TY  - JOUR
AU  - Franke, Vanessa
AU  - Breitling, Johannes
AU  - Boyd, Philip
AU  - Feignier, Antoine
AU  - Bangert, Renate
AU  - Weckesser, Nina
AU  - Schlemmer, Heinz-Peter
AU  - Ladd, Mark
AU  - Bachert, Peter
AU  - Paech, Daniel
AU  - Korzowski, Andreas
TI  - A versatile look-up algorithm for mapping pH values and magnesium ion content using 31 P MRSI.
JO  - NMR in biomedicine
VL  - 37
IS  - 6
SN  - 0952-3480
CY  - New York, NY
PB  - Wiley
M1  - DKFZ-2024-00283
SP  - e5113
PY  - 2024
N1  - 2024 Jun;37(6):e5113 / #EA:E020#LA:E020#
AB  - 31 P MRSI allows for the non-invasive mapping of pH and magnesium ion content (Mg) in vivo, by translating the chemical shifts of inorganic phosphate and adenosine-5'-triphosphate (ATP) to pH and Mg via suitable calibration equations, such as the modified Henderson-Hasselbalch equation. However, the required constants in these calibration equations are typically only determined for physiological conditions, posing a particular challenge for their application to diseased tissue, where the biochemical conditions might change manyfold. In this article, we propose a multi-parametric look-up algorithm aiming at the condition-independent determination of pH and Mg by employing multiple quantifiable 31 P spectral properties simultaneously. To generate entries for an initial look-up table, measurements from 114 model solutions prepared with varying chemical properties were made at 9.4 T. The number of look-up table entries was increased by inter- and extrapolation using a multi-dimensional function developed based on the Hill equation. The assignment of biochemical parameters, that is, pH and Mg, is realized using probability distributions incorporating specific measurement uncertainties on the quantified spectral parameters, allowing for an estimation of most plausible output values. As proof of concept, we applied a version of the look-up algorithm employing only the chemical shifts of γ- and β-ATP for the determination of pH and Mg to in vivo 3D 31 P MRSI data acquired at 7 T from (i) the lower leg muscles of healthy volunteers and (ii) the brains of patients with glioblastoma. The resulting volumetric maps showed plausible values for pH and Mg, partly revealing differences from maps generated using the conventional calibration equations.
KW  - 31P MRS (Other)
KW  - 31P MRSI (Other)
KW  - magnesium (Other)
KW  - magnesium ion concentration (Other)
KW  - pH (Other)
KW  - pH imaging (Other)
LB  - PUB:(DE-HGF)16
C6  - pmid:38316107
DO  - DOI:10.1002/nbm.5113
UR  - https://inrepo02.dkfz.de/record/287629
ER  -