While MR techniques are widely used in cardiovascular imaging, involuntary motion of the heart can result in image degradation including blurring, ghosting and misregistration artifacts.

In a review article in the February issue of Radiology (RSNA.org/radiology), Andrew D. Scott, M.Sc., of the Royal Brompton Hospital in London, and colleagues describe the type and extent of heart motion due to the cardiac and respiratory cycles and discuss methods of eliminating or reducing image degradation during each cycle.

Magnitude MR images of a cross section of aortic valve at two time points (t) in the cardiac cycle, with and without section tracking (STrack). Section tracking enables valve to be seen with greater clarity at both time points. Arrows in b highlight left coronary root, which has moved into the imaging frame since a but is rightly absent in d.
(Radiology 2009;250:331–351) © RSNA, 2009. All rights reserved. Printed with permission.

Strategies detailed for the cardiac cycle include:

• Electrocardiogram gating

• Subject-specific acquisitions windows

• Section tracking

Strategies outlined for the respiratory cycle include:

• Breath holding

• Respiratory gating

• Section tracking

• Phase-encoding ordering

• Subject-specific translational models

Reviewers also discuss advanced techniques, including tracking imaging planes throughout the cardiac cycle and correcting blood velocities for through-plane motion, as well as image-based registration schemes that eliminate the need for navigator echoes and respiratory motion models.

"Several methods of reducing the acquisition time while maintaining much of the image quality exist," the authors conclude. "Many of the more recently developed of these techniques do not rely on an inaccurate generalized model, and some include correction for non-rigid tissue deformation and hysteresis."

MR Imaging in Patients at Risk for Developing Nephrogenic Systemic Fibrosis: Protocols, Practices, and Imaging Techniques to Maximize Patient Safety

This article meets the criteria for 1.0 AMA PRA Category 1 Credit™.

An article in the January-February issue of RadioGraphics (RSNA.org/radiographics), reports that nephrogenic systemic fibrosis (NSF) is a rare but potentially debilitating or even fatal fibrosing condition, most often affecting the skin but now also recognized to involve multiple organs.

Noncontrast MR imaging diagnosis of osteomyelitis. (a) Precontrast long-axis T1-weighted MR image of the right foot shows loss of signal intensity in the head of the first metatarsal bone. (b) Precontrast long-axis fat-saturated T2-weighted MR image shows high signal intensity in the first metatarsal head. In the appropriate clinical setting, the findings in a and b are consistent with osteomyelitis. (c) Postcontrast long-axis fat-saturated T1-weighted MR image shows mild enhancement of the first metatarsal head. This finding does not contribute to the diagnosis of osteomyelitis, which was already made with noncontrast techniques.

NSF is associated with renal failure after the administration of gadolinium in patients with renal insufficiency.

"Although gadolinium-enhanced MR angiography was once considered one of the safer imaging procedures, studies documenting the presence of gadolinium in the tissue of patients with NSF have forced the radiology community to rethink its imaging practices," Krishna Juluru, M.D., of Weill Cornell Medical Center in New York, and colleagues report.

In the article, the authors:

• List the risk factors for developing NSF

• Discuss the advantages and disadvantages of various MR contrast agents in at-risk patients

• Describe contrast-enhanced and non-enhanced MR imaging techniques that can help minimize risk for developing NSF

Authors stress the importance of developing a comprehensive approach for optimal patient safety within the setting of NSF.