An editorial in the Journal of Nuclear Medicine (J Nucl Med. 2007 Mar;48(3):331. PMID: 17332606) argues that combination PET/MRI systems are the future and will supplant PET/CT:
In a number of ways, the path to PET/MRI has been reverse of that to PET/CT. The first PET/CT design emerged from industry–academia collaboration and was a prototype for human clinical use that eventually stimulated a commercial response and led to the development of PET/CT for imaging small animals. In contrast, PET/MRI began with the small-animal design and then, over a decade later, the first PET/MRI brain images were acquired on a dedicated prototype system, following an impressive industrial backing that far exceeded that of the early PET/CT developments.
A mere 2 y after the advent of commercial PET/CT, Johannes Czernin from UCLA, at the 2003 annual DGN meeting, commented that “PET/CT is a technical evolution that has led to a medical revolution.” Today, at the dawn of PET/MRI, it may be said that “PET/MRI is a medical evolution based on a technical revolution.” Although PET/CT appears to have replaced stand-alone PET for most oncologic indications, it is reasonable to assume that PET/MRI will be the preferred imaging option for neurologic and central nervous system indications. Without doubt, such dual-modality combinations are here to stay because they incorporate the diagnostic power of PET. Thus, PET/CT and PET/MRI, by virtue of their combined anatometabolic imaging, will lead to a “new-clear” medicine and the demise of “unclear” medicine.
This piece has somewhat messianic feel to it. I remember looking for PET/MRI systems at Seattle ISMRM last year, there were only two talks as far as I recall (maybe someone can dig up the abstracts, I’ve lent out my CD and it never returned, grr). Is it really true that there is widespread industry commitment to making dual-mode systems a reality? The engeineering challenge seems an order of magnitude more complex than with the marriage of PET/CT. It would be a different matter if someone had built a prototype and was publishing extensively on the advantages, but the above implies that the manufacturers are making a leap of faith.
And I’m not sure either that of all the hybrid technologies that could be pursued, PET/MRI even makes sense. For one thing, SPECT seems to be making some inroads, and is not tied down to one radioisotope the way PET is. And of course the PET reimbursement issue is notoriously complicated, with no sign of improvement on the horizon. SPECT/CT hybrids are beginning to get more sophisticated, and it wouldn’t be hard to imagine a SPECT/MRI system. Or even a MRI/CT system, which would really be a money-saver from an outpatient imaging standpoint. If the hybrid has application to bread and butter imaging as well as exotic research and oncology applications, it’s going to do better on the market.
None of this is to say that no one should go for PET/MRI; it would be unquestionably cool and powerful. But is it really the inevitable slam-dunk as it’s being made out to be?
(full text of article available online)