European Journal of Radiology 80 (2011) 559–564 Contents lists available at ScienceDirect European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad Contrast visibility for indirect MR arthrography with different protein contents and agent relaxivities at different field strengths: An in vitro model M.R. Nouh a,∗ , M.E. Schweitzer b,1 , Ravinder R. Ragatte c,2 a Department of Radiodiagnosis and Diagnostic Imaging, Faculty of Medicine, Alexandria University, 1 Kolya-El Teb St., Mahata El-Ramel, Alexandria, Egypt b 501 Smyth Module S-1, The University of Ottawa, Ottawa, ON K1H 8L6, Canada c 301 E17th Street, Department of Radiology, Hospital for Joint Disease, New York University, New York, NY 10003, United States article info Article history: Received 20 September 2010 Received in revised form 27 November 2010 Accepted 2 December 2010 This work was presented at 17th ESSR Annual Meeting, 19 June 2010 Keywords: MRI MR arthrography MR contrast Joints abstract 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 relaxiv- ity 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 3 g/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 3 T 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 solu- tion 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 3 T. Conclusion: 1.25 mmol concentration of both gadoteridol and gadobenate solutions yields the best diagnostic T1 SI specially in higher fields (3 T and 7 T) and avoid the deleterious effect of increasing concentration on T2 SI. Gadoteridol is suggested on 3 T field indirect MR arthrograms. Protein had no positive effect on either SI or relaxivities in any joint model. © 2010 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Indirect magnetic resonance (MR) arthrography is a non- invasive imaging tool based on the premise that intravenous contrast material administered will diffuse into the joint space over time, owing to high vascularity of the synovial membrane and lack of basement membrane in its capillaries [1–3]. Hence after a delay following intravenous injection, synovial fluid should roughly equal plasma in contrast concentration and hence visibility [3]. Another, ∗ Corresponding author. Tel.: +20 115243367; fax: +20 3 4869754. E-mail addresses: mragab73@yahoo.com (M.R. Nouh), mschweitzer@toh.on.ca (M.E. Schweitzer), Ravinder.regatte@nyumc.org (R.R. Ragatte). 1 Tel.: +1 613 737 8571; fax: +1 613 737 8571. 2 Tel.: +1 212 598 6373; fax: +1 212 598 6125. advantage of indirect MR arthrography is the lack of logistic difficul- ties needed in the more invasive direct technique. On other hand, enhancement of both intra-articular and extra-articular patholo- gies may be a compromise for this technique [3]. Two major factors determining the relative effectiveness of an MR arthrographic contrast agent are protein binding, and relaxivity [4]. As agents have different relaxivities in the presence of proteins [5–8], we sought to evaluate the optimal concentrations of high and usual relaxivity agents in two protypical synovial environments at variable field strengths. 2. Materials and methods To mimic the situation of indirect MR arthrography in normal and diseased joints, two different concentrations of albumin were 0720-048X/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2010.12.011