Whole-body magnetic resonance imaging: an effective and underutilized technique

Radiol Bras. 2015 Mai/Jun;48(3):IX–X Among others, one particular advantage of whole-body magnetic resonance imaging (wbMRI) is the absence of ionizing radiation, a factor that is especially relevant in pediatric imaging, due to the increased sensitivity of children to ionizing radiation. Another important advantage is the high accuracy of the method in the investigation of bone marrow and solid organs, besides the better contrast resolution for soft tissues as compared with other techniques. There is a particular interest in the role played by this method in the field of pediatric oncology (for example, in cases of lymphoma, neuroblastoma, sarcoma and Langerhans’ cell disease). Main disadvantages of wbMRI include the relatively long images acquisition time and motion artifacts (requiring patient’s cooperation or general anesthesia). However, the developments in computational and imaging techniques, including additional sequences (fat saturation, diffusion-weighted imaging and use of gadolinium enhancement) have reduced the impact of some of these challenges. An accurate staging and a careful follow-up are essential for patients with neoplastic disease, to evaluate the prognosis and make a decision about the most appropriate therapeutic approach to be adopted. Imaging methods play a fundamental role in such evaluation steps. Computed tomography (CT) and, recently, positron emission tomography (PET/CT) has been widely utilized as an integrated diagnostic approach in cases of systemic cancer. In particular, up to the present moment, the use of the radiopharmaceutical 18-fluorodeoxyglucose (FDG) has given a relevant contribution in the Field of oncological imaging and has widely been indicated. However, such technique utilizes high ionizing radiation doses and presents some limitations regarding spatial and contrast resolution, besides false negative and false positive results in the evaluation of the skull and upper abdomen, already described in the literature. For these reasons, MRI, that is free from ionizing radiation, and presenting high contrast and spatial resolution for soft tissues, is an useful application for detecting and staging malignant tumors and can overcome the limitations of FDG-PET/ CT. In a recent meta-analysis, wbMRI showed to be as effective as PET/CT in oncology. This same study suggests that larger prospective studies and, particularly, a cost-effectiveness analysis comparing the methods are necessary to determine which should