Bolus-tracking arterial spin labelling: theoretical and experimental results

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Arterial spin labelling (ASL) is a magnetic resonance imaging (MRI) technique for quantitative cerebral perfusion assessment.
• Existing theoretical models for quantitative ASL face challenges, necessitating new approaches.

Purpose of the Study:

• To develop a novel quantitative ASL method utilizing a macroscopic model.
• To reduce the number of variables needed to describe physiological processes in ASL.

Main Methods:

• Derived a novel Fokker-Planck equation from a general Langevin equation with stochastically varying macroscopic variables.
• Acquired rat brain ASL data using a bolus-tracking protocol with varying bolus durations (1.5s, 2.0s, 3.0s).
• Fitted the Fokker-Planck equation solution to experimental data using a least-squares fit to calculate mean transit time (MTT), capillary transit time (CTT), and arterial transit time (ATT).

Main Results:

• Successfully developed and validated a new ASL protocol combining a theoretical model with experimental data.
• Calculated average MTT, CTT, and ATT values of 1.75 ± 0.22 s, 1.43 ± 0.12 s, and 0.32 ± 0.04 s, respectively.
• The new method provides solutions for varying bolus volumes and demonstrates generality by deriving solutions for continuous and pulsed ASL (CASL and PASL).

Conclusions:

• A novel quantitative ASL protocol has been successfully developed and validated.
• The technique offers solutions for varying bolus volumes and extends to CASL and PASL.
• This advancement improves quantitative assessment of cerebral perfusion using MRI.