Signal intensity artifacts in clinical MR imaging

Signal intensity artifacts are often encountered during magnetic resonance (MR) imaging. Occasionally, these artifacts are severe enough to degrade im age quality and interfere with interpretation. Signal intensity artifacts i nherent in local coil imaging include intensity gradients and local intensi ty shift artifact. The latter can be minimized but not eliminated with opti mal coil design and tuning. Improper coil or patient positioning can produc e subtle or, in some cases, severe signal intensity artifacts, and each is easily corrected. Signal intensity artifacts and image degradation can also occur in a perfectly functioning coil if protocols are not optimized. Fail ure of decoupling mechanisms can produce signal intensity artifacts that wi ll not respond to protocol optimization and will worsen with gradient imagi ng. Improper coil tuning manifests as a shading artifact that can mimic oth er findings. Signal-degrading artifacts may be caused by a ferromagnetic fo reign body in the imager. Signal intensity artifacts can also result from p erforming ultrafast imaging with coils that were not designed for this type of imaging or from MR imaging system malfunction. Familiarity with the var ious causes of signal intensity artifacts is necessary to maintain optimal image quality and should be required as part of any MR imaging quality assu rance program.