Kyunghyun Sung1, Krishna S Nayak. 1. Magnetic Resonance Engineering Laboratory, Ming Hsieh Department of Electrical Engineering-Systems, University of Southern California, Los Angeles, CA 90089-2564, USA. kyunghsu@sipi.usc.edu
Abstract
PURPOSE: To measure and characterize variations in the transmitted radio frequency (RF) (B1+) field in cardiac magnetic resonance imaging (MRI) at 3 Tesla. Knowledge of the B1+ field is necessary for the calibration of pulse sequences, image-based quantitation, and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) optimization. MATERIALS AND METHODS: A variation of the saturated double-angle method for cardiac B1+ mapping is described. A total of eight healthy volunteers and two cardiac patients were scanned using six parallel short-axis slices spanning the left ventricle (LV). B1+ profiles were analyzed to determine the amount of variation and dominant patterns of variation across the LV. A total of five to 10 measurements were obtained in each volunteer to determine an upper bound of measurement repeatability. RESULTS: The amount of flip angle variation was found to be 23% to 48% over the LV in mid-short-axis slices and 32% to 63% over the entire LV volume. The standard deviation (SD) of multiple flip angle measurements was <1.4 degrees over the LV in all subjects, indicating excellent repeatability of the proposed measurement method. The pattern of in-plane flip angle variation was found to be primarily unidirectional across the LV, with a residual variation of < or =3% in all subjects. CONCLUSION: The in-plane B1+ variation over the LV at 3T with body-coil transmission is on the order of 32% to 63% and is predominantly unidirectional in short-axis slices. Reproducible B1+ measurements over the whole heart can be obtained in a single breathhold of 16 heartbeats.
PURPOSE: To measure and characterize variations in the transmitted radio frequency (RF) (B1+) field in cardiac magnetic resonance imaging (MRI) at 3 Tesla. Knowledge of the B1+ field is necessary for the calibration of pulse sequences, image-based quantitation, and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) optimization. MATERIALS AND METHODS: A variation of the saturated double-angle method for cardiac B1+ mapping is described. A total of eight healthy volunteers and two cardiac patients were scanned using six parallel short-axis slices spanning the left ventricle (LV). B1+ profiles were analyzed to determine the amount of variation and dominant patterns of variation across the LV. A total of five to 10 measurements were obtained in each volunteer to determine an upper bound of measurement repeatability. RESULTS: The amount of flip angle variation was found to be 23% to 48% over the LV in mid-short-axis slices and 32% to 63% over the entire LV volume. The standard deviation (SD) of multiple flip angle measurements was <1.4 degrees over the LV in all subjects, indicating excellent repeatability of the proposed measurement method. The pattern of in-plane flip angle variation was found to be primarily unidirectional across the LV, with a residual variation of < or =3% in all subjects. CONCLUSION: The in-plane B1+ variation over the LV at 3T with body-coil transmission is on the order of 32% to 63% and is predominantly unidirectional in short-axis slices. Reproducible B1+ measurements over the whole heart can be obtained in a single breathhold of 16 heartbeats.
Authors: Ye Tian; Jason Mendes; Brent Wilson; Alexander Ross; Ravi Ranjan; Edward DiBella; Ganesh Adluru Journal: Magn Reson Med Date: 2020-06-03 Impact factor: 4.668
Authors: Yannick Bliesener; Xinran Zhong; Yi Guo; Michael Boss; Ryan Bosca; Hendrik Laue; Caroline Chung; Kyunghyun Sung; Krishna S Nayak Journal: Med Phys Date: 2019-04-15 Impact factor: 4.071
Authors: Michael Rasper; Jonathan Nadjiri; Alexandra S Sträter; Marcus Settles; Karl-Ludwig Laugwitz; Ernst J Rummeny; Armin M Huber Journal: Int J Cardiovasc Imaging Date: 2017-01-30 Impact factor: 2.357
Authors: Hua Guo; Wing-Yan Au; Jerry S Cheung; Daniel Kim; Jens H Jensen; Pek-Lan Khong; Queenie Chan; Kevin C Chan; Christina Tosti; Haiying Tang; Truman R Brown; Wynnie W M Lam; Shau-Yin Ha; Gary M Brittenham; Ed X Wu Journal: J Magn Reson Imaging Date: 2009-08 Impact factor: 4.813