High Signal Intensity in the Dentate Nucleus and Globus Pallidus on Unenhanced T1-Weighted MR Images: Comparison between Gadobutrol and Linear Gadolinium-Based Contrast Agents

How often should we perform magnetic resonance imaging (MRI) for the follow-up of pituitary adenoma?

Magnetic resonance imaging (MRI) is the examination of choice for diagnosing and monitoring pituitary adenoma (also known as pituitary neuroendocrine tumor or PitNET), whether treated or not. However, repeating the examination too often (and sometimes unnecessarily) is costly, and worrying data on tissue accumulation (brain, bone, etc.) of gadolinium atoms dissociated from their carrier molecule (chelator) have led European authorities to ban contrast agents based on linear chelators of gadolinium, which are particularly susceptible to rapid dissociation, in favor of chemically more stable macrocyclic chelators. It is therefore important to determine the optimal frequency for pituitary MRI monitoring in order to safely assess the natural history or therapeutic response of pituitary adenomas. The aim of this article is to summarize the most recent data on optimal follow-up intervals depending on the type, size and location of the pituitary tumor and the clinical situation in general, in order to generate monitoring algorithms to guide clinicians.

Gadolinium contrast agents- challenges and opportunities of a multidisciplinary approach: Literature review

Contrast agents is used in magnetic resonance imaging (MRI) to improve the visibility of the details of the organ structures. Gadolinium-based contrast agent (GBCA) has been used since 1988 in MRI for diagnostic and follow-up of patients, the gadolinium good properties make it an effective choice for enhance the signal in MRI by increase its intensity and shortening the relaxation time of the proton. Recently, many studies show a gadolinium deposition in different human organs due to release of free gadolinium various body organs or tissue, which led to increased concern about the use of gadolinium agents, in this study, the potential diseases that may affect the patient and side effects that appear on the patient and related to accumulation of gadolinium were clarified, the study focused on the organs such as brain and bones in which gadolinium deposition was found and the lesions associated with it, and the diseases associated with gadolinium retention includes Nephrogenic Systemic Fibrosis (NSF) and Gadolinium deposition disease (GDD). Some studies tended to improve the contrast agents by developing a new non-gadolinium agents or development of next-generation gadolinium agents. In this review article the latest knowledge about MRI contrast agent.

Reliability of signal intensity in the basal ganglia on non-contrast T1-weighted MR scans after repetitive application of a gadolinium-based contrast agent in pediatric neuro-oncology patients

PURPOSE

To evaluate the reliability of signal intensity (SI) changes in the basal ganglia as a supposed indicator of gadolinium deposition in the brain after repetitive application of gadolinium-based contrast agents (GBCAs) in a pediatric neuro-oncological collective.

METHODS

One hundred and eight neuropediatric patients (54 male, 54 female, 0-17 years old), with repetitive GBCA-enhanced cranial MRIs between 2003 and 2017, were retrospectively analyzed. Two radiologists measured SI in the nucleus dentatus (ND), globus pallidus (GP), thalamus (T), and the pons (P). The NDP and GPT ratio were calculated. An intraclass correlation coefficient, and multiple linear regressions with subsequent stepwise backward variable selection were performed to evaluate the influence of gender, patient's age at the first MRI, time interval between the first and last MRI, linear or macrocyclic GBCAs, residual pathology, treatments, and magnet field strengths.

RESULTS

The inter-reader agreement was good for GPT and NDP in the whole collective (ICC = 0.837 and ICC = 0.793) and for children >2 years of age (ICC = 0.874 and ICC = 0.790), but poor to moderate for children ≤2 years of age (ICC = 0.397 and ICC = 0.748). The intra-reader agreement was good (ICC = 0.910 and ICC = 0.882). An SI increase was only observed for both readers in GPT (p = 0.003, or p < 0.001). None of the considered cofactors showed a consistent effect on SI changes for either readers or regions.

CONCLUSION

Measurements of SI changes in the basal ganglia are not a reliable parameter with which to evaluate or estimate gadolinium deposition in the brain or to identify suspicious influential factors after repeated GBCA applications.

Multi-parametric MRI for radiotherapy simulation

Magnetic resonance imaging (MRI) has become an important imaging modality in the field of radiotherapy (RT) in the past decade, especially with the development of various novel MRI and image-guidance techniques. In this review article, we will describe recent developments and discuss the applications of multi-parametric MRI (mpMRI) in RT simulation. In this review, mpMRI refers to a general and loose definition which includes various multi-contrast MRI techniques. Specifically, we will focus on the implementation, challenges, and future directions of mpMRI techniques for RT simulation.

Gadolinium-based contrast agents suppress adipocyte differentiation in 3T3-L1 cells

Gadolinium-based contrast agents (GBCAs) are widely used in magnetic resonance imaging (MRI) to improve the sensitivity and enhance diagnostic performance. GBCAs are mostly eliminated from the body through the kidney after administration; however small amounts of gadolinium are retained in the brain and other tissues. Although there is increasing concern about the adverse health effects of gadolinium, the cellular effects of GBCAs remains poorly understood. Here, we elucidated the potential cytotoxicity of the GBCAs Omniscan and Gadovist in 12 different cell lines, especially 3T3-L1 adipocyte cell line. Omniscan and Gadovist treatments significantly increased intracellular gadolinium levels in 3T3-L1 cells in a time- and dose-dependent manner. Additionally, Omniscan and Gadovist treatments downregulated the expression of adipocyte differentiation markers, including peroxisome proliferator-activated receptor γ (PPARG), adiponectin (ADIPOQ), and fatty acid-binding protein (FABP4), in 3T3-L1 cells, especially during early differentiation (day 0-2). Moreover, histological analysis using Oil red O staining showed that gadolinium chloride (GdCl₃) treatment suppressed lipid droplet accumulation and the expression of adipocyte differentiation markers. Overall, the results showed that Omniscan and Gadovist treatment suppressed adipocyte differentiation in 3T3-L1 cells, contributing to the understanding of the potential toxic effects of GBCA exposure.

Vestibular paroxysmia entails vestibular nerve function, microstructure and endolymphatic space changes linked to root-entry zone neurovascular compression

Combining magnetic resonance imaging (MRI) sequences that permit the determination of vestibular nerve angulation (NA = change of nerve caliber or direction), structural nerve integrity via diffusion tensor imaging (DTI), and exclusion of endolymphatic hydrops (ELH) via delayed gadolinium-enhanced MRI of the inner ear (iMRI) could increase the diagnostic accuracy in patients with vestibular paroxysmia (VP). Thirty-six participants were examined, 18 with VP (52.6 ± 18.1 years) and 18 age-matched with normal vestibulocochlear testing (NP 50.3 ± 16.5 years). This study investigated whether (i) NA, (ii) DTI changes, or (iii) ELH occur in VP, and (iv) to what extent said parameters relate. Methods included vestibulocochlear testing and MRI data analyses for neurovascular compression (NVC) and NA verification, DTI and ELS quantification. As a result, (i) NA increased NVC specificity. (ii) DTI structural integrity was reduced on the side affected by VP (p < 0.05). (iii) 61.1% VP showed mild ELH and higher asymmetry indices than NP (p > 0.05). (iv) "Disease duration" and "total number of attacks" correlated with the decreased structural integrity of the affected nerve in DTI (p < 0.001). NVC distance within the nerve's root-entry zone correlated with nerve function (Roh = 0.72, p < 0.001), nerve integrity loss (Roh = - 0.638, p < 0.001), and ELS volume (Roh = - 0.604, p < 0.001) in VP. In conclusion, this study is the first to link eighth cranial nerve function, microstructure, and ELS changes in VP to clinical features and increased vulnerability of NVC in the root-entry zone. Combined MRI with NVC or NA verification, DTI and ELS quantification increased the diagnostic accuracy at group-level but did not suffice to diagnose VP on a single-subject level due to individual variability and lack of diagnostic specificity.

Diffusion Tensor Imaging of the Dentate Nucleus After Repeated Administration of Gadobutrol in Children

This study aimed to investigate possible signal changes in the dentate nucleus (DN) on diffusion tensor imaging (DTI) after administration of gadobutrol in a pediatric cohort. Total of 50 pediatric patients (mean age: 6.2 ± 4.3 years) with normal renal function exposed exclusively to the macrocyclic GBCA (mcGBCA) gadobutrol and 50 age- and sex-matched control patients with nonpathological neuroimaging findings (and no GBCA administration). Mean diffusivity (MD) and fractional anisotropy (FA) values were determined in the DN. A paired t test was performed to compare FA, MD values, and DN-to-middle cerebral peduncle (MCP) T1WI SI ratios between children exposed to gadobutrol and controls. Pearson correlation analysis was conducted to determine any correlation between FA and MD values as well as T1WI SI ratios and confounding parameters. The mean FA values of DN was significantly lower in children with mcGBCA than in the control group (p < 0.001; non-GBCA group, 0.299 ± 0.03; mcGBCA group, 0.254 ± 0.05), but no significant difference of the T1WI SI ratio was noted between the mcGBCA group (0.946 ± 0.06) and the control group (0.963 ± 0.05; p = 0.336). There was also a significant MD value difference between mcGBCA group and control group (p < 0.001; non-GBCA group, 0.152 ± 0.02 × 10^-3 mm²/s; mcGBCA group, 0.173 ± 0.03 × 10^-3 mm²/s). A significant correlation was identified between FA/MD values and the number of mcGBCA administration (FA; correlation coefficient =  - 0.355, p = 0.011 and MD; correlation coefficient = 0.334, p = 0.018). The administration of the gadobutrol was associated with higher MD and lower FA values in DN suggesting a difference in cerebellar tissue integrity between children exposed to mcGBCAs and control group.

Assessment of genetic damage induced by gadolinium-based radiocontrast agents

BACKGROUND

Today, although gadolinium based contrast agents have been frequently used in the field of medicine, there is limited data available whether gadolinium based agents affect the genome.

AIM

The present study aimed to investigate the genotoxic and cytotoxic potentials of gadoteric acid and gadoversetamide used as gadolinium-based contrast agents for magnetic resonance (MR) imaging.

MATERIAL AND METHODS

The cytokinesis-block micronucleus assay was applied to human peripheral blood lymphocytes to assess the genotoxicity measured as micronucleus (MN), nucleoplasmic bridge (NPBs) and nuclear bud (NBUDs) frequencies. Furthermore, cytokinesis-block proliferation index (CBPI) was calculated to determine cytostasis. Lymphocytes were treated with gadoteric acid at concentrations of 1.0, 2.5, 5.0, and 25 mM and with gadoversetamide at concentrations of 0.25, 1.0, 2.5, and 5.0 mM for 48 h.

RESULTS

Gadoteric acid did not cause significant increase in MN, NBPs and NBUDs frequencies and CBPI values at any concentration. Gadoversetamide induced significantly increase MN formation at concentration of 2.5 mM, NBP formation at concentrations of 1.0 and 2.5 mM, and NBUD formation at concentrations of 0.25, 1.0 and 2.5 mM. Additionally, gadoversetamide exposure resulted in statistically significant decrease in CBPI values compared to the control at concentrations of 2.5 and 5.0 mM. In addition, CBPI levels in response to concentrations of gadoversetamide was negatively and significantly associated with concentration.

CONCLUSION

These findings show that gadoteric acid does not have genotoxic or cytotoxic potential, while gadoversetamide might have both genotoxic and cytotoxic potential on human peripheral blood lymphocytes. As a comparison, gadoversetamide was found more genotoxic and cytotoxic.

Susceptibility-Weighted Imaging of the Pediatric Brain after Repeat Doses of Gadolinium-Based Contrast Agent

BACKGROUND AND PURPOSE

Gadolinium complexes have paramagnetic properties; thus, we aimed to determine the susceptibility changes in the globus pallidus and dentate nucleus following administration of linear or macrocyclic gadolinium-based contrast agents in children.

MATERIALS AND METHODS

Thirty-three patients with linear gadolinium-based contrast agent gadopentetate dimeglumine administration, 33 age- and sex-matched patients with macrocyclic gadolinium-based contrast agent gadobutrol administration, and 33 age- and sex-matched control subjects without gadolinium exposure were enrolled in this retrospective study. The signal intensity on SWI and T1WI was determined in the dentate nucleus, middle cerebellar peduncle, globus pallidus, and pulvinar of the thalamus in an ROI-based analysis to calculate dentate nucleus-to-middle cerebellar peduncle and globus pallidus-to-thalamus ratios. A repeated measures ANOVA was performed to compare SWI_minimum, SWI_mean, and T1WI signal intensity ratios between gadolinium-based contrast agent groups and control subjects. Pearson correlation analysis was performed to determine any correlation between signal intensity ratios and variables.

RESULTS

Dentate nucleus-to-middle cerebellar peduncle and globus pallidus-to-thalamus ratios for both SWI_mean and SWI_minimum were lower for the linear gadolinium-based contrast agent group compared with macrocyclic gadolinium-based contrast agent and control groups (P < .05). No significant difference of the SWI_mean and SWI_minimum ratios were noted between the macrocyclic gadolinium-based contrast agent group and the control group (P > .05). Both dentate nucleus-to-middle cerebellar peduncle and globus pallidus-to-thalamus ratios on T1WI in the linear gadolinium-based contrast agent group were higher than in the control group and the macrocyclic gadolinium-based contrast agent group (P < .05). A negative correlation was identified between SWI_mean and SWI_minimum ratios and the number of linear gadolinium-based contrast agent administrations (dentate nucleus-to-middle cerebellar peduncle ratio: SWI_mean, r = -0.43, P = .005; SWI_minimum, r = -0.38, P = .011; globus pallidus-to-thalamus ratio: SWI_mean, r = -0.39, P = .009; SWI_minimum, r = -0.33, P = .017).

CONCLUSIONS

SWI analysis of the pediatric brain demonstrated a statistically significant decrease in SWI_minimum and SWI_mean values for the dentate nucleus and globus pallidus after administration of linear gadolinium-based contrast agents but not macrocyclic gadolinium-based contrast agents.

Dentate Nucleus Signal Intensity Changes in Children with Adrenoleukodystrophy in Comparison to Primary Brain Tumor with and without Radiotherapy after Gadobutrol Administration

BACKGROUND AND PURPOSE

To determine whether cerebral adrenoleukodystrophy (cALD) or brain irradiation in patients with primary brain tumor affects T1-weighted imaging (T1WI) signal intensity (SI) of the dentate nucleus (DN) in a pediatric cohort who had received consecutive macrocyclic gadolinium-based contrast agent (mcGBCA) gadobutrol.

METHODS

This study included 97 pediatric patients who underwent mcGBCA-enhanced MRI from 2010 to 2020 (29 children with primary brain tumors without brain radiation therapy [mcGBCA group-1], 33 children with primary brain tumors and radiation treatment [mcGBCA group-2], 35 children with cALD [mcGBCA group-3], and 97 sex-/age-matched control subjects [subgroups matched to each of the three subject groups] without GBCA administration). The DN-to-middle cerebellar peduncle (MCP) SI ratios on T1WI were then determined. A paired t-test was performed to compare SI ratios between children exposed to mcGBCA in each group and control subjects. The relationships between SI ratios and confounding variables were analyzed utilizing the Pearson correlation analysis.

RESULTS

The DN-to-MCP SI ratio was significantly higher of mcGBCA group-2 (1.046±.071) or mcGBCA group-3 (.972±.038) than in the control group-2 (.983±.041, P<.001) and control group-3 (.937±.051, P = .002), respectively, but no significant difference of the SI ratio was noted between mcGBCA group-1 (.984±.032) and control-group-1 (.982±.035, P = .860). No significant correlation was noted between SI ratio values and the cumulative dose or number of mcGBCA administrations, age, or the elapsed time between the MRI examinations (all P>.05).

CONCLUSIONS

Hyperintense T1WI signal in the DN may be seen in children with brain tumors undergoing brain irradiation, as well as in children with cALD.

Automated workflow for volumetric assessment of signal intensity ratio on T1-weighted MR images after multiple gadolinium administrations

Purpose: Repeated injections of linear gadolinium-based contrast agent (GBCA) have shown correlations with increased signal intensities (SI) on unenhanced T1-weighted (T1w) images. Assessment is usually performed manually on a single slice and the SI as an average of a freehand region-of-interest is reported. We aim to develop a fully automated software that segments and computes SI ratio of dentate nucleus (DN) to pons (DN/P) and globus pallidus (GP) to thalamus (GP/T) for the assessment of gadolinium presence in the brain after a serial GBCA administrations. Approach: All patients ( N = 113 ) underwent at least eight GBCA enhanced scans. The modal SI in the DN, GP, pons, and thalamus were measured volumetrically on unenhanced T1w images and corrected based on the reference protocol (measurement 1) and compared to the SI-uncorrected-modal-volume (measurement 2), SI-corrected-mean-volume (measurement 3), as well as SI-corrected-modal-single slice (measurement 4) approaches. Results: Automatic processing worked on all 2119 studies (1150 at 1.5 T and 969 at 3 T). DN/P were 1.085 ± 0.048 (1.5 T) and 0.979 ± 0.061 (3 T). GP/T were 1.084 ± 0.039 (1.5 T) and 1.069 ± 0.042 (3 T). Modal DN/P ratios from volumetric assessment at 1.5 T failed to show a statistical difference with or without SI corrections ( p = 0.71 ). All other t -tests demonstrated significant differences (measurement 2, 3, 4 compared to 1, p < 0.001 ). Conclusion: The fully automatic method is an effective powerful tool to streamline the analysis of SI ratios in the deep brain tissues. Divergent SI ratios using different approaches reinforces the need to standardize the measurement for the research in this field.

Effect of at Least 10 Serial Gadobutrol Administrations on Brain Signal Intensity Ratios on T1-Weighted MRI in Children: A Matched Case-Control Study

BACKGROUND. An association is recognized between linear gadolinium-based contrast agents (GBCAs) and intracranial gadolinium retention in children. The relation between macrocyclic GBCAs and gadolinium retention remains incompletely understood. OBJECTIVE. The purpose of this study was to assess whether 10 or more administrations of the macrocyclic GBCA gadobutrol are associated with increased signal intensity (SI) in the dentate nucleus (DN) and globus pallidus (GP) on unenhanced T1-weighted MRI of children and to explore clinical variables potentially associated with T1 hyperintensity. METHODS. The case group consisted of 25 children (13 boys, 12 girls; mean age, 7 ± 4 years; range, 2-18 years) who underwent at least 10 (mean, 15 ± 6; range, 10-34) contrast-enhanced MRI examinations exclusively with gadobutrol. The control group consisted of 25 age- and sex-matched patients undergoing MRI who had never been exposed to gadolinium. Two observers in consensus using a 3-point scale assessed visual T1 hyperintensity in the DN and GP. One observer placed ROIs on T1-weighted images to mark the DN, GP, middle cerebellar peduncle (MCP), and pulvinar of the thalamus bilaterally to compute mean DN-to-MCP and GP-to-thalamus SI ratios. SI ratios were compared between the macrocyclic GBCA and control groups. In the macrocyclic GBCA group, Pearson correlation analysis was conducted between SI ratios and clinical variables. ROI measurements were repeated by the original reader and an independent reader, and interobserver and intraobserver agreement were computed by means of Lin concordance correlation coefficient (ρ_c). RESULTS. No patient had visual T1 hyperintensity in the DN or GP. No significant difference between the macrocyclic GBCA and control groups was observed for DN-to-MCP SI ratio (0.95 ± 0.05 vs 0.95 ± 0.03; p = .67) or GP-to-thalamus SI ratio (1.05 ± 0.06 vs 1.04 ± 0.06; p = .65). In the macrocyclic GBCA group, no significant correlation was observed between DN-to-MCP SI ratio or GP-to-thalamus SI ratio and age (r = 0.355, p = .08; r = 0.167, p = .42), number of contrast-enhanced MRI examinations (r = 0.247, p = .23; r = 0.203, p = .33), mean time between examinations (r = 0.193, p = .36; r = 0.047, p = .82), or cumulative macrocyclic GBCA dose (r = 0.434, p = .07; r = 0.270, p = .19). Interobserver and intraobserver agreement was substantial for DN-to-MCP SI and GP-to-TH SI ratios (ρ_c = 0.931-0.974). CONCLUSION. Ten or more serial gadobutrol administrations were not associated with T1 hyperintensity in the DN or GP of children. CLINICAL IMPACT. Selection of gadobutrol as an MRI contrast agent may reduce risk of gadolinium retention in children. The findings may help guide practices for GBCA administration to children.

T1 signal intensity in the dentate nucleus after the administration of the macrocyclic gadolinium-based contrast agent gadoterate meglumine: an observational study

INTRODUCTION AND AIMS

Contradictory results have been reported about hyperintensity of the globus pallidus and/or dentate nucleus on unenhanced T1-weighted magnetic resonance (MR) images after exposure to various gadolinium-based contrast agents. This change in signal intensity varies with different gadolinium-based contrast agents. We aimed to determine whether signal intensity in the dentate nucleus is increased in unenhanced T1-weighted images in patients who have undergone multiple studies with the macrocyclic gadolinium-based contrast agent gadoterate meglumine. We thoroughly reviewed the literature to corroborate our results.

MATERIALS AND METHODS

We included patients who had undergone more than 10 MR studies with gadoterate meglumine. We quantitatively analyzed the signal intensity in unenhanced T1-weighted MR images measured in regions of interest placed in the dentate nucleus and the pons, and we calculated the dentate nucleus-to-pons signal intensity ratios and the differences between the ratio in the first MR study and the last MR study. We used t-tests to evaluate whether the differences between the signal intensity ratios were different from 0. We also analyzed the subgroups of patients who had been administered<15 and ≥15 doses of gadoterate meglumine. We used Pearson correlation to determine the relationships between the differences in the signal intensity ratios and the number of doses of gadoterate meglumine administered.

RESULTS

The 54 patients (26 men) had received a mean of 13.8±3.47 doses (range, 10-23 doses). The difference in the dentate nucleus-pons signal intensity ratio between the first and last MR study was -0.0275±0.1917 (not significantly different from 0; p=0.2968) in the entire group, -0.0357±0.2204 (not significantly different from 0; p=0.351 in the patients who had received <15 doses (n=34), and -0.0135±0.1332 (not significantly different from 0; p=0.655) in those who had received ≥15 doses (n=20). Differences in signal intensity ratios did not correlate significantly with the accumulated dose of gadoterate meglumine (P=0.9064; ρ=-0.0164 [95%]).

CONCLUSIONS

Receiving more than 10 doses of gadoterate meglumine was not associated with increased signal intensity in the dentate nucleus.

New Strategies in the Design of Paramagnetic CAs

Nowadays, magnetic resonance imaging (MRI) is the first diagnostic imaging modality for numerous indications able to provide anatomical information with high spatial resolution through the use of magnetic fields and gradients. Indeed, thanks to the characteristic relaxation time of each tissue, it is possible to distinguish between healthy and pathological ones. However, the need to have brighter images to increase differences and catch important diagnostic details has led to the use of contrast agents (CAs). Among them, Gadolinium-based CAs (Gd-CAs) are routinely used in clinical MRI practice. During these last years, FDA highlighted many risks related to the use of Gd-CAs such as nephrotoxicity, heavy allergic effects, and, recently, about the deposition within the brain. These alerts opened a debate about the opportunity to formulate Gd-CAs in a different way but also to the use of alternative and safer compounds to be administered, such as manganese- (Mn-) based agents. In this review, the physical principle behind the role of relaxivity and the T₁ boosting will be described in terms of characteristic correlation times and inner and outer spheres. Then, the recent advances in the entrapment of Gd-CAs within nanostructures will be analyzed in terms of relaxivity boosting obtained without the chemical modification of CAs as approved in the chemical practice. Finally, a critical evaluation of the use of manganese-based CAs will be illustrated as an alternative ion to Gd due to its excellent properties and endogenous elimination pathway.

VOLT: a novel open-source pipeline for automatic segmentation of endolymphatic space in inner ear MRI

Background

Objective and volumetric quantification is a necessary step in the assessment and comparison of endolymphatic hydrops (ELH) results. Here, we introduce a novel tool for automatic volumetric segmentation of the endolymphatic space (ELS) for ELH detection in delayed intravenous gadolinium-enhanced magnetic resonance imaging of inner ear (iMRI) data.

Methods

The core component is a novel algorithm based on Volumetric Local Thresholding (VOLT). The study included three different data sets: a real-world data set (D1) to develop the novel ELH detection algorithm and two validating data sets, one artificial (D2) and one entirely unseen prospective real-world data set (D3). D1 included 210 inner ears of 105 patients (50 male; mean age 50.4 ± 17.1 years), and D3 included 20 inner ears of 10 patients (5 male; mean age 46.8 ± 14.4 years) with episodic vertigo attacks of different etiology. D1 and D3 did not differ significantly concerning age, gender, the grade of ELH, or data quality. As an artificial data set, D2 provided a known ground truth and consisted of an 8-bit cuboid volume using the same voxel-size and grid as real-world data with different sized cylindrical and cuboid-shaped cutouts (signal) whose grayscale values matched the real-world data set D1 (mean 68.7 ± 7.8; range 48.9–92.8). The evaluation included segmentation accuracy using the Sørensen-Dice overlap coefficient and segmentation precision by comparing the volume of the ELS.

Results

VOLT resulted in a high level of performance and accuracy in comparison with the respective gold standard. In the case of the artificial data set, VOLT outperformed the gold standard in higher noise levels. Data processing steps are fully automated and run without further user input in less than 60 s. ELS volume measured by automatic segmentation correlated significantly with the clinical grading of the ELS (p < 0.01).

Conclusion

VOLT enables an open-source reproducible, reliable, and automatic volumetric quantification of the inner ears’ fluid space using MR volumetric assessment of endolymphatic hydrops. This tool constitutes an important step towards comparable and systematic big data analyses of the ELS in patients with the frequent syndrome of episodic vertigo attacks. A generic version of our three-dimensional thresholding algorithm has been made available to the scientific community via GitHub as an ImageJ-plugin.

Nephrogenic Systemic Fibrosis Risk Assessment and Skin Biopsy Quantification in Patients with Renal Disease following Gadobenate Contrast Administration

BACKGROUND AND PURPOSE

Nephrogenic systemic fibrosis following administration of intravenous gadobenate during MR imaging is rare. This study aimed to analyze any nephrogenic systemic fibrosis-related risks and quantify skin gadolinium levels in patients with impaired renal function but without nephrogenic systemic fibrosis who had received gadobenate.

MATERIALS AND METHODS

In this retrospective study with a prospective skin biopsy phase, patients with estimated glomerular filtration rates of <60 mL/min/1.73 m² undergoing contrast-enhanced MR imaging from July 2007 through June 2014 were screened for nephrogenic systemic fibrosis using a questionnaire. This was highly sensitive but not specific and reliably excluded nephrogenic systemic fibrosis if responses to at least 6 of the 8 questions were negative. If no nephrogenic systemic fibrosis was detected, a skin biopsy was requested.

RESULTS

Of 2914 patients who met these criteria, 1988 were excluded for various reasons. Of the remaining 926 patients, 860 were screened negative for nephrogenic systemic fibrosis. Of these, 17 (2%) had estimated glomerular filtration rates of <15 mL/min/1.73 m², 51 (6%) had levels of 15 < 30 mL/min/1.73 m², 234 (27%) had levels of 30 < 45 mL/min/1.73 m², and 534 (62%) had levels of 45 < 60 mL/min/1.73 m². Of the 66 who were not cleared of nephrogenic systemic fibrosis by the questionnaire, 6 patients were evaluated by a dermatologist and confirmed not to have nephrogenic systemic fibrosis (no biopsy required).

CONCLUSIONS

A diagnosis of nephrogenic systemic fibrosis was excluded in 860 patients with impaired renal function who were followed up and received gadobenate during MR imaging. In 14 such patients who underwent at least 1 gadobenate-enhanced MR imaging examination and did not have nephrogenic systemic fibrosis, gadolinium levels in the skin were exceedingly low.

Gadolinium deposition in the brain of dogs after multiple intravenous administrations of linear gadolinium based contrast agents

Objective

To determine the effect of a linear gadolinium-based contrast agent (GBCA) on the signal intensity (SI) of the deep cerebellar nuclei (DCN) in a retrospective clinical study on dogs after multiple magnetic resonance (MR) examinations with intravenous injections of gadodiamide and LA-ICP-MS analysis of a canine cerebellum after gadodiamide administration.

Animals

15 client-owned dogs of different breeds and additionally 1 research beagle dog cadaver.

Procedures

In the retrospective study part, 15 dogs who underwent multiple consecutive MR imaging examinations with intravenous injection of linear GBCA gadodiamide were analyzed. SI ratio differences on unenhanced T1-weighted MR images before and after gadodiamide injections was calculated by subtracting SI ratios between DCN and pons of the first examination from the ratio of the last examination. Additionally, 1 research beagle dog cadaver was used for LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) analysis of gadolinium in the cerebellum as an add-on to another animal study. Descriptive and non-parametrical statistical analysis was performed and a p-value of < 0.05 was considered significant.

Results

No statistically significant differences of SI ratios, between DCN and pons, were detectable based on unenhanced T1-weighted MR images. LA-ICP-MS analyses showed between 1.5 to 2.5 μg gadolinium/g tissue in the cerebellum of the examined dog, 35 months after the last of 3 MRI examination with gadodiamide (two examinations at a dose of 1 x 0.1mmol/kg, last examination at a dose of 3 x 0.05mmol/kg).

Conclusion and clinical relevance

Although the retrospective MRI study did not indicate any visible effect of SI increase after multiple gadodiamide exposures, further studies based on LA-ICP-MS showed that the optical threshold was not reached for a potential visible effect. Gadolinium was detectable at a level of 1.5 to 2.5 μg gadolinium/g tissue by using LA-ICP-MS in the cerebellum 35 months after last MRI examination. The general importance of gadolinium retention of subvisible contents requires further investigation.

Endolymphatic volume in patients with meniere's disease and healthy controls: Three-dimensional analysis with magnetic resonance imaging

Objective

Recently, 3-Tesla magnetic resonance imaging (MRI) with intravenous gadolinium injection has been used to reveal endolymphatic hydrops (EH). In the present study, we aimed to evaluate EH in patients with Meniere's disease (MD) objectively and quantitatively, and compared the endolymphatic space (ELS) in individuals with MD and healthy controls, to gain understanding of the characteristics of MD.

Methods

Eighty-two patients with unilateral MD (uMD), 16 patients with bilateral MD (bMD), and 47 healthy volunteers were enrolled. All participants underwent 3-T MRI at 4 hours after intravenous gadolinium injection. The volumes of the total fluid space (TFS) and ELS were measured semiautomatically using our workstation, and the percentage of ELS to TFS (ELS percentage) was calculated.

Results

The ELS percentage was 13.9 in the ears of controls, 18.2 in the contralateral ear of individuals with uMD, 26.1 in the affected ears of these individuals, and 23.0 in both ears of individuals with bMD. The ELS percentages in the affected ear of uMD and the ears of bMD individuals were significantly higher than that in the ears of control individuals (P < .01, one-way analysis of variance (ANOVA), Tukey's test).

Conclusion

The ELS is significantly larger in the affected ears of uMD and in both ears of bMD individuals. Accurate diagnosis of MD can be facilitated by using 3-T MRI 4 hours after intravenous gadolinium injection and performing volumetric measurements of the ELS.

Level of Evidence

2b.

Gadoterate Meglumine Administration in Multiple Sclerosis has no Effect on the Dentate Nucleus and the Globus Pallidus Signal Intensities

RATIONALE AND OBJECTIVES

Previous studies on possible accumulation of gadolinium-based contrast agents (GBCA) in the brain suggest that macrocyclic GBCA are less likely to accumulate than linear GBCA. However, conflicting results have been reported, especially in MS. The aim of this study is to investigate retrospectively the correlation between gadoterate-meglumine (macrocyclic GBCA) use and T1 signal intensity changes (SI) in the dentate nucleus and the GP on unenhanced T1-weighted images in a large cohort of MS patients.

MATERIALS AND METHODS

Unenhanced T1-weighted images of 232 MS patients who previously received multiple intravenous administrations of 0.1 mmol/kg of gadoterate-meglumine were reviewed. The change in T1 SI ratios of dentate nucleus/central pons (DN/CP) and globus pallidus/centrum semiovale (GP/CSO) was calculated between the first and last MRIs and correlated with age, number of injections, time interval between MRIs, disease duration, activity, and therapy.

RESULTS

DN/CP ratio showed no significant changes whereas the GP/CSO ratio showed a significant decrease (p < 0.0001) between the first and last MRIs. Multivariable analyses of both ratios, controlling for age, disease duration, and time interval between MRIs, showed no significant correlation between the number of gadolinium injections and the differences in DN/CP (standardized beta = -0.018, p = 0.811) or GP/CSO SI ratios (standardized beta = -0.049, p = 0.499).

CONCLUSION

Repeated administration of gadoterate-meglumine in MS patients did not result in increased T1 SI in the DN or the GP. The significant decrease of GP/CSO ratio between the first and last MRIs is not due to gadolinium accumulation but rather to varying MR parameters.

A probabilistic atlas of the human inner ear's bony labyrinth enables reliable atlas-based segmentation of the total fluid space

Intravenous contrast agent-enhanced magnetic resonance imaging of the endolymphatic space (ELS) of the inner ear permits direct, in-vivo, non-invasive visualization of labyrinthine structures and thus verification of endolymphatic hydrops (ELH). However, current volumetric assessment approaches lack normalization. The aim of this study was to develop a probabilistic atlas of the inner ear's bony labyrinth as a first step towards an automated and reproducible volume-based quantification of the ELS. The study included three different datasets: a source dataset (D1) to build the probabilistic atlas and two testing sets (D2, D3). D1 included 24 right-handed patients (12 females; mean age 51.5 ± 3.9 years) and D2 5 patients (3 female; mean age 48.8 ± 5.01 years) with vestibular migraine without ELH or any measurable vestibular deficits. D3 consisted of five patients (one female; mean age 46 ± 5.2 years) suffering from unilateral Menière's disease and ELH. Data processing comprised three steps: preprocessing using an affine and deformable fusion registration pipeline, computation of an atlas for the left and right inner ear using a label-assisted approach, and validation of the atlas based on localizing and segmenting previously unseen ears. The three-dimensional probabilistic atlas of the inner ear's bony labyrinth consisted of the internal acoustic meatus and inner ears (including cochlea, otoliths, and semicircular canals) for both sides separately. The analyses showed a high level of agreement between the atlas-based segmentation and the manual gold standard with an overlap of 89% for the right ear and 86% for the left ear (measured by dice scores). This probabilistic in vivo atlas of the human inner ear's bony labyrinth and thus of the inner ear's total fluid space for both ears represents a necessary step towards a normalized, easily reproducible and reliable volumetric quantification of the perilymphatic and endolymphatic space in view of MR volumetric assessment of ELH. The proposed atlas lays the groundwork for state-of-the-art approaches (e.g., deep learning) and will be provided to the scientific community.

Gadolinium Deposition in Neurology Clinical Practice

Background: Magnetic resonance imaging (MRI) enhanced with gadolinium-based contrast agents (GBCAs) is an essential tool in the diagnosis and management of many neurologic diseases, including multiple sclerosis, brain tumors, and infections. The clinical utility of GBCAs is evidenced by their widespread use. GBCAs are produced in macrocyclic and linear forms. Since 2014, evidence has suggested that repeated administration of GBCAs can lead to gadolinium deposition in the brain. Methods: We review the literature on gadolinium deposition, including both animal and human studies, as well as the literature on GBCA-associated health outcomes. Additionally, we summarize and discuss the updated medical society recommendations and perspectives on GBCA use in clinical practice. Results: The first publication reporting gadolinium deposition in the human brain was published in 2014. Since that seminal report, multiple studies have demonstrated that exposure to linear GBCAs is associated with gadolinium deposition in the dentate nucleus and globus pallidus as seen on brain MRI. Macrocyclic GBCA exposure has not convincingly been associated with gadolinium deposition evident on brain MRI. Conclusion: Clear evidence demonstrates that GBCAs lead to gadolinium deposition in the brain in a dose-dependent manner; however, only linear GBCAs have been associated with gadolinium deposition visualized on MRI. To date, no evidence links gadolinium deposition with any adverse health outcome. Updated medical society guidelines emphasize the importance of an individualized risk-benefit analysis with each administration of GBCAs.

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.