Motion artifacts can be due to physiologic causes (cardiac, respiratory, or pulsation of blood vessels) or to nonphysiologic motion. MRI motion artifacts are a significant problem often seen while imaging elderly patients. Artifacts from blood flow as well as cardiac (Fig. 38.12), ­respiratory, and patient motion all propagate in the phase-encoding direction, regardless of the direction of the motion. Motion results in blurring of moving tissues and also causes a structured noise pattern known as “ghosting” of brighter moving tissues in the phase-encoding direction (Rausch and Hendrick 2006; Pusey et al. 1986).

Ghosting is a form of phase-encoding artifact (Morris 2002; Harvey et al. 2007). To eliminate ghosting, a saturation band can be placed over the moving structure using a standard sequence. Reducing the repetition time may help reduce ghosting so that it is not propagated throughout the entire image, but doing so is often impractical in breast MRI.

Nonphysiologic motion is due to patient movement during the scan and can lead to unsatisfactory images affecting the entire series (Coulthard and Potterton 2000). Claustrophobia and patient anxiety remain the major causes of this artifact, which are more common in the elderly. Patient motion can be reduced by optimizing patient comfort: explain the study to the patient, reassure the patient before the examination, provide appropriate positioning with comfortable arm and head rests, optimize examination time, provide sedatives, use physical restraints only if absolutely necessary, provide earplugs and blankets, and maintain constant communication with the patient throughout the procedure (Rausch and Hendrick 2006).

Ferromagnetic metals (such as iron, nickel, cobalt) cause severe inhomogeneity in the magnetic field. Metallic objects, including surgical biopsy clips (Fig. 38.13a–c), jewelry, fasteners on clothing, or imaging equipment on or near the patient can disturb the main magnetic field, resulting in a local signal intensity void in the vicinity of the metal, often with a surrounding area of high signal intensity and image distortion (Ojeda-Fournier et al. 2007). If extensive, the artifact could hinder or preclude diagnosis of local recurrence at the lumpectomy site. On the other hand, the signal intensity void from percutaneous biopsy clips may help confirm the biopsy location (Haigh et al. 2000a; Genson et al. 2007; Finder et al. 1998) (Fig. 38.14a–d). A complete history of previous breast interventions, removal of all metallic objects from the patient and the immediate environment, and using titanium metallic markers are some remedial measures to minimize distortion.

Breast MRI can be compromised by breast tissue outside the coil. Breast tissue excluded from the coil may become folded and compressed, resulting in loss of symmetry. Poor visualization of axillary and retroglandular tissue can result from inadequate positioning of the breast in the coil; generally, this happens in the elderly due to sagging skin and glandular involution. Maintenance of bilateral symmetry is ensured by proper positioning of both breasts in the breast coil (Friedman et al. 2006).

At our institution, we often perform MRI for geriatric patients. Artifacts related to improper positioning tend to occur more frequently with elderly women, and hence, we recommend training mammographic technologists in proper positioning of patients and how to manipulate and position the breast within the compression paddles. Do not allow the patient to position herself in the coil. A radiology nurse or patient care assistant can also be trained to properly perform this task. A female staff member should be present during positioning.

Each breast should be centered from superior to inferior within the aperture of the dedicated breast coil. Areas of high signal intensity will result where breast tissue is adjacent to coil elements. The breasts should be pulled away from the chest wall into the two holes in the bilateral breast coil. As little breast tissue as possible should remain above the coil apertures. Improper positioning can result in compression of breast tissue between the chest wall and the center partition of the breast coil (Rausch and Hendrick 2006). Ideally, breast coils of various sizes will be available so that breast size can be matched to coil size. This option improves both patient comfort and image signal-to-noise ratios (Zhuo and Gullapalli 2006).