Magnetosomen als biologisches Modell der Eisenbindung: Messung der Relaxivitaet in der MRT

Purpose: In vitro characterization of iron-containing bacterial particles (magnetosomes) as superparamagnetic contrast agents for MRI. Material and Methods: Different concentrations of magnetosomes were examined with a 1.5 T clinical whole-body MR system at 21°C using the transit/receive extremity coil. Both longitudinal and transversal relaxivities (R1 and R2) of the magnetosomes were determined by an inversion recovery snapshot gradient recall echo (1R FLASH) with various inversion times and a multi echo spin echo sequence. Atomic absorption spectrometry (AAS) and electron microscopy were used as reference standard. Results: Longitudinal and transverse relaxivities of the magnetosomes were calculated to be R1 = 7.688 mmol-1 s-1 and R2 = 147.67 mmol-1 s-1, respectively. The corresponding iron concentrations were determined in all dilutions using AAS, while the magnetosomes were morphologically delineated by electron microscopy. Conclusion: Magnetosomes represent a new and interesting class of iron-containing contrast agents warranting further evaluation in cellular cultures and animal models. Magnetosomes may be suited for displaying the vector distribution and gene expression of new molecular therapies

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 k 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 < .0001) and detection of clinically relevant disease (P < .0028) were significantly improved with gadobenate dimeglumine. Interreader agreement for stenosis detection and grading was good to excellent (k = 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. (c) RSNA, 2010Cardiovascular Aspects of Radiolog

Diagnostic performance of gadobenate dimeglumine enhanced MR angiography of the iliofemoral and calf arteries: a large-scale multicenter trial

OBJECTIVE. The purpose of this study was to compare gadobenate dimeglumine\u2013enhanced MR angiography and unenhanced time-of-flight MR angiography for the detection of significant peripheral arterial occlusive disease using digital subtraction angiography as our reference standard. SUBJECTS AND METHODS. Two hundred seventy-two patients underwent MR angiography and digital subtraction angiography of the iliofemoral arteries. MR angiography was performed before (2D time-of-flight acquisitions) and after (spoiled gradient-echo acquisitions) the administration of 0.1 mmol/kg of gadobenate dimeglumine at 1\u20132 mL/s. Contrast-enhanced MR angiography and digital subtraction angiography of the calf arteries were performed in 241 of 272 participants. Images were evaluated on-site and by four blinded reviewers (three for MR angiography, one for digital subtraction angiography). Comparative diagnostic performance for the detection of significant ( 65 51% vessel lumen narrowing) disease was evaluated using the McNemar test and generalized estimating equations. Interobserver agreement was assessed with generalized kappa statistics. The chi-square test was used to compare technical failure rates. RESULTS. Digital subtraction angiography confirmed significant disease (597 stenoses, 386 occlusions) in 983 iliofemoral segments. The sensitivity (54\u201380.9%), specificity (89.7\u201395.3%), and accuracy (85\u201387.5%) of contrast-enhanced MR angiography for the detection of significant iliofemoral disease were significantly (p < 0.001, all reviewers) better than those of time-of-flight MR angiography (33.2\u201362.8%, 74.3\u201388.9%, and 68\u201377.3%, respectively). Similar diagnostic performance was obtained for the calf arteries. The technical failure rate with contrast-enhanced MR angiography (2.5\u20133.4%) was similar to that of digital subtraction angiography (1.4%) and significantly (p < 0.001) lower than that of time-of-flight MR angiography (6.2\u201318.0%). Significantly better reproducibility (p < 0.001) was obtained with contrast- enhanced MR angiography (82% vs 65.2% agreement; \u3ba = 0.66 vs 0.45). CONCLUSION. Improved diagnostic performance and reproducibility are achievable with gadobenate dimeglumine\u2013enhanced MR angiography in patients with peripheral arterial occlusive disease