MR physics of body MR imaging

Body MR imaging ha progressed significantly in recent years due to a number of developments in the MR pulse sequence design and acquisition techniques [1]. This article reviews some of the challenges of MR imaging in the body, and describes a number of proposed solutions. Successful MR imaging in the body requires that a number of conditions be satisfied. These include the need for high-resolution images, large field of view (FOV), and insensitivity to field inhomogeneities and motion. The need to satisfy all of these requirements make imaging of the body much more difficult than imaging of the head or extremity, which may require that only a small subset of these conditions be satisfied. Motion is one of the primary challenges in body imaging because it produces artifacts from many sources including movement of the cardiac wall, blood flow effects in the chambers or vessels, respiratory effects, and peristalsis. Many advances have been made in body imaging that minimize these problems and satisfy the basic requirements for successful image acquisition. To understand these methods and develop improved methods, it is necessary to first understand the underlying physics of MR signal behavior. This article focuses on the physics of MR, in particular, the process of data acquisition in MR and the influence of motion on different acquisition strategies.