Placidi G. MRI: Essentials for Innovative Technologies

Boca Raton, FL, CRC Press, 2012. — 194 p. — ISBN: 9781439840627, 1439840628.MRI: Essentials for Innovative Technologies describes novel methods to improve magnetic resonance imaging (MRI) beyond its current limitations. It proposes smart encoding methods and acquisition sequences to deal with frequency displacement due to residual static magnetic field inhomogeneity, motion, and undersampling. Requiring few or no hardware modifications, these speculative methods offer building blocks that can be combined and refined to overcome barriers to more advanced MRI applications, such as real-time imaging and open systems.After a concise review of basic mathematical tools and the physics of MRI, the book describes the severe artifacts produced by conventional MRI techniques. It first tackles magnetic field inhomogeneities, outlining conventional solutions as well as a completely different approach based on time-varying gradients and temporal frequency variation coding (acceleration). The book then proposes two innovative acquisition methods for reducing acquisition time, motion, and undersampling artifacts: adaptive acquisition and compressed sensing. The concluding chapter lays out the author’s predictions for the future of MRI.For some of the proposed solutions, this is the first time the reported results have been published. Where experimental data is preliminary or unavailable, the book presents only numerical solutions. Offering insight into emerging MRI techniques, this book provides readers with specialized knowledge to help them design better acquisition sequences and select appropriate correction methods.Basic Concepts
Mathematical Tools
Frequency Encoding and Fourier Transform
FT Properties
Sampling, Interpolation, and Aliasing
Instruments for Image AnalysisMRI: Conventional Imaging Techniques and Instruments
Magnetic Resonance Phenomenon
References Frames
Excitation and Resonance
Relaxation of Magnetization
Longitudinal Relaxation
Transverse Relaxation
Signal Detection
Imaging Gradients
Frequency Encoding
Phase Encoding
Slice Selection
Conventional Imaging Techniques
Spin Warp Imaging
Imaging from Projections
Bandwidth, Sampling, Resolution, and Sensitivity
An MRI Scanner
Bloch Equations and Numerical MRI SimulatorsLimitations of Conventional MRILimiting Artifacts for Advanced Applications
Magnetic Field Inhomogeneity
Motion
UndersamplingAdvanced SolutionsMethods for Magnetic Field Inhomogeneity ReductionConventionalMethods
FieldMapping
Field Gradients Modulation
Some Remarks
An Unconventional Solution
Spatial Encoding by Nonconstant Gradients
Numerical Simulations
Noise ToleranceMethods to Handle UndersamplingSparseMethods without Restoration
SparseMethods with Restoration
Sample Adaptive Acquisition/Restoration Methods
Entropy-Based Adaptive Acquisition Method
Adaptive Acquisition Results
An Adaptive Acquisition Improvement
Sample Independent Acquisition/Restoration Methods
Compressed Sensing
Compressed Sensing Results
Some Remarks on Compressed Sensing in MRI
Compressed Sensing on Adaptively Collected DataThe Future
Conclusions and perspectives
Some Hypothesis