Whole-body PET/MRI for colorectal cancer staging: Is it the way forward?

Magnetic resonance imaging (MRI) is presently the modality of choice for the local staging of rectal cancer, with positron emission tomography (PET) being optional for the evaluation of colorectal cancer. Indeed, previous studies have demonstrated that liver MRI using hepatocyte-specific contrast agents can provide high diagnostic performance in the detection of colorectal cancer liver metastases. Recently, however, whole-body PET/MRI, which can provide information regarding both anatomy and metabolism, has been introduced to clinical imaging, and studies are under way to assess whether it can improve diagnostic performance for oncologic diseases as well as provide additional information regarding the disease phenotype and biology compared to conventional imaging modalities of computed tomography (CT), PET, or MRI. This review offers a brief overview of the technical considerations of the PET/MRI system, and the current status of imaging modalities in the staging of colorectal cancer. The potential of whole-body PET/MRI to improve the performance of colorectal cancer staging and the results of several recent studies will be discussed, and workflow considerations of whole-body PET/MRI for patients with colorectal cancer will be addressed. LEVEL OF EVIDENCE: 5 J. Magn. Reson. Imaging 2017;45:21-35.