The curse of physiological variability

Cerebral perfusion is affected by numerous metabolic and non-metabolic factors, termed modifiers, such as age, sex, lifestyle, physical exercise, caffeine, alcohol and medication. (Clement, et al (2017)) Each factor influences global and regional cerebral perfusion in its unique way, often interacting with each other. This large variability especially complicates the use of absolute perfusion maps and the application of the technique in personalized medicine. Thus, it might be crucial to take the impact of those modifiers into account when performing ASL-imaging, for clinical or research purposes, using relative or absolute quantification, in group, individual and longitudinal analysis. For more information about the impact of each modifier, the recommended modifiers to take into account, and the methodology, we would like to refer to (Clement et al (2017)).

Fig. Effects of modifiers on global brain perfusion summarized as a color gradient: factors in the green area induce no effect, the blue and red areas represent global decrease and increase respectively. All factors are classified both according to their effect and the corresponding magnitude on global perfusion changes.

Clement P, Mutsaerts H, Vaclavu L, Ghariq E, Pizzini F, Smits M et al. Variability of physiological brain perfusion in healthy subjects – a systematic review of modifiers. Considerations for multi-center ASL studies. Journal of Cerebral Blood Flow and Metabolism 2017; In Press