Optimization of pseudo-continuous arterial spin labeling for renal perfusion imaging

Area of Science:

• Medical Imaging
• Biophysics
• Nephrology

Background:

• Pseudo-continuous arterial spin labeling (PCASL) is a non-invasive MRI technique for measuring blood flow.
• Optimizing PCASL parameters is crucial for accurate renal perfusion assessment, especially in patients with chronic kidney disease (CKD).
• Understanding the impact of gradient parameters on labeling efficiency and robustness is key to improving PCASL performance.

Purpose of the Study:

• To evaluate the labeling efficiency of PCASL.
• To determine gradient parameters that enhance PCASL robustness for renal perfusion measurements.
• To assess renal blood flow (RBF) in healthy controls and CKD patients using an optimized PCASL method.

Main Methods:

• Characterized aortic blood flow in young healthy volunteers, CKD patients, and healthy controls.
• Performed numeric simulations to evaluate PCASL inversion efficiency across various gradient parameters, considering pulsatile flow and off-resonance effects.
• Assessed PCASL implementation in vivo and measured RBF in CKD patients and healthy controls.

Main Results:

• Aortic blood velocities varied significantly between age groups and patient cohorts.
• Reduced gradient average (G_ave) and selective to average gradient ratio (G_max/G_ave) maximized labeling efficiency and improved PCASL robustness.
• Significant differences in RBF were observed between CKD patients and healthy controls.

Conclusions:

• An optimal PCASL scheme for renal applications requires a G_max/G_ave ratio of 6-7.
• The G_ave value should be adjusted based on aortic blood flow velocities (e.g., 0.5 mT/m for CKD patients and controls).
• This optimized PCASL approach enables robust renal perfusion measurements and reveals differences in RBF between patient groups.