title: Simultaneous in vivo pH and temperature mapping using a PARACEST-MRI contrast agent.
abstract: Altered tissue temperature and/or pH is a common feature in pathological conditions, where metabolic demand exceeds oxygen supply such as in tumors and following stroke. Therefore, in vivo tissue temperature and pH may become valuable biomarkers for disease detection and the monitoring of disease progression or treatment response in conditions with altered metabolic demand. In this study, pH is measured using the amide protons of a thulium (Tm(3+)) complex with a DOTAM-Glycine-Lysine (ligand: Tm(3+)-DOTAM-Gly-Lys). The pH was uniquely determined from the linewidth of the asymmetry curve of the chemical exchange saturation transfer spectrum, independent of contrast agent concentration, or temperature for a given saturation pulse. pH maps with an inter-pixel standard deviation of less than 0.1 pH units were obtained in 10 mM Tm(3+)-DOTAM-Gly-Lys solutions with pH ranging from 6.0 to 8.0 pH units at 37°C. Temperature maps were simultaneously obtained using the chemical shift of the chemical exchange saturation transfer peak. Temperature and pH maps are demonstrated in the mouse leg (N = 3), where the mean and standard deviation for pH was 7.2 ± 0.2 pH unit and temperature was 37.4 ± 0.5°C.
authors.affiliation: Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.
authors.forename: Nevin
authors.initials: N
authors.lastname: McVicar
authors.forename: Alex X
authors.initials: AX
authors.lastname: Li
authors.forename: Mojmír
authors.initials: M
authors.lastname: Suchý
authors.forename: Robert H E
authors.initials: RH
authors.lastname: Hudson
authors.forename: Ravi S
authors.initials: RS
authors.lastname: Menon
authors.forename: Robert
authors.initials: R
authors.lastname: Bartha
mesh_terms: D000081:Acetamides / Q000737:chemistry*; D000465:Algorithms; D000818:Animals; D003287:Contrast Media / Q000737:chemistry; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry*; D006614:Hindlimb / Q000737:chemistry* / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013817:Thermography / Q000379:methods*
chemical_list: C522450:1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane; D000081:Acetamides; D003287:Contrast Media; D006573:Heterocyclic Compounds, 1-Ring