Signal intensity at unenhanced T1-weighted magnetic resonance in the globus pallidus and dentate nucleus after serial administrations of a macrocyclic gadolinium-based contrast agent in children

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.

Toxicity Mechanisms of Gadolinium and Gadolinium-Based Contrast Agents-A Review

Gadolinium-based contrast agents (GBCAs) have been used for more than 30 years to improve magnetic resonance imaging, a crucial tool for medical diagnosis and treatment monitoring across multiple clinical settings. Studies have shown that exposure to GBCAs is associated with gadolinium release and tissue deposition that may cause short- and long-term toxicity in several organs, including the kidney, the main excretion organ of most GBCAs. Considering the increasing prevalence of chronic kidney disease worldwide and that most of the complications following GBCA exposure are associated with renal dysfunction, the mechanisms underlying GBCA toxicity, especially renal toxicity, are particularly important. A better understanding of the gadolinium mechanisms of toxicity may contribute to clarify the safety and/or potential risks associated with the use of GBCAs. In this work, a review of the recent literature concerning gadolinium and GBCA mechanisms of toxicity was performed.

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.

MRI detection of brain gadolinium retention in multiple sclerosis: Magnetization transfer vs. T1-weighted imaging

BACKGROUND AND PURPOSE

Evidence of brain gadolinium retention has affected gadolinium-based contrast agent usage. It is, however, unclear to what extent macrocyclic agents are retained and whether their in vivo detection may necessitate nonconventional MRI. Magnetization transfer (MT) could prove suitable to detect gadolinium-related signal changes since dechelated gadolinium ions bind to macromolecules. Therefore, this study aimed to investigate associations of prior gadolinium administrations with MT and T1 signal abnormalities.

METHODS

A cohort of 23 persons with multiple sclerosis (MS) (18 females, 5 males, 57 ± 8.0 years) with multiple past gadolinium administrations (median 6, range 3-12) and 23 age- and sex-matched healthy controls underwent 1.5 Tesla MRI with MT, T1-weighted 2-dimensional spin echo, and T1-weighted 3-dimensional gradient echo. The signal intensity index was assessed by MRI in gadolinium retention predilection sites.

RESULTS

There were dose-dependent associations of the globus pallidus signal on gradient echo (r = .55, p < .001) and spin echo (r = .38, p = .013) T1-weighted imaging, but not on MT. Relative to controls, MS patients had higher signal intensity index in the dentate nucleus on T1-weighted gradient echo (1.037 ± 0.040 vs. 1.016 ± 0.023, p = .04) with a similar trend in the globus pallidus on T1-weighted spin echo (1.091 ± 0.034 vs. 1.076 ± 0.014, p = .06). MT detected no group differences.

CONCLUSIONS

Conventional T1-weighted imaging provided dose-dependent associations with gadolinium administrations in MS, while these could not be detected with 2-dimensional MT. Future studies could explore newer MT techniques like 3D and inhomogenous MT. Notably, these associations were identified with conventional MRI even though most patients had not received gadolinium administrations in the preceding 9 years, suggestive of long-term retention.

Magnetic Resonance Imaging of Primary Adult Brain Tumors: State of the Art and Future Perspectives

MRI is undoubtedly the cornerstone of brain tumor imaging, playing a key role in all phases of patient management, starting from diagnosis, through therapy planning, to treatment response and/or recurrence assessment. Currently, neuroimaging can describe morphologic and non-morphologic (functional, hemodynamic, metabolic, cellular, microstructural, and sometimes even genetic) characteristics of brain tumors, greatly contributing to diagnosis and follow-up. Knowing the technical aspects, strength and limits of each MR technique is crucial to correctly interpret MR brain studies and to address clinicians to the best treatment strategy. This article aimed to provide an overview of neuroimaging in the assessment of adult primary brain tumors. We started from the basilar role of conventional/morphological MR sequences, then analyzed, one by one, the non-morphological techniques, and finally highlighted future perspectives, such as radiomics and artificial intelligence.

Synthetic Post-Contrast Imaging through Artificial Intelligence: Clinical Applications of Virtual and Augmented Contrast Media

Contrast media are widely diffused in biomedical imaging, due to their relevance in the diagnosis of numerous disorders. However, the risk of adverse reactions, the concern of potential damage to sensitive organs, and the recently described brain deposition of gadolinium salts, limit the use of contrast media in clinical practice. In recent years, the application of artificial intelligence (AI) techniques to biomedical imaging has led to the development of 'virtual' and 'augmented' contrasts. The idea behind these applications is to generate synthetic post-contrast images through AI computational modeling starting from the information available on other images acquired during the same scan. In these AI models, non-contrast images (virtual contrast) or low-dose post-contrast images (augmented contrast) are used as input data to generate synthetic post-contrast images, which are often undistinguishable from the native ones. In this review, we discuss the most recent advances of AI applications to biomedical imaging relative to synthetic contrast media.

Role of Ultrasound Evaluation of Temporomandibular Joint in Juvenile Idiopathic Arthritis: A Systematic Review

Background: Juvenile idiopathic arthritis (JIA) is childhood’s most frequent chronic rheumatic disease. JIA is a broad term that includes all arthritides starting before 16 years, lasting at least six weeks, and of unknown cause. The temporomandibular joint (TMJ) could be involved in JIA both at onset and during the disease course. The presence of TMJ synovitis might severely impair dentofacial maturation in pediatric patients. The ultrasound (US) application to detect early signs of TMJ synovitis in children with JIA has provided contradictory results. We sought to assess the current role of TMJ US in JIA through a systematic literature review. Methods: The systematic review was conducted according to the recommendations of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA). Results: The literature search found 345 records. After duplicates removal, 253 records were screened, 20 full-text articles were reviewed to assess their eligibility, and 7 of them were included in the qualitative analysis. Joint effusion was the most recorded parameter, followed by bony condylar abnormalities. Compared to contrast enhancement MRI, the capability to detect signs of active synovitis of TMJ by US is low, especially at the early stages. Conclusion: Understanding how US may help diagnose and manage children with JIA is advisable for several reasons. MRI cannot be frequently repeated, may need sedation, and is expensive. The constant technical improvement of US will undoubtedly allow for better evaluation of what, in the past, was not clear or not even captured by sonography. So far, the role of US in the assessment of TMJ involvement in JIA is indubitably secondary to the MRI. Even so, we think that a baseline MRI of TMJ and the repetition of the sonography over time might both help the interpretation of US images and intercept significative changes.

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.

Small Brain Lesion Enhancement and Gadolinium Deposition in the Rat Brain: Comparison Between Gadopiclenol and Gadobenate Dimeglumine

OBJECTIVES

The aim of the set of studies was to compare gadopiclenol, a new high relaxivity gadolinium (Gd)-based contrast agent (GBCA) to gadobenate dimeglumine in terms of small brain lesion enhancement and Gd retention, including T1 enhancement in the cerebellum.

MATERIALS AND METHODS

In a first study, T1 enhancement at 0.1 mmol/kg body weight (bw) of gadopiclenol or gadobenate dimeglumine was evaluated in a small brain lesions rat model at 2.35 T. The 2 GBCAs were injected in an alternated and cross-over manner separated by an interval of 4.4 ± 1.0 hours (minimum, 3.5 hours; maximum, 6.1 hours; n = 6). In a second study, the passage of the GBCAs into cerebrospinal fluid (CSF) was evaluated by measuring the fourth ventricle T1 enhancement in healthy rats at 4.7 T over 23 minutes after a single intravenous (IV) injection of 1.2 mmol/kg bw of gadopiclenol or gadobenate dimeglumine (n = 6/group). In a third study, Gd retention at 1 month was evaluated in healthy rats who had received 20 IV injections of 1 of the 2 GBCAs (0.6 mmol/kg bw) or a similar volume of saline (n = 10/group) over 5 weeks. T1 enhancement of the deep cerebellar nuclei (DCN) was assessed by T1-weighted magnetic resonance imaging at 2.35 T, performed before the injection and thereafter once a week up to 1 month after the last injection. Elemental Gd levels in central nervous system structures, in muscle and in plasma were determined by inductively coupled plasma mass spectrometry (ICP-MS) 1 month after the last injection.

RESULTS

The first study in a small brain lesion rat model showed a ≈2-fold higher number of enhanced voxels in lesions with gadopiclenol compared with gadobenate dimeglumine. T1 enhancement of the fourth ventricle was observed in the first minutes after a single IV injection of gadopiclenol or gadobenate dimeglumine (study 2), resulting, in the case of gadopiclenol, in transient enhancement during the injection period of the repeated administrations study (study 3). In terms of Gd retention, T1 enhancement of the DCN was noted in the gadobenate dimeglumine group during the month after the injection period. No such enhancement of the DCN was observed in the gadopiclenol group. Gadolinium concentrations 1 month after the injection period in the gadopiclenol group were slightly increased in plasma and lower by a factor of 2 to 3 in the CNS structures and muscles, compared with gadobenate dimeglumine.

CONCLUSIONS

In the small brain lesion rat model, gadopiclenol provides significantly higher enhancement of brain lesions compared with gadobentate dimeglumine at the same dose. After repeated IV injections, as expected for a macrocyclic GBCA, Gd retention is minimalized in the case of gadopiclenol compared with gadobenate dimeglumine, resulting in no T1 hypersignal in the DCN.

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.

Cerebral Venous Thrombosis: A Challenging Diagnosis; A New Nonenhanced Computed Tomography Standardized Semi-Quantitative Method

Cerebral venous sinus thrombosis (CVST) on non-contrast CT (NCCT) is often challenging to detect. We retrospectively selected 41 children and 36 adults with confirmed CVST and two age-matched control groups with comparable initial symptoms. We evaluated NCCT placing four small circular ROIs in standardized regions of the cerebral dural venous system. The mean and maximum HU values were considered from each ROI, and the relative percentage variations were calculated (mean % variation and maximum % variation). We compared the highest measured value to the remaining three HU values through an ad-hoc formula based on the assumption that the thrombosed sinus has higher attenuation compared with the healthy sinuses. Percentage variations were employed to reflect how the attenuation of the thrombosed sinus deviates from the unaffected counterparts. The attenuation of the affected sinus was increased in patients with CVST, and consequently both the mean % and maximum % variations were increased. A mean % variation value of 12.97 and a maximum % variation value of 10.14 were found to be useful to distinguish patients with CVST from healthy subjects, with high sensitivity and specificity. Increased densitometric values were present in the site of venous thrombosis. A systematic, blind evaluation of the brain venous system can assist radiologists in identifying patients who need or do not need further imaging.

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.

MRI Protocol for Pituitary Assessment in Children with Growth or Puberty Disorders-Is Gadolinium Contrast Administration Actually Needed?

The aim of this study was to assess the diagnostic value of non-contrast pituitary MRI in children with growth or puberty disorders (GPDs) and to determine the criteria indicating the necessity to perform post-contrast examination. A retrospective study included re-analysis of 567 contrast-enhanced pituitary MRIs of children treated in a tertiary reference center. Two sets of sequences were created from each MRI examination: Set 1, including common sequences without contrast administration, and Set 2, which included common pre- and post-contrast sequences (conventional MRI examination). The differences in the visibility of pituitary lesions between pairs of sets were statistically analyzed. The overall frequency of Rathke’s cleft cysts was 11.6%, ectopic posterior pituitary 3.5%, and microadenomas 0.9%. Lesions visible without contrast administration accounted for 85% of cases. Lesions not visible before and diagnosed only after contrast injection accounted for only 0.18% of all patients. Statistical analysis showed the advantage of the antero-posterior (AP) pituitary dimension over the other criteria in determining the appropriateness of using contrast in pituitary MRIs. The AP dimension was the most significant factor in logistic regression analysis: OR = 2.23, 95% CI, 1.35–3.71, p-value = 0.002, and in ROC analysis: AUC: 72.9% with a cut-off value of 7.5 mm, with sensitivity/specificity rates of 69.2%/73.5%. In most cases, the use of gadolinium-based contrast agent (GBCA) in pituitary MRI in children with GPD is unnecessary. The advantages of GBCA omission include shortening the time of MRI examination and of general anesthesia; saving time for other examinations, thus increasing the availability of MRI for waiting children; and acceleration in their further clinical management.

In Vivo Brain GSH: MRS Methods and Clinical Applications

Glutathione (GSH) is an important antioxidant implicated in several physiological functions, including the oxidation−reduction reaction balance and brain antioxidant defense against endogenous and exogenous toxic agents. Altered brain GSH levels may reflect inflammatory processes associated with several neurologic disorders. An accurate and reliable estimation of cerebral GSH concentrations could give a clear and thorough understanding of its metabolism within the brain, thus providing a valuable benchmark for clinical applications. In this context, we aimed to provide an overview of the different magnetic resonance spectroscopy (MRS) technologies introduced for in vivo human brain GSH quantification both in healthy control (HC) volunteers and in subjects affected by different neurological disorders (e.g., brain tumors, and psychiatric and degenerative disorders). Additionally, we aimed to provide an exhaustive list of normal GSH concentrations within different brain areas. The definition of standard reference values for different brain areas could lead to a better interpretation of the altered GSH levels recorded in subjects with neurological disorders, with insights into the possible role of GSH as a biomarker and therapeutic target.

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.

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.

Safety and diagnostic efficacy of gadoteridol for magnetic resonance imaging of the brain and spine in children 2 years of age and younger

BACKGROUND

Neonates and young children require efficacious magnetic resonance imaging (MRI) examinations but are potentially more susceptible to the short- and long-term adverse effects of gadolinium-based contrast agents due to the immaturity of their body functions.

OBJECTIVE

To evaluate the acute safety and diagnostic efficacy of gadoteridol (ProHance) for contrast-enhanced MRI of the central nervous system (CNS) in children ≤2 years of age.

MATERIALS AND METHODS

One hundred twenty-five children ≤2 years old (including 57 children <6 months old) who underwent contrast-enhanced MRI of the CNS with gadoteridol at 0.1 mmol/kg body weight were retrospectively enrolled at five imaging centers. Safety data were assessed for acute/subacute adverse events in the 48 h following gadoteridol administration and, when available, vital signs, electrocardiogram (ECG) and clinical laboratory values obtained from blood samples taken from 48 h before until 48 h following the MRI exam. The efficacy of gadoteridol-enhanced MRI compared to unenhanced MRI for disease diagnosis was evaluated prospectively by three blinded, unaffiliated readers.

RESULTS

Thirteen changes of laboratory values (11 mild, 1 moderate, 1 unspecified) were reported as adverse events in 7 (5.6%) patients. A relationship to gadoteridol was deemed possible though doubtful for two of these adverse events in two patients (1.6%). There were no clinical adverse events, no serious adverse events and no clinically meaningful changes in vital signs or ECG recordings. Accurate differentiation of tumor from non-neoplastic disease, and exact matching of specific MRI-determined diagnoses with on-site final diagnoses, was achieved in significantly more patients by each reader following the evaluation of combined pre- and post-contrast images compared to pre-contrast images alone (84.6-88.0% vs. 70.9-76.9%; P≤0.006 and 67.5-79.5% vs. 47.0-66.7%; P≤0.011, respectively).

CONCLUSION

Gadoteridol at 0.1 mmol/kg body weight is safe, well tolerated and effective for contrast-enhanced MRI of the CNS in children ≤2 years of age.

Assessment of gadolinium deposition in the brain tissue of pediatric and adult congenital heart disease patients after contrast enhanced cardiovascular magnetic resonance

BACKGROUND

Contrast enhanced magnetic resonance imaging (MRI) is an important tool for the assessment of extracardiac vasculature and myocardial viability. Gadolinium (Gd) brain deposition after contrast enhanced MRI has recently been described and resulted in a warning issued by the United States Food and Drug Administration. However, the prevalence of brain deposition in children and adults with congenital heart disease (CHD) undergoing cardiovascular magnetic resonance (CMR) is unclear. We hypothesized that Gd exposure as part of one or more CMRs would lead to a low rate of brain deposition in pediatric and adult CHD patients.

METHODS

We queried our institutional electronic health record for all pediatric and adult CHD patients who underwent contrast enhanced CMR from 2005 to 2018 and had a subsequent brain MRI. Cases were age- and gender-matched to controls who were never exposed to Gd and underwent brain MRIs. The total number of contrast enhanced MRIs, type of Gd, and total Gd dose were determined. Brain MRIs were reviewed by a neuroradiologist for evidence of Gd deposition using qualitative and quantitative assessment. Quantitative assessment was performed using the dentate nucleus to pons signal intensity ratio (dp-SIR) on T1 weighted imaging. Continuous variables were analyzed using Mann-Whitney U and Spearman rank correlation tests. Normal SIR was defined as the 95% CI of the control population dp-SIR.

RESULTS

Sixty-two cases and 62 controls were identified. The most contrast enhanced MRIs in a single patient was five and the largest lifetime dose of Gd that any patient received was 0.75 mmol/kg. There was no significant difference in the mean dp-SIR of cases and controls (p = 0.11). The dp-SIR was not correlated with either the lifetime dose of Gd (rs = 0.21, p = 0.11) or the lifetime number of contrast enhanced studies (rs = 0.21, p = 0.11). Two cases and 2 controls had dp-SIRs above the upper bound of the 95% confidence interval for the control group. One case had qualitative imaging-based evidence of Gd deposition in the brain but had a dp-SIR within the normal range.

CONCLUSION

In our cohort of pediatric and adult CHD patients undergoing contrast enhanced CMR, there was a low incidence of qualitative and no significant quantitative imaging-based evidence of Gd brain deposition.

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.

Albumin-based nanoparticles as contrast medium for MRI: vascular imaging, tissue and cell interactions, and pharmacokinetics of second-generation nanoparticles

This multidisciplinary study examined the pharmacokinetics of nanoparticles based on albumin-DTPA-gadolinium chelates, testing the hypothesis that these nanoparticles create a stronger vessel signal than conventional gadolinium-based contrast agents and exploring if they are safe for clinical use. Nanoparticles based on human serum albumin, bearing gadolinium and designed for use in magnetic resonance imaging, were used to generate magnet resonance images (MRI) of the vascular system in rats ("blood pool imaging"). At the low nanoparticle doses used for radionuclide imaging, nanoparticle-associated metals were cleared from the blood into the liver during the first 4 h after nanoparticle application. At the higher doses required for MRI, the liver became saturated and kidney and spleen acted as additional sinks for the metals, and accounted for most processing of the nanoparticles. The multiple components of the nanoparticles were cleared independently of one another. Albumin was detected in liver, spleen, and kidneys for up to 2 days after intravenous injection. Gadolinium was retained in the liver, kidneys, and spleen in significant concentrations for much longer. Gadolinium was present as significant fractions of initial dose for longer than 2 weeks after application, and gadolinium clearance was only complete after 6 weeks. Our analysis could not account quantitatively for the full dose of gadolinium that was applied, but numerous organs were found to contain gadolinium in the collagen of their connective tissues. Multiple lines of evidence indicated intracellular processing opening the DTPA chelates and leading to gadolinium long-term storage, in particular inside lysosomes. Turnover of the stored gadolinium was found to occur in soluble form in the kidneys, the liver, and the colon for up to 3 weeks after application. Gadolinium overload poses a significant hazard due to the high toxicity of free gadolinium ions. We discuss the relevance of our findings to gadolinium-deposition diseases.

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.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

DISCUSSION

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

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.

Imaging tools for assessment of myocardial fibrosis in humans: the need for greater detail

Myocardial fibrosis is recognized as a key pathological process in the development of cardiac disease and a target for future therapeutics. Despite this recognition, the assessment of fibrosis is not a part of routine clinical practice. This is primarily due to the difficulties in obtaining an accurate assessment of fibrosis non-invasively. Moreover, there is a clear discrepancy between the understandings of myocardial fibrosis clinically where fibrosis is predominately studied with comparatively low-resolution medical imaging technologies like MRI compared with the basic science laboratories where fibrosis can be visualized invasively with high resolution using molecularly specific fluorescence microscopes at the microscopic and nanoscopic scales. In this article, we will first review current medical imaging technologies for assessing fibrosis including echo and MRI. We will then highlight the need for greater microscopic and nanoscopic analysis of human tissue and how this can be addressed through greater utilization of human tissue available through endomyocardial biopsies and cardiac surgeries. We will then describe the relatively new field of molecular imaging that promises to translate research findings to the clinical practice by non-invasively monitoring the molecular signature of fibrosis in patients.

Image quality of late gadolinium enhancement in cardiac magnetic resonance with different doses of contrast material in patients with chronic myocardial infarction

Background

Contrast-enhanced cardiac magnetic resonance (CMR) is pivotal for evaluating chronic myocardial infarction (CMI). Concerns about safety of gadolinium-based contrast agents favour dose reduction. We assessed image quality of scar tissue in CMRs performed with different doses of gadobutrol in CMI patients.

Methods

Informed consent was waived for this Ethics Committee-approved single-centre retrospective study. Consecutive contrast-enhanced CMRs from CMI patients were retrospectively analysed according to the administered gadobutrol dose (group A, 0.10 mmol/kg; group B, 0.15 mmol/kg; group C, 0.20 mmol/kg). We calculated the signal-to-noise ratio for scar tissue (SNR_scar) and contrast-to-noise ratio between scar and either remote myocardium (CNR_scar-rem) or blood (CNR_scar-blood).

Results

Of 79 CMRs from 79 patients, 22 belonged to group A, 26 to group B, and 31 to group C. The groups were homogeneous for age, sex, left ventricular morpho-functional parameters, and percentage of scar tissue over whole myocardium (p ≥ 0.300). SNR_scar was lower in group A (46.4; 40.3–65.1) than in group B (70.1; 52.2–111.5) (p = 0.013) and group C (72.1; 59.4–100.0) (p = 0.002), CNR_scar-rem was lower in group A (62.9; 52.2–87.4) than in group B (96.5; 73.1–152.8) (p = 0.008) and in group C (103.9; 83.9–132.0) (p = 0.001). No other significant differences were found (p ≥ 0.335).

Conclusions

Gadobutrol at 0.10 mmol/kg provides inferior scar image quality of CMI than 0.15 and 0.20 mmol/kg; the last two dosages seem to provide similar LGE. Thus, for CMR of CMI, 0.15 mmol/kg of gadobutrol can be suggested instead of 0.20 mmol/kg, with no hindrance to scar visualisation. Dose reduction would not impact on diagnostic utility of CMR examinations.

T1-Weighted Intensity Increase After a Single Administration of a Linear Gadolinium-Based Contrast Agent in Multiple Sclerosis

Purpose

Through analysis of T1-weighted (T1w) images this study investigated gadolinium (Gd) deposition in the brain after administration of a linear (gadopentetic acid) and a cyclic (gadoteric acid) gadolinium-based contrast agent (GBCA) in patients with multiple sclerosis (MS), a disorder frequently requiring magnetic resonance imaging (MRI) scans over years.

Methods

A total of 3233 T1w images (unenhanced with respect to the same scanning session) of 881 MS patients were retrospectively analyzed. After spatial normalization and intensity scaling using a sphere within the pons, differences of all pairs of subsequent scans were calculated and attributed to either linear (n = 2718) or cyclic (n = 385) or no GBCA (n = 130) according to the first scan. Regional analyses were performed, focusing on the dentate nucleus, and whole brain analyses. By 1‑sample t‑tests, signal intensity increases within conditions were searched for; conditions were compared by 2‑sample t‑tests. Furthermore, recent hypotheses on the reversibility of GBCA deposition were tested.

Results

In the dentate nucleus, a significant increase was observed only after administration of linear GBCA even after a single GBCA administration. This increase differed significantly (p < 0.001) from the other conditions (cyclic and no GBCA). Whole brain analyses revealed T1w signal increases only after administration of linear GBCA within two regions, the dentate nucleus and globus pallidus. Additional analyses did not indicate any decline of Gd deposition in the brain.

Conclusion

The data point towards Gd deposition in the brain after administration of linear GBCA even after a single administration.

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.

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.

Analysis of retention of gadolinium by brain, bone, and blood following linear gadolinium-based contrast agent administration in rats with experimental sepsis

PURPOSE

It is important to identify populations that may be vulnerable to the brain deposition of gadolinium (Gd) from MRI contrast agents. At intervals from 24 hours to 6 weeks following injection of a linear Gd contrast agent, the brain, blood and bone content of Gd were compared between control rats and those with experimental endotoxin-induced sepsis that results in neuroinflammation and blood-brain barrier disruption.

METHODS

Male rats were injected intraperitoneally with 10 mg/kg lipopolysaccharide. Control animals received no injection. Twenty-four hours later, 0.2 mmol/kg of gadobenate dimeglumine was injected intravenously. Brain, blood, and bone Gd levels were measured at 24 hours, 1 week, 3 weeks, and 6 weeks by inductively coupled plasma mass spectroscopy.

RESULTS

Blood Gd decreased rapidly between 24 hours and 1 week, and thereafter was undetectable, with no significant difference between lipopolysaccharide and control rats. Brain levels of Gd were significantly higher (4.29-2.36-fold) and bone levels slightly higher (1.35-1.11-fold) in lipopolysaccharide than control rats at all time points with significant retention at 6 weeks.

CONCLUSION

Experimental sepsis results in significantly higher deposition of Gd in the brain and bone in rats. While blood Gd clears rapidly, brain and bone retained substantial Gd even at 6 weeks following contrast injection.

Does Gadoterate Meglumine Cause Gadolinium Retention in the Brain of Children? A Case-Control Study

BACKGROUND

Accumulation of macrocyclic gadolinium agents in children's brains remain to be determined.

PURPOSE

To demonstrate whether there is an intracranial macrocyclic gadolinium deposition after multiple contrast-enhanced MRI with gadoterate meglumine in a pediatric population.

STUDY TYPE

Retrospective case-control.

POPULATION

In all, 45 children (age range: 5-17 years; mean, 13.7 ± 3.4 years) for the study group and 45 healthy children (age range: 5-17 years; mean, 13.7 ± 3.4 years) for the control group.

FIELD STRENGTH/SEQUENCE

T₁ - and T₂ -weighted axial images on a 1.5T scanner.

ASSESSMENT

Children with at least three enhanced brain MRIs and an age- and sex-matched control group with an unenhanced brain MRIs were compared in terms of T₁ signal intensity (SI). All patients in the study group received gadoterate meglumine intravenously (0.1 mmol/kg). SI measurements were made by drawing six regions of interest (ROIs): dentate nuclei (DN), pons, globus pallidi (GP), frontal white matter (FWM), thalamus (T), clivus, and cerebrospinal fluid (CSF) for both groups on unenhanced T₁ -weighted images.

STATISTICAL TESTS

Student's t-test was used for comparison of SI. The Pearson correlation was calculated for the correlation between the SI and the number of gadolinium administrations.

RESULTS

A significant difference was detected between two groups for DN/CSF, pons/CSF, GP/CSF, thalamus/CSF, and FWM/CSF (P < 0.001, P < 0.001, P = 0.002, P = 0.002, P = 0.024, respectively). There was no significant difference between the two groups for clivus/CSF (P = 0.15). A good correlation between the number of gadoterate meglumine administrations and the SI for DN/CSF, pons/CSF, GP/CSF, and T/CSF (r = 0.80, r = 0.73, r = 0.91, and r = 0.90, respectively) was found.

DATA CONCLUSION

A significant T₁ SI increase reflecting gadolinium retention in the brain was detected for children with at least three gadoterate meglumine administrations in this series. The number of administrations correlated well with the increased SI.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:1471-1477.

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.

Visible T1-hyperintensity of the dentate nucleus after multiple administrations of macrocyclic gadolinium-based contrast agents: yes or no?

OBJECTIVES

To investigate the appearance of visible dentate nucleus (DN) T1-hyperintensity and quantify changes in DN/pons (DN/P) signal intensity (SI) ratio in MS patients after the exclusive administration of macrocyclic GBCAs.

MATERIALS AND METHODS

One hundred forty-nine patients with confirmed MS were evaluated. Patients received at least two administrations of gadobutrol (n = 63), gadoterate (n = 57), or both (n = 29). Two experienced neuroradiologists in consensus evaluated unenhanced T1-weighted MR images from all examinations in each patient for evidence of visible DN hyperintensity. Thereafter, SI measurements were made in the left and right DN and pons on unenhanced T1-weighted images from the first and last scans. A two-sample t test compared the DN/P SI ratios for patients with and without visible T1-hyperintensity.

RESULTS

Visible T1-hyperintensity was observed in 42/149 (28.2%) patients (19 after gadobutrol only, 15 after gadoterate only, 8 after both), typically at the 4th or 5th follow-up exam at 3-4 years after the initial examination. Significant increases in DN/P SI ratio from first to last examination were determined for patients with visible T1-hyperintensity (0.998 ± 0.002 to 1.153 ± 0.016, p < 0.0001 for gadobutrol; 1.003 ± 0.004 to 1.110 ± 0.014, p < 0.0001 for gadoterate; 1.004 ± 0.011 to 1.163 ± 0.032, p = 0.0004 for both) but not for patients without visible T1-hyperintensity (p > 0.05; all groups).

CONCLUSION

Multiple injections of gadobutrol and/or gadoterate can lead to visible and quantifiable increases in DN/P SI ratio in some patients with MS.

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.

Is power Doppler ultrasound useful to evaluate temporomandibular joint inflammatory activity in juvenile idiopathic arthritis?

OBJECTIVE

To evaluate the effectiveness of power Doppler ultrasound (US) in assessing the temporomandibular joint (TMJ) involvement in juvenile idiopathic arthritis (JIA) patients using contrast-enhanced magnetic resonance imaging (MRI) as the reference standard.

METHODS

We evaluated the US and MRI examinations of the TMJs from 92 JIA patients. These exams were done and scored for inflammatory activity on the same date.

RESULTS

There were considerable differences between the US and MRI findings, with MRI detecting more effectively the TMJ involvement. No association was found between synovial inflammation obtained using power Doppler US to assess synovial vascularity determined by US images and synovial enhancement determined by MRI images. US had very poor sensitivity and very low positive predictive value to detect TMJ arthritis in JIA patients compared with MRI as the reference standard.

CONCLUSIONS

Power Doppler US cannot replace MRI for the detection of TMJ inflammatory involvement in JIA patients.Key Points• The early diagnosis of TMJ involvement in JIA patients is very important in order to prevent disturbances in the mandibular growth.• Power Doppler US could be a useful diagnostic tool as a screening exam to identify inflammatory activity in this joint.• However, power Doppler US did not show to have this function and cannot replace MRI for the detection of TMJ inflammatory involvement in JIA patients.

The gadolinium hypothesis for fibromyalgia and unexplained widespread chronic pain

Fibromyalgia (FM) is a chronic, painful, heterogeneous, and common disorder carrying a substantial socio-economical burden. It lacks effective cures and its aetiology is still unknown. There exists evidence for central and peripheral neurological contribution to the symptoms but grasping the real source of abnormal nervous system sensitization remains an ongoing challenge. There exists an association between an injury/trauma and the onset of the symptoms, but a causal relationship has not been yet sufficiently supported by scientific evidence. I postulate a role for gadolinium-based contrast agents and retention of gadolinium in the body. This conjecture breaks the hypothesis of a direct role for a physical injury/trauma per se in favour of an indirect one by the subsequent diagnostic procedures. It creates a new link between retention of gadolinium in the body and painful conditions as FM and unexplained chronic widespread pain reported after a trauma, surgery, or medical illness. Experimental evidence demonstrates possible retention of gadolinium species in human body, still lacking conclusive answers on their pathological consequences. Notwithstanding, there exist some initial data that report unexplained chronic widespread pain and symptoms of FM in those patients: they are suggestive for pathological consequences associated with gadolinium retention. Besides clear compelling symptoms overlapping, biochemical findings are provided to sustain the hypothesis of a role for gadolinium in the disease process focusing on neurotransmitters, endogenous metal cations, cytokines, and muscle tissue. Experimental findings strongly support the hypothesis of impairment at the cellular, intracellular, and systemic levels in FM. And these data are highly compatible with collateral effects associated with the interference of the gadolinium ion and its pharmaceutical chelates into biochemical pathways in vivo. The hypothesis presented in this article, along with the support of scientific evidence, links FM and unexplained chronic widespread pain reported after a trauma, surgery, or medical illness to retention of gadolinium in the body. If the hypothesis is confirmed, it could improve diagnosis and prevention, while providing a ground for development of new treatments.

Characterisation of computed tomography angiography findings in paediatric patients with heterotaxy

BACKGROUND

Heterotaxy refers to the abnormal arrangement of organs across the left-right axis and is typically associated with complex cardiovascular malformations.

OBJECTIVE

To characterise the range of cardiac and extracardiac CT angiography findings in children with heterotaxy using the latest nomenclature consensus and to compare the different types of isomerism.

MATERIALS AND METHODS

We retrospectively analysed the data of 64 consecutive paediatric patients referred to our tertiary paediatric cardiovascular centre who underwent CT angiography for the evaluation of known or suspected heterotaxy within a 52-month period.

RESULTS

Right atrial isomerism was identified in 44 (69%) children, while left atrial isomerism was identified in 18 (28%) children. Atrial appendage anatomy and situs could not be determined in 2 children (3%). Associated heart defects included complete atrioventricular canal (CAVC) in 51 (80%) children, total anomalous pulmonary venous return in 43 (67%) and pulmonary atresia in 23 (36%). The bronchial branching pattern corresponded to atrial appendage morphology in all children except in the two in whom atrial appendage morphology could not be defined. In children with right atrial isomerism, the most common associated abnormalities were CAVC (n=41, 93%) and asplenia (n=34, 77%), while in those with left atrial isomerism, the most common associated abnormalities were polysplenia (n=17, 94%) and an interrupted inferior vena cava with azygos continuation (n=15, 83%).

CONCLUSION

CT angiography provides useful cardiovascular and extracardiac data on heterotaxy, which frequently involves a pattern of side-related findings but has great anatomical variability.

The Effects of Gadolinium-Based Contrast Agents on the Cerebellum: from Basic Research to Neurological Practice and from Pregnancy to Adulthood

Gadolinium (Gd)-based contrast agents (GBCAs) are used in magnetic resonance imaging (MRI) to increase the diagnostic yield. Current reports using animal models or human subjects have shown that GBCAs may be deposited in brain including the cerebellum. Although further studies may be required to clarify the toxicity of GBCAs, we should be more cautious to use these agents particularly in patients who more likely to have repeated enhanced MRI along their lifespan. In this editorial, current studies to clarify the toxicity of GBCAs in the cerebellum are introduced.

Gadolinium Retention in the Brain: An MRI Relaxometry Study of Linear and Macrocyclic Gadolinium-Based Contrast Agents in Multiple Sclerosis

BACKGROUND AND PURPOSE

Brain gadolinium retention is consistently reported for linear gadolinium-based contrast agents, while the results for macrocyclics are contradictory and potential clinical manifestations remain controversial. Furthermore, most previous studies are based on conventional T1-weighted MR imaging. We therefore aimed to quantitatively investigate longitudinal and transversal relaxation in the brain in relation to previous gadolinium-based contrast agent administration and explore associations with disability in multiple sclerosis.

MATERIALS AND METHODS

Eighty-five patients with MS and 21 healthy controls underwent longitudinal and transverse relaxation rate (R₁ and R₂) relaxometry. Patients were divided into linear, mixed, and macrocyclic groups based on previous gadolinium-based contrast agent administration. Neuropsychological testing was performed in 53 patients. The dentate nucleus, globus pallidus, caudate nucleus, and thalamus were manually segmented. Repeatability measures were also performed.

RESULTS

The relaxometry was robust (2.0% scan-rescan difference) and detected higher R₁ (dentate nucleus, globus pallidus, caudate nucleus, thalamus) and R₂ (globus pallidus, caudate nucleus) in patients receiving linear gadolinium-based contrast agents compared with controls. The number of linear gadolinium-based contrast agent administrations was associated with higher R₁ and R₂ in all regions (except R₂ in the thalamus). No similar differences and associations were found for the macrocyclic group. Higher relaxation was associated with lower information-processing speed (dentate nucleus, thalamus) and verbal fluency (caudate nucleus, thalamus). No associations were found with physical disability or fatigue.

CONCLUSIONS

Previous linear, but not macrocyclic, gadolinium-based contrast agent administration is associated with higher relaxation rates in a dose-dependent manner. Higher relaxation in some regions is associated with cognitive impairment but not physical disability or fatigue in MS. The findings should be interpreted with care but encourage studies into gadolinium retention and cognition.

Gadobutrol enhances T1-weighted MRI of nerve cells

Three-dimensional T₁-weighted MRI of mouse brain in vivo (9.4 T, 80 μm isotropic resolution) identified assemblies of nerve cell bodies in the habenula, hippocampal formation, locus coeruleus, dorsal motor nucleus of vagus, and nucleus ambiguus as high signal intensities, while suppressing the signals of white matter by magnetization transfer and of extracellular water protons by saturation. These observations indicate the presence of intracellular water protons with T₁ values shortened by paramagnetic ions as the source of the bright signal. One day after an intraventricular injection of gadobutrol, a macrocyclic gadolinium-based contrast agent, T₁-weighted MRI signal intensities of the nerve cell assemblies in the habenula, hippocampal formation, and locus coeruleus increased significantly. With simultaneous saturation of long-T₁ protons of extracellular water, this finding indicates a T₁-shortening of the intracellular water protons as a result of their interaction with gadolinium ions.

Detection of recurrent brain tumors in children: No significant difference in sensitivity between unenhanced and contrast-enhanced MRI

BACKGROUND

Magnetic resonance imaging (MRI) with a gadolinium injection is currently used in the follow-up of children in remission of cerebral tumors (CTs). Intracerebral gadolinium deposition has been recently reported with unknown risks. The aim of this study was to evaluate the sensitivity of unenhanced brain MRI (U-MRI) in detection of tumor recurrence.

METHODS AND MATERIALS

A set of 58 U-MRIs of children in remission was retrospectively evaluated by three seniors (a neuroradiologist, a pediatric and a general radiologist) and one junior to look for any recurrence. Clinical, tumoral and imaging data were collected. The final diagnosis was anatomopathological when available, or the clinicoradiological evolution. Sensitivity, specificity, predictive values and interobserver agreement were calculated. A Fisher test and Fleiss kappa coefficient were performed.

RESULTS

For the seniors, the U-MRI had a sensitivity of 81% (95% confidence interval (CI): 0.56-0.90), and a negative predictive value (NPV) of 82% (95% CI: 0.63-0.94). The U-MRI sensitivity, regardless of the observer, was not significantly different from the contrast-enhanced MRI sensitivity (86%) according to a Fisher test (p > 0.05). No significant difference in sensitivity within the subgroups was found. The interobserver agreement of seniors was good (κ = 0.68).

CONCLUSION

U-MRI brain was suboptimal for 80% of patients. Three-dimensional millimetric, fluid-attenuated inversion recovery, and diffusion would constitute helpful sequences in follow-up. Further specific studies depending on each tumor type are still required to determine whether a potential abstention of gadolinium intravenous injection should be discussed for children.