There seem to be a variety of ASL techniques out there. Which one provides the best sensitivity for functional neuroimaging studies?
ASL contains a class of techniques and can be generally divided into two categories: continues and pulsed ASL. Continuous ASL, which utilizes long RF pulses for labeling, provides improved perfusion contrast at the cost of imaging time and a high level of RF power deposition. Pulsed ASL, which utilizes a nearly instant RF pulses for labeling, is easier to implement. Although the perfusion signal is smaller in pulsed ASL methods, more sample points can be acquired in the same amount of time in pulsed than in continuous ASL methods. As a consequence, these two types of ASL techniques provide comparable sensitivity and statistical power for functional activation studies. Pulsed ASL methods also contain a variety of subtypes, such as FAIR, PICORE and QUIPSS. The perfusion contrast in these techniques are fairly similar although subtle differences do exist. Keep in mind that the temporal stability of the MRI scanner plays an important role in determining the sensitivity of ASL methods.
