Book contents
- Frontmatter
- Contents
- Acknowledgements
- 1 MR: What's the attraction?
- Part A The basic stuff
- Part B The specialist stuff
- 11 Ghosts in the machine: quality control
- 12 Acronyms anonymous: a guide to the pulse sequence jungle
- 13 Go with the flow: MR angiography
- 14 A heart to heart discussion: cardiac MRI
- 15 It's not just squiggles: in vivo spectroscopy
- 16 To BOLDly go: new frontiers
- 17 The parallel universe: parallel imaging and novel acquisition techniques
- Appendix: maths revision
- Index
- Plate section
13 - Go with the flow: MR angiography
Published online by Cambridge University Press: 08 October 2009
- Frontmatter
- Contents
- Acknowledgements
- 1 MR: What's the attraction?
- Part A The basic stuff
- Part B The specialist stuff
- 11 Ghosts in the machine: quality control
- 12 Acronyms anonymous: a guide to the pulse sequence jungle
- 13 Go with the flow: MR angiography
- 14 A heart to heart discussion: cardiac MRI
- 15 It's not just squiggles: in vivo spectroscopy
- 16 To BOLDly go: new frontiers
- 17 The parallel universe: parallel imaging and novel acquisition techniques
- Appendix: maths revision
- Index
- Plate section
Summary
Introduction
Magnetic resonance angiography (MRA) uses the inherent motion sensitivity of MRI to visualize blood flow within vessels. There are two major classes of flow imaging methods that rely on the endogenous contrast of moving spins to produce angiographic images. The time-of-flight (TOF) technique relies on flow-dependent changes in longitudinal magnetization, whilst the phase-contrast (PC) technique relies on flow-dependent changes in transverse magnetization. In addition there are contrast-enhanced MRA techniques that employ exogenous contrast agents, such as gadolinium chelates, to provide vascular contrast. In this situation the intravascular signal is more dependent upon the T1 shortening properties of gadolinium than the TOF effect. Each method has particular advantages and disadvantages for angiographic imaging which are reflected in their applications.
Before we describe how MRA sequences work, we will look at the appearances of flowing blood in conventional spin-echo and gradient-echo scans. You should read (or review) section 6.4, as a foundation for the material in this chapter. This chapter will explain:
that flowing blood creates an in-flow or TOF effect in standard imaging, as well as velocity-induced phase artefacts, and how these can be avoided when angio imaging is not required;
how TOF MRA techniques take advantage of the inflow effect in blood vessels, and show how it is used in 2D and 3D techniques for carotids, Circle of Willis, and peripheral vessels;[…]
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- Information
- MRI from Picture to Proton , pp. 258 - 281Publisher: Cambridge University PressPrint publication year: 2006
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