MRI of Short- and Ultrashort-T2 Tissues

This book comprehensively covers ultrashort echo time (UTE), zero echo time (ZTE), and other magnetic resonance imaging (MRI) acquisition techniques for imaging of short and ultrashort-T2 tissues. MRI uses a large magnet and radio waves to generate images of tissues in the body. The MRI signal is characterized by two time constants, spin-lattice relaxation time (T1) which describes how fast the longitudinal magnetization recovers to its initial value after tipping to the transverse plane, and spin-spin relaxation time (T2) which describes how fast the transverse magnetization decays. Conventional MRI techniques have been developed to image and quantify tissues with relatively long T2s. However, the body also contains many tissues and tissue components such as cortical bone, menisci, ligaments, tendons, the osteochondral junction, calcified tissues, lung parenchyma, iron containing tissues, and myelin, which have short or ultrashort-T2s. These tissues are "e;invisible"e; with conventional MRI, and their MR and tissue properties are not measurable. UTE and ZTE type sequences resolve these challenges and make these tissues visible and quantifiable.This book first introduces the basic physics of conventional MRI as well as UTE and ZTE type MRI, including radiofrequency excitation, data acquisition, and image reconstruction. A series of contrast mechanisms are then introduced and these provide high resolution, high contrast imaging of short and ultrashort-T2 tissues. A series of quantitative UTE imaging techniques are described for measurement of MR tissue properties (proton density, T1, T2, T2*, T1p,magnetization transfer, susceptibility, perfusion and diffusion). Finally, clinical applications in the musculoskeletal, neurological, pulmonary and cardiovascular systems are described.This is an ideal guide for physicists and radiologists interested in learning more about the use of UTE and ZTE type techniques for MRI of short and ultrashort-T2 tissues.

This book comprehensively covers ultrashort echo time (UTE), zero echo time (ZTE), and other magnetic resonance imaging (MRI) acquisition techniques for imaging of short and ultrashort-T2 tissues. MRI uses a large magnet and radio waves to generate images of tissues in the body. The MRI signal is characterized by two time constants, spin-lattice relaxation time (T1) which describes how fast the longitudinal magnetization recovers to its initial value after tipping to the transverse plane, and spin-spin relaxation time (T2) which describes how fast the transverse magnetization decays. Conventional MRI techniques have been developed to image and quantify tissues with relatively long T2s. However, the body also contains many tissues and tissue components such as cortical bone, menisci, ligaments, tendons, the osteochondral junction, calcified tissues, lung parenchyma, iron containing tissues, and myelin, which have short or ultrashort-T2s. These tissues are “invisible” with conventional MRI, and their MR and tissue properties are not measurable. UTE and ZTE type sequences resolve these challenges and make these tissues visible and quantifiable.

This book first introduces the basic physics of conventional MRI as well as UTE and ZTE type MRI, including radiofrequency excitation, data acquisition, and image reconstruction. A series of contrast mechanisms are then introduced and these provide high resolution, high contrast imaging of short and ultrashort-T2 tissues. A series of quantitative UTE imaging techniques are described for measurement of MR tissue properties (proton density, T1, T2, T2*, T1p,magnetization transfer, susceptibility, perfusion and diffusion). Finally, clinical applications in the musculoskeletal, neurological, pulmonary and cardiovascular systems are described.

This is an ideal guide for physicists and radiologists interested in learning more about the use of UTE and ZTE type techniques for MRI of short and ultrashort-T2 tissues.

Part I: UTE MRI - Data Acquisition.- Basic Principles of MRI.- An Introduction to UTE MRI.- 2D UTE MRI.- 3D UTE MRI.- ZTE MRI.- PETRA MRI.- SWIFT MRI.- WASPI MRI.- Hybrid 3D UTE (Stack of STAR, AWSOS).- Cartesian Variable TE MRI.- Part II: UTE MRI - Contrast Mechanisms.- UTE with Echo Subtraction.- UTE with on/off Resonance Saturation.- UTE with Adiabatic Inversion (Single IR, Dual IR, Double IR, IR Fat Sat, DESIRE, STAIR).- UTE with Water Excitation.- UTE Fat/Water Imaging (UTE IDEAL, UTE Single Point Imaging).- UTE Spectroscopic Imaging.- Pulse Sequence as Tissue Property Filters.- Clinical Use of MASTIR Pulse Sequences.- Part III: UTE MRI – Quantification.- UTE T1 Quantification.- UTE T2* Quantification.- UTE Looping Star T2* Quantification.- UTE T1Quantification.- UTE Proton Density Quantification.- UTE Magnetization Transfer Imaging.- UTE Quantitative Susceptibility Mapping.- UTE Perfusion.- UTE Diffusion.- UTE with deep learning for fully automated segmentation and quantitativemapping.- Part IV: UTE MRI – Applications.- UTE T2* in Osteoarthritis.- UTE MRI Biomarker Panel in Osteoarthritis.- UTE Porosity Index and Suppression Ratio in Osteoporosis.- UTE Bound Water and Pore Water in Osteoporosis.- UTE MRI Biomarker Panel in Osteoporosis.- UTE MRI in the Spine.- UTE MRI in Tendinopathy.- UTE MRI in Psoriatic Arthropathy.- UTE MRI in Hemophilia Arthropathy.- UTE MRI in Temporomandibular Disorders.- UTE MRI in Multiple Sclerosis.- UTE MRI in Traumatic Brain Injury.- UTE MRI in the Lung.- UTE MRI in the Liver.- UTE MRI in cerebral aneurysm and coil embolization.- UTE MRI in Vascular Calcification.- UTE MRI in Cryotherapy.- UTE MRI of iron nanoparticles.- UTE in PET/MRI.- UTE MRI in “CT-like” bone imaging.- Challenges and future directions in UTE imaging.