Linear Gadolinium-Based Contrast Agents Are Associated With Brain Gadolinium Retention in Healthy Rats

Pediatric Brain: No Increased Signal Intensity in the Dentate Nucleus on Unenhanced T1-weighted MR Images after Consecutive Exposure to a Macrocyclic Gadolinium-based Contrast Agent

Purpose To determine the effect of at least five serial injections of the macrocyclic gadolinium-based contrast agent (GBCA) gadoterate meglumine on the signal intensity (SI) of the dentate nucleus (DN) of the pediatric brain on nonenhanced T1-weighted magnetic resonance (MR) images. Materials and Methods In this retrospective, institutional review board-approved study, 41 pediatric patients (age range, 3-17 years) who were imaged in at least five consecutive 1.5-T MR examinations with the exclusive use of gadoterate meglumine (plus a final additional nonenhanced MR imaging examination) were evaluated. SI ratio differences between the first and last MR examination were calculated for DN-to-pons and DN-to-middle cerebellar peduncle (MCP) ratios in a region-of-interest-based analysis, and one-sample t tests were used to examine if the SI ratio differences differed from 0. Bayes factors were calculated to quantify the strength of evidence for each test. Results Patients underwent a mean of 8.6 ± 3.9 GBCA administrations (mean accumulated dose, 32.07 mmol ± 17.62, with an average of 16.7 weeks ± 7.9 between every administration). Both ratio differences did not differ significantly from 0 (DN-to-pons ratio: -0.0012 ± 0.0101, P = .436; DN-to-MCP ratio: 0.0007 ± 0.0088, P = .604), and one-sided Bayes factors provided substantial evidence against an SI ratio increase (0.10 for DN-to-pons ratio; 0.27 for DN-to-MCP ratio). Conclusion No increase of the SI in the DN was found after a mean of 8.6 serial injections of the macrocyclic GBCA gadoterate meglumine in pediatric patients, confirming previous studies that did not find this effect after serial injections of macrocyclic GBCAs in adults. ^© RSNA, 2017.

Is There Long-term Signal Intensity Increase in the Central Nervous System on T1-weighted Images after MR Imaging with the Hepatospecific Contrast Agent Gadoxetic Acid? A Cross-sectional Study in 91 Patients

Purpose To evaluate whether there is T1-weighted signal intensity (SI) increase in the dentate nucleus (DN) and globus pallidus (GP) in relation to the middle cerebellar peduncle (MCP), pons, and thalamus after repeated administration of the liver-specific contrast agent gadoxetic acid. Materials and Methods This was an institutional review board-approved, prospectively conducted (written informed consent acquired), cross-sectional study performed in a consecutively selected patient group (n = 91; patients received one to 37 doses of gadoxetic acid) and a control group (n = 52; subjects had never received injections of gadolinium-based contrast agent) examined with a standard T1-weighted two-dimensional spin-echo pulse sequence of the brain at 1.5 T. DN/MCP, DN-to-pons, GP-to thalamus, and GP-to-cerebrospinal fluid ratios were measured and compared by using the nonparametric Kruskal-Wallis test, corresponding pairwise tests, and Spearman correlation. Results DN/MCP (ρ = 0.51, P < .0001) and DN-to-pons (ρ = 0.41, P = .0001) ratios correlated positively with the number of previous administrations of gadoxetic acid. DN/MCP and DN-to-pons ratios were significantly different between control subjects (medians of 1.016 and 1.034, respectively) and patients with more than 10 gadoxetic acid administrations (1.038 [P < .0001] and 1.053 [P = .0100], respectively), whereas no significant difference was found in the groups with five to 10 (1.029 [P = .053] and 1.044 [P = .072], respectively) and fewer than five (1.014 [P = .420] and 1.030 [P = .595], respectively) gadoxetic acid administrations. GP-to-thalamus ratios differed significantly between the study and control groups (P < .0001), whereas no significant correlation was found for GP-to-thalamus ratios and number of gadoxetic acid administrations (ρ = 0.13, P = .2304). Conclusion Results show a significant correlation between the number of gadoxetic acid administrations and the increase of SI in the DN, which is likely due to gadolinium retention. ^© RSNA, 2017.

The stability of gadolinium-based contrast agents in human serum: A reanalysis of literature data and association with clinical outcomes

PURPOSE

To reanalyze literature data of gadolinium (Gd)-based contrast agents (GBCAs) in plasma with a kinetic model of dissociation to provide a comprehensive assessment of equilibrium conditions for linear GBCAs.

METHODS

Data for the release of Gd from GBCAs in human serum was extracted from a previous report in the literature and fit to a kinetic dissociation/association model. The conditional stabilities (logK_cond) and percent intact over time were calculated using the model rate constants. The correlations between clinical outcomes and logK_cond or other stability indices were determined.

RESULTS

The release curves for Omniscan®, gadodiamide, OptiMARK®, gadoversetamide Magnevist® and Multihance® were extracted and all fit well to the kinetic model. The logK_conds calculated from the rate constants were on the order of ~4-6, and were not significantly altered by excess ligand or phosphate. The stability constant based on the amount intact by the initial elimination half-life of GBCAs in plasma provided good correlation with outcomes observed in patients.

CONCLUSIONS

Estimation of the kinetic constants for GBCA dissociation/association revealed that their stability in physiological fluid is much lower than previous approaches would suggest, which correlates well with deposition and pharmacokinetic observations of GBCAs in human patients.

3D Whole Heart Imaging for Congenital Heart Disease

Three-dimensional (3D) whole heart techniques form a cornerstone in cardiovascular magnetic resonance imaging of congenital heart disease (CHD). It offers significant advantages over other CHD imaging modalities and techniques: no ionizing radiation; ability to be run free-breathing; ECG-gated dual-phase imaging for accurate measurements and tissue properties estimation; and higher signal-to-noise ratio and isotropic voxel resolution for multiplanar reformatting assessment. However, there are limitations, such as potentially long acquisition times with image quality degradation. Recent advances in and current applications of 3D whole heart imaging in CHD are detailed, as well as future directions.

No Signal Intensity Increase in the Dentate Nucleus on Unenhanced T1-weighted MR Images after More than 20 Serial Injections of Macrocyclic Gadolinium-based Contrast Agents

Purpose To determine the effect of more than 20 serial injections of macrocyclic gadolinium-based contrast agents (GBCAs) on the signal intensity (SI) of the dentate nucleus (DN) on unenhanced T1-weighted magnetic resonance (MR) images. Materials and Methods In this retrospective, institutional review board-approved study, 33 patients who underwent at least 20 consecutive MR imaging examinations (plus an additional MR imaging for reference) with the exclusive use of macrocyclic GBCAs gadoterate meglumine and gadobutrol were analyzed. SI ratio differences were calculated for DN-to-pons and DN-to-middle cerebellar peduncle (MCP) ratios by subtracting the SI ratio at the first MR imaging examination from the SI ratio at the last MR imaging examination. One-sample t tests were used to examine if the SI ratio differences differed from 0, and Bayes factors were calculated to quantify the strength of evidence for each test. Results Patients underwent a mean of 23.03 ± (standard deviation) 4.20 GBCA administrations (mean accumulated dose, 491.21 mL ± 87.04 of a 0.5 M GBCA solution) with an average of 12.09 weeks ± 2.16 between every administration. Both ratio differences did not differ significantly from 0 (DN-to-pons ratio: -0.0032 ± 0.0154, P = .248; DN-to-MCP ratio: -0.0011 ± 0.0093, P = .521), and one-sided Bayes factors provided substantial to strong evidence against an SI ratio increase (Bayes factor for DN-to-pons ratio = 0.09 and that for DN-to-MCP ratio = 0.12). Conclusion The study indicates that 20 or more serial injections of macrocyclic GBCAs administered with on average 3 months between each injection are not associated with an SI increase in the DN. ^© RSNA, 2016.

Contrast-enhanced spectral mammography vs. mammography and MRI - clinical performance in a multi-reader evaluation

OBJECTIVES

To compare the diagnostic performance of contrast-enhanced spectral mammography (CESM) to digital mammography (MG) and magnetic resonance imaging (MRI) in a prospective two-centre, multi-reader study.

METHODS

One hundred seventy-eight women (mean age 53 years) with invasive breast cancer and/or DCIS were included after ethics board approval. MG, CESM and CESM + MG were evaluated by three blinded radiologists based on amended ACR BI-RADS criteria. MRI was assessed by another group of three readers. Receiver-operating characteristic (ROC) curves were compared. Size measurements for the 70 lesions detected by all readers in each modality were correlated with pathology.

RESULTS

Reading results for 604 lesions were available (273 malignant, 4 high-risk, 327 benign). The area under the ROC curve was significantly larger for CESM alone (0.84) and CESM + MG (0.83) compared to MG (0.76) (largest advantage in dense breasts) while it was not significantly different from MRI (0.85). Pearson correlation coefficients for size comparison were 0.61 for MG, 0.69 for CESM, 0.70 for CESM + MG and 0.79 for MRI.

CONCLUSIONS

This study showed that CESM, alone and in combination with MG, is as accurate as MRI but is superior to MG for lesion detection. Patients with dense breasts benefitted most from CESM with the smallest additional dose compared to MG.

KEY POINTS

• CESM has comparable diagnostic performance (ROC-AUC) to MRI for breast cancer diagnostics. • CESM in combination with MG does not improve diagnostic performance. • CESM has lower sensitivity but higher specificity than MRI. • Sensitivity differences are more pronounced in dense and not significant in non-dense breasts. • CESM and MRI are significantly superior to MG, particularly in dense breasts.

A clinical combined gadobutrol bolus and slow infusion protocol enabling angiography, inversion recovery whole heart, and late gadolinium enhancement imaging in a single study

BACKGROUND

The use of gadolinium contrast agents in cardiovascular magnetic resonance is well-established and serves to improve both vascular imaging as well as enable late gadolinium enhancement (LGE) imaging for tissue characterization. Currently, gadofosveset trisodium, an intravascular contrast agent, combined with a three-dimensional inversion recovery balanced steady state free precession (3D IR bSSFP) sequence, is commonly used in pediatric cardiac imaging and yields excellent vascular imaging, but cannot be used for late gadolinium enhancement. Gadofosveset use remains limited in clinical practice, and manufacture was recently halted, thus an alternative is needed to allow 3D IR bSSFP and LGE in the same study.

METHODS

Here we propose a protocol to give a bolus of 0.1 mL/kg = 0.1 mmol/kg gadobutrol (GADAVIST/GADOVIST) for time-resolved magnetic resonance angiography (MRA). Subsequently, 0.1 mmol/kg is diluted up to 5 or 7.5 mL with saline and then loaded into intravenous tubing connected to the patient. A 0.5 mL short bolus is infused, then a slow infusion is given at 0.02 or 0.03 mL/s. Image navigated (iNAV) 3D IR bSSFP imaging is initiated 45-60 s after the initiation of the infusion, with a total image acquisition time of ~5 min. If necessary, LGE imaging using phase sensitive inversion recovery reconstruction (PSIR) is performed at 10 min after the infusion is initiated.

RESULTS

We have successfully performed the above protocol with good image quality on 10 patients with both time-resolved MRA and 3D IR bSSFP iNAV imaging. Our initial attempts to use pencil beam respiratory navigation failed due to signal labeling in the liver by the navigator. We have also performed 2D PSIR LGE successfully, with both LGE positive and LGE negative results.

CONCLUSION

A bolus of gadobutrol, followed later by a slow infusion, allows time-resolved MRA, 3D IR bSSFP using the iNAV navigation technique, and LGE imaging, all in a single study with a single contrast agent.

Gadolinium toxicity and treatment

Gadolinium based contrast agents (GBCAs) play an important role in the diagnostic evaluation of many patients. The safety of these agents has been once again questioned after gadolinium deposits were observed and measured in brain and bone of patients with normal renal function. This retention of gadolinium in the human body has been termed "gadolinium storage condition". The long-term and cumulative effects of retained gadolinium in the brain and elsewhere are not as yet understood. Recently, patients who report that they suffer from chronic symptoms secondary to gadolinium exposure and retention created gadolinium-toxicity on-line support groups. Their self-reported symptoms have recently been published. Bone and joint complaints, and skin changes were two of the most common complaints. This condition has been termed "gadolinium deposition disease". In this review we will address gadolinium toxicity disorders, from acute adverse reactions to GBCAs to gadolinium deposition disease, with special emphasis on the latter, as it is the most recently described and least known.

Gadopentetate but not gadobutrol accumulates in the dentate nucleus of multiple sclerosis patients

Background:

Previous studies have postulated an association between dentate nucleus T1 hyperintensity and multiple sclerosis (MS)-related progressive neurodegeneration. Therefore, MS patients have been excluded from most studies investigating brain deposition of gadolinium-based contrast agents (GBCAs).

Objective:

To study the hypothesis that dentate nucleus T1 hyperintensity in MS patients is associated with GBCA administration.

Methods:

In a cohort of 97 MS patients, the dentate-to-pons signal intensity ratio (DPSIR) was calculated for 265 consecutive T1-weighted magnetic resonance (MR) scans (including sessions with and without the administration of GBCA). Patients exclusively received either gadopentetate dimeglumine (Gd-DTPA, linear) or gadobutrol (Gd-BT-DO3A, macrocyclic).

Results:

In patients receiving Gd-DTPA, DPSIR increased significantly between the first and the last scan (+0.009, p < 0.001), and following magnetic resonance imaging (MRI) with Gd-DTPA administration as compared to following an MRI without Gd-DTPA administration (+0.005 vs −0.001; p = 0.022). Additionally, there was a positive linear relationship between the number of Gd-DTPA administrations and the increase in DPSIR ( p = 0.017). No DPSIR increase was observed after Gd-BT-DO3A administration.

Conclusion:

Dentate nucleus T1 hyperintensity in MS patients is associated with Gd-DTPA (but not Gd-BT-DO3A) administration, suggesting an alternative explanation for the association of T1 hyperintensity with disease duration and severity.

Are some agents less likely to deposit gadolinium in the brain?

In December 2013, a groundbreaking study by Kanda et al. was published showing that the serial injection of gadolinium based contrast agents (GBCAs) is correlated with a signal intensity increase in the dentate nucleus and the globus pallidus on unenhanced T1 weighted MR images. Subsequent studies by Kanda et al. and McDonald et al. on brain tissue from deceased patients provided evidence that the reported signal intensity increase in the brain correlates with gadolinium deposits in the brain tissue. In the following, multiple retrospective patient studies and animal studies assessed the potential of the marketed GBCAs to cause hyperintensities or gadolinium deposits in the brain, respectively. This review summarizes the evidence provided by these studies and additionally takes into account data from in vitro studies on the stability of GBCAs. The author concludes that there is a body of evidence suggesting that the potential of a GBCA to cause hyperintensities or gadolinium deposition in the brain corresponds with its stability and is particularly depending on the group of the specific GBCA as either linear or macrocyclic.

Gadolinium deposition in the brain: Lessons learned from other metals known to cross the blood-brain barrier

The recent discovery of gadolinium (Gd) deposition in the brains of patients receiving Gd-based contrast agents (GBCAs) raises several important questions including by what mechanism Gd or GBCAs pass through the blood-brain barrier. Decades of research focused on the safety and stability of GBCAs have not identified any mechanism of uptake. Here we review findings of Gd deposition from human and animal data, and how distribution mechanisms elucidated for endogenous and toxic metals may explain entrance of Gd into the central nervous system. Three general uptake mechanisms are considered along with examples of metals known to enter the central nervous system by these routes: (1) carrier-mediated, (2) transporter-mediated and (3) passive. The potential for chelation therapy to reduce deposition is also discussed. The work reported for other metals provides guidance for how the mechanism of Gd deposition in the brain can be determined which is essential information for rational prevention or treatment.

Pediatric Patients Demonstrate Progressive T1-Weighted Hyperintensity in the Dentate Nucleus following Multiple Doses of Gadolinium-Based Contrast Agent

BACKGROUND AND PURPOSE

While there have been recent reports of brain retention of gadolinium following gadolinium-based contrast agent administration in adults, a retrospective series of pediatric patients has not previously been reported, to our knowledge. We investigated the relationship between the number of prior gadolinium-based contrast agent doses and increasing T1 signal in the dentate nucleus on unenhanced T1-weighted MR imaging. We hypothesized that despite differences in pediatric physiology and the smaller gadolinium-based contrast agent doses that pediatric patients are typically administered based on weighted-adjusted dosing, the pediatric brain would also demonstrate dose-dependent increasing T1 signal in the dentate nucleus.

MATERIALS AND METHODS

We included children with multiple gadolinium-based contrast agent administrations at our institution. A blinded reader placed ROIs within the dentate nucleus and adjacent cerebellar white matter. To eliminate reader bias, we also performed automated ROI delineation of the dentate nucleus, cerebellar white matter, and pons. Dentate-to-cerebellar white matter and dentate-to pons ratios were compared with the number of gadolinium-based contrast agent administrations.

RESULTS

During 20 years at our institution, 280 patients received at least 5 gadolinium-based contrast agent doses, with 1 patient receiving 38 doses. Sixteen patients met the inclusion/exclusion criteria for ROI analysis. Blinded reader dentate-to-cerebellar white matter ratios were significantly associated with gadolinium-based contrast agent doses (r_s = 0.77, P = .001). The dentate-to-pons ratio and dentate-to-cerebellar white matter ratios based on automated ROI placement were also significantly correlated with gadolinium-based contrast agent doses (t = 4.98, P < .0001 and t = 2.73, P < .02, respectively).

CONCLUSIONS

In pediatric patients, the number of prior gadolinium-based contrast agent doses is significantly correlated with progressive T1-weighted dentate hyperintensity. Definitive confirmation of gadolinium deposition requires tissue analysis. Any potential clinical sequelae of gadolinium retention in the developing brain are unknown. Given this uncertainty, we suggest taking a cautious stance, including the use, in pediatric patients, of higher stability, macrocyclic agents, which in both human and animal studies have been shown to be associated with lower levels of gadolinium deposition, and detailed documentation of dosing. Most important, a patient should not be deprived of a well-indicated contrasted MR examination.

Distribution and clearance of retained gadolinium in the brain: differences between linear and macrocyclic gadolinium based contrast agents in a mouse model

OBJECTIVE

To investigate the distribution and clearance of retained gadolinium (Gd) in various parts of the brain after intravenously administering a Gd-based contrast agent (GBCA) in normal and renal failure mouse models.

METHODS

Two different mouse models: normal (n = 12) and renal failure (n = 12) were used. Clinical GBCAs (Gd-DTPA-BMA, 5 mmol kg(-1), or Gd-DOTA, 5 mmol kg(-1)) were intravenously administered five times per week for 4 weeks. Both groups were divided into two subgroups based on the time point for sample collection: 3 days (3d) and 45 days (45d) after the last injection. Normal saline (5 ml kg(-1)) was intravenously administered to mice of the control groups in the same manner. Samples of the following parts of the mouse brain were obtained on dissection: olfactory bulb, cerebral cortex, hippocampus, thalamus, mid-brain, cerebellum, pons and medulla. (158)Gd concentrations in each sample were quantified using inductively coupled plasma mass spectrometry.

RESULTS

The olfactory bulb had the highest Gd concentration in both Gd-DTPA-BMA and Gd-DOTA groups. Gd retention was higher in the Gd-DTPA-BMA group than in the Gd-DOTA group (p < 0.01). In the Gd-DTPA-BMA group, Gd retention in the 3d subgroups of normal and renal failure models were similar (p = 0.4). At 45d, Gd in the Gd-DTPA-BMA group was not eliminated from the renal failure model (p = 0.1), while that in the Gd-DOTA group was eliminated from both the normal and renal failure mouse models (p < 0.01).

CONCLUSION

Gd distributions in the brain for both groups were similar, regardless of the renal function and GBCA type. The Gd concentration was highest in the olfactory bulb of both groups. In the Gd-DOTA group, Gd was eliminated from the brain in both mouse models, while in the Gd-DTPA-BMA group, Gd clearance was limited.

ADVANCES IN KNOWLEDGE

Gd concentration in the brain was not affected by renal function. The clearance of Gd from linear GBCA was limited in both the normal and impaired renal function mouse models.

In Vivo Detection of Amyloid Plaques by Gadolinium-Stained MRI Can Be Used to Demonstrate the Efficacy of an Anti-amyloid Immunotherapy

Extracellular deposition of β amyloid plaques is an early event associated to Alzheimer’s disease. Here, we have used in vivo gadolinium-stained high resolution (29^∗29^∗117 μm³) magnetic resonance imaging (MRI) to follow-up in a longitudinal way individual amyloid plaques in APP/PS1 mice and evaluate the efficacy of a new immunotherapy (SAR255952) directed against protofibrillar and fibrillary forms of Aβ. APP/PS1 mice were treated for 5 months between the age of 3.5 and 8.5 months. SAR255952 reduced amyloid load in 8.5-months-old animals, but not in 5.5-months animals compared to mice treated with a control antibody (DM4). Histological evaluation confirmed the reduction of amyloid load and revealed a lower density of amyloid plaques in 8.5-months SAR255952-treated animals. The longitudinal follow-up of individual amyloid plaques by MRI revealed that plaques that were visible at 5.5 months were still visible at 8.5 months in both SAR255952 and DM4-treated mice. This suggests that the amyloid load reduction induced by SAR255952 is related to a slowing down in the formation of new plaques rather than to the clearance of already formed plaques.

Contribution of metals to brain MR signal intensity: review articles

Various metals are essential nutrients in humans, and metal shortages lead to a variety of deficiency diseases. Metal concentration abnormalities may cause metal deposition in the brain, and magnetic resonance imaging (MRI) is the most potent and sensitive technique now available for detecting metal deposition given the difficulties associated with performing brain tissue biopsy. However, the brain contains many kinds of metals that affect the signal intensity of MRI, which has led to numerous misunderstandings in the history of metal analysis. We reviewed the history of brain metal analysis with histologic findings. Typically, manganese overload causes high signal intensity on T1-weighted images (T1WI) in the globus pallidus, iron overload causes low signal intensity in the globus pallidus on T2-weighted images, and gadolinium deposition causes high signal intensity in the dentate nucleus, globus pallidus, and pulvinar of thalamus on T1WI. However, because nonparamagnetic materials and other coexisting metals also affect the signal intensity of brain MRI, the quantitative analysis of metal concentrations is difficult. Thus, when analyzing metal deposition using MRI, caution should be exercised when interpreting the validity and reliability of the obtained data.

Gadolinium deposition within the dentate nucleus and globus pallidus after repeated administrations of gadolinium-based contrast agents-current status

INTRODUCTION

Gadolinium-based contrast agents (GBCAs) have been used clinically since 1988 for contrast-enhanced magnetic resonance imaging (CE-MRI). Generally, GBCAs are considered to have an excellent safety profile. However, GBCA administration has been associated with increased occurrence of nephrogenic systemic fibrosis (NSF) in patients with severely compromised renal function, and several studies have shown evidence of gadolinium deposition in specific brain structures, the globus pallidus and dentate nucleus, in patients with normal renal function.

METHODS

Gadolinium deposition in the brain following repeated CE-MRI scans has been demonstrated in patients using T1-weighted unenhanced MRI and inductively coupled plasma mass spectroscopy. Additionally, rodent studies with controlled GBCA administration also resulted in neural gadolinium deposits.

RESULTS

Repeated GBCA use is associated with gadolinium deposition in the brain. This is especially true with the use of less-stable, linear GBCAs. In spite of increasing evidence of gadolinium deposits in the brains of patients after multiple GBCA administrations, the clinical significance of these deposits continues to be unclear.

CONCLUSION

Here, we discuss the current state of scientific evidence surrounding gadolinium deposition in the brain following GBCA use, and the potential clinical significance of gadolinium deposition. There is considerable need for further research, both to understand the mechanism by which gadolinium deposition in the brain occurs and how it affects the patients in which it occurs.