Chemical exchange rotation transfer (CERT) on human brain at 3 Tesla

Area of Science:

• Magnetic Resonance Imaging
• Biophysics
• Biomedical Engineering

Background:

• Conventional chemical exchange saturation transfer (CEST) imaging faces challenges in isolating specific signal sources.
• Distinguishing between amide proton transfer (APT) and relayed nuclear Overhauser enhancement (rNOE) from background signals like direct water saturation and semisolid magnetization transfer (MT) has been difficult.

Purpose of the Study:

• To evaluate a novel pulse sequence for in vivo 3 Tesla MRI to differentiate APT and rNOE signals.
• To assess the efficacy of a new metric, MTRdouble, in isolating these specific contributions.

Main Methods:

• Quantified APT and rNOE signals using the chemical exchange rotation transfer (CERT) metric, MTRdouble.
• Compared MTRdouble with conventional CEST analyses, including asymmetry (MTRasym) and extrapolated magnetization transfer (EMR).
• Applied various duty cycles and average irradiation powers to test the MTRdouble metric.

Main Results:

• MTRdouble demonstrated higher specificity and speed compared to MTRasym and EMR, requiring only 3 data points.
• Successfully quantified APT (1.5 ± 0.5%) and rNOE (2.1 ± 0.7%) in white matter using MTRdouble.
• MTRdouble showed robustness to B0 inhomogeneity, enhancing its speed advantage over other CEST metrics.

Conclusions:

• MTRdouble serves as a viable alternative metric for evaluating APT and rNOE.
• The MTRdouble metric is characterized by its speed, robustness to B0 inhomogeneity, and ease of processing.
• This method offers improved signal source isolation in CEST imaging.