Hyperintense Dentate Nuclei on T1-Weighted MRI: Relation to Repeat Gadolinium Administration

MRI contrast agents and retention in the brain: review of contemporary knowledge and recommendations to the future

Gadolinium-based contrast agents (GBCA) were introduced with high expectations for favorable efficacy, low nephrotoxicity, and minimal allergic-like reactions. Nephrogenic systemic fibrosis and proven gadolinium retention in the body including the brain has led to the restriction of linear GBCAs and a more prudent approach regarding GBCA indication and dosing. In this review, we present the chemical, physical, and clinical aspects of this topic and aim to provide an equanimous and comprehensive summary of contemporary knowledge with a perspective of the future. In the first part of the review, we present various elements and compounds that may serve as MRI contrast agents. Several GBCAs are further discussed with consideration of their relaxivity, chelate structure, and stability. Gadolinium retention in the brain is explored including correlation with the presence of metalloprotein ferritin in the same regions where visible hyperintensity on unenhanced T1-weighted imaging occurs. Proven interaction between ferritin and gadolinium released from GBCAs is introduced and discussed, as well as the interaction of other elements with ferritin; and manganese in patients with impaired liver function or calcium in Fahr disease. We further present the concept that only high-molecular-weight forms of gadolinium can likely visibly change signal intensity on unenhanced T1-weighted imaging. Clinical data are also presented with respect to potential neurological manifestations originating from the deep-brain nuclei. Finally, new contrast agents with relatively high relaxivity and stability are introduced. CRITICAL RELEVANCE STATEMENT: GBCA may accumulate in the brain, especially in ferritin-rich areas; however, no adverse neurological manifestations have been detected in relation to gadolinium retention. KEY POINTS: Gadolinium currently serves as the basis for MRI contrast agents used clinically. No adverse neurological manifestations have been detected in relation to gadolinium retention. Future contrast agents must advance chelate stability and relativity, facilitating lower doses.

Data mining and analysis of the adverse events derived signals of 4 gadolinium-based contrast agents based on the US Food and drug administration adverse event reporting system

BACKGROUND

To detect and analyze risk signals of the drug-related adverse events (AEs) of 4 gadolinium-based contrast agents (GBCAs) (gadopentetate dimeglumine (Gd-DTPA), gadobenate dimeglumine (Gd-BOPTA), gadoteridol (Gd-HP-DO3A), and gadobutrol (Gd-BT-DO3A)) according to the US Food and Drug Administration Adverse Event Reporting System (FAERS) database and ensure the clinical safety.

RESEARCH DESIGN AND METHODS

The AEs that are associated with the 4 GBCAs were collected from the FAERS database from 2004Q1 to 2022Q3. The risk signals were mined using reporting odds ratio (ROR) and proportional reporting ratio (PRR).

RESULTS

424 risk signals were excavated, in which 151 risk signals were associated with Gd-DTPA, 93 risk signals were related to Gd-BOPTA, 79 risk signals were relevant to Gd-HP-DO3A, and 101 risk signals were associated with Gd-BT-DO3A. The AE signals involved 20 system organ classes (SOCs). Two of the top four SOCs were identical, namely 'skin and subcutaneous tissue disorders' and 'general disorders and administration site conditions.'

CONCLUSIONS

The safety signals of 4 GBCAs were detected, and the SOCs associated with the AEs of the 4 GBCAs were different. Besides, some AEs obtained in this study were not mentioned in the package inserts, which need more attention and research to ensure the clinical safety.

Where does the gadolinium go? A review into the excretion and retention of intravenous gadolinium

Gadolinium-based contrast agents (GBCAs) are commonly used in medical imaging. Most intravenously (IV) administered gadolinium is excreted via the kidneys, and pathological retention in renal failure leading to nephrogenic systemic fibrosis (NSF) is well described. More recently, retention of gadolinium in the body in the absence of renal disease has been identified, with unknown clinical consequences. Many patients are aware of this, either through the media or via comprehensive consent documentation. Some internet sites, without hard evidence, have suggested a constellation of possible symptoms associated with GBCA retention. Recent experience with patients ascribing symptoms to a contrast-enhanced MRI examination prompted this review of the fate of injected GBCA after MRI study, and of information available to patients online regarding gadolinium retention.

Endolymphatic space is age-dependent

Knowledge of the physiological endolymphatic space (ELS) is necessary to estimate endolymphatic hydrops (ELH) in patients with vestibulocochlear syndromes. Therefore, the current study investigated age-dependent changes in the ELS of participants with normal vestibulocochlear testing. Sixty-four ears of 32 participants with normal vestibulocochlear testing aged between 21 and 75 years (45.8 ± 17.2 years, 20 females, 30 right-handed, two left-handed) were examined by intravenous delayed gadolinium-enhanced magnetic resonance imaging of the inner ear (iMRI). Clinical diagnostics included neuro-otological assessment, video-oculography during caloric stimulation, and head-impulse test. iMRI data analysis provided semi-quantitative visual grading and automatic algorithmic quantitative segmentation of ELS volume (3D, mm³) using a deep learning-based segmentation of the inner ear's total fluid space (TFS) and volumetric local thresholding, as described earlier. As a result, following a 4-point ordinal scale, a mild ELH (grade 1) was found in 21/64 (32.8%) ears uni- or bilaterally in either cochlear, vestibulum, or both. Age and ELS were found to be positively correlated for the inner ear (r(64) = 0.33, p < 0.01), and vestibulum (r(64) = 0.25, p < 0.05). For the cochlea, the values correlated positively without reaching significance (r(64) = 0.21). In conclusion, age-dependent increases of the ELS should be considered when evaluating potential ELH in single subjects and statistical group comparisons.

c-Met-Targeting 19F MRI Nanoparticles with Ultralong Tumor Retention for Precisely Detecting Small or Ill-Defined Colorectal Liver Metastases

Purpose

Precisely detecting colorectal liver metastases (CLMs), the leading cause of colorectal cancer-associated mortality, is extremely important. ¹H MRI with high soft tissue resolution plays a key role in the diagnosing liver lesions; however, precise detecting CLMs by ¹H MRI is a great challenge due to the limited sensitivity. Even though contrast agents may improve the sensitivity, due to their short half-life, repeated injections are required to monitor the changes of CLMs. Herein, we synthesized c-Met-targeting peptide-functionalized perfluoro-15-crown-5-ether nanoparticles (AH111972-PFCE NPs), for highly sensitive and early diagnosis of small CLMs.

Methods

The size, morphology and optimal properties of the AH111972-PFCE NPs were characterized. c-Met specificity of the AH111972-PFCE NPs was validated by in vitro experiment and in vivo ¹⁹F MRI study in the subcutaneous tumor murine model. The molecular imaging practicability and long tumor retention of the AH111972-PFCE NPs were evaluated in the liver metastases mouse model. The biocompatibility of the AH111972-PFCE NPs was assessed by toxicity study.

Results

AH111972-PFCE NPs with regular shape have particle size of 89.3 ± 17.8 nm. The AH111972-PFCE NPs exhibit high specificity, strong c-Met-targeting ability, and precise detection capability of CLMs, especially small or ill-defined fused metastases in ¹H MRI. Moreover, AH111972-PFCE NPs could be ultralong retained in metastatic liver tumors for at least 7 days, which is conductive to the implementation of continuous therapeutic efficacy monitoring. The NPs with minimal side effects and good biocompatibility are cleared mainly via the spleen and liver.

Conclusion

The c-Met targeting and ultralong tumor retention of AH111972-PFCE NPs will contribute to increasing therapeutic agent accumulation in metastatic sites, laying a foundation for CLMs diagnosis and further c-Met targeted treatment integration. This work provides a promising nanoplatform for the future clinical application to patients with CLMs.

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.

Does Gadolinium Deposition Lead to Metabolite Alteration in the Dentate Nucleus? An MRS Study in Patients with MS

BACKGROUND AND PURPOSE

Repeat contrast-enhanced MR imaging exposes patients with relapsing-remitting MS to frequent administration of gadolinium-based contrast agents. We aimed to investigate the potential metabolite and neurochemical alterations of visible gadolinium deposition on unenhanced T1WI in the dentate nucleus using MRS.

MATERIALS AND METHODS

This prospective study was conducted in a referral university hospital from January 2020 to July 2021. The inclusion criteria for case and control groups were as follows: 1) case: patients with relapsing-remitting MS, visible gadolinium deposition in the dentate nucleus (ribbon sign), >5 contrast-enhanced MR images obtained; 2) control 1: patients with relapsing-remitting MS without visible gadolinium deposition in the dentate nucleus, >5 contrast-enhanced MR images obtained; 3) control 2: patients with relapsing-remitting MS without visible gadolinium deposition in the dentate nucleus, <5 contrast-enhanced-MR images obtained; and 4) control 3: adult healthy individuals, with no contrast-enhanced MR imaging. Dentate nucleus and pontine single-voxel 12 × 12 × 12 MRS were analyzed using short TEs.

RESULTS

Forty participants (10 per group; 27 [67.5%] female; mean age, 35.6 [SD, 9.6] years) were enrolled. We did not detect any significant alteration in the levels of NAA and choline between the studied groups. The mean concentrations of mIns were 2.7 (SD, 0.73) (case), 1.5 (SD, 0.8) (control 1), 2.4 (SD, 1.2) (control 2), and 1.7 (SD, 1.2) (control 3) (P = .04). The mean concentration of Cr and mIns (P = .04) and the relative metabolic concentration (dentate nucleus/pons) of lipid 1.3/Cr (P = .04) were significantly higher in the case-group than in healthy individuals (controls 1-3). Further analyses compared the case group with cumulative control 1 and 2 groups and showed a significant increase in lactate (P = .02), lactate/Cr (P = .04), and Cr (dentate nucleus/pons) (P = .03) in the case group.

CONCLUSIONS

Although elevated concentrations of Cr, lactate, mIns, and lipid in the dentate nucleus of the case group indicate a metabolic disturbance, NAA and choline levels were normal, implying no definite neuronal damage.

Safety considerations related to intravenous contrast agents in pediatric imaging

Intravenous contrast media are used in MRI, CT and US studies for anatomical evaluation and lesion characterization. Safety is always of paramount importance when administering any contrast media to children, and it is important for radiologists and ordering providers to be knowledgeable of the safety profiles and potential adverse events that can occur. This manuscript reviews the frequency and types of adverse events associated with intravenous contrast agents reported in the pediatric literature. Overall, intravenous contrast agents are very safe to use in children. However, familiarity with how to treat and prevent these uncommon events is crucial in preventing poor outcomes. In addition, an understanding of gadolinium deposition in tissues can help facilitate conversations with concerned physicians and parents. This review provides a concise yet comprehensive reference for radiologists and ordering providers on intravenous contrast safety considerations in the pediatric patient.

Gadolinium retention after contrast-enhanced magnetic resonance imaging: A narratative review

Over the past five years, several studies have reported deposition and retention of gadolinium in the brain after administration of gadolinium-based contrast agents (GBCAs) during radiological procedures. Patients with renal insufficiency cannot filter gadolinium efficiently; however, gadolinium is also retained in the brain of some adults and pediatrics with no renal impairment. In the literature, data is mostly available from retrospective magnetic resonance imaging (MRI) studies, where gadolinium deposition may be indirectly measured by evaluating changes in T1 signal intensity in the brain tissues, particularly in the deep gray matter such as the dentate nucleus and/or globus pallidus. Many pathological studies have reported a direct correlation between T1 signal changes and gadolinium deposition in human and animal autopsy specimens, which raised concerns on the use of GBCAs, particularly with linear chelators. The association between gadolinium accumulation and occurrence of physical and neurological side effects or neurotoxic damage has not yet been conclusively demonstrated. Studies have also observed that gadolinium is deposited in the extracranial tissues, such as the liver, skin, and bone, of patients with normal kidney function. This narrative review describes the effects of different types of GBCAs in relation to gadolinium deposition, evaluates current evidence on gadolinium deposition in various tissues of the human body, and summarizes the current recommendations regarding the use of GBCAs.

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.

Evaluation of the effect of multiple administrations of gadopentetate dimeglumine or gadoterate meglumine on brain T1-weighted hyperintensity in pediatric patients

BACKGROUND

Repeated administrations of linear gadolinium-based contrast media (GBCM) are associated with T1-weighted (T1-W) signal intensity change in brain structures.

OBJECTIVE

The purpose of this study was to compare different brain structures in children after unconfounded, repeated administrations of either a macrocyclic or linear GBCM.

MATERIALS AND METHODS

We performed a retrospective cohort study, identifying subjects with ≥5 unconfounded administrations of gadoterate meglumine. We matched subjects with repeated administrations of gadopentetate dimeglumine to the gadoterate meglumine arm based on the number of unconfounded GBCM administrations. Two reviewers drew regions of interest on 27 structures in and around the brain. We recorded demographic, modality and study parameters and evaluated them to determine whether they were associated with T1-W signal intensity (SI) changes. Linear mixed effects models evaluated the relationships between the number of GBCM doses and T1-W SI ratio. Finally, we identified differences in the rate of T1-W SI ratio change among individuals using a linear mixed effects model with random slope.

RESULTS

We included a total of 52 patients (age range at first MRI: 6.0 months to 17.1 years), 26 in each arm. We detected a significant change in the T1-W SI ratio with repeated administrations of GBCM in one location in the gadoterate meglumine arm and in four locations in the gadopentetate dimeglumine arm. Patient gender and age were not associated with T1-W SI change. Modality vendor, imaging sequence and field strength were variably associated with a systematic difference in the ability to detect a T1-W SI change. Finally, linear mixed effects model with random slope showed that there were individual differences in the slope of SI change at various structures among individuals for both arms. This effect was present in more brain structures in the gadopentetate dimeglumine arm (14 vs. 8).

CONCLUSION

There is a significant change in the T1-W SI ratio over time in multiple brain structures after repeated gadopentetate dimeglumine administrations. This effect was only seen in one ratio after repeated administrations of gadoterate meglumine. There are individual differences in the rate of change of SI ratios over time after repeated administration of gadopentetate dimeglumine and gadoterate meglumine, suggesting that individual differences are present.

Gadolinium Tissue Distribution in a Large-Animal Model after a Single Dose of Gadolinium-based Contrast Agents

Background There is an ongoing scientific debate about the degree and clinical importance of gadolinium deposition in the brain and other organs after administration of gadolinium-based contrast agents (GBCAs). While most published data focus on gadolinium deposition in the brain, other organs are rarely investigated. Purpose To compare gadolinium tissue concentrations in various organs 10 weeks after one injection (comparable to a clinically applied dose) of linear and macrocyclic GBCAs in a large-animal model. Materials and Methods In this prospective animal study conducted from March to May 2018, 36 female Swiss-Alpine sheep (age range, 4-10 years) received one injection (0.1 mmol/kg) of macrocyclic GBCAs (gadobutrol, gadoteridol, and gadoterate meglumine), linear GBCAs (gadodiamide and gadobenate dimeglumine), or saline. Ten weeks after injection, sheep were sacrificed and tissues were harvested. Gadolinium concentrations were quantified with inductively coupled plasma mass spectrometry (ICP-MS). Histologic staining was performed. Data were analyzed with nonparametric tests. Results At 10 weeks after injection, linear GBCAs resulted in highest mean gadolinium concentrations in the kidney (502 ng/g [95% CI: 270, 734]) and liver (445 ng/g [95% CI: 202, 687]), while low concentrations were found in the deep cerebellar nuclei (DCN) (30 ng/g [95% CI: 20, 41]). Tissue concentrations of linear GBCAs were three to 21 times higher compared with those of macrocyclic GBCAs. Administered macrocyclic GBCAs resulted in mean gadolinium concentrations of 86 ng/g (95% CI: 31, 141) (P = .08) in the kidney, 21 ng/g (95% CI: 4, 39) (P = .15) in liver tissue, and 10 ng/g (95% CI: 9, 12) (P > .99) in the DCN, which were not significantly elevated when compared with concentrations in control animals. No histopathologic alterations were observed irrespective of tissue concentrations within any examined organ. Conclusion Ten weeks after one injection of a clinically relevant dose of gadolinium-based contrast agents, the liver and kidney appeared to be reservoirs of gadolinium; however, despite gadolinium presence, no tissue injury was detected. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Clément in this issue.

Gadolinium based contrast agents in current practice: Risks of accumulation and toxicity in patients with normal renal function

Despite being decked as the most prized compounds in the nugget box of contrast agents for clinical radiologists, and carrying an indisputable tag of safety of the US Food and Drug Administration for close to three decades, all may not be seemingly well with the family of gadolinium compounds. If the first signs of violations of primum non nocere in relation to gadolinium-based contrast agents (GBCAs) appeared in the millennium year with the first published report of skin fibrosis in patients with compromised renal function, the causal relationship between the development of nephrogenic systemic fibrosis (NSF) and GBCAs, first proposed by two European groups in 2006, further precluded their use in renocompromised patients. The toxicity, pharmacokinetics, and pharmacodynamics of GBCAs, however, has come under hawk-eyed scrutiny with recent reports that gadolinium tends to deposit cumulatively in the brain of patients with normal hepatobiliary function and intact blood–brain barrier. While the jury on the long-term hazard significance of this critical scientific finding is still out, the use of GBCAs must be guided by due clinical diligence, avoidance of repeated doses, and preferring GBCAs with the best safety profiles.

Gray Matter Nucleus Hyperintensity After Monthly Triple-Dose Gadopentetate Dimeglumine With Long-term Magnetic Resonance Imaging

OBJECTIVES

Gadolinium deposition is widely believed to occur, but questions regarding accumulation pattern and permanence remain. We conducted a retrospective study of intracranial signal changes on monthly triple-dose contrast-enhanced magnetic resonance imaging (MRI) examinations from the previously published Betaseron vs. Copaxone in Multiple Sclerosis With Triple-Dose Gadolinium and 3-Tesla MRI Endpoints Trial (N = 67) to characterize the dynamics of gadolinium deposition in several deep brain nuclei and track persistence versus washout of gadolinium deposition on long-term follow-up (LTFU) examinations (N = 28) obtained approximately 10 years after enrollment in the Betaseron vs. Copaxone in Multiple Sclerosis With Triple-Dose Gadolinium and 3-Tesla MRI Endpoints Trial.

MATERIALS AND METHODS

Using T2 and proton density images and using image analysis software (ITK-SNAP), manual regions of interest were created ascribing boundaries of the caudate nucleus, dentate nucleus, globus pallidus, pulvinar, putamen, white matter, and air. Intensity analysis was conducted on T1-weighted fat-saturated (fat-sat) images using the FSL package. A linear rigid-body transform was calculated from the fat-sat image at each target time point to the region of interest segmentation reference time point fat-sat image. Serial MRI signal was analyzed using linear mixed regression modeling with random intercept. Annual MRI signal changes including LTFU scans were assessed with t test.

RESULTS

During monthly scanning, all gray matter structures demonstrated a significant (P < 0.0001) increase in contrast-to-noise ratio. Yearly changes in deposition showed distinctive patterns for the specific nucleus: globus pallidus showed complete retention, pulvinar showed partial washout, while dentate, caudate, and putamen returned to baseline (ie, complete washout).

CONCLUSIONS

Monthly increased contrast-to-noise ratio in gray matter nuclei is consistent with gadolinium deposition over time. The study also suggests that some deep gray matter nuclei permanently retain gadolinium, whereas others demonstrate washout of soluble gadolinium.

Intravenous Delayed Gadolinium-Enhanced MR Imaging of the Endolymphatic Space: A Methodological Comparative Study

In-vivo non-invasive verification of endolymphatic hydrops (ELH) by means of intravenous delayed gadolinium (Gd) enhanced magnetic resonance imaging of the inner ear (iMRI) is rapidly developing into a standard clinical tool to investigate peripheral vestibulo-cochlear syndromes. In this context, methodological comparative studies providing standardization and comparability between labs seem even more important, but so far very few are available. One hundred eight participants [75 patients with Meniere's disease (MD; 55.2 ± 14.9 years) and 33 vestibular healthy controls (HC; 46.4 ± 15.6 years)] were examined. The aim was to understand (i) how variations in acquisition protocols influence endolymphatic space (ELS) MR-signals; (ii) how ELS quantification methods correlate to each other or clinical data; and finally, (iii) how ELS extent influences MR-signals. Diagnostics included neuro-otological assessment, video-oculography during caloric stimulation, head-impulse test, audiometry, and iMRI. Data analysis provided semi-quantitative (SQ) visual grading and automatic algorithmic quantitative segmentation of ELS area [2D, mm²] and volume [3D, mm³] using deep learning-based segmentation and volumetric local thresholding. Within the range of 0.1-0.2 mmol/kg Gd dosage and a 4 h ± 30 min time delay, SQ grading and 2D- or 3D-quantifications were independent of signal intensity (SI) and signal-to-noise ratio (SNR; FWE corrected, p < 0.05). The ELS quantification methods used were highly reproducible across raters or thresholds and correlated strongly (0.3-0.8). However, 3D-quantifications showed the least variability. Asymmetry indices and normalized ELH proved the most useful for predicting quantitative clinical data. ELH size influenced SI (cochlear basal turn p < 0.001), but not SNR. SI could not predict the presence of ELH. In conclusion, (1) Gd dosage of 0.1-0.2 mmol/kg after 4 h ± 30 min time delay suffices for ELS quantification. (2) A consensus is needed on a clinical SQ grading classification including a standardized level of evaluation reconstructed to anatomical fixpoints. (3) 3D-quantification methods of the ELS are best suited for correlations with clinical variables and should include both ears and ELS values reported relative or normalized to size. (4) The presence of ELH increases signal intensity in the basal cochlear turn weakly, but cannot predict the presence of ELH.

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.

A retrospective cohort evaluation of the effect of multiple administrations of gadopentetate dimeglumine on brain magnetic resonance imaging T1-weighted signal

BACKGROUND

Gadolinium deposition occurs following repeated administration of gadolinium-based contrast media. However, few studies have evaluated factors that lead to increased detection of deposition or the individual differences among patients.

OBJECTIVE

To measure the effect of repeated dosages of gadopentetate dimeglumine on pediatric brains and to determine the factors that influence signal intensity changes.

MATERIALS AND METHODS

A retrospective study evaluated magnetic resonance imaging (MRI) in patients <18 years of age who received >5 doses of gadopentetate dimeglumine. Regions of interest were placed in 30 locations in the brain on axial precontrast T1 images. Signal intensity ratios were evaluated throughout the brain. The effect of increasing gadopentetate dimeglumine exposure on signal intensity ratios was assessed using linear mixed models adjusted for gender, age, imaging sequence type (fast spin echo or gradient echo), MRI manufacturer (General Electric, Philips or Siemens), and field strength (1.5 tesla [T] or 3 T). Finally, the variance of the random slope in the linear mixed models was tested to determine if there were differences in the rate of signal intensity ratio change among individuals.

RESULTS

Fifty patients (M:F=25:25; mean age at first imaging: 6.4 years) with a mean of 21.5 gadopentetate dimeglumine administrations (range: 6-86) were included. There were significant increases in T1 signal in the globus pallidus, dentate nucleus and pulvinar with an increasing number of contrast administrations. Patient gender, age, and MRI field strength were not associated with changing signal intensity ratios. However, MRI sequence type and vendor significantly impacted some measured signal intensity ratios. Finally, significant differences in the slopes of the ratios were present among patients for multiple locations.

CONCLUSION

Repeated administration of gadopentetate dimeglumine is associated with T1 hyperintense signal in the dentate nucleus, globus pallidus and pulvinar. Detection is significantly affected by MRI sequence type and scanner vendor. Even when accounting for these differences, there are individual differences in the slope of signal intensity change suggesting a patient-level effect influences gadolinium deposition.

Five-dimensional quantitative low-dose Multitasking dynamic contrast- enhanced MRI: Preliminary study on breast cancer

PURPOSE

To develop a low-dose Multitasking DCE technique (LD-MT-DCE) for breast imaging, enabling dynamic T₁ mapping-based quantitative characterization of tumor blood flow and vascular properties with whole-breast coverage, a spatial resolution of 0.9 × 0.9 × 1.1 mm³ , and a temporal resolution of 1.4 seconds using a 20% gadolinium dose (0.02 mmol/kg).

METHODS

Magnetic resonance Multitasking was used to reconstruct 5D images with three spatial dimensions, one T₁ recovery dimension for dynamic T₁ quantification, and one DCE dimension for contrast kinetics. Kinetic parameters F p , v p , K trans , and v e were estimated from dynamic T₁ maps using the two-compartment exchange model. The LD-MT-DCE repeatability and agreement against standard-dose MT-DCE were evaluated in 20 healthy subjects. In 7 patients with triple-negative breast cancer, LD-MT-DCE image quality and diagnostic results were compared with that of standard-dose clinical DCE in the same imaging session. One-way unbalanced analysis of variance with Tukey test was performed to evaluate the statistical significance of the kinetic parameters between control and patient groups.

RESULTS

The LD-MT-DCE technique was repeatable, agreed with standard-dose MT-DCE, and showed excellent image quality. The diagnosis using LD-MT-DCE matched well with clinical results. The values of F p , v p , and K trans were significantly different between malignant tumors and normal breast tissue (P < .001, < .001, and < .001, respectively), and between malignant and benign tumors (P = .020, .003, and < .001, respectively).

CONCLUSION

The LD-MT-DCE technique was repeatable and showed excellent image quality and equivalent diagnosis compared with standard-dose clinical DCE. The estimated kinetic parameters were capable of differentiating between normal breast tissue and benign and malignant tumors.

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.

Signal changes in enhanced T1-weighted images related to gadolinium retention: A three-time-point imaging study

BACKGROUND AND PURPOSE

Concern has grown about the finding of gadolinium deposits in the brain after administering gadolinium-based contrast agents (GBCAs). The mechanism is unclear, and related questions remain unanswered, including the stability over time. Therefore, we conducted a three-time-point study to explore T1-weighted (W) signal changes in the dentate nucleus (DN) and globus pallidus (GP), after the first, fifth, and tenth injections of either a macrocyclic agent (gadoterate meglumine) or a linear agent (gadobenate dimeglumine).

MATERIALS AND METHODS

For this retrospective, multicenter, longitudinal study, two groups of 18 (gadoterate meglumine) and 19 (gadobenate dimeglumine) patients were identified. The evolution of the signal over time was analyzed using DN/pons (DN/P) and GP/thalamus (GP/T) ratios.

RESULTS

DN/P and GP/T ratios tended to increase after the fifth administration of gadobenate dimeglumine, following by a downward trend. A trend in a decrease in DN/P and GP/T ratios were found after the fifth and tenth administrations of gadoterate meglumine.

CONCLUSION

After exposure to gadobenate dimeglumine, the signal intensity (SI) tended to increase after the fifth injection owing to gadolinium accumulation, however, a SI increase was not found after the tenth administration supporting the hypothesis of a slow elimination of the previously retained gadolinium (wash-out effect) from the brain or of a change in form (by dechelation), causing the signal to fade. No increasing SI was found in the DN and GP after exclusive exposure to gadoterate meglumine, thus confirming its stability. We found, instead, a trend for a significative gadolinium elimination over time.

A comparison of arterial spin labelling with catheter angiography in evaluating arteriovenous malformations: a systematic review

OBJECTIVES

To compare the performance of arterial spin labelling (ASL) in evaluating arteriovenous malformations (AVMs) against the current gold standard of catheter angiography.

METHODS

We systematically reviewed the published literature using EMBASE and Medline. We included studies that compared ASL to catheter angiography in the assessment of AVMs in three outcome domains: detection, angioarchitectural and haemodynamic features.

RESULTS

From 314 unique citations, 19 studies representing 289 patients with intracranial AVMs met our inclusion criteria. We did not pool data due to marked heterogeneity in study outcome measures. Seven studies showed high diagnostic performance of ASL in identifying arterial feeders, with sensitivity ranging from 84.6 to 100% and specificity ranging from 93.3 to 100%. Six studies showed strong ability in detecting arteriovenous shunting, with sensitivity ranging from 91.7 to 100% and specificity ranging from 90 to 100%. Seven studies demonstrated that ASL could identify nidal location and size as well as catheter angiography, while five studies showed relatively poorer performance in delineating venous drainage. Two studies showed 100% sensitivity of ASL in the identification of residual or obliterated AVMs following stereotactic radiosurgery.

CONCLUSIONS

Despite limitations in the current evidence base and technical challenges, this review suggests that ASL has a promising role in the work-up and post-treatment follow-up of AVMs. Larger scale prospective studies assessing the diagnostic performance of ASL are warranted.

ADVANCES IN KNOWLEDGE

ASL demonstrates overall validity in the evaluation of intracranial AVMs.

Hot spot 19 F magnetic resonance imaging of inflammation

Among the preclinical molecular imaging approaches, lately fluorine (¹⁹ F) magnetic resonance imaging (MRI) has garnered significant scientific interest in the biomedical research community, due to the unique properties of fluorinated materials and the ¹⁹ F nucleus. Fluorine is an intrinsically sensitive nucleus for MRI-there is negligible endogenous ¹⁹ F in the body and, thus, no background signal which allows the detection of fluorinated materials as "hot spots" by combined ¹ H/¹⁹ F MRI and renders fluorine-containing molecules as ideal tracers with high specificity. In addition, perfluorocarbons are a family of compounds that exhibit a very high fluorine payload and are biochemically as well as physiologically inert. Perfluorocarbon nanoemulsions (PFCs) are well known to be readily taken up by immunocompetent cells, which can be exploited for the unequivocal identification of inflammatory foci by tracking the recruitment of PFC-loaded immune cells to affected tissues using ¹ H/¹⁹ F MRI. The required ¹⁹ F labeling of immune cells can be accomplished either ex vivo by PFC incubation of isolated endogenous immune cells followed by their re-injection or by intravenous application of PFCs for in situ uptake by circulating immune cells. With both approaches, inflamed tissues can unambiguously be detected via background-free ¹⁹ F signals due to trafficking of PFC-loaded immune cells to affected organs. To extend ¹⁹ F MRI tracking beyond cells with phagocytic properties, the PFC surface can further be equipped with distinct ligands to generate specificity against epitopes and/or types of immune cells independent of phagocytosis. Recent developments also allow for concurrent detection of different PFCs with distinct spectral signatures allowing the simultaneous visualization of several targets, such as various immune cell subtypes labeled with these PFCs. Since ligands and targets can easily be adapted to a variety of problems, this approach provides a general and versatile platform for inflammation imaging which will strongly extend the frontiers of molecular MRI. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease.

Investigation of potential adverse central nervous system effects after long term oral administration of gadolinium in mice

Objectives

To examine potential gadolinium (Gd) accumulation in the brain of healthy mice after long-term oral administration of Gd-containing food pellets and to investigate whether Gd leads to adverse central nervous system (CNS) effects, specifically focussing on locomotor impairment in Gd exposed compared to control animals.

Materials and methods

The local Animal Experimental Ethics Committee approved all procedures and applications. Fifteen female C57Bl/6 mice were orally exposed to a daily intake of 0.57 mmol Gd chloride/ kg body weight over a period of 90 weeks from the age of 4 weeks on. Gd-free, but otherwise equivalent experimental diets were given to the control group (N = 13). The animals were monitored daily by animal caretakers regarding any visible signs of distress and evaluated clinically every four weeks for the first 60 weeks and afterwards every two weeks for a better temporal resolution of potential long-term effects regarding impairment of motor performance and loss of body weight. The individual Gd content was measured using mass spectrometry in a sub-cohort of N = 6 mice.

Results

The absolute brain Gd levels of the Gd-exposed mice were significantly increased compared to control mice (0.033± 0.009 vs. 0.006± 0.002 nmol Gd/ g brain tissue). Long-term oral Gd exposure over almost the entire life-span did not lead to adverse CNS effects including locomotor changes (rotarod performance, p = 0.1467) in healthy mice throughout the study period. Gd-exposed mice showed less increased body weight compared to control mice during the study period (p = 0.0423). Histopathological alterations, such as hepatocellular vacuolization due to fatty change in the liver and a loss of nucleated cells in the red pulp of the spleen, were found in peripheral organs of both groups.

Conclusions

Low levels of intracerebral Gd caused by chronic oral exposure over almost the entire life span of mice did not lead to alterations in locomotor abilities in healthy mice throughout the normal aging process.

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

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

Absence of T1 Hyperintensity in the Brain of High-risk Patients After Multiple Administrations of High-dose Gadobutrol for Cardiac Magnetic Resonance

PURPOSE

A prospective study was conducted to evaluate signal changes in the dentate nucleus, globus pallidus, pons, and thalamus (normalized to the deep cerebellum white matter) in T1-weighted magnetic resonance (MR) images after serial injections of gadobutrol in patients with thalassemia without neurological lesions.

METHODS

In this study three groups were scanned at both 1.5 T and 3 T: 15 thalassemia patients transfused and chelated with ≥4 gadobutrol administrations at a high dose (0.2 mmol/kg per scan) for late gadolinium enhancement (LGE) cardiovascular MR, 8 thalassemia patients and 13 healthy subjects who had never received gadolinium-based contrast agents (GBCA).

RESULTS

Signal intensity (SI) ratios at 1.5 T in all regions were comparable among the three groups and were not correlated with the number of gadobutrol administrations. In healthy subjects SI ratios were significantly different among the 4 regions, being higher in the pallidus. The SI ratios at 1.5 T were significantly higher and not correlated with SI ratios at 3 T or with iron overload in the same regions assessed by the T2* technique.

CONCLUSION

This article describes the lack of increased SI in T1-weighted MR images after repeated administration of gadobutrol for cardiovascular MR studies in a high-risk population (high dose per scan, iron overload that can facilitate the transmetalation of gadolinium) scanned at 3 T and 1.5 T.

Fibromyalgia associated with repeated gadolinium contrast-enhanced MRI examinations

We report a case of a fibromyalgia (FM) patient with an history of brain-cancer presenting signs and symptoms of gadolinium toxicity following repeated administrations of a macrocyclic contrast agent, Gadovist. In the present report, we provide evidence supporting the hypothesis of a causal relationship linking gadolinium deposition to a clinical manifestation of disease, namely fibromyalgia. We unravel a role for gadolinium in the still unknown etiology of fibromyalgia as a metal toxicity disorder. Contrast agents are routinely administered in a clinical context. It is thus possible that the patients are mistakenly believed to show complaint of their primary disease, whereas, in some instances, their symptoms are associated with gadolinium deposition.

Follow-Up MRI for Small Brain AVMs Treated by Radiosurgery: Is Gadolinium Really Necessary?

BACKGROUND AND PURPOSE

Follow-up MR imaging of brain AVMs currently relies on contrast-enhanced sequences. Noncontrast techniques, including arterial spin-labeling and TOF, may have value in detecting a residual nidus after radiosurgery. The aim of this study was to compare noncontrast with contrast-enhanced MR imaging for the differentiation of residual-versus-obliterated brain AVMs in radiosurgically treated patients.

MATERIALS AND METHODS

Twenty-eight consecutive patients with small brain AVMs (<20 mm) treated by radiosurgery were followed with the same MR imaging protocol. Three neuroradiologists, blinded to the results, independently reviewed the following: 1) postcontrast images alone (4D contrast-enhanced MRA and postcontrast 3D T1 gradient recalled-echo), 2) arterial spin-labeling and TOF images alone, and 3) all MR images combined. The primary end point was the detection of residual brain AVMs using a 5-point scale, with DSA as the reference standard.

RESULTS

The highest interobserver agreement was for arterial spin-labeling/TOF (κ = 0.81; 95% confidence interval, 0.66-0.93). Regarding brain AVM detection, arterial spin-labeling/TOF had higher sensitivity (sensitivity, 85%; specificity, 100%; 95% CI, 62-97) than contrast-enhanced MR imaging (sensitivity, 55%; specificity, 100%; 95% CI, 27-73) and all MR images combined (sensitivity, 75%; specificity, 100%; 95% CI, 51-91) (P = .008). All nidus obliterations on DSA were detected on MR imaging. In 6 patients, a residual brain AVM present on DSA was only detected with arterial spin-labeling/TOF, including 3 based solely on arterial spin-labeling images.

CONCLUSIONS

In this study of radiosurgically treated patients with small brain AVMs, arterial spin-labeling/TOF was found to be superior to gadolinium-enhanced MR imaging in detecting residual AVMs.

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.

Chemokine receptor 4 targeted protein MRI contrast agent for early detection of liver metastases

Liver metastases often progress from primary cancers including uveal melanoma (UM), breast, and colon cancer. Molecular biomarker imaging is a new non-invasive approach for detecting early stage tumors. Here, we report the elevated expression of chemokine receptor 4 (CXCR4) in liver metastases in UM patients and metastatic UM mouse models, and development of a CXCR4-targeted MRI contrast agent, ProCA32.CXCR4, for sensitive MRI detection of UM liver metastases. ProCA32.CXCR4 exhibits high relaxivities (r ₁ = 30.9 mM^-1 s^-1, r ₂ = 43.2 mM^-1 s^-1, 1.5 T; r ₁ = 23.5 mM^-1 s^-1, r ₂ = 98.6 mM^-1 s^-1, 7.0 T), strong CXCR4 binding (K _d = 1.10 ± 0.18 μM), CXCR4 molecular imaging capability in metastatic and intrahepatic xenotransplantation UM mouse models. ProCA32.CXCR4 enables detecting UM liver metastases as small as 0.1 mm³. Further development of the CXCR4-targeted imaging agent should have strong translation potential for early detection, surveillance, and treatment stratification of liver metastases patients.

Low-dose imaging technique (LITE) MRI: initial experience in breast imaging

OBJECTIVES

To compare a low-dose dynamic contrast-enhanced breast MRI protocol (LITE MRI) to standard-dosage using a dual-dose injection technique.

METHODS

8 females with a total of 10 lesions with imaging features compatible with fibroadenoma were imaged using a dual-dose dynamic contrast-enhanced-MRI (DCE-MRI) technique. After pre-contrast scans, 15% of a standard dose of contrast was administered; approximately 10 min later, the remaining 85% of the standard dose was administered. Enhancement kinetic parameters, conspicuity and signal-to-noise ratio were measured quantitatively.

RESULTS

One lesion showed no enhancement in either DCE series. All nine of the enhancing lesions were visualized in both the low-dose and standard-dose images. While the (low-to-standard) ratio of contrast doses was roughly 0.18, this did not match the ratios of kinetic parameters. Lesion conspicuity and enhancement rate were both higher in the low-dose images, with (low-to-standard) ratios 1.5 ± 0.1 and 1.2 ± 0.4, respectively. The upper limit of enhancement (ratio 0.3 ± 0.1) and signal-to-noise ratio (ratio 0.5 ± 0.1) were higher in the standard-dose images, but less than expected based on the ratio of the doses.

CONCLUSIONS

This preliminary study demonstrates that LITE MRI has the potential to match standard DCE-MRI in the detection of enhancing lesions. Additionally, LITE MRI may enhance sensitivity to contrast media dynamics.

ADVANCES IN KNOWLEDGE

Lower doses of MRI contrast media may be equally effective in the detection of breast lesions, and increase sensitivity to contrast media dynamics. LITE MRI may help increase screening compliance and long-term patient safety.

Impact of brain tumors and radiotherapy on the presence of gadolinium in the brain after repeated administration of gadolinium-based contrast agents: an experimental study in rats

PURPOSE

To investigate the impact of blood-brain barrier (BBB) alterations induced by an experimental tumor and radiotherapy on MRI signal intensity (SI) in deep cerebellar nuclei (DCN) and the presence of gadolinium after repeated administration of a linear gadolinium-based contrast agent in rats.

METHODS

Eighteen Fischer rats were divided into a tumor (gliosarcoma, GS9L model), a radiotherapy, and a control group. All animals received 5 daily injections (1.8 mmol/kg) of gadopentetate dimeglumine. For tumor-bearing animals, the BBB disruption was confirmed by contrast-enhanced MRI. Animals from the tumor and radiation group underwent radiotherapy in 6 fractions of 5 Gray. The SI ratio between DCN and brain stem was evaluated on T1-weigthed MRI at baseline and 1 week after the last administration. Subsequently, the brain was dissected for gadolinium quantification by inductively coupled plasma-mass spectrometry. Statistical analysis was done with the Kruskal-Wallis test.

RESULTS

An increased but similar DCN/brain stem SI ratio was found for all three groups (p = 0.14). The gadolinium tissue concentrations (median, nmol/g) were 6.7 (tumor), 6.3 (radiotherapy), and 6.8 (control) in the cerebellum (p = 0.64) and 17.8/14.6 (tumor), 20.0/18.9 (radiotherapy), and 17.8/15.9 (control) for the primary tumor (p = 0.98) and the contralateral hemisphere (p = 0.41) of the cerebrum, respectively.

CONCLUSION

An experimental brain tumor treated by radiotherapy or radiotherapy alone did not alter DCN signal hyperintensity and gadolinium concentration in the rat brain 1 week after repeated administration of gadopentetate. This suggests that a local BBB disruption does not affect the amount of retained gadolinium in the brain.

Signal intensity increases in dentate nucleus/globus pallidus/pulvinar on unenhanced T1WI MR images after multiple examinations with gadodiamide

BACKGROUND AND PURPOSE

Elevated signal intensity (SI) in the dentate nucleus (DN), globus pallidus (GP) and pulvinar (PUL) was reportedly observed on unenhanced T1-weighted (T1WI) magnetic resonance (MR) images in patients receiving multiple enhanced MR examinations. We aimed to clarify whether this phenomenon influences the long-term neurological status of patients.

MATERIALS AND METHODS

We studied 196 radiosurgically treated patients undergoing ≥10 MR examinations using a single dose of gadodiamide and the same 1.5 Tesla MR unit. SI ratios were calculated by referencing the brainstem (BS) for the DN and the thalamus (TH) for the GP and PUL. We compared the SI ratios at the first, fifth, and 10th, and at the most recent examinations. The neurological symptoms of all 196 patients were assessed at each MR examination by one of the authors (MY).

RESULTS

The DN/BS and GP/TH SI ratios were significantly increased at the fifth examination ( p < .0001, p = 0.0094) and, thereafter, gradually increased. Although the PUL/TH SI ratio was not significantly increased at the fifth examination ( p = 0.2515), a significant increase was noted at the 10th examination ( p < .0001). There were no significant predictive factors for DN/BS SI increases. Younger age, no brain metastasis, and normal estimated glomerular filtration rate were related to GP/TH SI ratio increases ( p = 0.0308, p = 0.0001, p = 0.0306). Higher age and total bilirubin level were related to an increased PUL/TH SI ratio ( p = 0.0276, p = 0.0097). No patients experienced gadodiamide-related health problems.

CONCLUSIONS

Although the SI ratios rose as numbers of gadodiamide administrations increased, no adverse health effects have developed to date.

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.

Effect of Gadolinium on the Estimation of Myelin and Brain Tissue Volumes Based on Quantitative Synthetic MRI

BACKGROUND AND PURPOSE

The effect of gadolinium on the estimation of myelin has not been reported. The aim of the current study was to investigate the effects of gadolinium on automatic myelin and brain tissue volumetry via quantitative synthetic MR imaging.

MATERIALS AND METHODS

The study included 36 patients who were referred for brain metastases screening, and quantitative synthetic MR imaging data before and after gadolinium-based contrast agent administration were analyzed retrospectively. Brain metastases were detected in 17 patients. WM volume, GM volume, CSF volume, non-WM/GM/CSF volume, myelin volume, brain parenchymal volume, myelin fraction (myelin volume/brain parenchymal volume), and intracranial volume were estimated. T1 and T2 relaxation times, proton density, and myelin partial volume per voxel averaged across the brain parenchyma were also analyzed.

RESULTS

In patients with and without metastases after gadolinium-based contrast agent administration, measurements of WM and myelin volumes, and myelin fraction were significantly increased (+26.65 and +29.42 mL, +10.14 and +12.46 mL, +0.88% and +1.09%, respectively), whereas measurements of GM, CSF, brain parenchymal, and intracranial volumes were significantly decreased (-36.23 and -34.49 mL, -20.77 and -18.94 mL, -6.76 and -2.84 mL, -27.41 and -21.84 mL, respectively). Non-WM/GM/CSF volume did not show a significant change. T1, T2, and proton density were significantly decreased (-51.34 and -46.84 ms, -2.67 and -4.70 ms, -1.05%, and -1.28%, respectively) after gadolinium-based contrast agent administration, whereas measurements of myelin partial volume were significantly increased (+0.78% and +0.75%, respectively).

CONCLUSIONS

Gadolinium had a significant effect on the automatic calculation of myelin and brain tissue volumes using quantitative synthetic MR imaging, which can be explained by decreases in T1, T2, and proton density.

Gadolinium Deposition in the Brain: Current Updates

Gadolinium-based contrast agents (GBCAs) are commonly used for enhancement in MR imaging and have long been considered safe when administered at recommended doses. However, since the report that nephrogenic systemic fibrosis is linked to the use of GBCAs in subjects with severe renal diseases, accumulating evidence has suggested that GBCAs are not cleared entirely from our bodies; some GBCAs are deposited in our tissues, including the brain. GBCA deposition in the brain is mostly linked to the specific chelate structure of the GBCA: linear GBCAs were responsible for brain deposition in almost all reported studies. This review aimed to summarize the current knowledge about GBCA brain deposition and discuss its clinical implications.

Gadolinium use for interventional pain procedures: where we are and where we are heading

In recent years as the use of interventional pain procedures has soared, so too has outside and internal scrutiny. This scrutiny includes agreater emphasis on weighing the risks and benefits of procedures, increased surveillance for adverse events, and cost containment strategies. In 2016, the first reports of gadolinium deposition in the central nervous system began to surface, though retention in other organ systems has been appreciated for over a decade. In this issue of Regional Anesthesia & Pain Medicine, Benzon et al. report a series of patients with document edhypersensitivity reactions to iodinated contrast medium who were inadvertently administered iodine-based contrast without adverse consequences. In this article, we discuss the epidemiology of contrast-mediated adverse effects, the mechanistic basis for hypersensitivity reactions, the risks and benefits of various approaches in the patient with a documented contrast hypersensitivity reaction, and risk mitigation strategies.