Inter-Slice Blood Flow and Magnetization Transfer Effects as A New Simultaneous Imaging Strategy

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Neuroimaging
• Biomedical Engineering

Background:

• Conventional blood flow and magnetization transfer (MT) imaging methods have limitations, often requiring separate preparation radiofrequency (RF) pulses.
• The development of integrated techniques is crucial for improving imaging efficiency and diagnostic capabilities.

Purpose of the Study:

• To investigate the signal characteristics of the Alternate Ascending/Descending Directional Navigation (ALADDIN) technique for simultaneous blood flow and MT imaging.
• To compare ALADDIN's performance against pseudo-continuous arterial spin labeling (pCASL) and conventional MT asymmetry (MTA) methods.

Main Methods:

• Utilized Bloch-equation simulations and experimental data to analyze ALADDIN signal behavior.
• Compared ALADDIN with pCASL and conventional MTA using balanced steady-state free precession (bSSFP) readout.
• Emulated ALADDIN's labeling planes using pCASL and MTA under identical scan conditions.

Main Results:

• ALADDIN perfusion signals demonstrated a positive correlation with flip angle, while MTA signals peaked between 45°-60°.
• ALADDIN signals were comparable to pCASL and conventional MTA, suggesting a superposition of signals from multiple labeling planes.
• Quantitative cerebral blood flow (CBF) from a modified continuous ASL model overestimated perfusion compared to pulsed ASL.

Conclusions:

• ALADDIN enables simultaneous mapping of blood flow, MT asymmetry, and MT ratio within a clinically feasible timeframe.
• The technique overcomes limitations of conventional methods by integrating blood flow and MT contrast without separate RF pulses.
• ALADDIN holds potential for aiding in the diagnosis of various neurological diseases through efficient whole-brain imaging.