Fast and Robust B1 Mapping at 7T by the Bloch-Siegert Method
نویسندگان
چکیده
Introduction: B1 mapping has a variety of applications including the design of RF pulses in parallel transmit systems, and flip angle calibration for T1 mapping. Many existing B1 mapping methods suffer from T1 dependence, long scan time or inability to handle the large B1 inhomogeneity that occurs even across the human brain at 7T. The Bloch-Siegert B1 mapping method has been recently introduced [1], and shown to be independent of TR, T1 relaxation, flip angle, chemical shift, background field inhomogeneity, and magnetization transfer, thereby promising accurate and efficient B1 mapping. To date, BS B1 mapping has only been applied at 3T, which motivated us to implement and evaluate the method at 7T.
منابع مشابه
Bloch‐Siegert B1+‐mapping for human cardiac 31P‐MRS at 7 Tesla
PURPOSE Phosphorus MR spectroscopy ((31) P-MRS) is a powerful tool for investigating tissue energetics in vivo. Cardiac (31) P-MRS is typically performed using surface coils that create an inhomogeneous excitation field across the myocardium. Accurate measurements of B1+ (and hence flip angle) are necessary for quantitative analysis of (31) P-MR spectra. We demonstrate a Bloch-Siegert B1+-mappi...
متن کاملSignal to Noise Ratio Analysis of Bloch-Siegert B1 Mapping
Introduction: B1 mapping is important in a variety of new MR applications, including the design of RF pulses in parallel transmit systems and flip angle calibration for T1 mapping. The Bloch-Siegert (BS) B1 mapping method has been recently introduced as a fast, accurate and robust technique for B1 mapping [1]. In order to compare the quality of B1 maps acquired with the BS method to other metho...
متن کاملMotion-robust cardiac B1+ mapping at 3T using interleaved bloch-siegert shifts.
PURPOSE To develop and evaluate a robust motion-insensitive Bloch-Siegert shift based B1+ mapping method in the heart. METHODS Cardiac Bloch-Siegert B1+ mapping was performed with interleaved positive and negative off-resonance shifts and diastolic spoiled gradient echo imaging in 12 heartbeats. Numerical simulations were performed to study the impact of respiratory motion. The method was com...
متن کاملTurbo Spin Echo Bloch Siegert Shift B1 Mapping
An interesting method for B1 mapping based on the Bloch-Siegert (BLS) shift was recently presented (1,2) for gradient echo (FLASH) and Spin Echo (SE) sequences. This method uses off-resonant pulses before signal acquisition to encode the B1 information into the signal phase. Fast B1 mapping is possible since the repetition time has only minor influence on the quality of the phase information. I...
متن کاملRegularized Estimation of Magnitude and Phase of Multi-Coil $B_1$ Field Via Bloch-Siegert $B_1$ Mapping and Coil Combination Optimizations
Parallel excitation requires fast and accurate B1 map estimation. Bloch-Siegert (BS) B1 mapping is very fast and accurate over a large dynamic range. When applied to multi-coil systems, however, this phase-based method may produce low signal-to-noise ratio estimates in low magnitude regions due to localized excitation patterns of parallel excitation systems. Also, the imaging time increases wit...
متن کامل