Contrast-enhanced MR angiography of the run-off vasculature: intraindividual comparison of gadobenate dimeglumine with gadopentetate dimeglumine

Efficacy of Whole-Blood Model of Gadolinium-Based Contrast Agent Relaxivity in Predicting Vascular MR Signal Intensity In Vivo

BACKGROUND

Previous in vitro studies have described sub-linear longitudinal and heightened transverse H2 O relaxivities of gadolinium-based contrast agents (GBCAs) in blood due to their extracellular nature. However, in vivo validation is lacking.

PURPOSE

Validate theory describing blood behavior of R1 and R2 * in an animal model.

STUDY TYPE

Prospective, animal.

ANIMAL MODEL

Seven swine (54-65 kg).

FIELD STRENGTH/SEQUENCE

1.5 T; time-resolved 3D spoiled gradient-recalled echo (SPGR) and quantitative Look-Locker and multi-echo fast field echo sequences.

ASSESSMENT

Seven swine were each injected three times with 0.1 mmol/kg intravenous doses of one of three GBCAs: gadoteridol, gadobutrol, and gadobenate dimeglumine. Injections were randomized for rate (1, 2, and 3 mL/s) and order, during which time-resolved aortic 3D SPGR imaging was performed concurrently with aortic blood sampling via an indwelling catheter. Time-varying [GBCA] was measured by mass spectrometry of sampled blood. Predicted signal intensity (SI) was determined from a model incorporating sub-linear R1 and R2 * effects (whole-blood model) and simpler models incorporating linear R1 , with and without R2 * effects. Predicted SIs were compared to measured aortic SI.

STATISTICAL TESTS

Linear correlation (coefficient of determination, R2 ) and mean errors were compared across the SI prediction models.

RESULTS

There was an excellent correlation between predicted and measured SI across all injections and swine when accounting for the non-linear dependence of R1 and high blood R2 * (regression slopes 0.91-1.04, R2  ≥ 0.91). Simplified models (linear R1 with and without R2 * effects) showed poorer correlation (slopes 0.67-0.85 and 0.54-0.64 respectively, both R2  ≥ 0.89) and higher averaged mean absolute and mean square errors (128.4 and 177.4 vs. 42.0, respectively, and 5506 and 11,419 vs. 699, respectively).

DATA CONCLUSION

Incorporating sub-linear R1 and high first-pass R2 * effects in arterial blood models allows accurate SPGR SI prediction in an in vivo animal model, and might be utilized when modeling MR blood SI.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 1.

Gadolinium contrast agents for CNS imaging: current concepts and clinical evidence

SUMMARY

The aim of this article was to review the properties of the various gadolinium-based contrast agents used for CNS imaging along with the clinical evidence and published data that highlight the impact these different properties can have on diagnostic performance. In addition, approaches to optimizing image acquisition that take into account the different properties of specific gadolinium-based contrast agents and an extensive review of the safety profiles of the various agents are presented.

Pharmacokinetics of gadobenate dimeglumine in children 2 to 5 years of age undergoing MRI of the central nervous system

PURPOSE

To determine the pharmacokinetic profile of gadobenate dimeglumine in children aged between 2 and 5 years.

MATERIALS AND METHODS

Fifteen children scheduled to undergo contrast-enhanced MRI for suspected disease of the central nervous system received a single intravenous injection of 0.1 mmol/kg gadobenate dimeglumine. Children were stratified into three age groups: 2 to <3 years, 3 to <4 years, and 4 to 5 (i.e., <6 years). Serial blood and urine samples collected at prespecified time-points before and after contrast administration were analyzed for gadolinium concentrations. Pharmacokinetic parameters were calculated using noncompartmental and compartmental techniques.

RESULTS

Mean values of 65.7 μg/mL for highest blood gadolinium concentration, 0.2 L/h/kg for blood clearance, 0.32 L/kg for steady-state volume of distribution, and 1.2 h for terminal elimination half-life were determined across all age groups combined. On average, more than 80% of the dose was eliminated in the urine during the first 24 h after administration. All pharmacokinetic parameters were similar between age groups and no effects of gender were noted. No adverse events considered related to gadobenate dimeglumine administration were reported.

CONCLUSION

In terms of pharmacokinetic profile no dosage adjustment from the approved adult gadobenate dimeglumine dose of 0.1 mmol/kg bodyweight is necessary in children aged between 2 and 5 years.

3.0-T whole-heart coronary magnetic resonance angiography: comparison of gadobenate dimeglumine and gadofosveset trisodium

Gadolinium enhanced coronary magnetic resonance angiography (MRA) at 3 T appears to be superior to non-contrast methods. Gadofosveset is an intravascular contrast agent that may be well suited to this application. The purpose of this study was to perform an intra-individual comparison of gadofosveset and gadobenate for coronary MRA at 3 T. In this prospective randomized study, 22 study subjects [8 (36%) male; 27.9 ± 6 years; BMI = 22.8 ± 2 kg/m(2)] underwent two studies using a contrast-enhanced inversion recovery three-dimensional fast low angle shot MRA at 3 T. The order of contrast agent administration was varied randomly, separated by an average of 30 ± 5 days, using either gadobenate dimeglumine (Gd-BOPTA; Bracco, 0.1 mmol/Kg) or gadofosveset trisodium (MS-325; Lantheus Med, 0.03 mmol/Kg). Acquisition time, signal-to-noise ratio (SNR) of coronary vessels and contrast-to-noise ratio (CNR) were evaluated. Of 308 coronary arteries and veins segment analyzed, overall SNR of coronary arteries and veins segments were not different for the two contrast agents (132 ± 79 for gadofosveset vs. 135 ± 78 for gadobenate, p = 0.69). Coronary artery CNR was greater for gadofosveset in comparison to gadobenate (73.5 ± 46.9 vs. 59.3 ± 75.7 respectively, p = 0.03). Gadofosveset-enhanced MRA images displayed better image quality than gadobenate-enhanced MRA images (2.77 ± 0.61 for gadofosveset vs. 2.11 ± 0.51, p < .001). Inter- and intra-reader variability was excellent (ICC > 0.90) for both contrast agents. Gadofosveset trisodium appears to show slightly better performance for coronary MRA at 3 T compared to gadobenate.

Multicenter, intra-individual comparison of single dose gadobenate dimeglumine and double dose gadopentetate dimeglumine for MR angiography of the peripheral arteries (the Peripheral VALUE Study)

PURPOSE

To prospectively compare single dose gadobenate dimeglumine with double dose gadopentetate dimeglumine for CE-MRA in patients with peripheral arterial occlusive disease (PAOD) using an intra-individual crossover study design in which all patients received both contrast agents in otherwise identical CE-MRA examinations.

MATERIALS AND METHODS

Institutional review board and regulatory approval were granted and all patients provided written informed consent. Sixty-eight patients (53M/15F; 62.4 ± 15.7 years) with mild-to-severe PAOD were enrolled for randomized 3-station CE-MRA with 0.1 mmol/kg gadobenate dimeglumine and 0.2 mmol/kg gadopentetate dimeglumine. Three blinded readers assessed images for vessel anatomical delineation, disease detection/exclusion, and global preference. Diagnostic performance for detection of ≥51% stenosis was determined for 53 patients who underwent DSA. Noninferiority was assessed using the Wilcoxon Signed Rank, McNemar, and Wald tests. Quantitative enhancement was compared.

RESULTS

No differences (P ≥ 0.25) were noted for any qualitative parameter at any station. Equivalence was reported in at least 62/64 patients (93.8% 3-reader agreement) for diagnostic preference. Superiority for gadobenate dimeglumine was reported by all readers for diagnostic performance (sensitivity: 80.4-88.0% versus 75.2-85.8%; specificity: 89.8-96.0% versus 88.7-94.8%; accuracy: 87.4-91.7% versus 84.9-90.6%; PPV: 84.0-92.8% versus 82.3-90.8%; NPV: 88.5-92.4% versus 85.7-91.1%). Quantitative enhancement was similar in the pelvis but significantly (P < 0.05) greater with gadobenate dimeglumine in the thigh for two readers.

CONCLUSION

Image quality and diagnostic performance on peripheral CE-MRA with 0.1 mmol/kg gadobenate dimeglumine is at least equivalent to that with 0.2 mmol/kg gadopentetate dimeglumine.

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.

Multicenter, intraindividual comparison of single-dose gadobenate dimeglumine and double-dose gadopentetate dimeglumine for MR angiography of the supra-aortic arteries (the Supra-Aortic VALUE study)

BACKGROUND AND PURPOSE

Gadobenate dimeglumine has markedly higher R1 relaxivity compared to gadopentetate dimeglumine meaning that lower doses can be used to achieve similar contrast enhancement. Our aim was to prospectively compare single-dose gadobenate dimeglumine with double-dose gadopentetate dimeglumine for contrast-enhanced MRA of the supra-aortic vasculature.

MATERIALS AND METHODS

Forty-six patients (37 men, 9 women; mean age, 63.5±10.1 years) with known or suspected steno-occlusive disease of the supra-aortic vessels underwent 2 identical CE-MRA examinations at 1.5T. Contrast agents were administered in randomized order, with the 2-fold greater volume of gadopentetate dimeglumine injected at a 2 times faster rate. Image assessment was performed by 3 independent blinded readers for vessel anatomic delineation, detection/exclusion of pathology, and global preference. Diagnostic performance (sensitivity, specificity, accuracy, PPV, and NPV) for detection of ≥60% stenosis was determined for 39/46 patients who underwent preinterventional DSA. Data were analyzed by using the Wilcoxon signed-rank, McNemar, and Wald tests in terms of the noninferiority of single-dose gadobenate dimeglumine compared with double-dose gadopentetate dimeglumine. Quantitative enhancement (signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR)) was also compared.

RESULTS

All images were technically adequate. No differences (P=1.0) were noted by any reader for any qualitative parameter. All readers considered single-dose gadobenate dimeglumine and double-dose gadopentetate dimeglumine equivalent in at least 42/46 patients (91.3% three-reader agreement) for all parameters. Nonsignificant superiority for gadobenate dimeglumine was reported for all diagnostic performance indicators (sensitivity: 82.7%-88.5% versus 75.0%-80.8%; specificity: 96.4%-98.6% versus 94.6%-98.6%; accuracy: 94.6%-96.1% versus 92.4%-94.9%; PPV: 81.5%-91.5% versus 73.7%-90.7%; NPV: 96.8%-97.8% versus 95.4%-96.4%). No differences (P>.05) in quantitative enhancement were noted.

CONCLUSIONS

The image quality and diagnostic performance achieved with 0.1-mmol/kg gadobenate dimeglumine is at least equivalent to that achieved with 0.2-mmol/kg gadopentetate dimeglumine.

Current state-of-the-art 1.5 T and 3 T extracranial carotid contrast-enhanced magnetic resonance angiography

Recent advances in magnetic resonance (MR) hardware and software have improved the resolution and spatial coverage of head and neck first-pass contrast-enhanced (CE) MR angiography. Despite these improvements, high-quality submillimeter-resolution 1.5 T and 3 T carotid CE MR angiography is not consistently available in the general radiology practice. This article reviews the important imaging parameters and potential pitfalls that affect carotid CE MR angiography image quality, and the dose and timing of the gadolinium-based contrast agent, and summarizes vendor-specific protocols for high-quality submillimeter-resolution carotid CE MR angiography at 1.5 and 3 T.

Contrast-enhanced peripheral MRA: technique and contrast agents

In the last decade contrast-enhanced magnetic resonance angiography (CE-MRA) has gained wide acceptance as a valuable tool in the diagnostic work-up of patients with peripheral arterial disease. This review presents current concepts in peripheral CE-MRA with emphasis on MRI technique and contrast agents. Peripheral CE-MRA is defined as an MR angiogram of the arteries from the aortic bifurcation to the feet. Advantages of CE-MRA include minimal invasiveness and lack of ionizing radiation. The basic technique employed for peripheral CE-MRA is the bolus-chase method. With this method a paramagnetic MRI contrast agent is injected intravenously and T1-weighted images are acquired in the subsequent arterial first-pass phase. In order to achieve high quality MR angiograms without interfering venous contamination or artifacts, a number of factors need to be taken into account. This includes magnetic field strength of the MRI system, receiver coil configuration, use of parallel imaging, contrast bolus timing technique, and k-space filling strategies. Furthermore, it is possible to optimize peripheral CE-MRA using venous compression techniques, hybrid scan protocols, time-resolved imaging, and steady-state MRA. Gadolinium(Gd)-based contrast agents are used for CE-MRA of the peripheral arteries. Extracellular Gd agents have a pharmacokinetic profile similar to iodinated contrast media. Accordingly, these agents are employed for first-pass MRA. Blood-pool Gd-based agents are characterized by prolonged intravascular stay, due to macromolecular structure or protein binding. These agents can be used for first-pass, as well as steady-state MRA. Some Gd-based contrast agents with low thermodynamic stability have been linked to development of nephrogenic systemic fibrosis in patients with severe renal insufficiency. Using optimized technique and a stable MRI contrast agent, peripheral CE-MRA is a safe procedure with diagnostic accuracy close to that of conventional catheter X-ray angiography.

Prospective comparison of image quality and diagnostic accuracy of 0.5 molar gadobenate dimeglumine and 1.0 molar gadobutrol in contrast-enhanced run-off magnetic resonance angiography of the lower extremities

PURPOSE

To compare image quality and diagnostic accuracy of 0.5 molar gadobenate dimeglumine and 1.0 molar gadobutrol in contrast-enhanced (CE) magnetic resonance angiography (MRA) of the lower extremities interindividually.

MATERIALS AND METHODS

The study was approved by our Institutional Review Board. Written informed consent was obtained from all patients before enrollment in the study. We prospectively included 74 patients (21 women, 53 men; mean age ± SD: 67.9 ± 11.0 years) with suspected peripheral occlusive vascular disease. All patients underwent a contrast-enhanced MRA of both lower extremities with either 0.1 mL/kg body weight gadobutrol or gadobenate dimeglumine. Image quality, stenosis grade, and artifacts were assessed by two blinded, independent investigators. Signal intensity (SI), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured by a third investigator. Contrast agent groups were compared to each other using a two-sided Student's t-test.

RESULTS

The results did not show significant differences for SI, SNR, or CNR. Both investigators were in significant accordance (P < 0.05) with regard to stenosis detection.

CONCLUSION

We conclude that application of standard clinical doses (0.1 mL/kg body weight) of both contrast agents provides similar diagnostic results and gadolinium dose could be reduced by the application of a single dose of gadobenate dimeglumine for CE run-off MRA.

Evaluation of rHA labeled with Gd-DTPA for blood pool imaging and targeted contrast delivery

A new contrast agent was developed by linking Gd-DTPA chelate to recombinant human albumin in the laboratory. The molar relaxivity of the new agent was tested in aqueous solution at B(0) 1.5 T and temperature 20 degrees C. The soluble compound had a higher molar longitudinal relaxivity and molar transverse relaxivity in water (r(1) = 7.2 s(-1) mM(-1), r(2) = 18.4 s(-1) mM(-1)) than those measured for Gd-DTPA solution (r(1) = 3.5 s(-1) mM(-1), r(2) = 5.5 s(-1) mM(-1)). The performance of the compound as a blood pool agent was investigated with soluble and microparticulate forms of the compound and comparisons were made with Gd-DTPA and the polymeric blood-pool agent, Gadomer. T(1)-weighted imaging experiments show that the soluble compound acts as a highly effective blood pool agent with hyperintensity in the vasculature persisting beyond 2 h post administration, compared with free Gd-DTPA, which was cleared from the blood pool after approximately 10 min. The clearance kinetics of the new agents were examined, due to the incomplete elimination within 14 days post injection; both rHA labeled compounds are probably not suitable for development as routine blood pool contrast media. However, with free sites on the Gd-loaded rHA molecule, there are possibilities for binding the agent to antibodies in the laboratory, which was demonstrated, and thus there exist potential applications for in vivo molecular imaging with this agent.

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.

Optimization of the contrast dose and injection rates in whole-body MR angiography at 3.0T

PURPOSE

To optimize the contrast agent dose and delivery rate used in a novel whole-body magnetic resonance angiography (MRA) protocol using a 3.0T MR scanner.

MATERIALS AND METHODS

Six groups of 20 consenting volunteers underwent whole-body MRA, with each group receiving a different contrast dose and contrast delivery rate. The arterial tree was divided into 16 segments and the image quality at each of the anatomical locations, covering the whole body, was assessed. Qualitative analysis was carried out using a scoring assessment of image quality, and quantitative assessments were performed by measuring contrast-to-noise (CNR) and a signal-to-noise (SNR) index.

RESULTS

Reducing the contrast dose from 40 mL to 25 mL was found to significantly increase the CNR in several vessels of interest in the arterial tree. There was also a significant increase in the qualitative image quality score (P < 0.001).

CONCLUSION

This study demonstrates that reducing the contrast dose at 3.0T can result in an increase in the CNR in the vessels of interest without significantly affecting the SNR.

Comparison of gadobenate dimeglumine and gadodiamide in the evaluation of spinal vascular anatomy with MR angiography

BACKGROUND AND PURPOSE

Spinal MRA has been increasingly used to evaluate non-invasively the spinal cord vasculature. Our aim was to prospectively compare gadobenate dimeglumine with gadodiamide in the assessment of the normal spinal cord vasculature by using contrast-enhanced MRA, with the hypothesis that high T1 relaxivity gadolinium compounds may improve visualization of the intradural vessels.

MATERIALS AND METHODS

Twenty subjects underwent 2 temporally separated contrast-enhanced spinal MRAs with gadobenate dimeglumine and gadodiamide (0.2 mmol/kg). Two blinded observers rated postprocessed images on the following qualitative parameters: background homogeneity, sharpness, vascular continuity, and contrast enhancement. Delineation of the ASA, AKA, hairpin configuration of the ASA-AKA connection, and visualized ASA length were recorded. Each observer indicated which of the 2 matched studies he or she thought was of the best overall diagnostic quality.

RESULTS

According to both observers gadobenate dimeglumine was superior to gadodiamide in the representation of vascular continuity and contrast (P value < .05). Background homogeneity was not significantly different between the studies. One observer favored gadobenate dimeglumine over gadodiamide in the demonstration of vascular sharpness, while the second observer did not find any significant difference between contrast agents. There was no significant difference between contrast agents in the visualization of the ASA, AKA, hairpin-shaped ASA-AKA connection, and visualized length of the ASA. The overall quality of the gadobenate dimeglumine-enhanced MRA was deemed superior in 15 and 16 cases, respectively, by the 2 observers.

CONCLUSIONS

Improved image quality and vascular contrast enhancement of spinal MRA at 1.5T is achieved with high T1 relaxivity gadolinium contrast agents compared with conventional agents at equivalent doses.

New dual mode gadolinium nanoparticle contrast agent for magnetic resonance imaging

BACKGROUND

Liposomal-based gadolinium (Gd) nanoparticles have elicited significant interest for use as blood pool and molecular magnetic resonance imaging (MRI) contrast agents. Previous generations of liposomal MR agents contained gadolinium-chelates either within the interior of liposomes (core-encapsulated gadolinium liposomes) or presented on the surface of liposomes (surface-conjugated gadolinium liposomes). We hypothesized that a liposomal agent that contained both core-encapsulated gadolinium and surface-conjugated gadolinium, defined herein as dual-mode gadolinium (Dual-Gd) liposomes, would result in a significant improvement in nanoparticle-based T1 relaxivity over the previous generations of liposomal agents. In this study, we have developed and tested, both in vitro and in vivo, such a dual-mode liposomal-based gadolinium contrast agent.

METHODOLOGY/PRINCIPAL FINDINGS

THREE TYPES OF LIPOSOMAL AGENTS WERE FABRICATED: core-encapsulated, surface-conjugated and dual-mode gadolinium liposomes. In vitro physico-chemical characterizations of the agents were performed to determine particle size and elemental composition. Gadolinium-based and nanoparticle-based T1 relaxivities of various agents were determined in bovine plasma. Subsequently, the agents were tested in vivo for contrast-enhanced magnetic resonance angiography (CE-MRA) studies. Characterization of the agents demonstrated the highest gadolinium atoms per nanoparticle for Dual-Gd liposomes. In vitro, surface-conjugated gadolinium liposomes demonstrated the highest T1 relaxivity on a gadolinium-basis. However, Dual-Gd liposomes demonstrated the highest T1 relaxivity on a nanoparticle-basis. In vivo, Dual-Gd liposomes resulted in the highest signal-to-noise ratio (SNR) and contrast-to-noise ratio in CE-MRA studies.

CONCLUSIONS/SIGNIFICANCE

The dual-mode gadolinium liposomal contrast agent demonstrated higher particle-based T1 relaxivity, both in vitro and in vivo, compared to either the core-encapsulated or the surface-conjugated liposomal agent. The dual-mode gadolinium liposomes could enable reduced particle dose for use in CE-MRA and increased contrast sensitivity for use in molecular imaging.

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.

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.

Follow-up of coiled cerebral aneurysms at 3T: comparison of 3D time-of-flight MR angiography and contrast-enhanced MR angiography

BACKGROUND AND PURPOSE

Our aim was to compare contrast-enhanced MR angiography (CE-MRA) and 3D time-of-flight (TOF) MRA at 3T for follow-up of coiled cerebral aneurysms.

MATERIALS AND METHODS

Fifty-two patients treated with Guglielmi detachable coils for 54 cerebral aneurysms were evaluated at 3T MRA. 3D TOF MRA (TR/TE = 23/3.5; SENSE factor = 2.5) and CE-MRA by using a 3D ultrafast gradient-echo sequence (TR/TE = 5.9/1.8; SENSE factor = 3) enhanced with 0.1-mmol/kg gadobenate dimeglumine were performed in the same session. Source images, 3D maximum intensity projection, 3D shaded surface display, and/or 3D volume-rendered reconstructions were evaluated in terms of aneurysm occlusion/patency and artifact presence.

RESULTS

In terms of clinical classification, the 2 MRA sequences were equivalent for 53 of the 54 treated aneurysms: 21 were considered fully occluded, whereas 16 were considered to have a residual neck and 16 were considered residually patent at follow-up MRA. The remaining aneurysm appeared fully occluded at TOF MRA but had a residual patent neck at CE-MRA. Visualization of residual aneurysm patency was significantly (P = .001) better with CE-MRA compared with TOF MRA for 10 (31.3%) of the 32 treated aneurysms considered residually patent with both sequences. Coil artifacts were present in 5 cases at TOF MRA but in none at CE-MRA. No relationship was apparent between the visualization of patency and either the size of the aneurysm or the interval between embolization and follow-up.

CONCLUSION

At follow-up MRA at 3T, unenhanced TOF and CE-MRA sequences are similarly effective at classifying coiled aneurysms as occluded or residually patent. However, CE-MRA is superior to TOF MRA for visualization of residual patency and is associated with fewer artifacts.

Extracellular gadolinium-based contrast media: differences in diagnostic efficacy

Since the introduction of the first gadolinium-based contrast agent (Gd-CA) in 1988 it has become clear that these agents significantly improve the diagnostic efficacy of MRI. Studies on single agents have shown that, in comparison to unenhanced sequences, all agents help to improve the detection and delineation of lesions which can alter diagnosis in up to 40% of patients. Doubling or tripling the standard dose of 0.1 mmol/kg body weight may be beneficial for selected indications (e.g. brain perfusion, equivocal single dose study in MRI for brain metastasis, small vessel MR angiography). A more limited number of studies have compared the various agents. These studies do not show clinically significant differences in diagnostic efficacy between the various extracellular Gd-CA. Agents with higher concentration or protein binding may be relatively better suitable for selected applications (e.g. perfusion MRI). The higher relaxivity agents may be used in somewhat lower doses than the extracellular agents.

Evaluation of a Novel Time-Efficient Protocol for Gadobenate Dimeglumine (Gd-BOPTA)-Enhanced Liver Magnetic Resonance Imaging

OBJECTIVE

We sought to evaluate gadobenate dimeglumine for the detection and characterization of focal liver lesions in the unenhanced and already pre-enhanced liver.

MATERIALS AND METHODS

Sixty patients were evaluated prospectively. Unenhanced T1-weighted gradient echo (T1wGRE) and T2-weighted turbo spin echo (T2wTSE) images were acquired followed by contrast-enhanced T1wGRE images during the dynamic, equilibrium, and delayed phases after the bolus injection of 0.05 mmol/kg gadobenate dimeglumine. An identical series of dynamic images was then acquired after the delayed scan following a second 0.05 mmol/kg bolus of gadobenate dimeglumine. Images were evaluated randomly in 2 sessions by 3 independent blinded readers. Evaluated images in the first session comprised the unenhanced images, the first or second set of dynamic images, and the delayed images. The second session included the unenhanced images, the dynamic images not yet evaluated in the first session, and the delayed images. The 2 reading sessions were compared for lesion characterization and diagnosis, and kappa (kappa) values for interobserver agreement were determined. Quantitative evaluation of lesion contrast enhancement was also performed.

RESULTS

The enhancement behavior in the second dynamic series was similar to that in the first series, although pre-enhancement of the normal liver resulted in reduced lesion-liver contrast-to-noise ratios and the visualization of some lesions only on arterial phase images. Typical imaging features for the lesions included in the study were visualized clearly in both series. Strong agreement (kappa=0.56-0.89; all evaluations) between the 2 images sets was noted by all readers for differentiation of benign from malignant lesions and for definition of specific diagnosis, and between readers for diagnoses established based on images acquired in the unenhanced and pre-enhanced liver.

CONCLUSION

Dynamic imaging in the hepatobiliary phase gives similar information as dynamic imaging of the unenhanced liver. This might prove advantageous for screening protocols involving same session imaging of primary extrahepatic tumors and liver.

Gadobenate dimeglumine-enhanced MR angiography: Diagnostic performance of four doses for detection and grading of carotid, renal, and aorto-iliac stenoses compared to digital subtraction angiography

PURPOSE

To determine the diagnostic performance of contrast-enhanced MR angiography (CE-MRA) with four doses of gadobenate dimeglumine for detection of significant steno-occlusive disease of the carotid, renal, and pelvic vasculature.

MATERIALS AND METHODS

Eighty-four patients with suspected disease of the renal (n = 16), pelvic (n = 41), or carotid (n = 27) arteries underwent CE-MRA (3D-spoiled gradient-echo sequences) at 1.5T. CE-MRA was performed with gadobenate dimeglumine at 0.025, 0.05, 0.1, or 0.2 mmol/kg (23, 24, 19, and 18 patients, respectively) administered at 2 mL/sec. Accuracy, sensitivity, specificity, and positive and negative predictive values (PPV and NPV, respectively) for detection of significant disease (>50% stenosis or occlusion for renal/pelvic arteries; >70% stenosis or occlusion for carotid arteries) was determined by three fully blinded, independent radiologists using conventional digital subtraction angiography (DSA) as reference standard. All comparisons were tested statistically (ANOVA, chi-square, and Mantel-Haenszel tests as appropriate) and reader agreement (kappa) was assessed.

RESULTS

Values for accuracy, sensitivity, specificity, PPV, and NPV on CE-MRA were consistently higher for 0.1 mmol/kg gadobenate dimeglumine (accuracy = 95.2-97.3%, sensitivity = 84.2% (all readers), specificity = 96.9-99.2%, PPV = 80.0-94.1%, NPV = 97.6-97.7%). The greater accuracy of the 0.1 mmol/kg dose was significant (P < 0.01, all readers) compared to all other dose groups. Agreement between the three readers was good for all dose groups (kappa >/=0.58), with the highest percent agreement (85.7%) noted for the 0.1 mmol/kg dose.

CONCLUSION

Significantly better diagnostic performance on CE-MRA of the renal, pelvic, and carotid arteries is achieved with a gadobenate dimeglumine dose of 0.1 mmol/kg bodyweight.

3D contrast-enhanced MR angiography

Safe, fast, accurate contrast arteriography can be obtained utilizing gadolinium (Gd) and 3D MR data acquisition for diagnosing vascular diseases. Optimizing contrast enhanced MRA (CE MRA), however, requires understanding the complex interplay between Gd injection timing, the Fourier mapping of 3D MR data acquisition and a multitude of parameters determining resolution, anatomic coverage, and sensitivity to motion artifacts. It is critical to time the bolus peak to coincide with central k-space data acquisition, which dominates image contrast. Oversampling the center of k-space allows reconstruction of multiple 3D acquisitions in rapid succession to time-resolve the passage of the contrast bolus. Parallel imaging increases resolution, shortens scan time and compresses the center of k-space into a shorter period of time, thereby minimizing motion and timing artifacts. Absence of ionizing radiation allows MRA to be repeated and combined with additional sequences to more fully characterize anatomy, flow, and physiology. Utilizing stepping table technology and thigh compression, whole body MRA is possible with a single contrast injection. As MR technology continues to advance, CE MRA becomes better and simpler to perform, increasing its efficacy in the diagnosis and management of vascular diseases.

[CTA and MRA in peripheral arterial disease--is DSA out?]

New developments in technique and postprocessing have led to further improvement in diagnosing and evaluating peripheral arterial disease (PAD) by noninvasive computed tomographic angiography (CTA) and magnetic resonance angiography (MRA). Under clinical conditions diagnostic conventional angiography (DSA) will be increasingly replaced by CTA and MRA. The radiologist has to become familiar with the field of indications, the different techniques, postprocessing tools, and effective visualization. In consideration of the current literature some methodological aspects and the role of CTA and MRA in PAD will be discussed.

Contrast Enhancement of Central Nervous System Lesions: Multicenter Intraindividual Crossover Comparative Study of Two MR Contrast Agents

PURPOSE

To prospectively compare gadobenate dimeglumine with gadopentetate dimeglumine (0.1 mmol per kilogram body weight) for enhanced magnetic resonance (MR) imaging of central nervous system (CNS) lesions.

MATERIALS AND METHODS

This study was HIPAA-compliant at U.S. centers and was conducted at all centers according to the Good Clinical Practice standard. Institutional review board and regulatory approval were granted; written informed consent was obtained. Seventy-nine men and 78 women (mean age, 50.5 years +/- 14.4 [standard deviation]) were randomized to group A (n = 78) or B (n = 79). Patients underwent two temporally separated 1.5-T MR imaging examinations. In randomized order, gadobenate followed by gadopentetate was administered in group A; order of administration was reversed in group B. Contrast agent administration (volume, speed of injection), imaging parameters before and after injection, and time between injections and postinjection acquisitions were identical for both examinations. Three blinded neuroradiologists evaluated images by using objective image interpretation criteria for diagnostic information end points (lesion border delineation, definition of disease extent, visualization of internal morphologic features of the lesion, enhancement of the lesion) and quantitative parameters (percentage of lesion enhancement, contrast-to-noise ratio [CNR]). Overall diagnostic preference in terms of lesion conspicuity, detectability, and diagnostic confidence was assessed. Between-group comparisons were performed with Wilcoxon signed rank test.

RESULTS

Readers 1, 2, and 3 demonstrated overall preference for gadobenate in 75, 89, and 103 patients, compared with that for gadopentetate in seven, 10, and six patients, respectively (P < .0001). Significant (P < .0001) preference for gadobenate was demonstrated for diagnostic information end points, percentage of lesion enhancement, and CNR. Superiority of gadobenate was significant (P < .001) in patients with intraaxial and extraaxial lesions.

CONCLUSION

Gadobenate compared with gadopentetate at an equivalent dose provides significantly better enhancement and diagnostic information for CNS MR imaging.

Safety of Gadobenate Dimeglumine (MultiHance)

OBJECTIVES

Prospective studies and retrospective analyses were undertaken to evaluate the clinical safety of gadobenate dimeglumine (MultiHance) and to assess tolerability in special populations.

MATERIALS AND METHODS

A total of 3092 subjects received MultiHance in 79 clinical trials. Data from comparisons with other contrast agents and studies in children, subjects with hepatic or renal impairment, or subjects with coronary artery disease were reviewed. Postmarketing safety surveillance data after more than 1.5 million applications were also evaluated.

RESULTS

In total, 413 of 2982 (14%) adult subjects receiving MultiHance reported at least one adverse event (AE) definitely or potentially related to MultiHance, an incidence that was similar to that observed with placebo (21/127, 17%) or active controls (59/723, 8%). In crossover studies, 23 of 287 (8%) subjects receiving MultiHance experienced AE compared with 25 of 295 (9%) receiving gadopentetate dimeglumine (Magnevist). No increased AE rate was observed in children and no worsening of renal or liver function was observed in subjects with hepatic or renal impairment. No detrimental effect on cardiac electrophysiology could be observed from a retrospective analysis of ECG parameters in more than 1000 patients and healthy volunteers. The AE reporting rate from postmarketing safety surveillance of MultiHance was 0.05%. Serious AEs were rarely reported and included dyspnea, nausea, urticaria, hypotension, and anaphylactoid reactions.

CONCLUSIONS

MultiHance appears to be well tolerated in adults and children and in subjects with impaired liver or kidney function or coronary artery disease. In controlled trials, MultiHance demonstrated a similar safety profile to that of Magnevist.

Enhancing lesions of the brain: intraindividual crossover comparison of contrast enhancement after gadobenate dimeglumine versus established gadolinium comparators

RATIONALE AND OBJECTIVES

Gadobenate dimeglumine (Gd-BOPTA) possesses a two-fold higher T1 relaxivity compared to other available gadolinium contrast agents. The study was conducted to evaluate the benefits of this increased relaxivity for MR imaging of intracranial enhancing brain lesions.

MATERIALS AND METHODS

Forty-five patients (31 males, 14 females) with suspected glioma or cerebral metastases were evaluated. Patients received Gd-BOPTA and either Gd-DTPA (n = 23) or Gd-DOTA (n = 22) in fully randomized order at 0.1 mmol/kg body weight and at a flow rate of 2 ml/s. The second agent was administered 1-14 days after the first agent. Images were acquired precontrast (T1wSE, T2wFSE sequences) and at sequential postcontrast time-points (T1wSE sequences at 0, 2, 4, 6, and 8 and 15 min and a T1wSE-MT sequence at 12 min) at 1.0 or 1.5 T using a head coil. Determination of contrast enhancement was performed quantitatively (lesion-to-brain ratio, contrast-to-noise ratio, and percent enhancement) and qualitatively (border delineation, internal morphology, contrast enhancement, and diagnostic preference) by two independent, fully blinded readers.

RESULTS

Images from 43/45 patients were available for quantitative assessment. After correction for precontrast values, significantly greater lesion-to-brain ratio (P < .003), contrast-to-noise ratio (P < .03), and percent enhancement (P < .0001) was noted by both readers for Gd-BOPTA-enhanced images at all time-points from 2 min postcontrast. Qualitative assessment of all patients similarly revealed significant preference for Gd-BOPTA for lesion border delineation (P < .004), lesion internal morphology (P < .008), contrast enhancement (P < .0001), and diagnostic preference (P < .0005).

CONCLUSIONS

The greater T1 relaxivity of Gd-BOPTA permits improved visualization of intracranial enhancing lesions compared to conventional gadolinium agents.

The Efficacy of Gadobenate Dimeglumine (Gd-BOPTA) at 3 Tesla in Brain Magnetic Resonance Imaging

OBJECTIVES

The objectives of this study were to analyze the differences in contrast enhancement using gadobenate dimeglumine (Gd-BOPTA or MultiHance) at 3 T versus 1.5 T and to compare Gd-BOPTA with a standard gadolinium chelate, gadopentetate dimeglumine (Gd-DTPA or Magnevist), at 3 T in a rat glioma model.

MATERIALS AND METHODS

Twelve rats with surgically implanted gliomas were randomized to either comparing Gd-BOPTA at 1.5 T versus 3 T (n=7) or comparing Gd-BOPTA and Gd-DTPA at 3 T (n=5). Matched T1-weighted spin-echo techniques were used for both comparisons and the order of examinations was randomized. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and lesion enhancement (LE) were evaluated using a region-of-interest analysis. A veterinary histopathologist evaluated all brain specimens.

RESULTS

In the evaluation of Gd-BOPTA at 3 T and 1.5 T, there were significant increases in SNR, LE, and CNR at 3 T. Average increases in brain and tumor SNR were 93% (P<0.0001) and 92% (P<0.0001), respectively. CNR increased by 121% (P<0.0001). Comparison of Gd-BOPTA and Gd-DTPA at 3 T demonstrated significantly higher CNR and LE with Gd-BOPTA. CNR increased by 35% (P=0.002). LE increased by 44% (P=0.03).

CONCLUSIONS

Gd-BOPTA provides significantly higher CNR at 3 T compared with 1.5 T and also demonstrates significantly higher CNR when compared with a standard Gd-chelate at 3 T. As a result of transient protein binding, Gd-BOPTA may be superior to standard gadolinium chelates in neurologic imaging at 3 T.

Influence of Human Serum Albumin on Longitudinal and Transverse Relaxation Rates (R1 and R2) of Magnetic Resonance Contrast Agents

OBJECTIVES

Exogenous magnetic resonance (MR) contrast media (CM) are used to improve detection and delineation of physiological and pathologic structures. Temporary binding between CM and proteins such as human serum albumin (HSA) may alter the relaxation-enhancing properties of specific contrast agents. In this study, the presence and strength of HSA interaction with different CM was investigated.

MATERIAL AND METHODS

Three contrast agents were chosen: Gd-DTPA, Gd-BT-DO3A, and Gd-BOPTA, each of which is known to have a different protein interaction. Samples were prepared using 7 different HSA concentrations, all at a constant CM concentration of 0.5 mmol/L. The relaxation rates, R1 and R2, of each sample were measured at 1.5 T. Virtual docking studies were performed to estimate the number of high affinity-binding sites of Gd-BOPTA and the surface of the HSA dimer.

RESULTS

Gd-BOPTA caused the greatest increase in R1 and R2, which followed an exponential dependency with increasing HSA concentration. Between the range of 0 and 7 g/dL of HSA, Gd-DTPA and Gd-BT-DO3A showed a relative change in both relaxation rates of approximately 13% and 22% for R1 and 26% and 30% for R2, respectively. In contrast, Gd-BOPTA demonstrated a relative increase of approximately 108% and 363% for R1 and R2, respectively. Changes of HSA concentration within physiological range (3.5-5.5 g/dL) resulted in an increase of R1 and R2 of approximately 40% when using Gd-BOPTA. The docking study revealed that approximately 10 small hydrophobic pockets exist on the HSA surface where the aromatic tail of Gd-BOPTA can fit in and a stronger noncovalent binding can occur compared with Gd-DTPA and Gd-BT-DO3A.

CONCLUSION

Relaxation rates of Gd-BOPTA showed a strong dependency on HSA. In contrast, Gd-DTPA and Gd-BT-DO3A demonstrated little or no relevant dependency. On the basis of these results, the influence of serum protein concentration should be considered in both research studies and in clinical use.

Relaxivity of Gadopentetate Dimeglumine (Magnevist), Gadobutrol (Gadovist), and Gadobenate Dimeglumine (MultiHance) in Human Blood Plasma at 0.2, 1.5, and 3 Tesla

OBJECTIVES

We sought to determine the relaxivity and accurate relaxation rates of Gd-DTPA, Gd-BT-DO3A, and Gd-BOPTA at 0.2, 1.5, and 3 T in human blood plasma.

MATERIALS AND METHODS

Contrast media concentrations between 0.01 and 16 mM in human plasma were used for relaxation measurements. The R1 and R2 relaxation rates and r1 and r2 relaxivities were determined.

RESULTS

Gd-BOPTA produced the highest relaxation rates and relaxivities at all field strengths. The r1 and r2 values for Gd-BOPTA were 107-131% and 91-244% higher than for Gd-DTPA, respectively, and 72-98% and 82-166% higher than for Gd-BT-DO3A. Higher field strengths resulted in lower values of R1, R2, and r1 for all contrast agents tested and of r2 for Gd-DTPA and Gd-BT-DO3A. A linear dependence of R1 and R2 on concentration was found for Gd-DTPA and Gd-BT-DO3A and a nonlinear dependence for Gd-BOPTA for concentrations larger than 1 mM. The r1 and r2 relaxivity of Gd-BOPTA increased with decreasing concentration.

CONCLUSIONS

Gd-BOPTA demonstrates the highest longitudinal r1 at all field strengths, which is ascribable to weak protein interaction. The R2/R1 ratio increases at higher field strength only for Gd-BOPTA, hence very short echo times are required for Gd-BOPTA to benefit from the higher longitudinal relaxivity.

Safety characteristics of gadobenate dimeglumine: Clinical experience from intra- and interindividual comparison studies with gadopentetate dimeglumine

PURPOSE

To evaluate the safety and tolerability of gadobenate dimeglumine (Gd-BOPTA) relative to that of gadopentetate dimeglumine (Gd-DTPA) in patients and volunteers undergoing MRI for various clinical conditions.

MATERIALS AND METHODS

A total of 924 subjects were enrolled in 10 clinical trials in which Gd-BOPTA was compared with Gd-DTPA. Of these subjects, 893 were patients with known or suspected disease and 31 were healthy adult volunteers. Of the 893 patients, 174 were pediatric subjects (aged two days to 17 years) referred for MRI of the brain or spine. Safety evaluations included monitoring vital signs, laboratory values, and adverse events (AE).

RESULTS

The rate of AE in adults was similar between the two agents (Gd-BOPTA: 51/561, 9.1%; Gd-DTPA: 33/472, 7.0%; P = 0.22). In parallel-group studies in which subjects were randomized to either agent, the rate of AE was 10.9% for Gd-BOPTA and 7.9% for Gd-DTPA (P = 0.21). In the subset of subjects receiving both agents in intraindividual crossover trials, the rate of AE was 8.0% for Gd-BOPTA and 8.5% for Gd-DTPA (P = 0.84). Results of other safety assessments (laboratory tests, vital signs) were similar for the two agents.

CONCLUSION

The safety profile of Gd-BOPTA is similar to Gd-DTPA in patients and volunteers. Both compounds are equally well-tolerated in patients with various disease states undergoing MRI.