MAGNETIC RESONANCE IMAGING
greater r1 relaxivity of MultiHance on diagnostic performance in brain tumor imaging is shown in Figure 1. Similarly improved diagnostic performance has been shown for other routine MR imag- ing applications including MR angiog- raphy (MRA) and MR mammography (MRM) [15-18]. A second GBCA with unique
properties is Gadovist (gadobutrol; Bayer Healthcare, Berlin, Germany). This contrast agent has a reported r1 relaxivity of 4.7–5.2 L/mmol/sec at 1.5T [10, 11] but differs principally from MultiHance and other approved GBCAs in that it is formulated at twice the concentration (1 mol/L rather than 0.5 mol/L) meaning that twice the concentration of gadolinium is present per unit volume in the vial. The clini- cal questions to answer therefore are whether the two-fold higher concen- tration of Gadovist is of any benefit in the clinical setting and how the two- fold higher concentration of Gadovist compares with the higher r1 relaxivity of MultiHance in terms of diagnostic imaging performance.
COMPARATIVE STUDIES
To answer these questions two stud- ies have recently been performed. In the first study, Achenbach et al. [19] compared Gadovist and MultiHance at equivalent total volume (0.1 mL/ kg body weight,
corresponding to
a full dose of Gadovist [0.1 mmol/ kg body weight] but only a half dose of MultiHance [0.05 mmol/kg body
weight]) for contrast-enhanced MRA of the peripheral arteries. In that study no differences were found in terms of quantitative enhancement, image quality or diagnostic accuracy indi- cating that the T1 shortening achieved by a 0.1 mmol/kg dose of Gadovist per unit time was of no benefit when compared to the greater relaxivity of MultiHance at only half the dose. In the second study (the MERIT
study), which was performed more recently and has recently been published in AJNR [20] MultiHance and Gado- vist were compared at an equivalent dose of 0.1 mmol/kg body weight for brain tumor imaging using an identical imaging protocol and methodological approach to that adopted in previous intra-individual crossover studies [2-8]. In total, 114 out of 123 enrolled adult patients with suspected or known brain tumors each underwent two identical MRI exams at 1.5T, one exam with Mul- tiHance and the other with Gadovist, both at a dose of 0.1 mmol/kg body weight. The agents were injected in ran- domized order separated by 3–14 days with care taken to ensure identical imag- ing sequences and acquisition timing for the two exams in each patient. Thereafter,
three blinded readers
evaluated all images qualitatively for diagnostic information (lesion extent, delineation, morphology, enhancement, global preference) and quantitatively for % lesion enhancement, contrast-to- noise ratio (CNR) and lesion-to-back- ground ratio (LBR).
RESULTS OF THE MERIT STUDY In common with findings from previ- ous large-scale intra-individual studies versus Magnevist [4-6] and Omniscan [7] all three readers consistently dem- onstrated highly significant (p<0.0001; all readers) preference for Multi- Hance for all qualitative end-points. In terms of global preference, readers 1, 2 and 3 preferred MultiHance in 46 (40.7%), 54 (47.4%) and 49 (43.0%) patients, respectively, compared with only 6, 7 and 7 patients for Gadovist (p<0.0001; all
readers). Inter-reader
agreement was good for all evalua- tions (к=0.414−0.629) confirming the consistency, reproducibility and low variability of evaluation results (pref- erence selection for contrast agent) across all readers. In terms of the per- cent enhancement of lesions, highly significant (p<0.0001; all readers) mean differences of approximately 22% were noted between MultiHance and Gado- vist [Figure 2]. Again, these findings are in agreement with those noted in previous comparative studies [2-8]. The unequivocal conclusion of this study is that despite the two-fold higher con- centration of the Gadovist formulation, it is the higher r1 relaxivity of Multi- Hance that is instrumental in affecting significant improvements in both qual- itative lesion visualization and quan- titative lesion enhancement when the two contrast agents are administered at equivalent doses of 0.1 mmol/kg body weight.
OTHER STUDIES In support of this
conclusion, yet
FigUre 1. Improved enhancement and lesion delineation is seen on MRI enhanced with MultiHance (A) than on MRI enhanced with Magnevist (B) when both contrast agents are administered under identical conditions at an equivalent dose of 0.1 mmol/kg bodyweight. The improved diagnostic performance is attributable solely to the greater r1 relaxivity of MultiHance..
42 DI EUROPE
another intra-individual crossover study has recently been published [21]. In this study, Anzalone et al. compared Gadovist and Dotarem at identical doses of 0.1 mmol/kg body weight in 136 patients with known cerebral intra-axial or extra-axial neoplastic lesions using a similar study design and methodologi- cal approach to that utilized in the vari- ous studies involving MultiHance [2, 4-8, 20]. Like Gadovist, Dotarem is a macrocyclic contrast agent which shows no appreciable interaction with serum albumin. However, like MultiHance it is an ionic agent and is formulated at a concentration of 0.5 mol/L. Of the vari- ous GBCAs approved for MR imaging of the CNS, Dotarem is considered to have the lowest r1 relaxivity in plasma
APRIL/MAY 2012
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56