Development of High Signal Intensity within the Globus Pallidus and Dentate Nucleus following Multiple Administrations of Gadobenate Dimeglumine

Optimization of Detection of Gadodiamide Brain Retention in Rats Using Quantitative T2 Mapping and Intraperitoneal Administration

BACKGROUND

Currently, the gadolinium retention in the brain after the use of contrast agents is studied by T₁ -weighted magnetic resonance imaging (MRI) (T₁ w) and T₁ mapping. The former does not provide easily quantifiable data and the latter requires prolonged scanning and is sensitive to motion. T₂ mapping may provide an alternative approach. Animal studies of gadolinium retention are complicated by repeated intravenous (IV) dosing, whereas intraperitoneal (IP) injections might be sufficient.

HYPOTHESIS

T₂ mapping will detect the changes in the rat brain due to gadolinium retention, and IP administration is equivalent to IV for long-term studies.

STUDY TYPE

Prospective longitudinal.

ANIMAL MODEL

A total of 31 Sprague-Dawley rats administered gadodiamide IV (N = 8) or IP (N = 8), or saline IV (N = 6) or IP (N = 9) 4 days per week for 5 weeks.

FIELD STRENGTH/SEQUENCES

A 7 T, T₁ w, and T₂ mapping.

ASSESSMENT

T₂ relaxation and image intensities in the deep cerebellar nuclei were measured pre-treatment and weekly for 5 weeks. Then brains were assessed for neuropathology (N = 4) or gadolinium content using inductively coupled plasma mass spectrometry (ICP-MS, N = 12).

STATISTICAL TESTS

Repeated measures analysis of variance with post hoc Student-Newman-Keuls tests and Hedges' effect size.

RESULTS

Gadolinium was detected by both approaches; however, T₂ mapping was more sensitive (effect size 2.32 for T₂ vs. 0.95 for T₁ w), and earlier detection (week 3 for T₂ vs. week 4 for T₁ w). ICP-MS confirmed the presence of gadolinium (3.076 ± 0.909 nmol/g in the IV group and 3.948 ± 0.806 nmol/g in the IP group). There was no significant difference between IP and IV groups (ICP-MS, P = 0.109; MRI, P = 0.696). No histopathological abnormalities were detected in any studied animal.

CONCLUSION

T₂ relaxometry detects gadolinium retention in the rat brain after multiple doses of gadodiamide irrespective of the route of administration.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 1.

Undetectable gadolinium brain retention in individuals with an age-dependent blood-brain barrier breakdown in the hippocampus and mild cognitive impairment

INTRODUCTION

Blood-brain barrier (BBB) breakdown is an early independent biomarker of human cognitive dysfunction, as found using gadolinium (Gd) as a contrast agent. Whether Gd accumulates in brains of individuals with an age-dependent BBB breakdown and/or mild cognitive impairment remains unclear.

METHODS

We analyzed T1-weighted magnetic resonance imaging (MRI) scans from 52 older participants with BBB breakdown in the hippocampus 19-28 months after either cyclic or linear Gd agent.

RESULTS

There was no change in T1-weighted signal intensity between the baseline contrast MRI and unenhanced MRI on re-examination in any of the studied 10 brain regions with either Gd agent suggesting undetectable Gd brain retention.

DISCUSSION

Gd does not accumulate in brains of older individuals with a BBB breakdown in the hippocampus. Thus, Gd agents can be used without risk of brain retention within a ∼2-year follow-up to study BBB in the aging human brain in relation to cognition and/or other pathologies.

WITHDRAWN: Risks and Benefits of Gadolinium-Based Contrast Enhanced MRI

The Publisher regrets that this article is an accidental duplication of an article that has already been published in [Seminars in Ultrasound, CT, and MRI, 41/2 (2020) 170–182], https://dx.doi.org/10.1053/j.sult.2019.12.005. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal

GdVO4:Eu3+,Bi3+ Nanoparticles as a Contrast Agent for MRI and Luminescence Bioimaging

With the development of multifunctional imaging, gadolinium (Gd)-bearing inorganic nanoparticles (NPs), which were doped with trivalent lanthanide (Ln3+), have been applied in magnetic resonance imaging (MRI) and optical imaging owing to their high payload of Gd3+ ions and specific optical characteristics. In this study, we chose GdVO4 codoped with Eu3+ and Bi3+ as the host material to generate a highly efficient contrast agent (CA) for MRI and long-term luminescence imaging. The new CA emits strong and stable luminescence because of its strong characteristic emissions, resulting from the energy-transfer process from the vanadate groups (VO4 3-) to the Eu3+ and Bi3+ dopants. Additionally, these NPs provided conspicuous T 1 and T 2 relaxation time-shortening characteristics, which result in MRI enhancement. GdVO4:Eu3+,Bi3+ NPs were tested on liver tumor-bearing nude mice, and showed improved liver tumor contrast in T 2-weighted MR images (T 2WI). The dual-modal imaging probe exhibited no cytotoxicity or organ toxicity, reflecting its excellent biocompatibility. Thus, GdVO4:Eu3+,Bi3+ has the potential to be used for bioassays in vitro and liver tumor targeting in vivo. The results reveal the great promise of using the designed GdVO4:Eu3+,Bi3+ NPs as luminescent and MRI dual-mode bioprobes for clinical bioimaging applications.

Measurements of signal intensity of globus pallidus and dentate nucleus suggest different deposition characteristics of macrocyclic GBCAs in children

Introduction

The safety of using GBCAs to enhance the visibility of body structures is currently discussed due to possible gadolinium retention in brain structures. The aim of the study was to evaluate the effect of multiple exposures to macrocyclic GBCAs in children.

Materials and methods

This retrospective, single-center study included data from 43 patients who had received ≥4 injections of macrocyclic GBCAs during MRI examinations over performed over 8 to 84 months. Signal intensity was measured on unenhanced T1-weighted MRI, and globus pallidus to thalamus (GP/Th) and dentate nucleus to pons (DN/P) ratios were calculated. The differences in ratios were tested with the Student’s t-test or the Wilcoxon rank sum test. For categorical data, Pearson's chi-squared test was used. Relationships were analyzed with the Spearman's rank correlation coefficient.

Results

Patients with the mean age of 7.5 years (SD = 4.2) received 8.19 (SD = 3.63) injections of GBCAs on average. Differences in GP/Th and DN/P ratios between the first and the last measurement were insignificant. Children before the end of myelination process (≤2 years of age) had the first GP/Th ratio values significantly lower than those >2 years of age (p = 0.0284), which than increased at the final scan and reached the level similar to values obtained in the group of >2 years of age.

Conclusions

Maturation of the brain may affect both signal intensity of brain structures and susceptibility to GBCAs; thus, assessment of signal intensity of the brain structures should be conducted taking into account the age of a child.

Standardized assessment of the signal intensity increase on unenhanced T1-weighted images in the brain: the European Gadolinium Retention Evaluation Consortium (GREC) Task Force position statement

After the initial report in 2014 on T1-weighted (T1w) hyperintensity of deep brain nuclei following serial injections of linear gadolinium-based contrast agents (GBCAs), a multitude of studies on the potential of the marketed GBCAs to cause T1w hyperintensity in the brain have been published. The vast majority of these studies found a signal intensity (SI) increase for linear GBCAs in the brain-first and foremost in the dentate nucleus-while no SI increase was found for macrocyclic GBCAs. However, the scientific debate about this finding is kept alive by the fact that SI differences do not unequivocally represent the amount of gadolinium retained. Since the study design of the SI measurement in various brain structures is relatively simple, MRI studies investigating gadolinium-dependent T1w hyperintensity are currently conducted at multiple institutions worldwide. However, methodological mistakes may result in flawed conclusions. In this position statement, we assess the methodological basis of the published retrospective studies and define quality standards for future studies to give guidance to the scientific community and to help identify studies with potentially flawed methodology and misleading results. KEY POINTS: • A multitude of studies has been published on the potential of the marketed GBCAs to cause T1w hyperintensity in the brain. • The gadolinium-dependent T1w hyperintensity in the brain depends on patient's history, types of GBCAs used (i.e., linear vs. macrocyclic GBCAs) and MR imaging setup and protocols. • Quality standards for the design of future studies are needed to standardize methodology and avoid potentially misleading results from retrospective studies.