MRT der arthritis mit dem USPIO SH U 555 C: Optimierung des T1-enhancements

Purpose: To optimize contrast agent dose and pulse sequence parameters in order to achieve a maximal T1 enhancement in arthritic knee joints with ultra small superparamagnetic iron oxides (USPIO)-enhanced MRI. Materials and Methods: Antigen-mediated arthritis was induced in the right knee of nine Sprague Dawley rats. The arthritic knee joint as well as the contralateral normal knee were investigated in a 2 Tesla MR scanner before as well as in short intervals up to 2 h after USPIO injection, using T1-weighted gradient echo (GE) sequences. Three rats each received intravenous injections of the new USPIO SHU 555 C (SH U 555 C, Schering AG, Berlin) at doses of 40,100 and 200 μmol Fe/kg. Pulse sequence parameters of the GE-sequence were optimized by varying flip angles (a) and echo times (TE). Changes in signal intensities (SI) of the arthritic knee and contralateral normal knee were quantified as ΔSI(%) = [([SIpost - SIpre]/SIpre) × 100%] and compared with histopathology. Results: Histology of the arthritic knees demonstrated a marked inflammatory proliferation of the synovium. The USPIO SH U 555 C caused a significant increase in signal intensity of the arthritic joints on T1-weighted MR images (p < 0.05). This effect was optimized using a flip angle of 60 - 70°, a minimal TE and a dose of 200 μmol Fe/kg. Visually the contralateral normal knee did not show any USPIO enhancement. Conclusion: Inflammation can be depicted with marked T1 enhancement by the USPIO SH U 555 C using high contrast agent doses and optimized MR pulse sequence parameters.