Gadolinium deposition in the brain

WITHDRAWN: Risks and Benefits of Gadolinium-Based Contrast Enhanced MRI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 The duplicate article has therefore been withdrawn.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

Repaired Congenital Heart Disease in Older Children and Adults: Up-to-Date Practical Assessment and Characteristic Imaging Findings

Because of a recent increase in survival rates and life expectancy of patients with congenital heart disease (CHD), radiologists are facing new challenges when imaging the peculiar anatomy of individuals with repaired CHD. Cardiac computed tomography and magnetic resonance are paramount noninvasive imaging tools that are useful in assessing patients with repaired CHD, and both techniques are increasingly performed in centers where CHD is not the main specialization. This review provides general radiologists with insight into the main issues of imaging patients with repaired CHD, and the most common findings and complications of each individual pathology and its repair.

Value of tomography in detecting breast masses and discriminating malign and benign lesions

Objectives

The main purpose of the present study was to determine the effectivity of computerized tomography (CT) in detecting breast masses and discriminating masses as malignant or benign.

Material and Methods

After having received the institutional local ethics committee approval, an experienced radiologist who did not participate in the study created a patient pool by searching our health center's Pathology department database between 2010 and 2018. The group created consisted of dense and non-dense breast types equally and included approximately similar percentages of benign and malignant breast mass sizes. Finally, 70 subjects were included: 30 females with definite malign, 20 with definite benign breast masses, and 20 without any breast pathology based on mammography and ultrasonography results, who were considered as the control group. Three experienced Radiologists (R1, R2, R3) who were not aware of the final diagnosis evaluated all images independently. Radiologist performance was assessed by calculating the area under the receiver operating characteristic curve (AUC) and interobserver reliability values were estimated by intraclass correlation coefficient (ICC) analysis.

Results

The diagnostic accuracy suitability of CT according to BI-RADS scores for R1, R2 and R3 were found as p <0.001, p <0.001 and p <0.001, respectively. There were significant interobserver reliability rates between all investigators (p= 0.0001).

Conclusion

CT may be used as a valuable diagnostic tool in discriminating breast masses with further training in widely varying appearances of normal breast tissues leading to false positive findings.

Stability evaluation of Gd chelates for macromolecular MRI contrast agents

OBJECTIVE

We try to establish designs for the macromolecular agents possessing high Gd³⁺-chelating stability, because free Gd³⁺ ion released from Gd chelates is known as a risk factor to cause toxic side effects and a safety concern.

MATERIALS AND METHODS

We prepared three types of Gd-based macromolecular MRI contrast agents from a synthetic polymer (poly(glutamic acid) homopolymer or poly(ethylene glycol)-b-poly(lysine) block copolymer) and a chelating moiety (DO3A or DOTA) having two strategic designs for high chelate stability. Then, we examine the in vitro Gd³⁺-chelate stability of these macromolecular MRI contrast agents.

RESULTS

The prepared macromolecular agents exhibited the same or higher Gd³⁺-chelate stability as/than did Gd-DOTA that possesses the highest Gd³⁺-chelate stability among the approved small-MW Gd-chelate MRI contrast agent.

DISCUSSION

Our macromolecular design was considered to work well for high Gd³⁺-chelate stability.

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

RATIONALE AND OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Predictive measures and outcomes of extent of resection in juvenile pilocytic astrocytoma

PURPOSE

The present study aims to determine the tumor-related, clinical, and demographic factors associated with extent of resection (EOR) and post-operative outcomes in JPA patients.

METHODS

All patients with JPA, identified from a single-center brain tumour data base, were included in this retrospective analysis. Pre-operative MRI scans were reviewed by a single neurosurgeon blinded to the EOR. JPA cases that exhibited no residual tumor post-operatively were assigned to the GTR group, all other tumors were assigned to the <GTR group. Tumor-related, clinical and demographic variables as well as perioperative morbidities were compared between both groups.

RESULTS

Of the 28 patients included, 15 had a GTR (46% male; median age: 7.5 years; range: 1.16-14.9) and 13 had <GTR (69.2% male; median age: 10.6 years; range: 0.66-17.68). Tumor location reached statistical significance, as there were significantly more cerebellar tumors in the GTR group (86.7%) compared to the <GTR group (38.5%) (p = 0.016). GTR cases had a significantly longer average follow-up interval (6.6 months) than <GTR cases (4.5 months) (p = 0.031). All demographic variables, clinical variables and tumor-related factors showed no significant differences between the two groups. There were no differences between GTR and <GTR cases in terms of perioperative outcomes.

CONCLUSIONS

This study shows other than location of the lesion in the cerebellum, demographic, clinical and tumor-related variables are not associated with EOR in children with JPA. GTR was associated with an extended follow-up interval but not with increased perioperative morbidities compared to those with <GTR.

First-Trimester Exposure to Gadolinium-based Contrast Agents: A Utilization Study of 4.6 Million U.S. Pregnancies

BackgroundThe safety of gadolinium-based contrast agent (GBCA) exposure during pregnancy has not been established, and the use of GBCAs during pregnancy is not recommended unless it is essential to the health of the woman or fetus.PurposeTo examine the prevalence of GBCA exposure in a large sample of pregnancies resulting in a live birth.Materials and MethodsThe Sentinel Distributed Database was used to retrospectively identify U.S. pregnancies that resulted in live births between 2006 and 2017 from 16 data partners. The main outcome was the prevalence of MRI procedures with and without GBCAs, sorted by anatomic location and trimester, among pregnant and matched comparator women.ResultsAmong 4 692 744 pregnancies resulting in a live birth, we identified 6879 exposures to GBCAs in 5457 pregnancies, representing one contrast-enhanced MRI examination per 860 pregnancies (0.12% of all pregnancies). Most contrast-enhanced MRI examinations were performed in the head (n = 3499), although pelvic and abdominal MRI constituted 22.3% (n = 1536) of all contrast-enhanced MRI examinations during pregnancy. The majority (70.2%) of GBCA exposures occurred during the first trimester, with a 4.3-fold greater prevalence compared with that in the second trimester and a 5.1-fold greater prevalence compared with that in the third trimester.ConclusionThis study identified higher rates of gadolinium-based contrast agent (GBCA) exposure during the first few weeks of pregnancy compared with the later weeks of pregnancy, suggesting inadvertent exposure to GBCAs might occur before pregnancy is recognized.© RSNA, 2019Online supplemental material is available for this article.See also the editorial by Kallmes and Watson in this issue.

Applications of Deep Learning to Neuro-Imaging Techniques

Many clinical applications based on deep learning and pertaining to radiology have been proposed and studied in radiology for classification, risk assessment, segmentation tasks, diagnosis, prognosis, and even prediction of therapy responses. There are many other innovative applications of AI in various technical aspects of medical imaging, particularly applied to the acquisition of images, ranging from removing image artifacts, normalizing/harmonizing images, improving image quality, lowering radiation and contrast dose, and shortening the duration of imaging studies. This article will address this topic and will seek to present an overview of deep learning applied to neuroimaging techniques.

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.

Noncontrast vestibular schwannoma surveillance imaging including an MR cisternographic sequence: is there a need for postcontrast imaging?

OBJECTIVE

The purpose of this study was to evaluate the use of a noncontrast MRI protocol that includes a cisternographic sequence (CISS/FIESTA/3D DRIVE) compared to a protocol that includes a gadolinium-enhanced sequence in order to determine whether a noncontrast approach could be utilized to follow vestibular schwannomas.

METHODS

A total of 251 patients with vestibular schwannomas who underwent MRI of the temporal bones that included both cisternographic sequence and postcontrast T1 imaging between January 2000 and January 2016 for surveillance were included in this retrospective study. The size of the vestibular schwannomas was independently assessed on a noncontrast MR cisternographic sequence and compared to size measurements on a postcontrast sequence. The evaluation of intralesional cystic components (identified as T2 signal hyperintensity) and hemorrhagic components (identified with intrinsic T1 hyperintensity) on noncontrast MR sequences was compared to evaluation on postcontrast MR sequences to determine whether additional information could be derived from the postcontrast sequences. Additionally, any potentially clinically significant, incidentally detected findings on the postcontrast T1 sequences were documented and compared with the detection of these findings on the precontrast images.

RESULTS

No significant difference in vestibular schwannoma size was found when comparing measurements made on the images obtained with the MR cisternographic sequence and those made on images obtained with the postcontrast sequence (p = 0.99). Noncontrast MR images were better (detection rate of 87%) than postcontrast images for detection of cystic components. Noncontrast MR images were also better for identifying hemorrhagic components. No additional clinically relevant information regarding the tumors was identified on the postcontrast sequences.

CONCLUSIONS

Based on the results of this study, a noncontrast MR protocol that includes a cisternographic sequence would be sufficient for the accurate characterization of size and signal characteristics of vestibular schwannomas, obviating the need for gadolinium contrast administration for the routine surveillance of these lesions.

Multimodal Imaging Study of Gadolinium Presence in Rat Cerebellum: Differences Between Gd Chelates, Presence in the Virchow-Robin Space, Association With Lipofuscin, and Hypotheses About Distribution Pathway

Purpose

The aim of this study was to investigate, based on in-depth multimodal imaging, the presence of Gd deposits, their ultrastructure, location, and co-location with endogenous elements, in the cerebellum, after repeated administrations of gadolinium-based contrast agents (GBCAs).

Methods

Rats sensitized by subtotal nephrectomy received 20 daily intravenous injections of 0.6 mmol Gd/kg for 5 weeks of commercial forms of either gadoterate, gadobenate or gadodiamide, or saline (n = 2/group). The study was randomized and blinded. Magnetic resonance imaging examination was performed weekly. One month after the last injection, electron microscopy analysis of the deep cerebellar nuclei, the granular layer of cerebellar cortex, and the choroid plexus was performed. Elemental analysis of deposits was carried out by electron energy loss spectroscopy. Secondary ion mass spectroscopy was used for complementary chemical mapping.

Results

A T1 hypersignal was evidenced in the deep cerebellar nuclei of rats treated with linear GBCAs, and Gd deposits were identified in all the studied cerebellar structures with gadobenate and gadodiamide (except in the granular layer in gadobenate-treated rats). No such effect was found with the macrocyclic GBCA gadoterate. Most of the Gd deposits revealed a characteristic spheroid “sea urchin-like” morphology, rich in phosphorus, and were localized in the basal lamina of microvessels, in the perivascular Virchow-Robin space, and in the interstitium. Gd was also identified in the glial cells, associated with lipofuscin pigments, for these same groups.

Conclusions

Transmission electron microscopy analysis of cerebellums of renally impaired rats repeatedly injected with gadobenate and gadodiamide revealed the presence of Gd. Spheroid Gd depositions consisting of a filamentous meshwork were observed in the wall of microvessels, in perivascular Virchow-Robin space, and in the interstitium. Gd was also found in choroid plexus and was associated with pigments (likely lipofuscin) in glial cells. This is consistent with the involvement of the glymphatic distribution pathway for GBCAs. No insoluble Gd deposits were detected in rats injected with the macrocyclic GBCA gadoterate and controls.

Microbubbles as a contrast agent in grating interferometry mammography: an ex vivo proof-of-mechanism study

Grating interferometry mammography (GIM) is an experimental breast imaging method at the edge of being clinically implemented. Besides attenuation, GIM can measure the refraction and scattering of x-rays resulting in differential phase contrast (DPC) and dark-field (DF) images. In this exploratory study, we assessed the feasibility of using microbubbles as a contrast agent in GIM. Two millilitres of microbubbles and iodine were respectively injected into ex vivo breast phantoms, consisting of fresh chicken breasts. Native and postcontrast images were acquired with a clinically compatible GIM setup, operated at 38 kVp, 14-s acquisition time, and with a dose of 1.3 mGy. The visibility of the contrast agents was analysed in a side-by-side comparison by three radiologists. The contrast-to-noise-ratio (CNR) was calculated for each contrast agent. We found that both contrast agents were judged to be visible by the readers. The mean CNR was 3.1 ± 1.9 for microbubbles in DF and 24.2 ± 6.5 for iodine in attenuation. In conclusion, this is a first proof-of-mechanism study that microbubbles could be used as a contrast agent in clinically compatible GIM, due to their scattering properties, which implies the potential use of a contrast agent with a high safety profile in x-ray-based breast imaging.

Non-contrast-enhanced magnetic resonance imaging for visualization and quantification of endovascular aortic prosthesis, their endoleaks and aneurysm sacs at 1.5 T

PURPOSE

After an endovascular aortic aneurysm repair (EVAR), a follow-up at 1, 6 and every 12 months is recommended for remainder of the patient's life. The diagnostic standard methods for diagnosing endoleaks and visualization of aneurysms in EVAR-patients are: invasive digital subtraction angiography (DSA), contrast enhanced (CE) computed tomographic angiography (CE-CTA), and magnetic resonance angiography (CE-MRA). These techniques, however, require the use of iodine- or gadolinium-based contrast agents with rare, but possibly life threatening side effects such as renal impairment, thyrotoxicosis and allergic reactions, nephrogenic systemic fibrosis, and cerebral gadolinium deposition. The aim of this prospective study was to compare a non-contrast-enhanced MRI protocol (consist of four MRI methods) with DSA and CE-CTA for visualization and quantification of endovascular aortic prosthesis, their endoleaks and aneurysms.

MATERIAL AND METHODS

Eight patients (mean age 76.8 ± 4.9 years, 63% male), whose thoracic, abdominal, or iliac aneurysms were treated with different endovascular prosthesis and suffered from type I-V endoleaks, were examined on a 1.5 Tesla MR system. Quiescent-interval slice selective MR angiography (QISS-MRA), 4-dimensional (4D)-flow MRI, T₁- and T₂-mapping, as well as DSA and CE-CTA were used for the visualization and quantification of endoprosthesis, endoleaks, and aneurysms in these patients.

RESULTS

QISS-MRA provided good visualization of endoleaks and comparable quantification of aneurysm size with respect to CE-CTA and DSA. The 4D-flow MRI provided additional information about the wall shear stress, which could not be determined using DSA. In contrast to CE-CTA, T₁- and T₂-mapping provided detailed information about heterogeneous areas within an aneurysm sac.

CONCLUSIONS

Compared to DSA and CE-CTA, the proposed MRI methods provide improved anatomical and functional information for various types of endoprostheses and endoleaks. In addition, hemodynamic parameters of the aorta and information on the content of aneurysm sac are provided as well. Within the frame of personalized medicine, the personalized diagnosis enabled by this non-CE MRI protocol is the foundation for a personalized and successful treatment.

Gadolinium Retention and Clearance in the Diabetic Brain after Administrations of Gadodiamide, Gadopentetate Dimeglumine, and Gadoterate Meglumine in a Rat Model

Purpose

To evaluate gadolinium (Gd) retention and clearance in the brain of diabetic rats after administrations of gadodiamide, gadopentetate dimeglumine, and gadoterate meglumine.

Materials and Methods

Both diabetic rats (n = 52) and normal rats (n = 52) intravenously received 20 injections of 0.6 mmol Gd/kg gadodiamide, gadopentetate dimeglumine, gadoterate meglumine, or saline. Both diabetic rats and normal rats were divided into 2 subgroups of 24 and 28 rats for the 7-day and 42-day evaluations (i.e., they were sacrificed at 7 days (n = 6 per group) and 42 days (n = 7 per group)), respectively, after the last injection. For the 7-day subgroup, 6 rats were euthanized for inductively coupled plasma mass spectrometry (ICP-MS) analysis. For the 42-day subgroup, 6 rats underwent T1-weighted magnetic resonance imaging (MRI) and ICP-MS, and 1 rat was analyzed by transmission electron microscopy (TEM).

Results

The T1 enhancements in the deep cerebellar nuclei (DCNs) of diabetic rats were lower than those of normal rats in both linear Gd-based contrast agent (GBCA) groups (p < 0.05). The average Gd concentrations in the brains of diabetic rats were significantly lower than those of healthy rats in both the short-term groups and long-term groups (p < 0.05). The highest Gd retentions were in the olfactory bulb, DCN, and striatum with gadodiamide. Compared with the results obtained 7 days after the last injection, the residual Gd concentrations of the 42-day subgroups in the brains of diabetic rats showed no significant difference in both linear GBCA groups (p>0.05).

Conclusions

Compared with normal rats, the diabetic status decreased the residual Gd concentrations in the brain after multiple administrations of gadodiamide, gadopentetate dimeglumine, and gadoterate meglumine. The clearable fraction of Gd in the brain was eliminated faster in diabetic rats than in normal rats.

Serum tumor marker levels at the development of intracranial metastasis in patients with lung or breast cancer

Background

Intracranial metastasis (IM) is observed in various cancers, including in lung and breast cancer, and its timely diagnosis is required for successful patient treatment. Various tumor serum markers, such as carcinoembryonic antigen (CEA), pro-gastrin-releasing peptide (ProGRP), neuron-specific enolase (NSE), and cancer antigen 15-3 (CA15-3), serve not only as prognostic indicators in lung and breast cancer but also as risk factors for IM development. This study is the first to assess a subgroup of cancer patients with IM that did not show elevated serum tumor marker levels.

Methods

This retrospective study included 53 patients with lung or breast cancer in which IM was detected by enhanced brain magnetic resonance imaging between January 2013 and December 2018. IM was classified into three types [parenchymal metastasis (PM), leptomeningeal metastasis and dural metastasis]. Serum CEA level was measured using an electrochemiluminescence immunoassay (ECLIA) or chemiluminescent immunoassay. Plasma ProGRP level was measured using a chemiluminescent enzyme immunoassay (CLEIA), and the serum NSE level was measured using ECLIA. The serum CA15-3 level was measured using CLEIA. Univariate and multivariate analyses were performed using Pearson's χ² test and logistic regression analysis, respectively.

Results

Among the total 53 patients, 15 patients (28.3%) did not show elevated serum tumor marker levels. Univariate analysis showed that the patients with PM only significantly correlated with no increasing tumor marker level compared with other IM types (P=0.030), as well as female patients and patients without symptoms (P=0.010 and 0.046, respectively). Multivariate showed that the patients with PM only and female patients significantly correlated with no increasing tumor marker level (P=0.038 and 0.014, respectively).

Conclusions

Our findings describe a subgroup of lung and breast cancer patients with IM that do not show elevated tumor marker levels, indicating the need for the identification of novel indicators for IM or increased monitoring of these patients.

EDTA Chelation Therapy for the Treatment of Neurotoxicity

Neurotoxicity can be caused by numerous direct agents, of which toxic metals, organophosphorus pesticides, air pollution, radiation and electromagnetic fields, neurotoxins, chemotherapeutic and anesthetic drugs, and pathogens are the most important. Other indirect causes of neurotoxicity are cytokine and/or reactive oxygen species production and adoptive immunotherapy. The development of neurodegenerative diseases has been associated with neurotoxicity. Which arms are useful to prevent or eliminate neurotoxicity? The chelating agent calcium disodium ethylenediaminetetraacetic acid (EDTA)-previously used to treat cardiovascular diseases-is known to be useful for the treatment of neurodegenerative diseases. This review describes how EDTA functions as a therapeutic agent for these diseases. Some case studies are reported to confirm our findings.

Gadolinium as an Emerging Microcontaminant in Water Resources: Threats and Opportunities

As a result of high doses of paramagnetic gadolinium (Gd) chelates administered in magnetic resonance imaging (MRI) exams, their unmetabolized excretion, and insufficient removal in wastewater treatment plants (WWTPs), large amounts of anthropogenic Gd (Gdanth) are released into surface water. The upward trend of gadolinium-based contrast agent (Gd-CA) administrations is expected to continue growing and consequently higher and higher anthropogenic Gd concentrations are annually recorded in water resources, which can pose a great threat to aquatic organisms and human beings. In addition, the feasibility of Gd retention in patients administered with Gd-CAs repeatedly, and even potentially fatal diseases, including nephrogenic systemic fibrosis (NSF), due to trace amounts of Gd have recently arisen severe health concerns. Thus, there is a need to investigate probable adverse health effects of currently marketed Gd-CAs meticulously and to modify the actual approach in using Gd contrast media in daily practice in order to minimize unknown possible health risks. Furthermore, the employment of enhanced wastewater treatment processes that are capable of removing the stable contrast agents, and the evaluation of the ecotoxicity of Gd chelates and human exposure to these emerging contaminants through dermal and ingestion pathways deserve more attention. On the other hand, point source releases of anthropogenic Gd into the aquatic environment presents the opportunity to assess surface water—groundwater interactions and trace the fate of wastewater plume as a proxy for the potential presence of other microcontaminants associated with treated wastewater in freshwater and marine systems.

Positive magnetic resonance angiography using ultrafine ferritin-based iron oxide nanoparticles

Iron oxide nanoparticles with good biocompatibility can serve as safe magnetic resonance imaging contrast agents. Herein, we report that ultrafine ferritin-based iron oxide (hematite/maghemite) nanoparticles synthesized by controlled biomimetic mineralization using genetically recombinant human H chain ferritin can be used as a positive contrast agent in magnetic resonance angiography. The synthesized magnetoferritin with an averaged core size of 2.2 ± 0.7 nm (hereafter named M-HFn-2.2) shows a r1 value of 0.86 mM-1 s-1 and a r2/r1 ratio of 25.1 at a 7 T magnetic field. Blood pool imaging on mice using the M-HFn-2.2 nanoparticles that were injected through a tail vein by single injection at a dose of 0.54 mM Fe per kg mouse body weight enabled detecting detailed vascular nets at 3 minutes post-injection; the MR signal intensity continuously enhanced up to 2 hours post-injection, which is much longer than that of the commercial magnevist (Gd-DTPA) contrast. Moreover, biodistribution examination indicates that organs such as liver, spleen and kidney safely cleared the injected nanoparticles within one day after the injection, demonstrating no risk of iron overload in test mice. Therefore, this study sheds light on developing high-performance gadolinium free positive magnetic resonance contrast agents for biomedical applications.

Standardizing Magnetic Resonance Imaging Protocols, Requisitions, and Reports in Multiple Sclerosis: An Update for Radiologist Based on 2017 Magnetic Resonance Imaging in Multiple Sclerosis and 2018 Consortium of Multiple Sclerosis Centers Consensus Guidelines

The advent of magnetic resonance imaging has improved our understanding of the pathophysiology and natural course of multiple sclerosis (MS). The ability of magnetic resonance imaging to show the evolution of MS lesions on sequential scans has brought it to be one of the endpoints in clinical trials for disease-modifying therapies. Based on the most updated consensus guidelines from the American (Consortium of MS Centers) and European (Magnetic Resonance Imaging in MS) boards of experts in MS, this document shows the most relevant landmarks related to imaging findings, diagnostic criteria, indications to obtain a magnetic resonance, scan protocols and sequence options for patients with MS. Although incorporating the knowledge derived from the research arena into the daily clinical practice is always challenging, in this article, the authors provide useful recommendations to improve the information contained in the magnetic resonance report oriented to facilitate communication between radiologists and specialized medical teams involved in MS patients' multidisciplinary care.

Optimization of 3D phase contrast venography for the assessment of the cranio-cervical venous system at 1.5 T

PURPOSE

The aim of this work was to optimize a three-dimensional (3D) phase-contrast venography (PCV) product MR pulse sequence in order to obtain clinically reliable images with less artifacts for an improved depiction of the cranio-cervical venous vessels.

METHODS

Starting from the product sequence, the 3D PCV protocol was optimized in eight steps with respect to the velocity encoding (V_enc) direction and value, slice thickness, reduction of susceptibility artifacts and arterial contamination, gradient mode and radio-frequency (RF)-spoiling, B₀-Shimming, asymmetric echo technique and RF-pulse type, and flip angle. The product and optimized protocol was used to perform 3D PCV in 12 healthy male volunteers with a median age of 50 years using a state-of-the-art 1.5-T MR system. For evaluation, the cranio-cervical venous system was divided into 15 segments. These segments were evaluated by three radiologists with experience in neuroradiology. An ordinal scoring system was used to access the overall diagnostic quality, arterial contamination, and the quality of visualization.

RESULTS

Image quality in the optimized 3D PCV was graded as "excellent" by all readers in 65.3% of the cases (p < 0.0001). The visualization of venous segments was strongly improved: it was considered diagnostic in 81.8% of all cases using the optimized sequence and in 47.6% for the product 3D PCV (p < 0.0001), respectively. The optimized protocol improved the imaging of all venous segments (p < 0.0001).

CONCLUSION

The optimized 3D PCV pulse sequence showed superior results compared to the product 3D PCV for the visualization and evaluation of the venous system in all healthy volunteers.

Detection of pediatric musculoskeletal pathology using the fluid-sensitive sequence

BACKGROUND

Musculoskeletal complaints are common among children, and magnetic resonance (MR) is increasingly used to supplement the clinical assessment. The validation of a short triage protocol could reduce the number of unnecessary contrast-enhanced MR studies that sometimes also require the need for sedation.

OBJECTIVE

To compare the diagnostic accuracy between fluid-sensitive sequence and contrast-enhanced MR study in the detection of musculoskeletal pathology in the pelvis and the appendicular skeleton in children older than 2 years.

MATERIALS AND METHODS

We performed a retrospective review between Feb. 1, 2016, and Oct. 31, 2016, and identified 99 studies from 96 patients (48 boys and 48 girls; mean age ± standard deviation, 11.1±4.6 years) without syndromic deformity, recent trauma, a history of infectious or inflammatory arthropathy, prior instrumentation or incomplete records. Two radiologists reviewed each study twice, at least 1 month apart, first using only the fluid-sensitive sequences (triage study) and later using the contrast-enhanced study. Readers rated the presence or absence of pathology independently and generated final impressions in consensus. We used Cohen's kappa (κ) and percentage agreement to compare agreement between readers and between studies, respectively.

RESULTS

Inter-reader agreement was overall higher for the contrast-enhanced studies (κ range = 0.91-1) than for the triage studies (κ range = 0.49-1). Percentage agreement between studies was high for the detection of pathology (97-100%) and for the impressions (93%). Clinical diagnoses were stress reaction or overuse in 31%, infection in 21%, space-occupying process in 17%, normal in 15%, inflammatory in 14%, and both inflammatory and overuse in 1%. The full study increased diagnostic confidence in five studies and accuracy in two but did not alter management.

CONCLUSION

The fluid-sensitive sequence had a near-perfect percentage of agreement with the contrast-enhanced study in the detection of musculoskeletal pathology and could possibly be used to screen children who need a contrast-enhanced MR study.

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.

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Clinical Tracking of Cell Transfer and Cell Transplantation: Trials and Tribulations

Cell therapy has provided unprecedented opportunities for tissue repair and cancer therapy. Imaging tools for in vivo tracking of therapeutic cells have entered the clinic to evaluate therapeutic cell delivery and retention in patients. Thus far, clinical cell tracking studies have been a mere proof of principle of the feasibility of cell detection. This review centers around the main clinical queries associated with cell therapy: Have cells been delivered correctly at the targeted site of injection? Are cells still alive, and, if so, how many? Are cells being rejected by the host, and, if so, how severe is the immune response? For stem cell therapeutics, have cells differentiated into downstream cell lineages? Is there cell proliferation including tumor formation? At present, clinical cell tracking trials have only provided information on immediate cell delivery and short-term cell retention. The next big question is if these cell tracking tools can improve the clinical management of the patients and, if so, by how much, for how many, and for whom; in addition, it must be determined whether tracking therapeutic cells in every patient is needed. To become clinically relevant, it must now be demonstrated how cell tracking techniques can inform patient treatment and affect clinical outcomes.

Gadolinium and Multiple Sclerosis: Vessels, Barriers of the Brain, and Glymphatics

The pathogenesis of multiple sclerosis is characterized by a cascade of pathobiologic events, ranging from focal lymphocytic infiltration and microglia activation to demyelination and axonal degeneration. MS has several of the hallmarks of an inflammatory autoimmune disorder, including breakdown of the BBB. Gadolinium-enhanced MR imaging is currently the reference standard to detect active inflammatory lesions in MS. Knowledge of the patterns and mechanisms of contrast enhancement is vital to limit the radiologic differential diagnosis in the staging and evaluation of MS lesion activity. The aim of this review was the following: 1) to outline the pathophysiology of the effect of lymphocyte-driven inflammation in MS, 2) to describe the effects of gadolinium on the BBB and glymphatic system, and 3) to describe gadolinium enhancement patterns and artifacts that can mimic lesions in MS.

Linear gadolinium-based contrast agent (gadodiamide and gadopentetate dimeglumine)-induced high signal intensity on unenhanced T1 -weighted images in pediatric patients

BACKGROUND

Recent studies of adults have found an association between hyperintensity of the dentate nucleus (DN) and globus pallidus (GP) on T₁ -weighted images (T₁ WI) and a history of linear gadolinium-based contrast agent (GBCA) administration. Several reports have also focused on this phenomenon in pediatric patients; however, data in the current literature remains limited.

PURPOSE/HYPOTHESIS

To evaluate the associations between DN and GP T₁ -signal increase and previous administration of linear GBCAs in pediatric patients.

STUDY TYPE

Single-center, retrospective, cross-sectional study.

POPULATION

We included pediatric patients with histories of ≥5 linear GBCA (gadodiamide and gadopentetate dimeglumine) administrations (the "≥5 Linear GBCA administrations" group), 1-4 administrations (the "1-4 Linear GBCA administrations" group), and no history of GBCA administration (the "No GBCA administration" group). Each group included 42 patients. Therefore, 126 patients (male:female, 72:54; median age, 16 [range, 4-18] years) were included in this study.

FIELD STRENGTH/SEQUENCE

1.5T/ Spin-echo unenhanced T₁ -weighted imaging.

ASSESSMENT

Unenhanced T₁ -weighted images were quantitatively analyzed by two radiologists. The DN-to-pons and GP-to-thalamus signal intensity ratios (DN-to-pons and GP-to-thalamus ratios, respectively) were compared.

STATISTICAL TESTS

Wilcoxon test with the Bonferroni correction and intraclass correlation coefficients.

RESULTS

The DN-to-pons ratio increased as the number of GBCA administrations increased (P < 0.0063). The GP-to-thalamus ratio of the "≥5 Linear GBCA administrations" group was significantly higher than those of the other two groups (P < 0.0001). The GP-to-thalamus ratio of the "1-4 Linear GBCA administrations" group did not differ significantly from that of the "No GBCA administration" group (P = 1.000). The DN-to-pons and GP-to-thalamus ratios' interobserver intraclass correlation coefficients were excellent (0.8236) and good (0.6738), respectively.

DATA CONCLUSION

High signal intensities in the DN and GP on T₁ WI were associated with previous linear GBCA administration in pediatric patients.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1046-1052.

Non-enhanced MR imaging for preinterventional assessment of the angioarchitecture in vein of Galen malformations

BACKGROUND AND PURPOSE

Endovascular treatment of vein of Galen malformations (VGMs) requires sufficient preceding MR imaging. Standardized, preinterventional, non-invasive imaging has not been established. Our study is the first to examine the role of a dedicated, standardized, non-invasive imaging protocol in the evaluation of VGM angioarchitecture by non-contrast MRI/MR angiography.

MATERIALS AND METHODS

We retrospectively evaluated a consecutive series of VGM patients who underwent a 1.5 T MRI protocol, including standard T2 weighted images (T2WI), arterial time of flight (TOF), and thin T2WI without flow compensation (T2OffPh). The primary outcome was the proportion of patients in whom VGM subtypes and all arterial feeders (anterior (AChA) and posterior (PChA) choroidal arteries, pericallosal arteries, basilar tip, and leptomeningeal supply) could be accurately identified compared with a DSA gold standard.

RESULTS

A total of 26 VGM patients who underwent 108 studies were used in the statistical analysis. VGM subtype was best seen in axial T2OffPh (92.1%) and TOF (89.8%). AChA feeders were best seen in TOF (86.5%) and axial T2OffPh (72.2%). PChA feeders were best seen in TOF (95.1%) and axial T2OffPh (88.1%). Pericallosal feeders were best seen in axial T2OffPh (95.4%) and TOF (95.1%). Basilar tip feeders were best seen in TOF (90.6%) and axial T2OffPh (88.4%).

CONCLUSION

VGM angioarchitecture is best seen in TOF and axial T2OffPh. It can be used as an alternative to global angiographic series.

Gadolinium Retention: A Research Roadmap from the 2018 NIH/ACR/RSNA Workshop on Gadolinium Chelates

Gadolinium-based contrast agents (GBCAs) have revolutionized MRI, enabling physicians to obtain crucial life-saving medical information that often cannot be obtained with other imaging modalities. Since initial approval in 1988, over 450 million intravenous GBCA doses have been administered worldwide, with an extremely favorable pharmacologic safety profile; however, recent information has raised new concerns over the safety of GBCAs. Mounting evidence has shown there is long-term retention of gadolinium in human tissues. Further, a small subset of patients have attributed a constellation of symptoms to GBCA exposure, although the association of these symptoms with GBCA administration or gadolinium retention has not been proven by scientific investigation. Despite evidence that macrocyclic GBCAs show less gadolinium retention than linear GBCAs, the safety implications of gadolinium retention are unknown. The mechanism and chemical forms of gadolinium retention, as well as the biologic activity and clinical importance of these retained gadolinium species, remain poorly understood and underscore the need for additional research. In February 2018, an international meeting was held in Bethesda, Md, at the National Institutes of Health to discuss the current literature and knowledge gaps about gadolinium retention, to prioritize future research initiatives to better understand this phenomenon, and to foster collaborative standardized studies. The greatest priorities are to determine (a) if gadolinium retention adversely affects the function of human tissues, (b) if retention is causally associated with short- or long-term clinical manifestations of disease, and (c) if vulnerable populations, such as children, are at greater risk for experiencing clinical disease. The purpose of the research roadmap is to highlight important information that is not known and to identify and prioritize needed research. ©RSNA, 2018 Online supplemental material is available for this article .

Determination of Hepatocellular Carcinoma and Characterization of Hepatic Focal Lesions with Adaptive Multi-Exponential Intravoxel Incoherent Motion Model

PURPOSE: To distinguish hepatocellular carcinoma (HCC) from other types of hepatic lesions with the adaptive multi-exponential IVIM model. METHODS: 94 hepatic focal lesions, including 38 HCC, 16 metastasis, 12 focal nodular hyperplasia, 13 cholangiocarcinoma, and 15 hemangioma, were examined in this study. Diffusion-weighted images were acquired with 13 b values (b = 0, 3, …, 500 s/mm²) to measure the adaptive multi-exponential IVIM parameters, namely, pure diffusion coefficient (D), diffusion fraction (f_d), pseudo-diffusion coefficient (D_i*) and perfusion-related diffusion fraction (f_i) of the ith perfusion component. Comparison of the parameters of and their diagnostic performance was determined using Mann-Whitney U test, independent-sample t test, one-way analysis of variance, Z test and receiver-operating characteristic analysis. RESULTS: D, D₁* and D₂* presented significantly difference between HCCs and other hepatic lesions, whereas f_d, f₁ and f₂ did not show statistical differences. In the differential diagnosis of HCCs from other hepatic lesions, D₂* (AUC, 0.927) provided best diagnostic performance among all parameters. Additionally, the number of exponential terms in the model was also an important indicator for distinguishing HCCs from other hepatic lesions. In the benign and malignant analysis, D gave the greatest AUC values, 0.895 or 0.853, for differentiation between malignant and benign lesions with three or two exponential terms. Most parameters were not significantly different between hypovascular and hypervascular lesions. For multiple comparisons, significant differences of D, D₁* or D₂* were found between certain lesion types. CONCLUSION: The adaptive multi-exponential IVIM model was useful and reliable to distinguish HCC from other hepatic lesions.

A Multidisciplinary Consensus for Clinical Care and Research Needs for Sturge-Weber Syndrome

BACKGROUND

Sturge-Weber syndrome is a neurocutaneous disorder associated with port-wine birthmark, leptomeningeal capillary malformations, and glaucoma. It is associated with an unpredictable clinical course. Because of its rarity and complexity, many physicians are unaware of the disease and its complications. A major focus moving ahead will be to turn knowledge gaps and unmet needs into new research directions.

METHODS

On October 1-3, 2017, the Sturge-Weber Foundation assembled clinicians from the Clinical Care Network with patients from the Patient Engagement Network of the Sturge-Weber Foundation to identify our current state of knowledge, knowledge gaps, and unmet needs.

RESULTS

One clear unmet need is a need for consensus guidelines on care and surveillance. It was strongly recommended that patients be followed by multidisciplinary clinical teams with life-long follow-up for children and adults to monitor disease progression in the skin, eye, and brain. Standardized neuroimaging modalities at specified time points are needed together with a stronger clinicopathologic understanding. Uniform tissue banking and clinical data acquisition strategies are needed with cross-center, longitudinal studies that will set the stage for new clinical trials. A better understanding of the pathogenic roles of cerebral calcifications and stroke-like symptoms is a clear unmet need with potentially devastating consequences.

CONCLUSIONS

Biomarkers capable of predicting disease progression will be needed to advance new therapeutic strategies. Importantly, how to deal with the emotional and psychological effects of Sturge-Weber syndrome and its impact on quality of life is a clear unmet need.

Anatomy of the deep venous system in vein of Galen malformation and its changes after endovascular treatment depicted by magnetic resonance venography

BACKGROUND AND PURPOSE

It is classically thought that the internal cerebral veins (ICV) do not communicate with the venous pouch of vein of Galen malformations (VGM). We report on the anatomy of the deep venous system in VGM with special emphasis on the drainage of the ICV and possible changes after endovascular treatment.

MATERIALS AND METHODS

We retrospectively analyzed DSA and 2D time-of-flight MR venograms of 55 children with VGM. We evaluated all pre- and post-operative images for the presence of the ICVs and determined their route of venous drainage.

RESULTS

Of 55 children, pre-operative 2D MRV detected the ICVs in 19 cases (35%) compared with one case (2%) for pre-embolization DSA (2%) (P<0.0001). Of the cases in which the ICVs were seen preoperatively, in 15 cases (78.9%) the ICV drained directly into the VGM while in the other four cases, the ICV used alternative venous drainage routes. On post-operative MRV, the ICVs were seen in 17 cases (31%) on MRV and 10 cases (18.2%) on DSA with drainage into an adult-like vein of Galen in 13 cases (76%), respectively (P=0.08). In four cases normal ICV drainage into the vein of Galen was seen even when the venous sac was closed. In two cases there was a change in ICV drainage from the vein of Galen to the lateral mesencephalic vein.

CONCLUSION

The communication of the ICV with the VGM is a common phenomenon. Different changes of venous drainage routes do occur after treatment and are best seen on MRV.

Does renal function affect gadolinium deposition in the brain?

OBJECTIVE

Was to compare T1 signal intensity ratios of dentate nucleus to cerebellar white matter (DN/cerebellum), dentate nucleus to pons (DN/pons) and globus pallidus to thalamus (GP/thalamus) in patients with normal renal function and in patients on chronic hemodialysis. To find out if renal function affects the deposition of gadolinium in brain after administration of linear gadolinium based contrast agents (GBCA).

METHODS

Seventy eight contrast enhanced brain MRIs (Magnetic Resonance Imaging) with linear GBCA of 13 patients on chronic hemodialysis and 13 patients with normal renal function retrospectively evaluated. The DN/pons, DN/cerebellum and GP/thalamus signal intensity ratios were measured from each brain MRI on unenhanced axial T1 weighted images.

RESULTS

In hemodialysis group statistically significant increase in the signal intensity ratios of DN/pons, DN/cerebellum and GP/thalamus were found between the first and the last brain MRIs (p = .001). The increase in the signal intensity ratios of DN/pons, DN/cerebellum and GP/thalamus between the first and the last brain MRIs in control group were not significant (p > 0.05). The signal intensity increase in DN and globus pallidus were significantly higher in hemodialysis group than control group (p < 0.05).

CONCLUSIONS

Patients on hemodialysis had significantly higher DN and GP signal intensity increase compared to the patients with normal renal function. Renal function affects the rate of gadolinium deposition in the brain after administration of linear GBCA.

Commentary on "A Microfluidic Platform to Design Crosslinked Hyaluronic Acid Nanoparticles (cHANPs) for Enhanced MRI"

Strategies to enhance the relaxometric properties of gadolinium (Gd)-based contrast agents (CAs) for magnetic resonance imaging (MRI), without the chemical modification of chelates, have recently had a strong impact on the diagnostic field. We have taken advantage of the interaction between Gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) and the hydrogel structure of hyaluronic acid to design cross-linked hyaluronic acid nanoparticles down to 35 nm for use in MRI applications. The proposed bioformulations enable the control of the relaxometric properties of CAs, thus boosting the relaxation rate of T1. Our results led us to identify this approach as an adjustable scenario to design intravascularly injectable hydrogel nanoparticles entrapping Gd-DTPA. This approach overcomes the general drawbacks of clinically approved CAs having poor relaxivity and toxic effects.

Variability of non-Gaussian diffusion MRI and intravoxel incoherent motion (IVIM) measurements in the breast

We prospectively examined the variability of non-Gaussian diffusion magnetic resonance imaging (MRI) and intravoxel incoherent motion (IVIM) measurements with different numbers of b-values and excitations in normal breast tissue and breast lesions. Thirteen volunteers and fourteen patients with breast lesions (seven malignant, eight benign; one patient had bilateral lesions) were recruited in this prospective study (approved by the Internal Review Board). Diffusion-weighted MRI was performed with 16 b-values (0–2500 s/mm² with one number of excitations [NEX]) and five b-values (0–2500 s/mm², 3 NEX), using a 3T breast MRI. Intravoxel incoherent motion (flowing blood volume fraction [fIVIM] and pseudodiffusion coefficient [D*]) and non-Gaussian diffusion (theoretical apparent diffusion coefficient [ADC] at b value of 0 sec/mm² [ADC₀] and kurtosis [K]) parameters were estimated from IVIM and Kurtosis models using 16 b-values, and synthetic apparent diffusion coefficient (sADC) values were obtained from two key b-values. The variabilities between and within subjects and between different diffusion acquisition methods were estimated. There were no statistical differences in ADC₀, K, or sADC values between the different b-values or NEX. A good agreement of diffusion parameters was observed between 16 b-values (one NEX), five b-values (one NEX), and five b-values (three NEX) in normal breast tissue or breast lesions. Insufficient agreement was observed for IVIM parameters. There were no statistical differences in the non-Gaussian diffusion MRI estimated values obtained from a different number of b-values or excitations in normal breast tissue or breast lesions. These data suggest that a limited MRI protocol using a few b-values might be relevant in a clinical setting for the estimation of non-Gaussian diffusion MRI parameters in normal breast tissue and breast lesions.

Quantification and Assessment of the Chemical Form of Residual Gadolinium in the Brain After Repeated Administration of Gadolinium-Based Contrast Agents: Comparative Study in Rats

Supplemental digital content is available in the text.

Objective

Multiple clinical and preclinical studies have reported a signal intensity increase and the presence of gadolinium (Gd) in the brain after repeated administration of Gd-based contrast agents (GBCAs). This bioanalytical study in rat brain tissue was initiated to investigate whether the residual Gd is present as intact GBCA or in other chemical forms by using tissue fractionation and chromatography.

Materials and Methods

Rats were divided randomly in 6 groups of 10 animals each. They received 10 daily injections of 2.5 mmol/kg bodyweight of 1 of 5 different GBCAs: linear GBCAs such as gadodiamide (Omniscan; GE Healthcare), gadopentetate dimeglumine (Gd-DTPA, Magnevist; Bayer), or gadobenate dimeglumine (Multihance; Bracco) and macrocyclic GBCAs such as gadobutrol (Gadovist; Bayer) and gadoterate meglumine (Gd-DOTA, Dotarem; Guerbet) or saline. On days 3 and 24 after the last injection (p.i.), 5 randomly chosen animals of each group were killed by exsanguination, and their brains were excised and divided into cerebrum, pons, and cerebellum. The brain sections were homogenized by sonication in ice-cold buffer at pH 7.4. Soluble and insoluble fractions were separated by centrifugation, and the soluble fractions were further separated by gel permeation chromatography (GPC). The Gd concentration in all tissue fractions and in the GPC eluate was measured by inductively coupled plasma–mass spectrometry. In a recovery control experiment, all GBCAs were spiked to blank brain tissue and more than 94% recovery of Gd in the tissue fractions was demonstrated.

Results

Only traces of the administered Gd were found in the rat brain tissue on day 3 and day 24 p.i. In the animals treated with macrocyclic GBCAs, Gd was found only in the soluble brain fraction and was present solely as low molecular weight molecules, most likely the intact GBCA. In the animals treated with linear GBCAs Gd was found to a large extent in the insoluble tissue fraction. The Gd concentration in the soluble fraction was comparable to the macrocyclic agents. According to GPC, a smaller portion of the Gd in the soluble fraction of the linear GBCAs groups was bound to macromolecules larger than 250 to 300 kDa. The nature of the Gd-containing macromolecules and the insoluble species were not determined, but they appeared to be saturable with Gd. The excretion of the soluble Gd species in the linear and macrocyclic GBCA groups was still ongoing between days 3 and 24 p.i. This was also observed for the macromolecular Gd species in the linear GBCA groups, but at a slower rate.

Conclusions

The residual Gd found in the rat brain after repeated administration of all 3 linear GBCAs was present in at least 3 distinctive forms—soluble small molecules, including the intact GBCA, soluble macromolecules, and to a large extent in insoluble form. The latter 2 are most likely responsible for the prolonged signal intensity enhancement in brain structures observed in magnetic resonance imaging. No relevant differences between the 3 linear GBCAs were observed. The Gd concentrations in the brain after administration of macrocyclic GBCAs are lower, and the Gd is only present in soluble small molecules, which were slowly excreted. This underlines the crucial importance of the kinetic inertness of macrocyclic agents in the prevention of potential retention of Gd in the brain compared with the 3 linear, kinetically less restricted GBCAs.

Gadolinium-based Contrast Media, Cerebrospinal Fluid and the Glymphatic System: Possible Mechanisms for the Deposition of Gadolinium in the Brain

After Kanda’s first report in 2014 on gadolinium (Gd) deposition in brain tissue, a considerable number of studies have investigated the explanation for the observation. Gd deposition in brain tissue after repeated administration of gadolinium-based contrast medium (GBCM) has been histologically proven, and chelate stability has been shown to affect the deposition. However, the mechanism for this deposition has not been fully elucidated. Recently, a hypothesis was introduced that involves the ‘glymphatic system’, which is a coined word that combines ‘gl’ for glia cell and ‘lymphatic’ system. According to this hypothesis, the perivascular space functions as a conduit for cerebrospinal fluid to flow into the brain parenchyma. The perivascular space around the arteries allows cerebrospinal fluid to enter the interstitial space of the brain tissue through water channels controlled by aquaporin 4. The cerebrospinal fluid entering the interstitial space clears waste proteins from the tissue. It then flows into the perivascular space around the vein and is discharged outside the brain. In addition to the hypothesis regarding the glymphatic system, some reports have described that after GBCM administration, some of the GBCM distributes through systemic blood circulation and remains in other compartments including the cerebrospinal fluid. It is thought that the GBCM distributed into the cerebrospinal fluid cavity via the glymphatic system may remain in brain tissue for a longer duration compared to the GBCM in systemic circulation. Glymphatic system may of course act as a clearance system for GBCM from brain tissue. Based on these findings, the mechanism for Gd deposition in the brain will be discussed in this review. The authors speculate that the glymphatic system may be the major contributory factor to the deposition and clearance of gadolinium in brain tissue.

Assessing treatment outcomes in multiple sclerosis trials and in the clinical setting

Increasing numbers of drugs are being developed for the treatment of multiple sclerosis (MS). Measurement of relevant outcomes is key for assessing the efficacy of new drugs in clinical trials and for monitoring responses to disease-modifying drugs in individual patients. Most outcomes used in trial and clinical settings reflect either clinical or neuroimaging aspects of MS (such as relapse and accrual of disability or the presence of visible inflammation and brain tissue loss, respectively). However, most measures employed in clinical trials to assess treatment effects are not used in routine practice. In clinical trials, the appropriate choice of outcome measures is crucial because the results determine whether a drug is considered effective and therefore worthy of further development; in the clinic, outcome measures can guide treatment decisions, such as choosing a first-line disease-modifying drug or escalating to second-line treatment. This Review discusses clinical, neuroimaging and composite outcome measures for MS, including patient-reported outcome measures, used in both trials and the clinical setting. Its aim is to help clinicians and researchers navigate through the multiple options encountered when choosing an outcome measure. Barriers and limitations that need to be overcome to translate trial outcome measures into the clinical setting are also discussed.

Evaluation and treatment of Langerhans cell histiocytosis patients with central nervous system abnormalities: Current views and new vistas

Central nervous system (CNS) involvement in Langerhans cell histiocytosis (LCH) can include mass lesions of the hypothalamic pituitary axis, choroid plexus, cerebrum, and cerebellum or magnetic resonance imaging (MRI) signal abnormalities of the cerebellum, pons, and basal ganglia. The term neurodegenerative (ND) CNS-LCH has been given to the MRI signal abnormalities and neurologic dysfunction, although initially patients may have no clinical symptoms. Standardized evaluations to better understand the natural history and response to therapy are needed. We propose guidelines for clinical, radiologic, and physiologic tests as a framework for developing the best methods of evaluation, which can then be tested in prospective treatment protocols.

Intravoxel Incoherent Motion and Quantitative Non-Gaussian Diffusion MR Imaging: Evaluation of the Diagnostic and Prognostic Value of Several Markers of Malignant and Benign Breast Lesions

Purpose To investigate the performance of integrated approaches that combined intravoxel incoherent motion (IVIM) and non-Gaussian diffusion parameters compared with the Breast Imaging and Reporting Data System (BI-RADS) to establish multiparameter thresholds scores or probabilities by using Bayesian analysis to distinguish malignant from benign breast lesions and their correlation with molecular prognostic factors. Materials and Methods Between May 2013 and March 2015, 411 patients were prospectively enrolled and 199 patients (allocated to training [n = 99] and validation [n = 100] sets) were included in this study. IVIM parameters (flowing blood volume fraction [fIVIM] and pseudodiffusion coefficient [D*]) and non-Gaussian diffusion parameters (theoretical apparent diffusion coefficient [ADC] at b value of 0 sec/mm² [ADC₀] and kurtosis [K]) by using IVIM and kurtosis models were estimated from diffusion-weighted image series (16 b values up to 2500 sec/mm²), as well as a synthetic ADC (sADC) calculated by using b values of 200 and 1500 (sADC_200-1500) and a standard ADC calculated by using b values of 0 and 800 sec/mm² (ADC_0-800). The performance of two diagnostic approaches (combined parameter thresholds and Bayesian analysis) combining IVIM and diffusion parameters was evaluated and compared with BI-RADS performance. The Mann-Whitney U test and a nonparametric multiple comparison test were used to compare their performance to determine benignity or malignancy and as molecular prognostic biomarkers and subtypes of breast cancer. Results Significant differences were found between malignant and benign breast lesions for IVIM and non-Gaussian diffusion parameters (ADC₀, K, fIVIM, fIVIM · D*, sADC_200-1500, and ADC_0-800; P < .05). Sensitivity and specificity for the validation set by radiologists A and B were as follows: sensitivity, 94.7% and 89.5%, and specificity, 75.0% and 79.2% for sADC_200-1500, respectively; sensitivity, 94.7% and 96.1%, and specificity, 75.0% and 66.7%, for the combined thresholds approach, respectively; sensitivity, 92.1% and 92.1%, and specificity, 83.3% and 66.7%, for Bayesian analysis, respectively; and sensitivity and specificity, 100% and 79.2%, for BI-RADS, respectively. The significant difference in values of sADC_200-1500 in progesterone receptor status (P = .002) was noted. sADC_200-1500 was significantly different between histologic subtypes (P = .006). Conclusion Approaches that combined various IVIM and non-Gaussian diffusion MR imaging parameters may provide BI-RADS-equivalent scores almost comparable to BI-RADS categories without the use of contrast agents. Non-Gaussian diffusion parameters also differed by biologic prognostic factors. ^© RSNA, 2017 Online supplemental material is available for this article.

Comparison of nephrotoxicity between two gadolinium-contrasts, gadodiamide and gadopentetate in patients with mildly diminished renal failure

Although gadolinium (Gd)-based contrast media have been found to be nephrotoxic, their nephrotoxicity, and the dependence of nephrotoxicity on chelate types, have not been assessed in patients with normal or mildly diminished renal failure. This prospective, randomized study compared the nephrotoxicity of low doses of the nonionic Gd-based contrast medium gadodiamide (Omniscan®) and the ionic Gd-based contrast medium gadopentetate (Magnevist®) in patients with serum creatinine < 1.6 mg/dL. Patients aged 20 to 80 years, weighing 45 to 70 kg and with normal or < 1.6 mg/dL Serum-creatinine in the 3 months prior to undergoing magnetic resonance imaging (MRI) of brain, were enrolled. Patients were randomized to receive 0.1 mol/kg gadodiamide or gadopentetate. Serum-creatinine, serum cystatin-C, estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease (MDRD) formula, and estimated creatinine clearance rate (eCCr) using the Cockcroft-Gault formula were measured just before and 16-80 hr after MRI. Groups were compared statistically by Mann-Whitney U-tests and Wilcoxon signed-rank tests. There were no significant differences in clinical characteristics between the gadodiamide (n = 43) and gadopentetate (n = 59) groups. Serum-creatinine, eGFR and eCCr before and 16-80 hr after MRI did not differ significantly within either group or between the two groups. Serum cystatin-C was significantly higher 16-80 hr after than before MRI only in the gadodiamide group (0.79 ± 0.21 vs. 0.74 ± 0.14 mg/L, p = 0.028). The ionic contrast medium, gadopentetate, did not affect renal function during MRI, whereas the nonionic contrast medium, gadodiamide, affected renal function transiently.