Dual-source radiofrequency transmission with patient-adaptive local radiofrequency shimming for 3.0-T cardiac MR imaging: initial experience.

PURPOSE: To evaluate the effect of dual-source parallel radiofrequency (RF) transmission with patient-adaptive local RF shimming on image quality, image contrast, and diagnostic confidence at routine clinical cardiac magnetic resonance (MR) imaging with use of a 3.0-T dual-channel transmit whole-body MR system.
MATERIALS AND METHODS: Written informed consent was obtained from all patients, and the study protocol was approved by the local institutional review board. Cardiac MR imaging was performed in 28 patients by using a 3.0-T MR unit equipped with a dual-source RF transmission system. The effect of conventional versus dual-source RF transmission on steady-state free precession (SSFP) cine sequences and turbo spin-echo (TSE) black-blood (BB) sequences was evaluated. The homogeneity of the B1 field and contrast-to-noise ratios (CNRs) were measured and tested for statistical significance with the paired t test. Images were analyzed qualitatively for homogeneity, the presence of off-resonance artifacts, and diagnostic confidence independently by two readers. Statistical significance was assessed with the Wilcoxon signed rank test. Inter- and intraobserver agreement was assessed with κ statistics.
RESULTS: Quantitative image analysis revealed that B1 homogeneity and CNR were significantly improved for images acquired with dual-source RF transmission compared with conventional RF transmission (P = .005). The quality of SSFP and TSE BB images of the left and the right ventricles showed a significant improvement with respect to image homogeneity and diagnostic confidence as evaluated by the readers (P = .0001, κ > 0.74). As a side effect, off-resonance artifacts were significantly reduced on SSFP images (P = .0001, κ > 0.76).
CONCLUSION: Dual-source parallel RF transmission significantly improves image homogeneity, image contrast, and diagnostic confidence compared with conventional RF transmission of cardiac SSFP and TSE BB sequences. © RSNA, 2012.