Arterial spin labeling using spatio-temporal encoding readout for robust perfusion imaging in inhomogenous magnetic...

Area of Science:

• Magnetic Resonance Imaging
• Neuroimaging
• Biomedical Engineering

Background:

• Pseudo-continuous arterial spin labeling (pCASL) is a key technique for non-invasive brain perfusion measurement.
• Susceptibility artifacts from metallic implants, like aneurysm clips, pose a significant challenge in MRI.
• Spatio-temporal encoding (SPEN) is an advanced MRI technique with potential for artifact reduction.

Purpose of the Study:

• To assess the feasibility of using SPEN for pCASL brain imaging.
• To evaluate the robustness of SPEN-based pCASL against susceptibility artifacts caused by aneurysm clips.

Main Methods:

• A 2D hybrid SPEN sequence with super-resolution reconstruction was implemented on a 1.5T MRI system.
• The impact of varying the SPEN encoding parameter (Q) on artifact reduction was investigated in phantoms and in vivo.
• SPEN performance was compared against gradient-echo EPI (GE-EPI) and spin-echo EPI (SE-EPI) regarding artifact levels and temporal signal-to-noise ratio (tSNR).

Main Results:

• SPEN demonstrated reduced aneurysm clip-induced artifacts compared to GE-EPI and SE-EPI, especially at higher Q values (Q > 75).
• SPEN achieved higher tSNR at a repetition time (TR) of 4000 ms compared to 2100 ms, unlike SE-EPI.
• tSNR in SPEN remained stable when the interval between excitation and labeling exceeded approximately 1000 ms.

Conclusions:

• SPEN is a feasible readout for pCASL, providing enhanced robustness to field inhomogeneities and artifacts from aneurysm clips.
• Higher Q values in SPEN improve artifact resistance but can reduce labeling efficiency at shorter TRs due to blood saturation.
• Further development is needed to adapt SPEN for 3D brain imaging applications.