PET/MR imaging could improve accuracy, patient care over PET/CT

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In comparison with same-day PET/CT, PET/MR imaging could allow for more accurate staging of patients with cancer in certain populations, as well as improve patient care, according to a study published in the December 2013 issue of Radiology.

The advent of combined, hybrid PET/MR scanners in 2011 allowed for the benefits of each modality to be situated in one place. However, the scanner’s potential value and role in clinical practice are still being demonstrated.

“MR imaging has a superior soft-tissue contrast-to-noise ratio when compared to that of CT, which enables detailed evaluation of soft tissues with the abdomen, pelvis, and central nervous system,” wrote the study’s lead author, Onofrio A. Catalano, MD, of the SDN Istituto Ricerca Diagnostica Nucleare of Naples, Italy, and colleagues. “Moreover, MR imaging affords us the opportunity to evaluate tissue function with diffusion-weighted imaging, MR spectroscopy, and perfusion-weighted imaging. These MR features, combined with the metabolic information from PET, suggest the potential for PET/MR imaging to have an extensive effect on patient care.”

The authors designed a retrospective study to compare the relative clinical impact of PET/MR imaging to that of PET/CT performed on the same day in patients with cancer. The study’s population was comprised of 134 patients with cancer with a non-central nervous system primary neoplasm. Participants underwent same-day fluorodeoxyglucose (FDG) PET/CT and FDG PET/MR imaging.

The imaging studies were independently interpreted by teams of radiologists and nuclear medicine physicians. The referring physician then classified differences between PET/CT and PET/MR observations as either findings that affected clinical management or findings that did not affect clinical management.

Results indicated that two of the 134 patients had findings  that affected clinical management on PET/CT but not on PET/MR. On the other hand, findings that affected clinical management noted on the PET/MR studies but not noted on the PET/CT studies were found in 24 of the 134 patients. The discrepancies between findings that affected clinical management detected with PET/MR imaging over those detected with PET/CT were statistically significant.

“In summary, in 17.9 percent of the patients with cancer in our selected population, PET/MR imaging furnished information, especially on staging of the liver, lymph nodes, and pelvis, that was unavailable with PET/CT and that affected clinical management,” concluded the authors.