Quantification issues in arterial spin labeling perfusion magnetic resonance imaging.

Area of Science:

• Medical Imaging
• Neuroscience
• Biophysics

Background:

• Arterial spin labeling (ASL) is increasingly used for noninvasive perfusion quantification in clinical and neuroscience research.
• Its ability to measure absolute perfusion makes it valuable for various applications.

Purpose of the Study:

• To review factors affecting the accuracy and reliability of ASL perfusion measurements.
• To propose solutions for enhancing ASL accuracy in clinical practice.

Main Methods:

• Theoretical analysis of ASL perfusion quantification.
• Discussion of parameters influencing ASL measurements, including tagging efficiency, blood magnetization, T1, arterial transit time, and T2.
• Review of in vivo calibration and estimation techniques.

Main Results:

• Flow quantification is highly sensitive to tagging efficiency and blood equilibrium magnetization (M(0b)).
• Blood T1 variations significantly impact quantification more than tissue T1.
• Arterial transit time is critical when exceeding postlabeling delay.

Conclusions:

• Optimizing ASL accuracy requires careful consideration of key parameters and potential confounding factors.
• In vivo calibration methods and specific imaging protocols can improve ASL reliability.
• Understanding limitations, such as venous outflow effects, is crucial for accurate clinical interpretation.