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

Gadolinium Contrast Agent Deposition in Children

Over the past few years, a large number of studies have evidenced increased signal intensity in the deep brain nuclei on unenhanced T1-MRI images achieved by the application of gadolinium-based contrast agents (GBCAs). The deposition of gadolinium in the brain, bone, and other tissues following administration of GBCAs has also been confirmed in histological studies in rodents and in necropsy studies in adults and children. Given the distinct physiological characteristics of children, this review focuses on examining the current research on gadolinium deposition in children, particularly studies utilizing novel methods and technologies. Furthermore, the article compares safety research findings of linear GBCAs and macrocyclic GBCAs in children, with the aim of offering clinicians practical guidance based on the most recent research outcomes. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 2.

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.

Complications of Cancer Therapy in Children: A Comprehensive Review of Neuroimaging Findings

ABSTRACT

Complications of cancer therapy in children can result in a spectrum of neurologic toxicities that may occur at the initiation of therapy or months to years after treatment. Although childhood cancer remains rare, increasing survival rates mean that more children will be living longer after cancer treatment. Therefore, complications of cancer therapy will most likely occur with increasing frequency.At times, it is very difficult to differentiate between therapeutic complications and other entities such as tumor recurrence, development of secondary malignancy, and infection (among other conditions). Radiologists often play a key role in the diagnosis and evaluation of pediatric patients with malignancies, and thus, awareness of imaging findings of cancer complications and alternative diagnoses is essential in guiding management and avoiding misdiagnosis. The aim of this review article is to illustrate the typical neuroimaging findings of cancer therapy-related toxicities, including both early and late treatment effects, highlighting pearls that may aid in making the appropriate diagnosis.

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.

Dentate nucleus signal intensity changes on T1-weighted MRI after repeated administrations of linear and macrocyclic gadolinium-based contrast agents: a pediatric intraindividual case-control study

BACKGROUND

An association between consecutive administrations of macrocyclic gadolinium-based contrast agent (mcGBCA) gadobutrol and linear (L)-GBCA gadopentetate dimeglumine and gadolinium retention in the pediatric brain remains incompletely understood.

PURPOSE

To compare signal intensity (SI) changes in the dentate nucleus (DN) on unenhanced T1-weighted imaging (T1WI) in children who obtained mcGBCA gadobutrol with those who had previously received L-GBCA gadopentetate dimeglumine.

MATERIAL AND METHODS

This retrospective study included 27 children who received L-GBCA gadopentetate dimeglumine followed by mcGBCA gadobutrol and two different control groups matched for age and sex for both periods, each involving 27 individuals with no GBCA administration from January 2010 to January 2020. DN-to-middle cerebellar peduncle (MCP) SI ratios on T1WI were determined. A repeated-measures ANOVA was performed to compare the T1WI SI ratio between children exposed to GBCA in each of the two periods and controls. Pearson correlation analysis was conducted to determine any correlation between SI ratios and confounding parameters.

RESULTS

T1WI SI ratio was significantly higher in those who had only L-GBCA (1.005±0.087) or subsequent mcGBCA gadobutrol (1.002±0.104) than in control groups 1 (0.927±0.041; P<0.001) and 2 (0.930±0.041; P=0.002), respectively, but no significant difference of the T1WI SI ratio was noted between L-GBCA period and subsequent mcGBCA gadobutrol period (P=0.917). T1WI SI ratios and the L-GBCA administration number revealed a modest but significant correlation (correlation coefficient=0.034; P=0.016).

CONCLUSION

Previous administration of gadopentetate dimeglumine is associated with increased T1WI SI in the DN, while subsequent administration of gadobutrol does not demonstrate any additional SI increase in the pediatric brain.

Gadolinium retention in the tunica media of arterial walls - a complementary study using elemental bioimaging and immunogold staining

Gadolinium (Gd) deposition has been found in both animal and human tissues after serial injections of gadolinium-based contrast agents (GBCAs). Without the knowledge of which tissues are most affected, it is difficult to determine whether Gd accumulation could lead to any pathological changes. The current study aims at investigating histological sections of three patients who were exposed to GBCAs during their lifetime, and identify areas of Gd accumulation. Tissue sections of three autopsy cases were investigated by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to assess the distribution of Gd, and the deposition within tissue sections was quantified. Additional application of laser ablation-inductively coupled plasma-optical emission spectroscopy (LA-ICP-OES) enabled a sensitive detection of calcium (Ca) in the vessel walls, which is usually impeded in LA-ICP-MS due to the isobaric interference with argon. Complementary LA-ICP-MS and LA-ICP-OES analysis revealed that Gd was co-localized with zinc and calcium, in the area where smooth muscle actin was present. Notably, high levels of Gd were found in the tunica media of arterial walls, which requires further research into potential Gd-related toxicity in this specific location.

Gadolinium retention: should pediatric radiologists be concerned, and how to frame conversations with families

Gadolinium retention in the brain and other organs has recently been identified by imaging and confirmed histologically. No direct clinical effects of gadolinium retention, which occurs after gadolinium-based contrast agent (GBCA) administration for MRI, have been scientifically accepted at this time. However, there is understandable concern among medical professionals and the public about the potential effects of gadolinium retention, particularly in the brain. Part of this concern might stem from the identification of nephrogenic systemic fibrosis caused by GBCAs in people with severe renal failure in 2006. This article briefly describes the characteristics of GBCAs; reviews and differentiates gadolinium retention, nephrogenic systemic fibrosis, and "gadolinium deposition disease" or "gadolinium toxicity"; and discusses societal guidelines and current usage in children. With the belief that GBCAs should not be withheld for appropriate indications in the absence of evidence of its potential risks, we offer a framework for determining when GBCA use is appropriate and suggestions for discussing its risks and benefits with children and their families.

How the Chemical Properties of GBCAs Influence Their Safety Profiles In Vivo

The extracellular class of gadolinium-based contrast agents (GBCAs) is an essential tool for clinical diagnosis and disease management. In order to better understand the issues associated with GBCA administration and gadolinium retention and deposition in the human brain, the chemical properties of GBCAs such as relative thermodynamic and kinetic stabilities and their likelihood of forming gadolinium deposits in vivo will be reviewed. The chemical form of gadolinium causing the hyperintensity is an open question. On the basis of estimates of total gadolinium concentration present, it is highly unlikely that the intact chelate is causing the T1 hyperintensities observed in the human brain. Although it is possible that there is a water-soluble form of gadolinium that has high relaxitvity present, our experience indicates that the insoluble gadolinium-based agents/salts could have high relaxivities on the surface of the solid due to higher water access. This review assesses the safety of GBCAs from a chemical point of view based on their thermodynamic and kinetic properties, discusses how these properties influence in vivo behavior, and highlights some clinical implications regarding the development of future imaging agents.

Influence of aging and gadolinium exposure on T1, T2, and T2*-relaxation in healthy women with an increased risk of breast cancer with and without prior exposure to gadoterate meglumine at 3.0-T brain MR imaging

Objectives

We examined the effects of aging and of gadolinium-based contrast agent (GBCA) exposure on MRI measurements in brain nuclei of healthy women.

Methods

This prospective, IRB-approved single-center case-control study enrolled 100 healthy participants of our high-risk screening center for hereditary breast cancer, who had received at least six doses of macrocyclic GBCA (exposed group) or were newly entering the program (GBCA-naïve group). The cutoff “at least six doses” was chosen to be able to include a sufficient number of highly exposed participants. All participants underwent unenhanced 3.0-T brain MRI including quantitative T1, T2, and R2* mapping and T1- and T2-weighted imaging. The relaxation times/signal intensities were derived from region of interest measurements in the brain nuclei performed by a radiologist and a neuroradiologist, both board certified. Statistical analysis was based on descriptive evaluations and uni-/multivariable analyses.

Results

The participants (exposed group: 49, control group: 51) were aged 42 ± 9 years. In a multivariable model, age had a clear impact on R2* (p < 0.001–0.012), T2 (p = 0.003–0.048), and T1 relaxation times/signal intensities (p < 0.004–0.046) for the majority of deep brain nuclei, mostly affecting the substantia nigra, globus pallidus (GP), nucleus ruber, thalamus, and dentate nucleus (DN). The effect of prior GBCA administration on T1 relaxation times was statistically significant for the DN, GP, and pons (p = 0.019–0.037).

Conclusions

In a homogeneous group of young to middle-aged healthy females aging had an effect on T2 and R2* relaxation times and former GBCA applications influenced the measured T1 relaxation times.

Key Points

The quantitative T1, T2, and R2* relaxation times measured in women at high risk of developing breast cancer showed characteristic bandwidth for all brain nuclei examined at 3.0-T MRI.

The effect of participant age had a comparatively strong impact on R2*, T2, and T1 relaxation times for the majority of brain nuclei examined.

The effect of prior GBCA administrations on T1 relaxation times rates was comparatively less pronounced, yielding statistically significant results for the dentate nucleus, globus pallidus, and pons.

Summary statement

Healthy women with and without previous GBCA-enhanced breast MRI exhibited age-related T2* and T2 relaxation alterations at 3.0 T-brain MRI. T1 relaxation alterations due to prior GBCA administration were comparatively less pronounced.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00330-021-08069-4.

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.

The switch from Gd-DTPA to Gd-DOTA is not associated with decrease of the T1 signal intensity of the pallidus and dentate in a pediatric population

BACKGROUND

The switch from the linear gadolinium-based contrast agent (GBCA) gadopentate dimeglumine (Gd_DTPA) to the macrocyclic GBCA gadobutrol is associated with a decrease of the T1 signal intensity (SI) in brain gray matter nuclei. The effects of the switch to other macrocyclic GBCAs are not yet established.

PURPOSE

To explore the effects of switching from Gd-DTPA to the macrocyclic GBCA gadoterate meglumine (Gd-DOTA) in pediatric patients.

MATERIAL AND METHODS

We measured the pallidus/middle cerebellar peduncle (MCP) SI ratio and the dentate/MCP SI ratio in pre-contrast sagittal T1-weighted spin-echo images in nine patients who had received ≥6 administrations of Gd-DTPA and then of Gd-DOTA, in 18 patients who had received ≥6 administrations of Gd-DOTA alone, and in nine age-matched controls without prior GBCA administrations. Serial assessment was performed in patients who switched from Gd-DTPA to Gd-DOTA. Finally, the rate of change of pallidal/MCP and dentate/MCP SI ratios between the first and last Gd-DOTA administrations was compared.

RESULTS

The pallidal/MCP and dentate/MCP SI ratios were (P < 0.05) higher in patients with prior Gd-DTPA and Gd-DOTA administrations compared to the controls. After the switch, the pallidal/MCP SI ratio increased in nine patients and the dentate/MCP ratio in seven patients. The rate of change of pallidal/MCP SI ratio after Gd-DOTA was higher (P < 0.01) in patients who had previously received Gd-DTPA (mean 2.89 ± 2.6%) than in patients who had received Gd-DOTA alone (mean 0.53 ± 0.89%).

CONCLUSION

T1 SI in gray matter nuclei does not decrease after switching from Gd-DTPA to Gd-DOTA. The switch effects from Gd-DTPA to each macrocyclic GBCA should be individually evaluated.

Impact of Kidney Function on CNS Gadolinium Deposition in Patients Receiving Repeated Doses of Gadobutrol

BACKGROUND AND PURPOSE

Studies associate repeat gadolinium-based contrast agent administration with T1 shortening in the dentate nucleus and globus pallidus, indicating CNS gadolinium deposition, most strongly with linear agents but also reportedly with macrocyclics. Renal impairment effects on long-term CNS gadolinium deposition remain underexplored. We investigated the relationship between signal intensity changes and renal function in patients who received ≥10 administrations of the macrocyclic agent gadobutrol.

MATERIALS AND METHODS

Patients who underwent ≥10 brain MR imaging examinations with administration of intravenous gadobutrol between February 1, 2014, and January 1, 2018, were included in this retrospective study. Dentate nucleus-to-pons and globus pallidus-to-thalamus signal intensity ratios were calculated, and correlations were calculated between the estimated glomerular filtration rate (minimum and mean) and the percentage change in signal intensity ratios from the first to last scan. Partial correlations were calculated to control for potential confounders.

RESULTS

One hundred thirty-one patients (73 women; mean age at last scan, 55.9 years) showed a mean percentage change of the dentate nucleus-to-pons of 0.31%, a mean percentage change of the globus pallidus-to-thalamus of 0.15%, a mean minimum estimated glomerular filtration rate of 69.65 (range, 10.16-132.26), and a mean average estimated glomerular filtration rate at 89.48 (range, 38.24-145.93). No significant association was found between the estimated glomerular filtration rate and percentage change of the dentate nucleus-to-pons (minimum estimated glomerular filtration rate, r = -0.09, P = .28; average estimated glomerular filtration rate, r = -0.09, P = .30,) or percentage change of the globus pallidus-to-thalamus (r = 0.07, P = .43; r = 0.07, P = .40). When we controlled for age, sex, number of scans, and total dose, there were no significant associations between the estimated glomerular filtration rate and the percentage change of the dentate nucleus-to-pons (r = 0.16, P = .07; r = 0.15, P = .08) or percentage change of the globus pallidus-to-thalamus (r = -0.14, P = .12; r = -0.15, P = .09).

CONCLUSIONS

In patients receiving an average of 12 intravenous gadobutrol administrations, no correlation was found between renal function and signal intensity ratio changes, even in those with mild or moderate renal impairment.

Dynamic Glucose-Enhanced MR Imaging

Conventional medical imaging techniques use contrast agents that are chemically labeled, for example, iodine in the case of computed tomography, radioisotopes in the case of PET, or gadolinium in the case of MR imaging to create or enhance signal contrast and to visualize tissue compartments and features. Dynamic glucose-enhanced MR imaging represents a novel technique that uses natural, unlabeled d-glucose as a nontoxic biodegradable contrast agent in chemical exchange-sensitive MR imaging approaches.

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.

Magnetic resonance imaging diagnosis of subependymal giant cell astrocytomas in follow-up of children with tuberous sclerosis complex: should we always use contrast enhancement?

BACKGROUND

Subependymal giant cell astrocytomas (SEGAs) arise in 10-26% of tuberous sclerosis complex (TSC) patients. SEGAs cause obstructive hydrocephalus and increase morbi-mortality. It is recommended that TSC patients be followed with contrast enhanced magnetic resonance imaging (CE-MRI), but repetitive use of gadolinium-based contrast-agents (GBCAs) may cause organ deposits.

OBJECTIVE

To compare the diagnostic performances of non-CE- and CE-MRI to differentiate SEGAs from subependymal nodules in TSC patients during follow-up.

MATERIALS AND METHODS

Thirty-five TSC patients (median age: 2.4 years) were enrolled in this retrospective single-center study from September 2007 to January 2019. Inclusion criteria were a certain diagnosis of TSC and at least three follow-up brain MRIs with GBCA injection. Two consecutive MRI scans per patient were selected and anonymized. Three radiologists performed a blinded review of non-enhanced and enhanced MRI sequences during different sessions. The diagnostic performances were compared (sensitivity, specificity, positive/negative predictive values, accuracy, inter/intra-observer agreements).

RESULTS

The accuracies for detecting SEGAs were good and similar between the non-enhanced and enhanced MRI sequences. The sensitivity and specificity of non-CE-MRI to diagnose SEGA ranged from 75% to 100% and from 94% to 100%, respectively. The differences in numbers of false-positive and false-negative patients between non-CE- and CE-MRI never exceeded one case. Nodules size >10 mm, location near the Monro foramen, hydrocephalus and modifications between two consecutive MRI scans were significantly associated with the diagnosis of SEGA for the three readers (all P-values <0.05). Inter- and intra-observer agreements were also excellent for non-enhanced and enhanced MRI sequences (kappa=0.85-1 and 0.81-0.93, respectively).

CONCLUSION

The performances of non-enhanced and enhanced MRI sequences are comparable for detecting SEGAs, questioning the need for systematic GBCA injections for TSC patients.

Abdominal Applications of Pediatric Body MR Angiography: Tailored Optimization for Successful Outcome

OBJECTIVE. The purpose of this article is to summarize current common techniques and indications for pediatric abdominopelvic MR angiography and strategies for optimizing them to achieve successful outcomes. We also discuss newer MR angiography techniques, including whole-body imaging and blood pool contrast agents, as well as various approaches to reducing the need for anesthesia in pediatric MRI. CONCLUSION. Pediatric body vascular imaging presents a unique set of challenges that require a tailored approach. Emerging pediatric abdominopelvic MR angiography techniques hold promise for continued improvement in pediatric body MR angiography.

Brain tissue gadolinium retention in pediatric patients after contrast-enhanced magnetic resonance exams: pathological confirmation

BACKGROUND

Retained gadolinium from gadolinium-based contrast agents (GBCAs) used in MR exams has been inferred based on signal changes on serial brain MRI and subsequently demonstrated pathologically in adults. Retention has been similarly inferred in children but pathological demonstration in pediatric patients is limited. The long-term effects of retained gadolinium are unknown but are potentially of greater concern in children given their increased vulnerability from continuing development and their expected longer period of exposure. Several factors can influence gadolinium retention. In adults as well as in children, greater accumulation has been demonstrated based on MR signal changes with linear compared with macrocyclic gadolinium chelates, attributed to lower chelate affinity with linear agents. Effects of age at exposure on retention are unknown, while differences in GBCA washout rates are still under investigation and might affect gadolinium retention relative to time of GBCA administration.

OBJECTIVE

The purpose of this study was to confirm whether gadolinium brain deposits are present in pediatric patients who received GBCAs and to quantify the amounts present.

MATERIALS AND METHODS

Brain autopsy specimens from 10 pediatric patients between 1 year and 13 years of age who underwent at least one contrast-enhanced MR exam were analyzed for elemental gadolinium using inductively coupled plasma mass spectrometry. Brain samples included white matter, basal ganglia (putamen, globus pallidus), thalamus, dentate nucleus and tumor tissue as available. Type and dose of contrast agent, number and timing of contrast-enhanced MR exams and renal function (estimated glomerular filtration rate [eGFR]) were documented for each child.

RESULTS

Patient exposures ranged from 1 dose to 20 doses of GBCAs including both macrocyclic and linear ionic agents. Gadolinium was found to be present in brain tissue in all children and was generally highest in the globus pallidus. Those who received only macrocyclic agents showed lower levels of gadolinium retention.

CONCLUSION

This study demonstrates pathological confirmation of gadolinium retention in brain tissue of a series of pediatric patients exposed to GBCAs including not only linear ionic agents but also macrocyclic agents with both nonionic and ionic compounds. The distribution and deposition levels in this small pediatric population are comparable with the findings in adults. While the clinical significance of these deposits remains unknown, at this point it would be prudent to exert caution and avoid unnecessary use of GBCAs in pediatric patients.

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.

Clinical MR Biomarkers

Non-invasive magnetic resonance imaging (MRI) techniques are increasingly applied in the clinic with a fast growing body of evidence regarding its value for clinical decision making. In contrast to biochemical or histological markers, the key advantages of imaging biomarkers are the non-invasive nature and the spatial and temporal resolution of these approaches. The following chapter focuses on clinical applications of novel MR biomarkers in humans with a strong focus on oncologic diseases. These include both clinically established biomarkers (part 1-4) and novel MRI techniques that recently demonstrated high potential for clinical utility (part 5-7).

Safety and Diagnostic Efficacy of Gadobenate Dimeglumine in MRI of the Brain and Spine of Neonates and Infants

BACKGROUND AND PURPOSE

Contrast-enhanced MR imaging provides essential information for pediatric imaging applications. We evaluated gadobenate dimeglumine for contrast-enhanced MR imaging of infants younger than 2 years of age.

MATERIALS AND METHODS

Ninety children younger than 2 years of age (including 55 children younger than 1 year) who underwent enhanced MR imaging of the CNS with gadobenate dimeglumine at 0.1 mmol/kg body weight ± 25% by volume were retrospectively enrolled at 2 imaging centers. Safety data were assessed for adverse events and, when available, vital signs and electrocardiogram and clinical laboratory values obtained from 48 hours before until 48 hours after the MR imaging examination. The efficacy of gadobenate dimeglumine-enhanced MR imaging was evaluated prospectively by 3 blinded, unaffiliated readers in terms of the accuracy of combined pre- and postcontrast images relative to precontrast images alone for differentiation of tumor from non-neoplastic disease and the correct diagnosis of specific disease. Differences were tested using the McNemar test. A possible effect of dose on diagnostic accuracy was assessed using the Fisher exact test.

RESULTS

Nine nonserious adverse events were reported for 8 (8.8%) patients. Five adverse events occurred in patients 12 months of age or older. All events occurred at least 24 hours after gadobenate dimeglumine administration, and in each case, the investigating radiologist considered that there was no reasonable possibility of a relationship to gadobenate dimeglumine. No clinically meaningful changes in vital signs, electrocardiogram results, or laboratory parameters were reported. Accurate differentiation of tumor from non-neoplastic disease and exact matching of each specific MR imaging-determined diagnosis with the on-site final diagnosis were achieved in significantly more patients by each reader following evaluation of combined pre- and postcontrast images relative to precontrast images alone (91.0%-94.4% versus 75.3%-87.6%, P < .04, and 66.3%-73.0% versus 52.8%-58.4%, P < .02, respectively). No significant differences (P > .133) in diagnostic accuracy were noted between patients receiving ≤0.08 mmol/kg of gadobenate dimeglumine and patients receiving >0.08 mmol/kg of gadobenate dimeglumine.

CONCLUSIONS

Gadobenate dimeglumine is safe and effective for pediatric MR imaging.

Safety of gadoterate meglumine in over 1600 children included in the prospective observational SECURE study

Background

To date, few data on the safety profile of gadoterate meglumine in pediatric patients are available.

Purpose

To assess the safety profile of gadoterate meglumine in routine practice, to detect any case of nephrogenic systemic fibrosis (NSF) suspicion and to collect efficacy data.

Material and Methods

The pediatric population of the observational SECURE study comprised 1631 patients scheduled for contrast-enhanced magnetic resonance imaging (MRI) with gadoterate meglumine (dose: 0.1 mmol/kg). Risk factors, MRI types and immediate adverse events (AEs) were systematically recorded. Patients with moderate to severe renal impairment were followed up for at least 3 months for detection of any NSF suspicion. Efficacy was assessed by the on-site radiologist in terms of image quality and ability to come to diagnosis.

Results

The population included 106 children (6.5%) aged <2 years, 815 (50.0%) aged 2 to <12 years and 710 (43.5%) aged 12 to <18 years, with a mean (± SD) age of 10.2 (± 4.9) years. Central nervous system exploration was the most frequent MRI type (80.4%) and main risk factors were any stage of renal insufficiency (9.8%) and allergies (5.2%). Only one AE (vomiting) that was deemed doubtfully related to gadoterate meglumine was observed. No suspicions of NSF were reported. Good to very good image quality was obtained for 98.4% of pediatric patients and diagnosis was established in 99.6% of cases.

Conclusion

This study confirmed the good safety profile of gadoterate meglumine in routine practice in a large pediatric population. The study is registered on https://clinicaltrials.gov/ with the identifier NCT01523873.

Evaluation of 3.0-T MRI Brain Signal after Exposure to Gadoterate Meglumine in Women with High Breast Cancer Risk and Screening Breast MRI

Background Otherwise healthy women at high risk for breast cancer undergo annual contrast agent-enhanced breast MRI screening examinations, resulting in high cumulative doses of gadolinium-based contrast agents (GBCAs). Whereas the majority of studies showed no T1 signal ratio increase in deep brain nuclei after more than six doses of macrocyclic GBCA, this has not been explored in a healthy study population. Purpose To assess whether women who are administered large cumulative doses of macrocyclic GBCA with breast MRI at high-risk breast cancer screening exhibit T1 alterations in deep brain nuclei. Materials and Methods In this prospective study from November 2017 to March 2018, healthy women who were either exposed (because of high-risk breast cancer screening) or unexposed to only gadoterate meglumine underwent 3.0-T brain MRI with a dedicated head coil, including T1 mapping and magnetization-prepared rapid gradient-echo sequences. T1 times and T1 signal intensities were measured in the dentate nucleus (DN), globus pallidus (GP), crus anterior of capsula interna (CA), and pons. Ratios of DN to pons and GP to CA were calculated, and univariable Pearson correlation coefficients were calculated. Multivariable analysis included partial regression analysis. Results This study evaluated 25 women (mean age, 51 years ± 11 [standard deviation]) who were exposed to a mean GBCA dose of 129 mL (median 112 mL; range, 70-302 mL) and 16 women (mean age, 37 years ± 10) who were never exposed to any GBCA. Infratentorially, no correlation between cumulative GBCA dose and T1 times or signal intensity ratios was detected (P = .66 and .55, respectively). In partial correlation analysis by considering age as a confounder, there was a moderate negative correlation between GP-to-CA ratio and GBCA dose (r = -0.40; P = .01) but not for GP T1 times (r = 0.19; P = .24). Conclusion After administration of relatively large cumulative doses of gadoterate dimeglumine, healthy women at high risk for breast cancer who underwent annual contrast-enhanced breast MRI screening did not exhibit T1 signal increase in deep brain nuclei at 3.0-T MRI. © RSNA, 2019.

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.

Does Age Interfere With Gadolinium Toxicity and Presence in Brain and Bone Tissues?: A Comparative Gadoterate Versus Gadodiamide Study in Juvenile and Adult Rats

OBJECTIVES

The main objective of the study was to assess the effect of age on target tissue total gadolinium (Gd) retention after repeated administration of gadodiamide (linear) or gadoterate (macrocyclic) Gd-based contrast agent (GBCA) in rats. The secondary objective was to assess the potential developmental and long-term consequences of GBCA administration during neonatal and juvenile periods.

MATERIALS AND METHODS

A total of 20 equivalent human clinical doses (cumulated dose, 12 mmol Gd/kg) of either gadoterate or gadodiamide were administered concurrently by the intravenous route to healthy adult and juvenile rats. Saline was administered to juvenile rats forming the control group. In juvenile rats, the doses were administered from postnatal day 12, that is, once the blood-brain barrier is functional as in humans after birth. The tests were conducted on 5 juvenile rats per sex and per group and on 3 adult animals per sex and per group. T1-weighted magnetic resonance imaging of the cerebellum was performed at 4.7 T during both the treatment and treatment-free periods. Behavioral tests were performed in juvenile rats. Rats were euthanatized at 11 to 12 weeks (ie, approximately 3 months) after the last administration. Total Gd concentrations were measured in plasma, skin, bone, and brain by inductively coupled plasma mass spectrometry. Cerebellum samples from the juvenile rats were characterized by histopathological examination (including immunohistochemistry for glial fibrillary acidic protein or GFAP, and CD68). Lipofuscin pigments were also studied by fluorescence microscopy. All tests were performed blindly on randomized animals.

RESULTS

Transient skin lesions were observed in juvenile rats (5/5 females and 2/4 males) and not in adult rats having received gadodiamide. Persisting (up to completion of the study) T1 hyperintensity in the deep cerebellar nuclei (DCNs) was observed only in gadodiamide-treated rats. Quantitatively, a slightly higher progressive increase in the DCN/brain stem ratio was observed in adult rats compared with juvenile rats, whereas no difference was noted visually. In all tissues, total Gd concentrations were higher (10- to 30-fold higher) in the gadodiamide-treated groups than in the gadoterate groups. No age-related differences were observed except in bone marrow where total Gd concentrations in gadodiamide-treated juvenile rats were higher than those measured in adults and similar to those measured in cortical bone tissue. No significant treatment-related effects were observed in histopathological findings or in development, behavior, and biochemistry parameters. However, in the elevated plus maze test, a trend toward an anxiogenic effect was observed in the gadodiamide group compared with other groups (nonsignificant). Moreover, in the balance beam test, a high number of trials were excluded in the gadodiamide group because rats (mainly males) did not completely cross the beam, which may also reflect an anxiogenic effect.

CONCLUSIONS

No T1 hyperintensity was observed in the DCN after administration of the macrocyclic GBCA gadoterate regardless of age as opposed to administration of the linear GBCA gadodiamide. Repeated administration of gadodiamide in neonatal and juvenile rats resulted in similar total Gd retention in the skin, brain, and bone to that in adult rats with sex having no effect, whereas Gd distribution in bone marrow was influenced by age. Further studies are required to assess the form of the retained Gd and to investigate the potential risks associated with Gd retention in bone marrow in juvenile animals treated with gadodiamide. Regardless of age, total Gd concentration in the brain and bone was 10- to 30-fold higher after administration of gadodiamide compared with gadoterate.

Gadolinium-based contrast agents - review of recent literature on magnetic resonance imaging signal intensity changes and tissue deposits, with emphasis on pediatric patients

Gadolinium has been used as a base for contrast agents in MRI for the last three decades. Numerous studies over the last 4 years have reported increased signal intensity in deep brain nuclei in non-contrast MRI images following gadolinium-based contrast agent (GBCA) administration. Pathology studies performed on adults and children, and rodent necropsy studies have also shown gadolinium deposition in brain and other tissues after GBCA administration. The purpose of this review was to summarize and discuss the knowledge gained from these reports and the relevance for imaging pediatric patients.

Gadolinium Accumulation in the Deep Cerebellar Nuclei and Globus Pallidus After Exposure to Linear but Not Macrocyclic Gadolinium-Based Contrast Agents in a Retrospective Pig Study With High Similarity to Clinical Conditions

Objective

The aim of this retrospective study was to determine the gadolinium (Gd) concentration in different brain areas in a pig cohort that received repeated administration of Gd-based contrast agents (GBCAs) at standard doses over several years, comparable with a clinical setting.

Material and Methods

Brain tissue was collected from 13 Göttingen mini pigs that had received repeated intravenous injections of gadopentetate dimeglumine (Gd-DTPA; Magnevist) and/or gadobutrol (Gadovist). The animals have been included in several preclinical imaging studies since 2008 and received cumulative Gd doses ranging from 7 to 129 mmol per animal over an extended period. Two animals with no history of administration of GBCA were included as controls. Brain autopsies were performed not earlier than 8 and not later than 38 months after the last GBCA application. Tissues from multiple brain areas including cerebellar and cerebral deep nuclei, cerebellar and cerebral cortex, and pons were analyzed for Gd using inductively coupled plasma mass spectrometry.

Results

Of the 13 animals, 8 received up to 48 injections of gadobutrol and Gd-DTPA and 5 received up to 29 injections of gadobutrol only. In animals that had received both Gd-DTPA and gadobutrol, a median (interquartile range) Gd concentration of 1.0 nmol/g tissue (0.44-1.42) was measured in the cerebellar nuclei and 0.53 nmol/g (0.29-0.62) in the globus pallidus. The Gd concentration in these areas in gadobutrol-only animals was 50-fold lower with median concentrations of 0.02 nmol/g (0.01-0.02) for cerebellar nuclei and 0.01 nmol/g (0.01-0.01) for globus pallidus and was comparable with control animals with no GBCA history. Accordingly, in animals that received both GBCAs, the amount of residual Gd correlated with the administered dose of Gd-DTPA (P ≤ 0.002) but not with the total Gd dose, consisting of Gd-DTPA and gadobutrol. The Gd concentration in cortical tissue and in the pons was very low (≤0.07 nmol/g tissue) in all animals analyzed.

Conclusion

Multiple exposure to macrocyclic gadobutrol is not associated with Gd deposition in brain tissue of healthy pigs. A single additional administration of linear Gd-DTPA is sufficient for Gd accumulation in the nucleus dentatus and globus pallidus, underlining the importance of obtaining a complete GBCA history in clinical studies.

Pediatric Brain: Gadolinium Deposition in Dentate Nucleus and Globus Pallidus on Unenhanced T1-Weighted Images Is Dependent on the Type of Contrast Agent

PURPOSE

The aim of this study was to identify the signal intensity (SI) changes in the dentate nucleus (DN) and the globus pallidus (GP) on unenhanced T1-weighted magnetic resonance (MR) images after multiple administration of gadolinium-based contrast agents (GBCAs) in children and compare those changes between linear and macrocyclic GBCAs.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board and the requirement for informed consent was waived. We identified 92 children who underwent at least 4 consecutive MR examinations exclusively using either linear GBCA (gadodiamide or gadopentetate dimeglumine, n = 41) or macrocyclic GBCA (gadoterate meglumine, n = 51). Signal intensity ratio changes in the DN to pons and GP to thalamus between the first and last MR examinations were calculated.

RESULTS

The SI ratios in the linear group increased significantly between the first and last MR examinations (mean difference: DN to pons, 0.0461 ± 0.0480, P < 0.001; GP to thalamus, 0.0332 ± 0.0385, P < 0.001), but not in the macrocyclic group (mean difference: DN to pons, -0.0010 ± 0.0371, P = 0.855; GP to thalamus, 0.0007 ± 0.0294, P = 0.867). In the linear regression analysis, the numbers of administrations of gadodiamide and gadopentetate dimeglumine were highly associated with the differences in SI ratios (DN to pons, P < 0.001 and P = 0.003; GP to thalamus, P < 0.001 and P = 0.002, respectively).

CONCLUSION

The SIs of the DN and GP on unenhanced T1-weighted images increased after serial administrations of linear GBCA, but not macrocyclic GBCA, in children. The number of linear GBCA administration had a linear association with the SI changes in the DN and GP.

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.

Comparison of Unenhanced T1-Weighted Signal Intensities Within the Dentate Nucleus and the Globus Pallidus After Serial Applications of Gadopentetate Dimeglumine Versus Gadobutrol in a Pediatric Population

OBJECTIVE

The aim of this study was to evaluate and compare changes in T1-weighted signal intensity (SI) within the dentate nucleus (DN) and globus pallidus (GP) in a pediatric population after serial applications of the linear gadolinium-based magnetic resonance contrast medium gadopentetate dimeglumine and the more stable macrocyclic agent gadobutrol.

MATERIALS AND METHODS

Institutional review board approval was obtained. Two similar pediatric patient cohorts who underwent at least 3 serial contrast-enhanced magnetic resonance imaging (MRI) examinations with sole application of gadopentetate dimeglumine or gadobutrol were analyzed. All MRI examinations were performed on a 1.5 T system acquiring unenhanced T1-weighted spin echo sequences, which were evaluated on the baseline MRI and after the contrast medium administrations. For analysis of SI changes in the DN, the ratios of the DN to the pons (P) and to the middle cerebellar peduncle (MCP) were assessed. The GP was compared with the thalamus (TH) by dividing the SIs between GP and TH (GP-to-TH ratio).

RESULTS

Twenty-eight patients (13 boys, 15 girls; mean age, 8.4 ± 6.8 years) who received at least 3 applications of gadopentetate dimeglumine and 25 patients (13 boys, 12 girls; mean age, 9.7 ± 5.4 years) with 3 or more gadobutrol injections were included. After 3 administrations of gadopentetate dimeglumine, the T1-weighted SI ratios significantly increased: mean difference value of 0.036 ± 0.031 (DN-to-P; P < 0.001), 0.034 ± 0.032 (DN-to-MCP; P < 0.001), and 0.025 ± 0.025 (GP-to-TH; P = 0.001). In a subanalysis of 12 patients with more than 3 injections of gadopentetate dimeglumine, the mean differences of the SI ratios were slightly higher: 0.043 ± 0.032 (DN-to-P; P = 0.001), 0.041 ± 0.035 (DN-to-MCP; P = 0.002), and 0.028 ± 0.025 (GP-to-TH; P = 0.003). In contrast, gadobutrol did not show a significant influence on the SI ratios, neither after 3 nor after more than 3 applications.

CONCLUSIONS

The T1-weighted SI increase within the DN and GP after serial administrations of the linear contrast medium gadopentetate dimeglumine, but not after serial applications of the macrocyclic agent gadobutrol, found in a pediatric population, is consistent with results published for adult patients. The clinical impact of the intracranial T1-hyperintensities is currently unclear. However, in accordance with the recent decision of the Pharmacovigilance and Risk Assessment Committee of the European Medicines Agency, intravenous macrocyclic agents should be preferred and MR contrast media should be used with caution and awareness of the pediatric brain development in children and adolescents.

Gadolinium-enhanced imaging of pediatric thoracic lymphoma: is intravenous contrast really necessary?

OBJECTIVES

Increasing awareness of potential side effects from gadolinium-based contrast agents has underlined the need for contrast-free magnetic resonance imaging (MRI). Numerous recent articles evaluated the risk of potential brain deposits, with the result that research is putting the focus more on alternative unenhanced imaging techniques. The aim of this study was to determine the need for contrast media for chest MRI in primary staging and follow-up care of lymphoma.

METHODS

This monocentric, retrospective study encompassed patients under 25 years of age who had undergone histopathological examination of thoracic lymph nodes and at least one chest MRI examination with unenhanced and contrast-enhanced sequences. Seven different thoracic lymph node stations including mediastinal, hilar, periclavicular, and axillary regions were evaluated by two readers regarding lesion diameter, number, shape, necrosis, and infiltration of surrounding structures. Findings were categorized into suspicious (> 1 cm; round; necrosis; infiltration) or non-suspicious.

RESULTS

Fifty-one patients (mean age, 16.0 ± 3.7 yrs) with thoracic Hodgkin (70.6%) and non-Hodgkin lymphoma (25.5%) and lymphadenopathy (3.9%) were retrospectively included. Most lymph nodes categorized as suspicious were located in the mediastinal station (86.4%). High agreement (κ = 0.81) between unenhanced and contrast-enhanced sequences was found for both suspicious and non-suspicious lymph nodes. Significant (p < 0.001), but small difference (1 mm) was observed only in sizing mediastinal lymph nodes (all other p > 0.05). No significant difference (smallest p = 0.08) was shown for the use of five different types of contrast media.

CONCLUSION

MRI in young patients with thoracic lymphoma can safely be done without the use of contrast agent.

KEY POINT

• Thoracic magnetic resonance imaging in young lymphoma patients can safely be done without gadolinium-based contrast agents.

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.

Half-dose versus full-dose macrocyclic gadolinium at 3-T magnetic resonance imaging in paediatric bone and soft-tissue disease

BACKGROUND

Given the recent concerns about gadolinium-based contrast agent safety, dose reduction strategies are being investigated.

OBJECTIVE

To compare half-dose and standard full-dose gadoterate meglumine at 3-tesla (T) MRI in paediatric bone and soft-tissue diseases.

MATERIALS AND METHODS

We prospectively enrolled 45 children (age range 2.7 months to 17.5 years, median age 8.7 years, 49 total anatomical segments) with bone and soft-tissue diseases (neoplastic, inflammatory/infectious, ischaemic and vascular) imaged at 3-T MRI. Two consecutive half-doses of gadoterate meglumine (0.05 mmol/kg body weight) were administered. Two sets of post-contrast T1-weighted images were obtained, one after the first half dose and the other after the second half dose. For qualitative analysis, three radiologists, masked to the gadolinium dose, compared the diagnostic quality of the images. For quantitative analysis, we compared signal-to-noise ratio and contrast-to-noise ratio at half and full doses.

RESULTS

Signal-to-noise ratio and contrast-to-noise ratio did not vary significantly between the two groups. Qualitative analysis yielded excellent image quality in both post-contrast image datasets (Cohen κ=0.8).

CONCLUSION

In paediatric bone and soft-tissue 3-T MRI, it is feasible to halve the standard dose of gadoterate meglumine without losing image quality.

Gadolinium Deposition in Brain: Current Scientific Evidence and Future Perspectives

In the past 4 years, many publications described a concentration-dependent deposition of gadolinium in the brain both in adults and children, seen as high signal intensities in the globus pallidus and dentate nucleus on unenhanced T1-weighted images. Postmortem human or animal studies have validated gadolinium deposition in these T1-hyperintensity areas, raising new concerns on the safety of gadolinium-based contrast agents (GBCAs). Residual gadolinium is deposited not only in brain, but also in extracranial tissues such as liver, skin, and bone. This review summarizes the current evidence on gadolinium deposition in the human and animal bodies, evaluates the effects of different types of GBCAs on the gadolinium deposition, introduces the possible entrance or clearance mechanism of the gadolinium and potential side effects that may be related to the gadolinium deposition on human or animals, and puts forward some suggestions for further research.

Surveillance magnetic resonance imaging for isolated optic pathway gliomas: is gadolinium necessary?

BACKGROUND

Pediatric optic pathway gliomas are typically indolent but have a variable clinical course. Treatment is dictated by symptoms and changes on contrast-enhanced MRI examinations. Gadolinium retention in children has motivated parsimonious use of gadolinium-based contrast agents.

OBJECTIVES

To determine surveillance MR factors that motivate changes in tumor-directed therapies and extrapolate cost-efficacy of a non-contrast follow-up protocol.

MATERIALS AND METHODS

Using an imaging database search we identified children with isolated optic pathway gliomas and ≥3 follow-up contrast-enhanced MRIs. We reviewed medical records and imaging for: (1) coincident changes on contrast-enhanced MRI and tumor-directed therapy, (2) demographics and duration of follow-up, (3) motivations for intervention, (4) assessment of gadolinium-based contrast agents' utility and (5) health care utilization data. We assessed cost impact in terms of relative value unit (RVU) burden.

RESULTS

We included 17 neurofibromatosis type 1 (NF1) and 21 non-NF1 patients who underwent a median 16.9 and 24.3 cumulative contrast-enhanced MR exams over 7.7 years and 8.1 years of follow-up, respectively. Eight children (one with NF1) had intervention based on contrast-enhanced MR findings alone. For these eight, increased tumor size was the only common feature, and it was apparent on non-contrast T2 sequences. For the median patient, a non-contrast follow-up protocol could result in 15.9 (NF1) and 23.3 (non-NF1) fewer gadolinium-based contrast agent administrations, and a 39% lower yearly RVU burden.

CONCLUSION

Pediatric patients with isolated optic pathway gliomas undergo a large number of routine contrast-enhanced MR follow-up exams. Gadolinium might not be needed for these exams to inform management decisions. Secondary benefits of a non-contrast follow-up protocol include decreased cost and risk to the patient.

Safety of Gadolinium Administration in Children

The introduction of paramagnetic contrast in the late 1980s constituted a paradigm shift boosting the efficacy of magnetic resonance imaging. Due to its high magnetic moment, gadolinium-based contrast agent made its way smoothly as the flagship paramagnetic contrast. With the widespread application, reports of untoward effects started to surface. Allergic reactions, nephrogenic systemic sclerosis, and deposition in brain tissue dented the safety profile of gadolinium-based contrast agent. Better understanding of these adverse effects prompted preventive measures. This article elucidates the gadolinium-based contrast agent toxicity in the pediatric population based on the current available evidence.

Gadolinium Deposition within the Pediatric Brain: No Increased Intrinsic T1-Weighted Signal Intensity within the Dentate Nucleus following the Administration of a Minimum of 4 Doses of the Macrocyclic Agent Gadoteridol

BACKGROUND AND PURPOSE

Our aim was to evaluate whether serial administration of the macrocyclic gadolinium-based contrast agent gadoteridol in children is associated with T1-weighted hyperintensity within the dentate nucleus, an imaging surrogate for gadolinium deposition.

MATERIALS AND METHODS

We identified a retrospective cohort of 10 patients younger than 18 years of age who underwent between 4 and 8 gadoteridol-enhanced MR imaging examinations of the brain from 2016 to 2017. For comparison, we identified a retrospective cohort of 9 pediatric patients who each underwent 6 gadodiamide-enhanced MR imaging examinations. For each examination, both dentate nuclei were contoured on unenhanced images and the mean dentate-to-pons signal intensity ratio was calculated. Dentate-to-pons signal intensity ratios from the first and last scans were compared using paired t tests.

RESULTS

In the gadoteridol group, there was no significant change in the mean dentate-to-pons signal intensity ratio from the first to the last scan (0.99 versus 0.99, P = .59). In the gadodiamide group, there was a significant increase in the mean dentate-to-pons signal intensity ratio from the first to the last scan (0.99 versus 1.10, P = .001).

CONCLUSIONS

Repeat administration of the macrocyclic gadolinium-based contrast agent gadoteridol in children was not associated with T1-weighted dentate hyperintensity, while the repeat administration of the linear gadolinium-based contrast agent gadodiamide was associated with T1-weighted dentate hyperintensity, presumably due to gadolinium deposition.

Gadolinium-based contrast agents in children

Gadolinium-based contrast agents (GBCAs) are widely used in medical imaging, with greater than 300 million doses administered since their introduction. The risk of adverse reactions is very low, and GBCAs were thought to be very safe until the discovery of nephrogenic systemic fibrosis (NSF). Since that time, gadolinium has been found to deposit throughout the body, including the brain, where it is visible on non-contrast T1-weighted MR images in people with normal renal function. The clinical effects of this deposition remain unknown and may not exist. In this review the authors provide a comprehensive update on GBCAs and their potential risks, within a historical context and through the lens of a pediatric radiologist.

Brain-wide glymphatic enhancement and clearance in humans assessed with MRI

To what extent does the subarachnoid cerebrospinal fluid (CSF) compartment communicate directly with the extravascular compartment of human brain tissue? Interconnection between the subarachnoid CSF compartment and brain perivascular spaces is reported in some animal studies, but with controversy, and in vivo CSF tracer studies in humans are lacking. In the present work, we examined the distribution of a CSF tracer in the human brain by MRI over a prolonged time span. For this, we included a reference cohort, representing close to healthy individuals, and a cohort of patients with dementia and anticipated compromise of CSF circulation (idiopathic normal pressure hydrocephalus). The MRI contrast agent gadobutrol, which is confined to the extravascular brain compartment by the intact blood-brain barrier, was used as a CSF tracer. Standardized T1-weighted MRI scans were performed before and after intrathecal gadobutrol at defined time points, including at 24 hours, 48 hours, and 4 weeks. All MRI scans were aligned and brain regions were segmented using FreeSurfer, and changes in normalized T1 signals over time were quantified as percentage change from baseline. The study provides in vivo evidence of access to all human brain subregions of a substance administered intrathecally. Clearance of the tracer substance was delayed in the dementia cohort. These observations translate previous findings in animal studies into humans and open new prospects concerning intrathecal treatment regimens, extravascular contrast-enhanced MRI, and assessment of brain clearance function.