor of medical physics and bioengineering, University College London.