Chapter
Precession and precessional (Larmor) frequency
The results of resonance – classical theory
The results of resonance – quantum theory
The free induction decay (FID) signal
2 Image weighting and contrast
Relaxation in different tissues
Other contrast mechanisms
Diffusion-weighted imaging (DWI)
Magnetization transfer contrast
Susceptibility weighting (SWI)
3 Spin-echo pulse sequences
Spin-echo using two echoes
Fast or turbo spin-echo (FSE/TSE)
Single-shot turbo spin-echo (SS-TSE)
Short tau inversion recovery (STIR)
Fluid attenuated inversion recovery (FLAIR)
4 Gradient-echo pulse sequences
Weighting in gradient-echo pulse sequences
Weighting mechanism 1 – extrinsic contrast parameters
Weighting mechanism 2 – the steady state
Weighting mechanism 3 – residual transverse magnetization
Coherent or rewound gradient-echo
Incoherent or spoiled gradient-echo
Reverse-echo gradient-echo
When does slice-selection occur?
Slice thickness and slice-selection
When does frequency encoding occur?
FOV and frequency encoding
When does phase encoding occur?
Phase matrix, phase resolution, and phase encoding
Bringing it all together – pulse sequence timing
Part 2: How are data acquired and how are images created from these data?
Sampling window (sampling time)
Fast Fourier transform (FFT)
Part 3: Some important facts about k-space!
Fact 1: k-Space is not the image
Fact 2: Data are symmetrical in k-space
Fact 3: Data acquired in the central lines contribute signal and contrast, while data acquired in the outer lines contribute resolution
Fact 4: The scan time is the time to fill k-space
Fact 5: The incremental step between each data point in k-space determines the FOV
Fact 6: The dimensions of k-space determine pixel size
Part 4: How do pulse sequences fill k-space?
Part 5: Options that fill k-space
Partial, fractional averaging, or half Fourier
Propeller or radial k-space filling
Sequential and 3D (volume) acquisition
Signal-to-noise ratio (SNR)
Number of signal averages (NSA or NEX)
Contrast-to-noise ratio (CNR)
Protocol development and modification
Out-of-phase signal cancellation
Magnetic susceptibility artifact
Cross-excitation/cross-talk
Entry-slice phenomenon (ESP)
Time-of-flight (TOF) phenomenon
Flow-dependent (non-contrast-enhanced) angiography
2D sequential inflow angiograms
3D volumetric inflow angiograms
ECG-triggered 3D FSE (flow-spoiled fresh blood imaging)
Superconducting electromagnets
Field strength (flux density)
Gradient offset (dynamic) shimming
Gradient power duty cycle
Computer system and graphical user interface
Introduction (and disclaimer)
Definitions used in MRI safety
The spatially varying static field
Transient biological effects
Torque on implanted devices
Foreign bodies in the static field
Electromagnetic (radiofrequency) fields
Induced currents in implanted devices
Time-varying gradient magnetic fields
Effect of time-varying gradients on implanted devices
MRI in Practice
Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.
