Evolving Characteristics of Gadolinium-Based Contrast Agents for MR Imaging: A Systematic Review of the Importance of Relaxivity.

Gadolinium-based contrast agents (GBCAs) are widely and routinely used to enhance the diagnostic performance of magnetic resonance imaging and magnetic resonance angiography examinations. T1 relaxivity (r1) is the measure of their ability to increase signal intensity in tissues and blood on T1-weighted images at a given dose. Pharmaceutical companies have invested in the design and development of GBCAs with higher and higher T1 relaxivity values, and "high relaxivity" is a claim frequently used to promote GBCAs, with no clear definition of what "high relaxivity" means, or general concurrence about its clinical benefit. To understand whether higher relaxivity values translate into a material clinical benefit, well-designed, and properly powered clinical studies are necessary, while mere in vitro measurements may be misleading. This systematic review of relevant peer-reviewed literature provides high-quality clinical evidence showing that a difference in relaxivity of at least 40% between two GBCAs results in superior diagnostic efficacy for the higher-relaxivity agent when this is used at the same equimolar gadolinium dose as the lower-relaxivity agent, or similar imaging performance when used at a lower dose. Either outcome clearly implies a relevant clinical benefit. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 3.

Dentate Nucleus Signal Intensity Increases Following Repeated Gadobenate Dimeglumine Administrations: A Retrospective Analysis.

Background Increased cerebral signal intensity (SI) has been reported in patients undergoing MRI with gadolinium-based contrast agents (GBCAs). Published data on gadobenate dimeglumine have been somewhat contradictory. Purpose To evaluate the relationship between dosage of gadobenate dimeglumine and SI change at MRI following multiple gadobenate dimeglumine administrations. Materials and Methods In this retrospective study, patients referred for clinically indicated brain MRI from January 2006 through May 2016 were evaluated for inclusion. Eligible patients were between 18 and 90 years old at their baseline brain MRI and had never received a GBCA, had undergone three or more MRI examinations with gadobenate dimeglumine, and had the baseline scan and another brain MRI scan available for comparison. The primary group consisted of patients with four or fewer supratentorial lesions smaller than 3 cm who underwent axial T1-weighted MRI at 1.5 T. One patient had also undergone prior radiation therapy. The secondary group consisted of patients with a history of brain radiation therapy or craniotomy who underwent 1.5-T and 3-T same-plane T1-weighted MRI (in any order). The SI for up to eight brain MRI examinations per patient was measured, and relative SI changes from baseline to interval scans were calculated. A subgroup analysis was performed to assess the gadobenate dimeglumine washout since the last gadolinium exposure. All patients had normal renal and liver functions. Linear mixed regression analyses were performed for variables with P < .05. Results In 43 patients (14 men, 29 women; median age, 49 years; age range, 25-73 years), the dentate nucleus (DN)-to-middle cerebral peduncle (MCP) SI ratio showed a mean increase of 6.7% ± 3.9 in the primary group and 4.0% ± 2.7 in the secondary group (both P < .001) following the administration of 134 mL ± 141 gadobenate dimeglumine over 55 months ± 35.2. The DN/MCP SI ratio increased linearly with the amount of gadobenate dimeglumine, with a mean increase of 0.015% ± 0.004 per 1 mL of gadobenate dimeglumine (R2 = 0.3, P < .001). Conclusion In patients receiving multiple doses of gadobenate dimeglumine, a linear relationship existed between gadobenate dimeglumine administrations and an increase in the dentate nucleus-to-middle cerebral peduncle signal intensity ratio at MRI. © RSNA, 2020 See also the editorial by McDonald and Kallmes in this issue.

ACR guidance document on MR safe practices: Updates and critical information 2019.

The need for a guidance document on MR safe practices arose from a growing awareness of the MR environment's potential risks and adverse event reports involving patients, equipment, and personnel. Initially published in 2002, the American College of Radiology White Paper on MR Safety established de facto industry standards for safe and responsible practices in clinical and research MR environments. The most recent version addresses new sources of risk of adverse events, increases awareness of dynamic MR environments, and recommends that those responsible for MR medical director safety undergo annual MR safety training. With regular updates to these guidelines, the latest MR safety concerns can be accounted for to ensure a safer MR environment where dangers are minimized. Level of Evidence: 1 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:331-338.

Safety Considerations of 7-T MRI in Clinical Practice.

Although 7-T MRI has recently received approval for use in clinical patient care, there are distinct safety issues associated with this relatively high magnetic field. Forces on metallic implants and radiofrequency power deposition and heating are safety considerations at 7 T. Patient bioeffects such as vertigo, dizziness, false feelings of motion, nausea, nystagmus, magnetophosphenes, and electrogustatory effects are more common and potentially more pronounced at 7 T than at lower field strengths. Herein the authors review safety issues associated with 7-T MRI. The rationale for safety concerns at this field strength are discussed as well as potential approaches to mitigate risk to patients and health care professionals.

Gadolinium Retention: A Research Roadmap from the 2018 NIH/ACR/RSNA Workshop on Gadolinium Chelates.

Gadolinium-based contrast agents (GBCAs) have revolutionized MRI, enabling physicians to obtain crucial life-saving medical information that often cannot be obtained with other imaging modalities. Since initial approval in 1988, over 450 million intravenous GBCA doses have been administered worldwide, with an extremely favorable pharmacologic safety profile; however, recent information has raised new concerns over the safety of GBCAs. Mounting evidence has shown there is long-term retention of gadolinium in human tissues. Further, a small subset of patients have attributed a constellation of symptoms to GBCA exposure, although the association of these symptoms with GBCA administration or gadolinium retention has not been proven by scientific investigation. Despite evidence that macrocyclic GBCAs show less gadolinium retention than linear GBCAs, the safety implications of gadolinium retention are unknown. The mechanism and chemical forms of gadolinium retention, as well as the biologic activity and clinical importance of these retained gadolinium species, remain poorly understood and underscore the need for additional research. In February 2018, an international meeting was held in Bethesda, Md, at the National Institutes of Health to discuss the current literature and knowledge gaps about gadolinium retention, to prioritize future research initiatives to better understand this phenomenon, and to foster collaborative standardized studies. The greatest priorities are to determine (a) if gadolinium retention adversely affects the function of human tissues, (b) if retention is causally associated with short- or long-term clinical manifestations of disease, and (c) if vulnerable populations, such as children, are at greater risk for experiencing clinical disease. The purpose of the research roadmap is to highlight important information that is not known and to identify and prioritize needed research. ©RSNA, 2018 Online supplemental material is available for this article .

Frequency of acute longus colli tendinitis on CT examinations.

PURPOSE: We attempted to determine the frequency of acute longus colli tendinitis on diagnostic CT imaging performed at a large multicenter health care system. By correlating with the pre-imaging clinical information, we investigated which patient presentations should lead the radiologist to increased suspicion for this condition. METHODS: Images from a total of 8101 adult CT examinations of the neck and cervical spine performed over a 3-month period were evaluated by researchers independent of the original clinical report. Clinical information available at the time of imaging was reviewed and assigned to one of five categories. Frequency of the condition was calculated by sex and clinical presentation. This retrospective study with waiver of consent and waiver of HIPPA was approved by our IRB. RESULTS: Nine positive scans were found for an overall frequency of 1.1 per 1000 examinations. The frequency was significantly higher (11.4 per thousand) on scans performed of patients presenting without history of recent trauma, concern for tumor, suspected postoperative complication, or clinical signs of infection localized to the neck. Although frequency in males was higher than in females, this did not reach statistical significance. In no positive or negative case was longus colli tendinitis considered in the pre-imaging documentation. CONCLUSIONS: Findings of acute longus colli tendinitis on CT examination generally occur in the absence of prior mention of this condition in the medical record. The radiologist should be particularly alert for this diagnosis when a patient presents with rapid-onset neck pain without a clear history of recent trauma or other etiologies.

Standardized MR terminology and reporting of implants and devices as recommended by the American College of Radiology Subcommittee on MR Safety.

Considerable confusion exists among the magnetic resonance (MR) imaging user community as to how to determine whether a patient with a metal implanted device can be safely imaged in an MR imaging unit. Although there has been progress by the device manufacturers in specifying device behavior in a magnetic field, and some MR imaging manufacturers provide maps of the "spatial gradients," there remains significant confusion because of the lack of standardized terminology and reporting guidelines. The American College of Radiology, through its Subcommittee on MR Safety, has proposed standardized terminology that will contribute to greater safety and understanding for screening metal implants and/or devices prior to MR imaging.

Planning an MR suite: What can be done to enhance safety?

Magnetic resonance imaging (MRI), frequently touted as the "the safe modality," suffers from significant, and growing, numbers of preventable adverse events. Improvements in MR safety can result from enhancements to expected operational elements: training, screening, and patient-management protocols. Less frequently considered is the safety benefits that may be realized through smart design of MR facilities. Through conscientious and thorough prospective site planning involving MR staff and radiologists in the design process for MR physical facilities, MR providers can have a positive impact on improving safety as well as efficiency for the benefit of their patients, for ancillary healthcare workers, and for themselves.

MR system operator: recommended minimum requirements for performing MRI in human subjects in a research setting.

This article is intended to provide guidelines for the minimum level of safety and operational knowledge that an MR system operator should exhibit in order to safely perform an MR procedure in a human subject in a research setting. This article represents the position of the International Society for Magnetic Resonance in Medicine (ISMRM) regarding this important topic and was developed by members of this society's MR Safety Committee.

Assessment of rates of acute adverse reactions to gadobenate dimeglumine: review of more than 130,000 administrations in 7.5 years.

OBJECTIVE: The purpose of this study was to determine the incidence of adverse events associated with gadobenate dimeglumine over 7.5 years in a major hospital system consisting of both academic and community hospitals. SUBJECTS AND METHODS: As part of a regular and continuous prospective quality assurance project, MRI technologists contemporaneously recorded all gadolinium-based contrast administrations and any associated adverse reactions, including type of reaction and treatment rendered, between August 1, 2005, and March 14, 2013. Weekly data review was performed by the director of MRI services, who evaluated data both by individual site and by comparison among the participating hospitals and sites within the hospital system. Comparison between reaction rates at different sites was performed with a chi-square test. RESULTS: Over 7.5 years, 132,252 doses of gadobenate dimeglumine were administered, and 236 reactions were recorded (0.18% of contrast-enhanced examinations). Of these, 133 (56.4% of all adverse reactions) required treatment and 12 (5.1%) qualified as serious. Reaction rates were significantly different between academic (0.23%) and community (0.07%) hospitals (p<0.001). Reaction rates were higher in the initial years of the study, tapering to a lower baseline rate, which was maintained over more than 5 years. The findings were consistent with the Weber and Lalli effects reported in the literature on other pharmaceutical agents. CONCLUSION: Rates of adverse reactions to gadobenate dimeglumine recorded over 7.5 years were comparable to those reported for other gadolinium-based contrast agents examined over smaller time ranges and populations. The findings reinforce the relatively robust safety profile of this agent.

Utility of additional CT examinations driven by completion of a standard trauma imaging protocol in patients transferred for minor trauma.

Many clinicians order focused computed tomography (CT) examinations for trauma patients based on history and physical examinations. Trauma patients transferred to our level I trauma center undergo an extensive, nonfocused standard trauma CT protocol. We hypothesize that the use of the standard trauma CT protocol does not contribute significant clinical information for patient care when compared with CT examinations based on history and physical examination. We aim to quantify the utility of the additional CT examinations required by our institution's trauma protocol compared with emergent CT examinations dictated by the patient's history and physical examination findings. In this IRB-approved study, we retrospectively evaluated 132 trauma patients transferred to our center who underwent additional CT examinations as determined by fulfillment of our institution's standard trauma CT protocol. The emergency radiologist evaluated the CT examinations acquired after the patient's transfer to determine if there were any additional acute findings that were identified on these additional examinations compared with the initial assessment undertaken at the outside institution. A total of 101 patients transferred to our trauma center met inclusion criteria. The majority of these patients sustained minor trauma. The standard trauma protocol generated 474 negative CT examinations in 101 patients. In seven patients, there were unexpected acute findings. However, these unexpected acute findings did not change clinical management in any of the patients. After initial evaluation, the acquisition of additional nonfocused CT examinations based on the standard trauma CT protocol provides little useful clinical information in patients who are transferred for minor trauma. Rather, CT utilization should be based on clinical findings. Replacement of standard trauma CT protocol with focused CT examinations in trauma patients is a way to curtail overutilization, thereby decreasing health care cost and the amount of patient radiation exposure.

Interrelating sentinel event alert #38 with the ACR guidance document on MR safe practices: 2013. An MRI accreditation safety review tool.

When, in 2008, the Joint Commission released its Sentinel Event Alert #38 regarding MRI safety, it joined the ACR's Guidance Document on MR Safe Practices as one of two radiology best-practice documents establishing MR safety protections. However, particularly for MR providers who held both modality-level accreditation from the ACR, and enterprise-level accreditation from the Joint Commission, there has been confusion about which institution's standard takes precedence, or whether there are inherent conflicts between the two. With the release of the 2013 update to the ACR Guidance Document on MR Safe Practices, the authors have cross-referenced the performance criteria of both MR safety standards, and correlated the ACR Guidance Document performance criteria with the Joint Commission's Environment of Care standards.

ACR guidance document on MR safe practices: 2013.

Because there are many potential risks in the MR environment and reports of adverse incidents involving patients, equipment and personnel, the need for a guidance document on MR safe practices emerged. Initially published in 2002, the ACR MR Safe Practices Guidelines established de facto industry standards for safe and responsible practices in clinical and research MR environments. As the MR industry changes the document is reviewed, modified and updated. The most recent version will reflect these changes.