· 2007 ACR Guidelines Stress New Safety Information
· fMRI Progresses Post-Haste: A Round-Up
· Tech Zoom: MR Method Could Reduce Need for Knee Arthroscopy

2007 ACR Guidelines Stress New Safety Information

By Tobias Gilk

Though the ACR Guidance Document for Safe MR Practices: 2007 won’t be printed in the American Journal of Roentgenology (AJR) until June, the American College of Radiology (ACR) and AJR have decided to provide an advanced release of the full text online. This rare move was motivated by the desire to promulgate new safety information on a number of topics, including risks associated with the use of gadolinium.

The document, which replaces prior publications under the former title, ACR White Paper on MR Safety, contains significant revisions. The following is a brief summary of the more substantial changes:

  • Applicability: Language in prior editions left questions about whether the directives of the document applied equally to existing facilities and proposed facilities. The new document states that all MR sites, whether in existing buildings or proposed with new construction, are covered by the guidelines’ provisions. This extends beyond traditional clinical settings to include research MR.
  • Ferromagnetic detection: Though prior publications eschewed the use of conventional or “airport style” metal detectors, the MR Safety Committee recognizes a new type of ferromagnetic-only detector and endorses the use of this product as an adjunct to conventional screening practices.
  • Contraindicated implants discovered during scan: Many technologists have stories of discovering unknown or undisclosed implants during the scanning process. The document gives advice on how best to assess the risks to the patient in the scanner and remove him or her from the bore and Zone IV with the least risk.
  • FDA/ASTM standards: The Guidance Document acknowledges the labeling criteria developed by the American Standards for Testing and Materials (ASTM) and adopted by the FDA. The new “MR Safe,” “MR Conditional,” and “MR Unsafe” criteria replace the previous “MR Safe” and “MR Conditional” criteria. Basic instructions are included to aid MR facilities with identification of existing objects under the new standard, at least for projectile threats.
  • Resonant circuitry: The publication warns about the phenomenon of resonant circuitry, where electrically conductive materials—including implanted leads or wires—can undergo significant heating through electromagnetic excitation. Because of the frequencies at which different MR systems operate, lengths and configurations of electrically conductive materials will have significantly different risks on systems of different field strengths. This hazard is nonlinear—unlike projectile risks, if a particular configuration is determined to be safe at 3T, that same configuration may be extremely hazardous at higher or lower field strengths.
  • Gadolinium contrast and NSF: A new section focuses on nephrogenic systemic fibrosis (NSF), a condition that recently has been associated with the use of gadolinium-based MR contrast agents in patients with impaired kidney function. This section outlines the data from all documented cases at the time of publication and the most current thinking available from multiple sources of ongoing research, including the FDA.
  • Pacemakers: The section on pacemakers and implantable cardiac devices has been rewritten to clarify recent publications attesting to the safety of MR scanning of cardiac-device patients. This section highlights the fact that the FDA has not yet approved a single cardiac device as safe for MR scanning. Further, it identifies the extensive criteria that should be in place for MR scanning of cardiac-device patients.
  • Design guidelines: The new Appendix 2 sets forth guidelines specifically to address safety for the planning and design of MR suites. The appendix does not provide suite layout templates, but rather identifies a number of risk factors for patients, staff, and equipment that can be mitigated by effective MR facility planning and design.

The ACR Guidance Document for Safe MR Practices: 2007 and its predecessors have been the de facto standard of care for issues of safety in the MR suite for the past 5 years. This new document, which is poised to serve as a reference standard for a number of governmental and professional organizations, offers significant updates to best practice standards for clinical, operational, and physical components of safety in the MR suite.

The ACR Guidance Document for Safe MR Practices: 2007 can be downloaded from the ACR’s Web site at www.ACR.org/MR_safety.

Tobias Gilk is an imaging consultant for MRI-Planning in Kansas City, Mo, which specializes in MRI and multimodal suite planning. He is also an editor of the MRI Newsletter and a member of the American College of Radiology’s MR Safety Committee. For more information, contact .

fMRI Progresses Post-Haste: A Round-Up

By Cat Vasko

One of the most exciting subfields in radiology today, functional MRI (f MRI) is ever-expanding, thanks to the tireless work of researchers worldwide. A plethora of new studies demonstrate the versatility and clinical potential of the technique; technology is keeping pace, with vendors churning out a variety of products intended to streamline f MRI workflow and handle f MRI data.

Scientists at The Neuroscience Institute at University Hospital, Cincinnati, are integrating f MRI data into high-tech surgical navigation systems using iPlan BOLD (blood oxygen level dependent) MRI mapping from BrainLAB Inc, Westchester, Ill. Neurosurgeons at the University of Cincinnati are leveraging the iPlan system to help them identify active areas of the brain—a necessary step in planning any neurosurgery. This identification is traditionally performed using electrode stimulation, which can cause seizures and lengthens a surgical procedure by 30 to 60 minutes.

“This is a quantum leap in what we’re able to do,” said James Leach, MD, a neuroradiologist at The Neuroscience Institute. “It has significantly affected how neurosurgeons plan to do surgery and how much tumor they can remove while still avoiding critical areas of brain function.”

The VirtuaStim headset from Resonance Technology is aiding in f MRI exams.

Even the most immobile patient tends to shift position by 1 to 3 mm during an MR, and any patient movement can cause artifacts in the image. To minimize these motion artifacts, researchers at the Fraunhofer Institute for Computer Graphics, Rostock, Germany, have developed the PROMO technique to correct motion errors—while the scan is still in process.

“PROMO determines the patient’s current head position immediately prior to each individual scan,” explained project manager Christian Dold. “The system transmits the exact position to the scanner of the tomograph 60 times per second. Before the scanner takes another picture, it adjusts the scanning image section to the current head position.”

New research from the Department of Radiology and the Health Outcomes Policy and Economics Center at Miami Children’s Hospital has determined that the use of f MRI is effective when seeking to determine hemispheric language dominance in populations both with and without epilepsy. Using a Bayesian analysis of data from published literature, the study derived its likelihood ratios from the sensitivity and specificity of f MRI using electrocortical stimulation and the Wada test—behavioral testing after the injection of an anesthetic into the right or left internal carotid artery—as reference standards.

“The future of f MRI lies in research,” said Stephan G. Erberich, PhD, assistant professor of research radiology and biomedical engineering at Children’s Hospital Los Angeles. “Finding new f MRI paths is exciting.”

Because Erberich works with children, he understands firsthand the importance of patient comfort, always a concern with claustrophobia-inducing MRI scanners. “f MRI is usually best done at 3 Tesla,” he noted. “In order to have a usable system, patient comfort is important. If the patient becomes distracted, it can lead to false activations, making it more difficult for the radiologist to interpret the data.”

One solution to this problem is the VirtuaStim system from Resonance Technology Inc, Northridge, Calif. VirtuaStim is a headset, including goggles and earphones, on which patients can watch a favorite DVD or view instructional screens to streamline the imaging process. “When we do f MRI, we have patients tap their fingers or clench their hands, and we might even do foot pointing and flexing,” explained Linda Poff, RT, chief technician at the Rolling Oaks Radiology Center, Thousand Oaks, Calif. “We have visual, and we’re working on developing audio. We position the goggles so the patients can see; the screen turns green when we want the patients to do the activity, and [it turns] red when we want them to stop. It’s really very stress-free.”

Erberich notes that the implications of this ease-of-use are far-reaching, because it facilitates the kind of surgical planning in use at The Neuroscience Institute while addressing some of the same issues as the PROMO technique. “If you find brain activation to be dislocated from the typical reference location, that information is very helpful to the neurosurgeon so he can plan around the healthy tissue,” he said. “You need to know what is the most valuable tissue in the brain; otherwise, there’s always the risk you’ll damage the ability to move an arm or a leg.”

One difficulty that f MRI faces as it advances, according to Erberich, is a lack of understanding. “It’s not good enough just to have a software solution,” he said. “You must educate radiologists in how to interpret the data. f MRI is still more of a research tool than a modality operating at full clinical capacity; even though there are now reimbursement codes for f MRI, you can still see that a lot of learning is needed to interpret the data, especially from radiologists.”

Cat Vasko is associate editor of  Medical Imaging. For more information, contact .

MR Method Could Reduce Need for Knee Arthroscopy

Noninvasive assessment of articular cartilage integrity may be possible with a new MR method, highlighted by GE Healthcare, Waukesha, Wis, at the annual meeting of the American Academy of Orthopaedic Surgeons, held on February 14?18 in San Diego.

Available only on the GE Signa MRI system, the CartiGram application allows clinicians to visualize collagen fiber degradation by looking at the T2 relaxation times and generating a color map based on a scale of T2 values. As collagen breaks down, the increased mobility of water in the knee cartilage makes this form of imaging possible. Using the T2 color map, physicians can track changes in the composition of articular cartilage—in some cases, before changes in thickness can be seen.

Above left: This axial cartilage sensitive FSE image demonstrates uniform thickness of cartilage. Above right: This CartiGram image demonstrates prolongation of T2 values focally over the lateral facet, indicating abnormal collagen orientation.

“CartiGram is an extremely powerful diagnostic tool to noninvasively assess articular cartilage integrity,” said Hollis G. Potter, MD, chief of MRI at the Hospital for Special Surgery, New York City. “The quantitative T2 mapping has allowed us to discern cartilage breakdown prior to alteration in cartilage thickness.”

—C. Vasko