Realistic phantoms for quantitative MR: the need and a proposal (the B1 sleeve)

Quantitative MR (qMR) has offered direct access to in-vivo biology and physiology for over three decades, yet it has failed to translate into the clinic. Why is this? The development of suitable phantoms is a key stage in the evolution of qMR, and here a systematic categorisation is proposed. Currently there is much attention paid to creating simple head phantoms containing materials with metrologically traceable values of MR quantities. However these are usually unrealistic; many of the disrupting phenomena present in clinical imaging are absent. Good performance with a simple traceable phantom is a necessary but not sufficient requirement for the establishment of good in-vivo measurement performance. There is therefore a premium on developing realistic phantoms. A proposal made for a more realistic body phantom that includes RF B₁ imperfections. It consists of lossy annuli placed around a standard head phantom. Other confounding phenomena could be identified, possibly built into an appropriate annulus around a simple head phantom, to form realistic phantoms; these would enable validation of qMR methods and translation to the clinic. The concept is probably applicable to other quantitative diagnostic imaging modalities.