Introduction: Hybrid imaging is now widely accepted in cancer imaging with increasing use of PET/CT in clinical practice. The advantages of MRI compared to CT with respect to radiation exposure and soft-tissue lesion contrast, as well as the possibility of performing more sophisticated assessment of tissue chemistry, have stimulated interest in the development of hybrid PET/MR imaging systems.
Objective: While PET/CT simultaneously increases diagnostic quality and patient throughput compared to PET, offsetting the higher cost of this instrumentation, PET/MRI will likely be more expensive again and is currently unlikely to be competitive in terms of throughput.
Discussion: To realize the unique potential advantages of combined PET/MRI, we believe that PET/MRI devices should be designed to be a complementary tool running in parallel with PET/CT. The use of PET/CT for whole-body screening could identify lesions requiring more detailed anatomical and biological characterization. Selection of only those patients and those lesions for which this information is critical for treatment selection and planning will provide efficient and easily justified use of what will, for the foreseeable future, be an expensive and limited resource.