Implementation of bidirectional crusher gradient method for measuring labelling efficiency of pseudocontinuous arterial spin labeling MRI in mice

The pseudocontinuous arterial spin labeling (pCASL) MRI technique provides a powerful tool for in vivo evaluation of microvascular functions, including cerebral blood flow, blood-brain barrier permeability, and blood-cerebrospinal fluid exchange. These microvascular parameters have emerged as promising biomarkers for tracking pathological progression and therapeutic efficacy in both preclinical and clinical settings. Accurate quantification of pCASL signals requires consideration of labeling efficiency, a critical parameter that can vary substantially in mice due to their small vessel size and intersubject vascular heterogeneity. Determination of labeling efficiency on an individual basis is therefore desirable. Recently, the bidirectional crusher gradient (BIC) method was proposed to measure labeling efficiency in mouse pCASL MRI. The present study aims to outline step-by-step procedures for implementing the BIC method and associated validation studies. (1) Measurement of mouse pCASL MRI labeling efficiency in approximately 3 min (2) Improved accuracy in pCASL-based cerebral perfusion imaging of mice.