Complexities of MRI and false positive findings.

MRI is a robust technology that allows for superior contrast of muscles, tissues, and bones within the body, which enables visualization of soft tissue pathology that cannot be seen with CT or plain film radiography. In order to appreciate the subtle (and sometimes not so subtle) intricacies of MRI, one must have a basic knowledge of the MRI physics involved to acquire an image, which leads to better recognition and a clearer understanding of some of the more important artifacts seen with MRI, including incomplete fat suppression, chemical shift, magnetic susceptibility, magic angle, partial volume, wraparound, and motion artifact. There are, however, many complexities and pitfalls in imaging the rheumatoid wrist. Normal anatomy such as capsular insertion sites and nutrient vessels can mimic erosion sites. The magic angle phenomenon can mimic tendon tears. Alignment abnormalities can be simulated based on wrist positioning. By having a solid understanding of the physics of magnetic resonance, anatomy, and the disease processes involved, many of these pitfalls can be avoided.