2 research outputs found
High-Resolution Numerical Simulation of Respiration-Induced Dynamic B0 Shift in the Head in High-Field MRI
Copyright © 2019 Korean Society of Magnetic Resonance in Medicine (KSMRM)
Purpose: To demonstrate the high-resolution numerical simulation of the respirationinduced
dynamic B0 shift in the head using generalized susceptibility voxel
convolution (gSVC).
Materials and Methods: Previous dynamic B0 simulation research has been limited
to low-resolution numerical models due to the large computational demands of
conventional Fourier-based B0 calculation methods. Here, we show that a recentlyproposed
gSVC method can simulate dynamic B0 maps from a realistic breathing
human body model with high spatiotemporal resolution in a time-efficient manner.
For a human body model, we used the Extended Cardiac And Torso (XCAT) phantom
originally developed for computed tomography. The spatial resolution (voxel size)
was kept isotropic and varied from 1 to 10 mm. We calculated B0 maps in the brain
of the model at 10 equally spaced points in a respiration cycle and analyzed the
spatial gradients of each of them. The results were compared with experimental
measurements in the literature.
Results: The simulation predicted a maximum temporal variation of the B0 shift
in the brain of about 7 Hz at 7T. The magnitudes of the respiration-induced B0
gradient in the x (right/left), y (anterior/posterior), and z (head/feet) directions
determined by volumetric linear fitting, were < 0.01 Hz/cm, 0.18 Hz/cm, and 0.26
Hz/cm, respectively. These compared favorably with previous reports. We found that
simulation voxel sizes greater than 5 mm can produce unreliable results.
Conclusion: We have presented an efficient simulation framework for respirationinduced
B0 variation in the head. The method can be used to predict B0 shifts with
high spatiotemporal resolution under different breathing conditions and aid in the
design of dynamic B0 compensation strategies
Rapid, theoretically artifact-free calculation of static magnetic field induced by voxelated susceptibility distribution in an arbitrary volume of interest
Purpose: To demonstrate a computationally efficient and theoretically artifact‐free method to calculate static field (B0) inhomogeneity in a volume of interest induced by an arbitrary voxelated susceptibility distribution. (2018 Magnetic Resonance in Medicine)ⓒ2018 International Society for Magnetic Resonance inMedicin