Bone marrow magnetic resonance imaging (MRI): morphological and functional features from reconversion to infiltration.

Bone marrow is a dynamic organ with variable composition in relation to age or pathophysiological changes. Magnetic resonance imaging (MRI) is the technique of choice to assess the different components of the bone marrow based on the different information provided by the different characteristics of the MRI sequences. This article provides an overview of the MRI appearances of normal and abnormal bone marrow. We review the MRI features of normal developmental red marrow- to yellow-conversion, reconversion and physiologic conditions. We review the key imaging techniques used in assessing bone marrow pathology in MRI, including T1-weighted, T2-weighted, Dixon chemical shift imaging and diffusion-weighted imaging, as well as dynamic contrast-enhanced (DCE) MRI. It is discussed the bone marrow characteristics in the different morphological and functional MRI sequences from the normal or abnormal conditions such as; infiltration (metastases), proliferation [multiple myeloma (MM)], vascular edema/necrosis and postreatment changes. We show the different MRI features to differentiate physiological processes from pathological processes in order to provide effective diagnoses, as well as to evaluate the optimal therapeutic monitoring assessment. Insights from recent advancements in imaging technology and emerging MRI techniques are also discussed, providing a comprehensive overview of bone marrow MRI and its clinical implications. This review provides a useful tool for radiologist to decide normal or abnormal findings from the analysis of bone marrow MRI; in order to manage and take decisions that will depend on the imaging findings. The optimal analysis of bone marrow MRI requires knowledge of the physiology of the bone marrow to interpret properly the pathology and avoid diagnostic errors.