3.6.1 Historical Perspective Since the early days of X-ray computerized tomography (CT) in the late 1970s, it has been possible to visualize the spinal cord in cross-section in vivo, and to make quantitative measurements of the cord diameter. Early studies…
3.5.1 Overview T 2 -weighted imaging plays a key role in clinical MR imaging of spinal cord. While T 2 weighting is highly sensitive, it is notoriously unspecific as very different pathological conditions can lead to similar increases in water…
Magnetization transfer (MT), first demonstrated in vivo by Wolff and Balaban, is a contrast mechanism based on the exchange of magnetization occurring between groups of spins characterized by different molecular environments. MT produces a source of contrast alternative to T…
3.3.1 Introduction: Diffusion Imaging and Tissue Microstructure Diffusion imaging and particularly diffusion tensor imaging (DTI) have become standard tools for assessment of white matter in the brain. Although somewhat more technically challenging to implement in the spinal cord, these methods…
In Chapter 3.1 , the diffusion of water molecules was described according to the diffusion tensor model, which assumes a Gaussian probability of displacement associated to the diffusion of water molecules. This assumption is true in free systems, but it…
3.1.1 Principles of Diffusion-Weighted Magnetic Resonance Imaging 3.1.1.1 Basic Concept of Diffusion Weighting Water molecules in tissue undergo Brownian motion, which means that molecules are not perfectly static over time but experience random microscopic displacements due to thermal agitation. This…
2.4.1 Background 2.4.1.1 Importance of High Field In the early 1980s, magnetic resonance imaging (MRI) was introduced into clinical practice and has subsequently undergone technical advancements that have resulted in improvements in image quality. For nearly 20 years, 1.5 T…
2.3.1 Introduction: Sources of Susceptibility Artifacts The uniformity of the B 0 main field in magnetic resonance imaging (MRI) is critical for artifact-free image formation. MRI scanners are manufactured with a stringent requirement of less than one part-per-million (ppm) a…
Acknowledgments The author is very grateful to Susann Boretius, Martin Busch, Yasar Goedecke, Martin Koch, Joost Kuijer, Marco Lawrenz, and Petra Pouwels for helpful discussions and to Joachim Graessner (Siemens Healthcare) and Jürgen Bunke (Philips Healthcare) for providing information about…
2.1.1 Introduction Essential parts of a magnetic resonance imaging (MRI) system, radiofrequency (RF) coils or antennas are used to transmit and/or receive signal. Phased-array coils combine multiple small coil elements to transmit or receive signal using independent channels. Array coils…