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Time-of-flight techniques. Pulse sequences and clinical protocols
1Department of Radiology, University of California at San Francisco, USA.
Magnetic Resonance Imaging Clinics of North America
|December 1, 1993
Summary
Time-of-flight angiography uses blood flow to create images. Optimizing pulse rates and flip angles is key for clear contrast by saturating background tissue without affecting blood signal.
Area of Science:
- Medical Imaging
- Radiology
- Biophysics
Background:
- Time-of-flight (TOF) is a common magnetic resonance angiography (MRA) technique.
- TOF MRA relies on the principle of fresh, non-magnetized blood flowing into the imaging slice.
- Contrast depends on suppressing background magnetization while preserving the signal from flowing blood.
Purpose of the Study:
- To explain the fundamental principles of time-of-flight angiography.
- To highlight the critical parameters for achieving optimal angiographic contrast.
Main Methods:
- Discussion of radiofrequency pulse sequences used in TOF angiography.
- Explanation of magnetization saturation effects on background tissue and blood.
Main Results:
- Effective angiographic contrast requires careful selection of pulse repetition times (TR) and flip angles.
- Parameters must be optimized to saturate stationary tissue magnetization without saturating inflowing blood.
Conclusions:
- Achieving high-quality TOF angiograms depends on precise control over pulse parameters.
- Understanding these principles is crucial for accurate vascular imaging.