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Magnetic resonance: perfusion and diffusion imaging
1NMR Unit, Royal Postgraduate Medical School, London, England.
Abstract:
The use of magnetic resonance imaging to detect normal and pathological problems of perfusion and diffusion is reviewed. Motion sensitised spin-echo images can be used to detect changes in slow flow velocity within a voxel (intravoxel coherent motion (IVCM)) as well as intravoxel incoherent motion (IVIM) effects attributable to both diffusion and perfusion. Changes have been identified in a variety of brain diseases in the absence of changes in conventional images but the techniques are very vulnerable to motion artefact of all types. More rapid and more sensitive approaches using steady state free precision and echo-planer imaging are being investigated. Anisotropic diffusion imaging enables white matter tracts to be demonstrated within the brain and spinal cord as a function of their direction because diffusion of water across axons is much more restricted than it is along them. This technique provides a unique method for localisation of lesions and displays obvious changes in disease in which diffusion becomes less restricted.
Insights
Magnetic resonance imaging techniques detect brain perfusion and diffusion changes. Advanced methods like anisotropic diffusion imaging reveal white matter tracts and lesions in various brain diseases.
Area of Science:
- Radiology
- Neuroimaging
- Medical Physics
Background:
- Magnetic resonance imaging (MRI) is crucial for assessing brain perfusion and diffusion.
- Conventional MRI sequences may not detect subtle changes in these processes.
- Understanding water molecule movement is key to diagnosing neurological conditions.
Purpose of the Study:
- To review MRI techniques for detecting normal and pathological perfusion and diffusion in the brain.
- To highlight the capabilities and limitations of intravoxel incoherent motion (IVIM) and anisotropic diffusion imaging.
- To discuss emerging MRI approaches for improved sensitivity and reduced motion artifacts.
Main Methods:
- Review of motion-sensitized spin-echo imaging for intravoxel coherent motion (IVCM) and IVIM.
- Discussion of steady-state free precession and echo-planar imaging for rapid and sensitive assessments.
- Explanation of anisotropic diffusion imaging for mapping white matter tract integrity.
Main Results:
- IVIM and IVCM techniques can identify changes in brain diseases not visible on conventional MRI.
- These techniques are highly susceptible to motion artifacts, impacting diagnostic accuracy.
- Anisotropic diffusion imaging effectively demonstrates white matter tracts and their directional properties.
- Diffusion changes are evident in diseases where water diffusion becomes less restricted.
Conclusions:
- MRI techniques offer valuable insights into brain perfusion and diffusion dynamics.
- Advanced methods like anisotropic diffusion imaging provide unique capabilities for lesion localization and characterization.
- Further development of rapid and motion-robust MRI sequences is essential for clinical translation.