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Abstract #2924

Homocarnosine Spectral Editing in the Human Brain: Repeatable Brain pH Measurements at 3T with 1H-MRS

Ryan R Armbruster1, Neil E Wilson2, Mark A Elliott2, Sophia Swago2, Walter Witschey2, and Ravinder Reddy2
1University of Pennsylvania, Philadelphia, PA, United States, 2Center for Advanced Metabolic Imaging in Precision Medicine, University of Pennsylvania, Philadelphia, PA, United States

Synopsis

Keywords: Spectroscopy, biomarkers

Motivation: pH variations in brain indicate disease and pathology. 1H-MRS is a sensitive technique to measure pH if homocarnosine can be easily isolated.

Goal(s): Detect homocarnosine in the human brain and measure repeatability in estimating pH.

Approach: Use optimal TE to isolate homocarnosine and measure its chemical shift. Henderson-Hasselbalch equation converts ppm to pH. Repeatability determined by intra- and inter-day coefficient of variation.

Results: NAA and baseline signals are nulled using an optimal TE with water suppression. pH values ranged 6.96–7.04 with intra- and inter-day CV% ranging 0–0.004%. The mean and standard deviation of the intra-day ppm difference was 0.01±0.01ppm.

Impact: We employ a long TE method that leverages the signal differences between homocarnosine and downfield NAA based on their T2 decay and NAA’s J-evolution which enables us to repeatably measure homocarnosine and approximate pH.

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Keywords