In one embodiment, a ferromagnetic frame for use in an MRI system comprises first and second opposing ferromagnetic elements magnetically coupled by a flux return path. First and second poles are provided, separated by a distance to define an imaging volume therebetween. The first pole is movably supported with respect to the first ferromagnetic element to vary the distance between the first and second poles. The first pole may have a first, imaging position and a second position wherein the first pole is farther from the second pole than in the first position. When the first pole is in the first, imaging position, a gap is provided between the first pole and the first ferromagnetic element. The second pole is supported by the second ferromagnetic element. When the first pole is in the second position, the imaging volume is made larger, providing room for medical personnel to access a patient. Performance of medical procedures on the patient is thereby facilitated. The flux return path may be two or more opposing ferromagnetic posts or plates, for example. Magnet assemblies, MRI systems, methods of conducting an MRI procedure and methods of conducting a medical procedure are also disclosed.