PET/MR: still struggling to solidify clinical practice

There are two main questions that remain on the minds of those evaluating PET/MR for clinical practice: Is PET/CT just as good? If yes, isn’t PET/CT cheaper? These questions are answered with a resounding ‘sometimes,’ according to a review published Feb. 20 in the Journal of Nuclear Medicine.

In the current climate of healthcare cost-cutting, the question of cost effectiveness is on the minds of anyone working in the realm of molecular imaging. Luigi Mansi, MD, professor of nuclear medicine at Seconda Second University of Naples, Italy, and Andrea Ciarmiello, MD, researcher of nuclear medicine at Sant’Andrea Hospital La Spezia in Italy, described the biggest challenges to the modalities' adoption by clinicians for general practice. These included weighing the risks and preconceived notions of both modalities and deciding on the best possible strategy for individual patient management.

The wide availability of PET/CT and lower price tag make it hard to justify the extra cost of PET/MR outside of the realm of special cases.

“The real problem that PET/MR imaging has to overcome in its competition with PET/CT is the need to demonstrate at least some degree of superiority in the evidence-based world of medicine, in which PET/CT dominates because of its wider distribution and lower cost and because medical staff are more skilled in its use,” commented Mansi and Ciarmiello.

The areas of specialty where PET/MR could potential shine are in neuroimaging, due to the fact that it is not moving in space as it functions and because it is not affected by different variables such as measurements of fat or gas like other areas of the body. One issue that adds complexity to the mix is the fact that there are different sets of pros and cons for each individual PET/MR set up—whether simultaneous or sequential. The authors thought that simultaneous systems help against issues with misalignment, but comparative studies have yet to prove how much impact the difference in design has on diagnostic effectiveness between the two.

Another issue that complicates matters is that healthcare professionals already are trained in PET/CT and may not fully understand or appreciate the advantage of morphostructural or functional MR data for their patients. Other populations that may benefit the most from this technology are pediatric patients, those suffering from inflammatory disease and those with chronic diseases requiring repeat imaging such as rheumatoid arthritis, fever of unknown origin or Crohn's disease. All of these groups especially benefit from the substantially lower exposure to ionizing radiation associated with PET/MR, but again, more training and clinical studies are needed.  

“Either nuclear physicians or radiologists have to better understand the significance of the pathophysiologic information that can be acquired by MR imaging,” the authors added. “Without waiting for new experts who are able to evaluate the entire diagnostic content of fused PET/MR images, nuclear physicians need to educate themselves more widely and in greater depth not only on the morphostructural information provided by PET/MR imaging but also on the entire spectrum of functional information that can be gained.”