Dedicated extremity MR imaging of the knee: how low can you go?

Low-field strength, dedicated extremity MR imaging systems can provide clinically effective MR images at substantially lower costs, compared with high-field strength, whole-body MR imaging machines. Dedicated extremity units also reduce risks of patient safety and claustrophobia. The diagnostic performance of presently existing extremity MR scanners rivals that of high-field strength units. Focusing on the imaging of the knee joint, this article discusses issues of technique, imaging protocol, clinical roles, and economics, and reviews diagnostic efficacy studies.