A serial dilution study of gadolinium-based MR imaging contrast agents

Optimization of micelle-encapsulated extremely small sized iron oxide nanoparticles as a T1 contrast imaging agent: biodistribution and safety profile

BACKGROUND

Iron oxide nanoparticles (IONPs) have been cleared by the Food and Drug Administration (FDA) for various clinical applications, such as tumor-targeted imaging, hyperthermia therapy, drug delivery, and live-cell tracking. However, the application of IONPs as T1 contrast agents has been restricted due to their high r2 values and r2/r1 ratios, which limit their effectiveness in T1 contrast enhancement. Notably, IONPs with diameters smaller than 5 nm, referred to as extremely small-sized IONPs (ESIONs), have demonstrated potential in overcoming these limitations. To advance the clinical application of ESIONs as T1 contrast agents, we have refined a scale-up process for micelle encapsulation aimed at improving the hydrophilization of ESIONs, and have carried out comprehensive in vivo biodistribution and preclinical toxicity assessments.

RESULTS

The optimization of the scale-up micelle-encapsulation process, specifically employing Tween60 at a concentration of 10% v/v, resulted in ESIONs that were uniformly hydrophilized, with an average size of 9.35 nm and a high purification yield. Stability tests showed that these ESIONs maintained consistent size over extended storage periods and dispersed effectively in blood and serum-mimicking environments. Relaxivity measurements indicated an r1 value of 3.43 mM- 1s- 1 and a favorable r2/r1 ratio of 5.36, suggesting their potential as T1 contrast agents. Biodistribution studies revealed that the ESIONs had extended circulation times in the bloodstream and were primarily cleared via the hepatobiliary route, with negligible renal excretion. We monitored blood clearance and organ distribution using positron emission tomography and magnetic resonance imaging (MRI). Additionally, MRI signal variations in a dose-dependent manner highlighted different behaviors at varying ESIONs concentrations, implying that optimal dosages might be specific to the intended imaging application. Preclinical safety evaluations indicated that ESIONs were tolerable in rats at doses up to 25 mg/kg.

CONCLUSIONS

This study effectively optimized a scale-up process for the micelle encapsulation of ESIONs, leading to the production of hydrophilic ESIONs at gram-scale levels. These optimized ESIONs showcased properties conducive to T1 contrast imaging, such as elevated r1 relaxivity and a reduced r2/r1 ratio. Biodistribution study underscored their prolonged bloodstream presence and efficient clearance through the liver and bile, without significant renal involvement. The preclinical toxicity tests affirmed the safety of the ESIONs, supporting their potential use as T1 contrast agent with versatile clinical application.

Imageable AuNP-ECM Hydrogel Tissue Implants for Regenerative Medicine

In myocardial infarction, a blockage in one of the coronary arteries leads to ischemic conditions in the left ventricle of the myocardium and, therefore, to significant death of contractile cardiac cells. This process leads to the formation of scar tissue, which reduces heart functionality. Cardiac tissue engineering is an interdisciplinary technology that treats the injured myocardium and improves its functionality. However, in many cases, mainly when employing injectable hydrogels, the treatment may be partial because it does not fully cover the diseased area and, therefore, may not be effective and even cause conduction disorders. Here, we report a hybrid nanocomposite material composed of gold nanoparticles and an extracellular matrix-based hydrogel. Such a hybrid hydrogel could support cardiac cell growth and promote cardiac tissue assembly. After injection of the hybrid material into the diseased area of the heart, it could be efficiently imaged by magnetic resonance imaging (MRI). Furthermore, as the scar tissue could also be detected by MRI, a distinction between the diseased area and the treatment could be made, providing information about the ability of the hydrogel to cover the scar. We envision that such a nanocomposite hydrogel may improve the accuracy of tissue engineering treatment.

The Dark Side of Gadolinium: A Study of Arthrographic Contrast at Extreme Concentrations

Magnetic resonance arthrography is used to optimally image the detailed intraarticular anatomy of the joint space. A common iatrogenic complication of arthrography is the extra-articular injection of the gadolinium solution in the periarticular tissues; however, a less common complication involves the abnormal concentration of gadolinium within the prepared injectate. The following describes the inadvertent injection of a hyper-concentrated intraarticular solution of gadolinium and the subsequent appearance that resulted in the post-procedure magnetic resonance imaging examination. In addition, an in-vitro experiment was performed to determine the exact etiology of the abnormal magnetic resonance imaging findings that resulted in this case. The subsequent discussion revisits the signal intensity of gadolinium at extreme concentration ranges and proposes modifications of procedure protocol to mitigate the chance of a repeat event.

[Gadolinium deposition-"gadolinium deposition disease"]

Gadolinium (Gd)-based contrast agents have been routinely used worldwide in diagnostic MRI since 1988. All routinely applied contrast agents for clinical use were considered extremely safe with regard to tolerance, adverse effects and diagnostic efficacy and when used at Food and Drug Administration-approved doses. With the identification of Gd-associated disorders, namely nephrogenic systemic fibrosis and adverse reactions, and in the longer term Gd-retention in the brain, this view changed and led to the withdrawal or restriction of approval of linear Gd chelates in Europe. Even though Gd deposition in different human body areas was described very early, recently published literature of intracerebral accumulation of contrast agents as well as deposition in bone have created surprising attention. Not only was the fact of Gd deposition in the body well known for many years, but there is currently no clinical evidence of patient symptoms and no resulting health issues of patients have been observed yet. The expression "gadolinium deposition disease" has been termed by active patient advocacy groups with an online presence with reports of individual members stating a broad spectrum of disorders yielding a large symptom complex after administration of Gd-based contrast agents without evidence of any pre-existing or otherwise underlying disease process which could explain the mentioned disorder.

In vitro T2 relaxivities of the Gd-based contrast agents (GBCAs) in human blood at 1.5 and 3 T

BACKGROUND

The availability of data in the medical literature for the T₂ relaxivities of the Gd-based contrast agents (GBCAs) is limited. A comprehensive comparison between the agents available commercially (other than in Europe) is lacking, with no data available that most closely reflect the clinic, which is in human whole blood at body temperature.

PURPOSE

To complement the existing literature by determining T₂ relaxivity data for eight GBCAs in vitro.

MATERIAL AND METHODS

The relaxivities of eight GBCAs diluted in human whole blood at 1.5 and 3 T were determined at 37 ± 0.5 °C. Gd was in the range of 0-4 mM. Multi-echo sequences with variable echo times were acquired using a phantom containing a dilution series with each agent, and SigmaPlot 12.0 was used to calculate the R₂ relaxation rate and finally r₂. Statistical comparisons between agents and field strengths were conducted.

RESULTS

The relationship between R₂ vs. Gd was observed to be linear at 1.5 and 3 T, with a mild increase in r₂ from 1.5 to 3 T for all GBCAs. T₂ relaxivity data were compared with prior results. The GBCAs are closely clustered into two groups, with higher r₂ noted for the two lipophilic (those with partial hepatobiliary excretion) compounds.

CONCLUSION

The r₂ values at 1.5 and 3 T, determined for the eight GBCAs still clinically available (other than in Europe), provide a definitive baseline for future evaluations, including theoretical calculations of signal intensity and their clinical impact on T2-weighted scans.

Large T1 contrast enhancement using superparamagnetic nanoparticles in ultra-low field MRI

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely investigated and utilized as magnetic resonance imaging (MRI) contrast and therapy agents due to their large magnetic moments. Local field inhomogeneities caused by these high magnetic moments are used to generate T₂ contrast in clinical high-field MRI, resulting in signal loss (darker contrast). Here we present strong T₁ contrast enhancement (brighter contrast) from SPIONs (diameters from 11 nm to 22 nm) as observed in the ultra-low field (ULF) MRI at 0.13 mT. We have achieved a high longitudinal relaxivity for 18 nm SPION solutions, r₁ = 615 s⁻¹ mM⁻¹, which is two orders of magnitude larger than typical commercial Gd-based T₁ contrast agents operating at high fields (1.5 T and 3 T). The significantly enhanced r₁ value at ultra-low fields is attributed to the coupling of proton spins with SPION magnetic fluctuations (Brownian and Néel) associated with a low frequency peak in the imaginary part of AC susceptibility (χ”). SPION-based T₁-weighted ULF MRI has the advantages of enhanced signal, shorter imaging times, and iron-oxide-based nontoxic biocompatible agents. This approach shows promise to become a functional imaging technique, similar to PET, where low spatial resolution is compensated for by important functional information.

Pathophysiology of Immediate Reactions to Injectable Gadolinium-based Contrast Agents

OBJECTIVE

The aim of this paper was to review the classification of adverse drug reactions, highlight the known pathophysiology of immediate hypersensitivity reactions, and discuss the utility of diagnostic testing for immunologically mediated immediate reactions to gadolinium-based contrast agents (GBCAs).

METHODS

Current literature on immediate reactions to GBCA was reviewed and summarized.

RESULTS

Adverse drug reactions to GBCA are rare, and can be attributed to physiologic, immunologic, and nonimmunologic processes. When immunologic reaction is suspected, particularly in the case of severe reactions, skin testing may be useful to confirm allergy and identify alternative agents for subsequent studies.

CONCLUSION

As GBCAs are widely used for the diagnosis and monitoring of disease, the incidence of adverse drug reactions to GBCA warrants ongoing development of approaches to diagnosis and avoidance of these adverse events.

Effects of Height and Blood Volume on Venous Enhancement After Gadolinium-Based Contrast Administration in MR Venography: A Paradigm Challenge and Implications for Clinical Imaging

OBJECTIVE

The purpose of this study was to analyze quantitative and qualitative effects of estimated blood volume on venous enhancement in patients undergoing cerebral MR venography (MRV) with standard weight-based dosing of a gadolinium-based contrast agent.

MATERIALS AND METHODS

Fifty-two patients with normal 1.5-T cerebral MRV findings and contemporaneous height and weight measurements were included. Estimated blood volume was calculated with the Nadler formula for blood volume. Standard weight-based cerebral MRV was performed after administration of gadobenate dimeglumine (0.1 mmol/kg up to 20 mL). Venous enhancement within the superior sagittal sinus, right jugular bulb, and left jugular bulb was measured. Patients were dichotomized on the basis of administration of less than versus a maximum weight-based gadolinium-based contrast dose of 20 mL. Venographic quality was assigned by two neuroradiologists. Correlational and multiple linear regression analyses were performed.

RESULTS

Among patients receiving less than the maximum 20 mL of gadolinium, no significant correlations were observed between weight and vascular enhancement (p > 0.05). Significant correlations between height and enhancement were observed in the superior sagittal sinus and left jugular bulb. This finding suggests that differences in estimated blood volume driven by height remain unaccounted for (p < 0.05). With the 20-mL maximal dose, a significant inverse relation was noted between estimated blood volume and contrast enhancement of all vascular segments (p < 0.05). Within all vascular segments, significant correlations were observed between enhancement and user-defined quality scores (p < 0.05). This finding suggests that optimized dosing may affect reader confidence.

CONCLUSION

Standard weight-based dosing for cerebral MRV insufficiently accounts for differences in circulating blood volume. An expanded biometric dosing paradigm leveraging readily attainable subject data may mitigate unintended variations in enhancement affecting venography and other clinical imaging modalities.

Effectiveness of a high relaxivity contrast agent administered at half dose in dynamic susceptibility contrast MRI of brain gliomas

PURPOSE

To determine whether half of the approved dose of gadobenate dimeglumine (MultiHance) is as effective as a full dose of gadoterate meglumine (Dotarem) for qualitative and quantitative cerebral blood volume (CBV) perfusion evaluation at 3T in patients with brain gliomas.

MATERIALS AND METHODS

We enrolled 65 adult patients in an interindividual comparative study. Patients were randomized to one of two study arms: 33 patients received 0.1 mmol/kg body weight (bw) of gadoterate, 32 patients received 0.05 mmol/kg bw of gadobenate. The patients underwent identical examinations at 3T. Arterial input function (AIF), tissue function (TF), and the maximum tumor CBV (CBV_T) were obtained from each patient. The quality of the CBV maps were independently reviewed by two neuroradiologists blinded to the administered contrast agent.

RESULTS

The administration of a half dose of gadobenate led to a roughly 40% reduction in signal drop compared to that achieved with a full dose of gadoterate (P values for AIF and TF maximum and integral were <0.01); quantitative and qualitative assessment of CBV maps revealed no difference between contrast agents (P values for CBV_T of high- and low-grade gliomas, image quality evaluation were 0.87, 0.48, >0.65, respectively) CONCLUSION: The CBV maps obtained with a half dose gadobenate (0.05 mmol/kg bw) are of comparable diagnostic quality as the corresponding images acquired with a full dose of gadoterate (0.1 mmol/kg bw).

LEVEL OF EVIDENCE

2 J. Magn. Reson. Imaging 2017;45:500-506.

Improved quality and diagnostic confidence achieved by use of dose-reduced gadolinium blood-pool agents for time-resolved intracranial MR angiography

BACKGROUND AND PURPOSE

Time-resolved MRA with the use of bolus injection of paramagnetic agents has proved valuable in neurovascular imaging. Standard contrast agents have limited blood-pool residence times, motivating the development of highly protein-bound blood-pool agents with greater relaxivity and longer intravascular residence, affording improved image quality at lesser doses. This study represents the first comparison of blood-pool agents to standard agents in time-resolved cerebral MRA.

MATERIALS AND METHODS

One hundred datasets were acquired at 1.5 T by use of a standardized, time-resolved MRA protocol. Patients received either unit dosing of a standard extracellular agent at 0.1 mmol/kg or a blood-pool agent at 0.03 mmol/kg. Peak arterial and venous enhancement phases were identified and subsequently scored qualitatively by use of a 4-point Likert scale, with attention to 6 vascular segments: 1) intracranial ICA; 2) MCA M1; 3) MCA M2; 4) MCA M3; 5) deep cerebral veins; and 6) dural venous sinuses.

RESULTS

Fifty MR angiographies were acquired with each agent. No significant differences were found between agents in generation of uncontaminated arteriograms. Blood-pool agents, at 67% dose reduction, were of significantly greater quality across most vascular segments, including ICA (P = .019), M2 (P = .003), and M3 (P < .01). Superiority in the M1 segment approached significance (P = .059). Significantly better venographic quality was noted for deep venous structures (P = .016) with the use of blood-pool agents.

CONCLUSIONS

Blood-pool agents provide superior demonstration of most intracranial vessels in time-resolved MRA compared with standard agents, at reduced doses. The greater relaxation enhancement and more favorable dosing profile make blood-pool agents superior to standard agents for use in cerebral time-resolved MRA.

Safety and adverse effects during 24 hours after contrast-enhanced MRI with gadobenate dimeglumine (MultiHance) in children

BACKGROUND

Gadolinium-based MR contrast agents have long been considered safe for routine diagnostic imaging. However, the advent of nephrogenic systemic fibrosis (NSF) among certain patients with severe renal insufficiency has brought the issue of safety into question. Nowhere is safety of greater concern than among children who frequently require multiple contrast-enhanced MRI examinations over an extended period of time.

OBJECTIVE

To retrospectively evaluate the safety of gadobenate dimeglumine for contrast-enhanced (CE) MRI across a range of indications.

MATERIALS AND METHODS

Two hundred pediatric inpatients (age: 4 days to 15 years) underwent CE MRI as part of clinical routine. The children received a gadobenate dimeglumine dose of either 0.05 mmol/kg body weight (liver, abdominal imaging, musculoskeletal imaging, brain and other rare indications) or 0.1 mmol/kg bodyweight (cardiovascular imaging, MR-urography). Young (< 8 years) children with congenital heart disease were intubated and underwent MRA evaluation with controlled ventilation. Monitoring for adverse events was performed for at least 24 h after each gadobenate dimeglumine injection. Depending on clinical necessity, laboratory measurements and, in some cases, vital sign and ECG determinations were made before and after contrast injection. Safety was evaluated by age group, indication and dose administered.

RESULTS

No clinically adverse events were reported among children who had one MRI scan only or among children who had several examinations. There were no changes in creatinine or bilirubin levels even in very young children.

CONCLUSIONS

No adverse events were recorded during the first 24 h following administration of gadobenate dimeglumine in 200 children.

Gadobenate dimeglumine (MultiHance) in MR angiography: an in-vitro phantom comparison with gadopentetate dimeglumine (Magnevist) at different concentrations

BACKGROUND

Numerous clinical studies suggest that gadobenate dimeglumine is diagnostically superior to other gadolinium chelates for MR imaging applications, including contrast-enhanced MR angiography (CE-MRA). However, confirmatory in-vitro phantom studies have thus far been lacking.

PURPOSE

To evaluate the difference in signal intensity achieved with the high-relaxivity MR contrast agent gadobenate dimeglumine (MultiHance) relative to that achieved with the standard-relaxivity non-specific agent gadopentetate dimeglumine (Magnevist) at different concentrations using an in-vitro phantom study design.

MATERIAL AND METHODS

Test tubes with whole human blood were prepared with concentrations of gadobenate dimeglumine or gadopentetate dimeglumine ranging from 0 to 12 mM. A three-dimensional (3D) T1-weighted gradient echo sequence normally used for CE-MRA of the renal arteries was performed at flip angles of 25° and 35°. The signal-to-noise ratio (SNR) was calculated for all concentrations of both contrast agents. Furthermore a Look-Locker sequence was used and quantitative T1 mapping was performed for all the test tubes. The contrast agent concentration in the aorta was simulated using previously published data on T1 in the aorta during the first pass of a contrast agent. The differences between gadobenate dimeglumine and gadopentetate dimeglumine were compared at the simulated concentrations.

RESULTS

The SNR achieved with gadobenate dimeglumine was consistently greater than that achieved with gadopentetate dimeglumine at all concentrations. An improvement of 15-25% in SNR was obtained when increasing the flip angle from 25° to 35°. The relative improvement in SNR with gadobenate dimeglumine relative to gadopentetate dimeglumine ranged from 25-72% and was markedly greater at lower concentrations with a flip angle of 35°.

CONCLUSION

Our findings suggest that the relative benefit of gadobenate dimeglumine over gadopentetate dimeglumine for CE-MRA applications is greater at lower concentrations.

Solid hypervascular liver lesions: accurate identification of true benign lesions on enhanced dynamic and hepatobiliary phase magnetic resonance imaging after gadobenate dimeglumine administration

PURPOSE

To evaluate hepatobiliary phase magnetic resonance imaging with gadobenate dimeglumine for differentiation of benign hypervascular liver lesions from malignant or high-risk lesions.

METHODS AND MATERIALS

Retrospective assessment was performed of 550 patients with 910 hypervascular lesions (302 focal nodular hyperplasia [FNH], 82 nodular regenerative hyperplasia [NRH], 59 hepatic adenoma or liver adenomatosis [HA/LA], 329 hepatocellular carcinomas [HCC], 12 fibrolamellar-HCC [FL-HCC], 21 peripheral cholangiocarcinomas [PCC], 105 metastases). Imaging was performed before and during the arterial, portal-venous, equilibrium, and hepatobiliary phases after gadobenate dimeglumine administration (0.05 mmol/kg). Histologic confirmation was available for ≥1 lesion per patient, except for patients with suspected FNH (diagnosis based on characteristic enhancement/follow-up). Lesion differentiation (benign/malignant) on the basis of contrast washout and lesion enhancement (hypo-/iso-/hyperintensity) was assessed (sensitivity, specificity, accuracy, PPV, and NPV) relative to histology or final diagnosis.

RESULTS

On portal-venous or equilibrium phase images, washout was not seen for 208 of 526 (39.5%) malignant (HCC, FL-HCC, PCC, metastases) and high-risk (HA/LA) lesions. Conversely, only 5 of 384 (1.3%) true benign lesions (FNH/NRH) showed washout. Taking washout as indicating malignancy, the sensitivity, specificity, and accuracy for malignant lesion identification during these phases was 61.8%, 98.7%, and 77.4%. On hepatobiliary phase images, 289 of 302 FNH, 82 of 82 NRH, 1 of 59 HA or LA, 62 of 341 HCC or FL-HCC, and 2 of 105 metastases were hyperintense or isointense. Taking iso- or hyperintensity as an indication for lesion benignity, the sensitivity, specificity, accuracy, PPV, and NPV for benign lesion identification was 96.6%, 87.6%, 91.4%, 85.1%, and 97.3%, respectively.

CONCLUSIONS

Hepatobiliary phase imaging with gadobenate dimeglumine is accurate for distinguishing benign lesions from malignant or high-risk lesions. Biopsy should be considered for hypointense lesions on hepatobiliary phase images after gadobenate dimeglumine.

Contrast visibility for indirect MR arthrography with different protein contents and agent relaxivities at different field strengths: an in vitro model

OBJECTIVES

Protein binding and relaxivity are major determinants of the relative effectiveness of an MR arthrographic contrast agent. We sought to evaluate the optimal concentrations of high and usual relaxivity agents in two different proteinous environments at variable field strength for two MR contrast agents of different relaxivities.

MATERIALS AND METHODS

At 1.5, 3.0 and 7.0 T, gadobenate dimeglumine (Multihance) with high-relaxivity in proteinous environment and gadoteridol (Prohance) with more typical behavior were studied at 1.25, 2.5, 5, and 10 mmol in 1.7 g/dL and 3g/dL albumin (mimicking protein content of normal and inflammatory synovial fluids, respectively) vs. pure normal saline, as a control. Analysis of image signal intensity (SI) and relaxivity values was done.

RESULTS

In our study a change in concentration had no significant effect on T1 SI. In contrast, nearly every change in concentration led to a significant change in T2 SI. In 1.25 mmol concentration, there was no effect on T1 SI of either protein concentrations while higher concentrations showed significant decreased SI in either protein carrier compared to saline. The SI of Gadoteridol was significantly higher (p<0.0001) than that of gadobenate at each of 3T and 7 T, but was significantly lower (p<0.001) at 1.5 T in saline solution while this was not significant for either protein carrier. Both protein carriers had significant effect on T1 (p=0.0124) and T2 (p=0.0118) relaxivities. Also solution concentration significantly (p<0.01) affected both T1 and T2 relaxivities. Field strength did not affect T1 relaxivity (p=0.02511) while it significantly affected T2 relaxivity (p<0.001). This was significant (p=0.035) in case of gadoteridol at 3T.

CONCLUSION

1.25 mmol concentration of both gadoteridol and gadobenate solutions yields the best diagnostic T1 SI specially in higher fields (3T and 7 T) and avoid the deleterious effect of increasing concentration on T2 SI. Gadoteridol is suggested on 3T field indirect MR arthrograms. Protein had no positive effect on either SI or relaxivities in any joint model.

Multicenter, double-blind, randomized, intraindividual crossover comparison of gadobenate dimeglumine and gadopentetate dimeglumine for MR angiography of peripheral arteries

PURPOSE

To prospectively compare the image quality and diagnostic performance achieved with doses of gadobenate dimeglumine and gadopentetate dimeglumine of 0.1 mmol per kilogram of body weight in patients undergoing contrast material-enhanced magnetic resonance (MR) angiography of the pelvis, thigh, and lower-leg (excluding foot) for suspected or known peripheral arterial occlusive disease.

MATERIALS AND METHODS

Institutional review board approval was granted from each center and informed written consent was obtained from all patients. Between November 2006 and January 2008, 96 patients (62 men, 34 women; mean age, 63.7 years +/- 10.4 [standard deviation]; range, 39-86 years) underwent two identical examinations at 1.5 T by using three-dimensional spoiled gradient-echo sequences and randomized 0.1-mmol/kg doses of each agent. Images were evaluated on-site for technical adequacy and quality of vessel visualization and offsite by three independent blinded readers for anatomic delineation and detection/exclusion of pathologic features. Comparative diagnostic performance was determined in 31 patients who underwent digital subtraction angiography. Data were analyzed by using the Wilcoxon signed-rank, McNemar, and Wald tests. Interreader agreement was determined by using generalized kappa statistics. Differences in quantitative contrast enhancement were assessed and a safety evaluation was performed.

RESULTS

Ninety-two patients received both agents. Significantly better performance (P < .0001; all evaluations) with gadobenate dimeglumine was noted on-site for technical adequacy and vessel visualization quality and offsite for anatomic delineation and detection/exclusion of pathologic features. Contrast enhancement (P < or = .0001) and detection of clinically relevant disease (P < or = .0028) were significantly improved with gadobenate dimeglumine. Interreader agreement for stenosis detection and grading was good to excellent (kappa = 0.749 and 0.805, respectively). Mild adverse events were reported for four (six events) and five (eight events) patients after gadobenate dimeglumine and gadopentetate dimeglumine, respectively.

CONCLUSION

Higher-quality vessel visualization, greater contrast enhancement, fewer technical failures, and improved diagnostic performance are obtained with gadobenate dimeglumine, relative to gadopentetate dimeglumine, when compared intraindividually at 0.1-mmol/kg doses in patients undergoing contrast-enhanced MR angiography for suspected peripheral arterial occlusive disease.

High-relaxivity contrast-enhanced magnetic resonance neuroimaging: a review

Evaluation of brain lesions using magnetic resonance imaging (MRI) provides information that is critical for accurate diagnosis, prognosis, therapeutic intervention and monitoring response. Conventional contrast-enhanced MR neuroimaging using gadolinium (Gd) contrast agents primarily depicts disruption of the blood-brain barrier, demonstrating location and extent of disease, and also the morphological details at the lesion site. However, conventional imaging results do not always accurately predict tumour aggressiveness. Advanced functional MRI techniques such as dynamic contrast-enhanced perfusion-weighted imaging utilise contrast agents to convey physiological information regarding the haemodynamics and neoangiogenic status of the lesion that is often complementary to anatomical information obtained through conventional imaging. Most of the Gd contrast agents available have similar T1 and T2 relaxivities, and thus their contrast-enhancing capabilities are comparable. Exceptions are gadobenate-dimeglumine, Gd-EOB-DTPA, Gadobutrol and gadofosveset, which, owing to their transient-protein-binding capability, possess almost twice (and more) the T1 and T2 relaxivities as other agents at all magnetic field strengths. Numerous comparative studies have demonstrated the advantages of the increased relaxivity in terms of enhanced image contrast, image quality and diagnostic confidence. Here we summarise the benefits of higher relaxivity for the most common neuroimaging applications including MRI, perfusion-weighted imaging and MRA for evaluation of brain tumours, cerebrovascular disease and other CNS lesions.

Decreased incidence of NSF in patients on dialysis after changing gadolinium contrast-enhanced MRI protocols

PURPOSE

To retrospectively determine the incidence of nephrogenic systemic fibrosis (NSF) in patients on dialysis administered either a lower dose high-relaxivity linear gadolinium-chelate, gadobenate dimeglumine (MultiHance, MH), compared to a standard dose linear gadolinium chelate, gadodiamide (Omniscan, OM).

MATERIALS AND METHODS

This study was Health Insurance Portability and Accountability Act (HIPAA)-compliant and Institutional Review Board (IRB)-approved. As per institution standardized contrast-enhanced magnetic resonance imaging (MRI) protocols, patients on dialysis were imaged using either MH, between 2/2007 to 9/2008, or OM between 10/2003 and 1/2007. Rates of NSF were compared using 95% score-based confidence intervals (CI). The Wilcoxon rank sum test was used to test similarity/difference between contrast doses given to each patient group.

RESULTS

Overall, 312 patients on dialysis received OM and eight (2.6%) developed NSF (95% CI: 1.30%-4.98%). In all, 784 patients on dialysis received MH at a mean cumulative dose of 0.11 mmol/kg (0.05-0.75 mmol/kg) and no cases of NSF were identified (upper 95% confidence bound of 0.45%). The mean cumulative dose of OM was 0.16 mmol/kg (0.1-0.9 mmol/kg) for all patients and 0.28 mmol/kg (0.1-0.8 mmol/kg) for the patients with NSF. The median OM dose was greater in patients who developed NSF (P = 0.03), and was greater than the median MH dose (P < 0.005).

CONCLUSION

NSF incidence in at-risk patients receiving contrast-enhanced MRI can be reduced after changing contrast administration protocols that includes changing the type and dose of contrast agent.

The challenge of imaging dense breast parenchyma: is magnetic resonance mammography the technique of choice? A comparative study with x-ray mammography and whole-breast ultrasound

PURPOSE

To establish the value of magnetic resonance imaging (MRI) of the breast in comparison to x-ray mammography and ultrasound for breast cancer evaluation in women with dense breast parenchyma.

MATERIALS AND METHODS

Two hundred thirty-eight women with dense breast parenchyma who were suspicious for breast cancer or inconclusive for the presence of breast lesions based on clinical examination, ultrasound or x-ray mammography, and who underwent breast MRI at 1.5 T before and after administration of 0.1 mmol/kg gadobenate dimeglumine were evaluated. Lesions considered malignant (Breast Imaging Reporting and Data System (BI-RADS) 4 or 5) on x-ray mammography and/or ultrasound and as BI-RADS 3, 4, or 5 on MRI were evaluated histologically. Other lesions were followed up at 6 and/or 18 months. The diagnostic performance (sensitivity, specificity, accuracy, and positive and negative predictive values) of each technique was determined and compared using a general linear mixed model with appropriate correction for multiplicity.

RESULTS

At final diagnosis 121 of 238 (50.8%) women had one or more confirmed malignant lesions, whereas 117 (49.2%) had benign lesions or no lesions. Among 97 women who underwent all 3 techniques more lesions (malignant and benign) were detected with breast MRI (n = 135) than with x-ray mammography (n = 85) or ultrasound (n = 107) and diagnostic confidence was greater. In terms of patient-based diagnostic accuracy breast MRI was significantly (P[r] < 0.0001) superior to both x-ray mammography and ultrasound (96.9% accuracy for MRI vs. 60.8% for mammography and 66.0% for US). Malignant lesions were histologically confirmed in 55 of 97 women who underwent all 3 techniques. Breast MRI detected more cases of multifocal, multicentric, and contralateral disease and fewer misdiagnoses occurred. Overall, breast MRI led to a modification of the surgical approach for 28 (23.1%) of the 121 women with diagnosed malignant disease.

CONCLUSION

Breast MRI should be considered for routine breast cancer evaluation in women with dense breast parenchyma.

Contrast-enhanced MRA of the renal and aorto-iliac-femoral arteries: comparison of gadobenate dimeglumine and gadofosveset trisodium

RATIONALE AND OBJECTIVES

Dedicated contrast agents are now available for contrast-enhanced magnetic resonance angiography (CE-MRA). This study retrospectively compares the safety and diagnostic performance data from Phase III regulatory trials performed to evaluate gadobenate dimeglumine (MultiHance(®)) and gadofosveset trisodium (Vasovist®)) for renal and peripheral CE-MRA.

MATERIALS AND METHODS

Similar examination and blinded assessment methodology was utilized in all studies to determine the safety and diagnostic performance of the agents for detection of significant (>50%) steno-occlusive disease. Digital Subtraction Angiography (DSA) was used as the standard of truth. Diagnostic performance data (sensitivity, specificity, predictive values [PVs], and likelihood ratios [LRs]) were compared (Chi-square test).

RESULTS

CE-MRA with gadobenate dimeglumine was more specific (92.4% vs. 80.5%, p < 0.0001) and accurate (83.6% vs. 77.1%, p = 0.022) than CE-MRA with gadofosveset in the detection of significant renal artery stenosis. The average sensitivity was higher for gadofosveset (74.4% vs. 67.3%, p = 0.011) in peripheral vessels although gadobenate dimeglumine was more specific (93.0% vs. 88.2%, p < 0.0001) with no difference in accuracy (86.6% vs. 86.3%, p = 0.66). PPVs were higher (p < 0.0001) for gadobenate dimeglumine in both vascular territories. Pre- to post-test shifts in the probability of detecting significant disease were greater after gadobenate dimeglumine. Adverse events in the renal and peripheral studies were reported by 9.2% and 7.7% of patients after gadobenate dimeglumine compared with 30.3% and 22.1% of patients after gadofosveset.

CONCLUSION

The diagnostic performance of CE-MRA for the detection of significant steno-occlusive disease is similar with gadofosveset and gadobenate dimeglumine although the rate of adverse events appears higher with gadofosveset.

Multicenter, double-blind, randomized, intra-individual crossover comparison of gadobenate dimeglumine and gadopentetate dimeglumine in MRI of brain tumors at 3 tesla

PURPOSE

To prospectively compare 0.1 mmol/kg doses of gadobenate dimeglumine and gadopentetate dimeglumine for contrast-enhanced MRI of brain lesions at 3 Tesla (T).

MATERIALS AND METHODS

Forty-six randomized patients underwent a first examination with gadobenate dimeglumine (n = 23) or gadopentetate dimeglumine (n = 23) and then, after 2-7 days, a second examination with the other agent. Contrast administration (volume, rate), sequence parameters (T1wSE; T1wGRE), and interval between injection and image acquisition were identical for examinations in each patient. Three blinded neuroradiologists evaluated images qualitatively (lesion delineation, lesion enhancement, global preference) and quantitatively (lesion-to-brain ratio [LBR], contrast-to-noise ratio [CNR], % lesion enhancement). Differences were assessed using Wilcoxon's signed-rank test. Reader agreement was determined using kappa (kappa) statistics.

RESULTS

There were no demographic differences between groups. The three readers preferred gadobenate dimeglumine globally in 22 (53.7%), 21 (51.2%), and 27 (65.9%) patients, respectively, compared with 0, 1, and 0 patients for gadopentetate dimeglumine. Similar significant (P < 0.001) preference was expressed for lesion border delineation and enhancement. Reader agreement was consistently good (kappa = 0.48-0.64). Significantly (P < 0.05) higher LBR (+43.5- 61.2%), CNR (+51.3-147.6%), and % lesion enhancement (+45.9-49.5%) was noted with gadobenate dimeglumine.

CONCLUSION

Brain lesion depiction at 3T is significantly improved with 0.1 mmol/kg gadobenate dimeglumine.

Contrast-enhanced MR imaging of brain lesions: a large-scale intraindividual crossover comparison of gadobenate dimeglumine versus gadodiamide

BACKGROUND AND PURPOSE

The higher relaxivity of gadobenate dimeglumine compared with gadodiamide is potentially advantageous for contrast-enhanced brain MR imaging. This study intraindividually compared 0.1-mmol/kg doses of these agents for qualitative and quantitative lesion enhancement.

MATERIALS AND METHODS

Adult patients with suggested or known brain lesions underwent 2 identical MR imaging examinations at 1.5T, one with gadobenate dimeglumine and the other with gadodiamide. The agents were administered in randomized order separated by 3-14 days. Imaging sequences and postinjection acquisition timing were identical for the 2 examinations. Three blinded readers evaluated images qualitatively for diagnostic information (lesion extent, delineation, morphology, enhancement, and global preference) and quantitatively for contrast-to-noise ratio (CNR).

RESULTS

One hundred thirteen of 138 enrolled patients successfully underwent both examinations. Final diagnoses were intra-axial tumor, metastasis, extra-axial tumor, or other (47, 27, 18, and 21 subjects, respectively). Readers 1, 2, and 3 demonstrated global preference for gadobenate dimeglumine in 63 (55.8%), 77 (68.1%), and 73 (64.6%) patients, respectively, compared with 3, 2, and 3 patients for gadodiamide (P < .0001, all readers). Highly significant (P < .0001, all readers) preference for gadobenate dimeglumine was demonstrated for all qualitative end points and for CNR (increases of 23.3%-34.7% and 42.4%-48.9% [spin-echo and gradient-refocused echo sequences, respectively] for gadobenate dimeglumine compared with gadodiamide). Inter-reader agreement was good for all evaluations (kappa = 0.47-0.69). Significant preference for gadobenate dimeglumine was demonstrated for all lesion subgroup analyses.

CONCLUSION

Significantly greater diagnostic information and lesion enhancement are achieved on brain MR imaging with 0.1-mmol/kg gadobenate dimeglumine compared with gadodiamide at an equivalent dose.