ACDC Dynamic B0 Field Control — Gordon Conference Showcase

hhong6@mgh.harvard.edu (Haotian Hong) — Thu, 09 Jul 2026 15:09:46 +0800

ACDC Dynamic B0 Field Control: Additional Showcase

Related Repositories:

bughht/ACDC_Optim — Shim waveform optimization solvers
bughht/concomitant_sim — Concomitant field simulation toolkit

1. Short-Term Eddy Current Compensation: Correcting EPI Edge Ghosts

The Problem

In single-shot EPI, rapidly switching gradient waveforms induce short-term eddy currents (decay $\tau \sim 1$–$10$ ms) in the cryostat and surrounding conductors. These eddy currents create a time-varying gradient bias during the EPI readout train that manifests as Edge ghosts superimposed on the primary image.

Concomitant Field Simulation

hhong6@mgh.harvard.edu (Haotian Hong) — Sat, 20 Dec 2025 15:09:46 +0800

MRI Concomitant Field Simulation Tool

GitHub Repository: bughht/concomitant_sim

concomitant_sim is a fast, backend-agnostic Python package for simulating the phase accumulation caused by concomitant fields (Maxwell Terms) in MRI. It enables high-performance computations on both CPU and GPU by natively supporting NumPy arrays, PyTorch tensors, and CuPy arrays. The library uses an intelligent dispatching mechanism to adapt array operations to your inputs seamlessly.

Theoretical Modeling

The phase accumulation $\Phi_c$ caused by concomitant fields is modeled by integrating the magnetic field variation $\Delta B_c$ over time. Following the standard framework established by Bernstein et al. (1998), for a system with primary linear gradients, the concomitant field $B_c$ is approximated by second-order spatial terms: