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NMR techniques for temperature and pH measurements have attracted increasing interest in recent years, motivated in part by the growing importance of medical hyperthermia for the treatment of cancer. The chemical shifts of thulium 1, 4, 7, 10‐tetraazacyclododecane‐1, 4, 7, 10‐tetrakis(methylene phosphonate) (TmDOTP5−) have been studied as a function of temperature and pH. The results demonstrate that TmDOTP5−resonance shifts are highly sensitive to temperature (∼1.0 ppm/°C) and pH (∼3.2 ppm/pH unit) at clinically relevant field strengths. A new method is presented which utilizes two magnetically non‐equivalent protons in TmDOTP5−for simultaneous NMR measurements of both temperature and pH. The difference in the chemical shift values of pairs of 1H resonances provides a temperature sensitivity of about 1.6 ppm/°C. The technique is demonstrated in live rats undergoing ultrasound‐induced hyperthermia therapy. Copyright © 2000 John Wiley & Sons, Ltd.Abbreviations used:CSIchemical shift imagingTmDOTP5−thulium 1, 4, 7, 10‐tetraazacyclododecane‐1, 4, 7, 10‐tetrakis(methylene phosphonate)

NMR techniques for temperature and pH measurements have attracted increasing interest in recent years, motivated in part by the growing importance of medical hyperthermia for the treatment of cancer. The chemical shifts of thulium 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetrakis(methylene phosphonate) (TmDOTP⁵⁻) have been studied as a function of temperature and pH. The results demonstrate that TmDOTP⁵⁻ resonance shifts are highly sensitive to temperature (~1.0 ppm/°C) and pH (~3.2 ppm/pH unit) at clinically relevant field strengths. A new method is presented which utilizes two magnetically non-equivalent protons in TmDOTP⁵⁻ for simultaneous NMR measurements of both temperature and pH. The difference in the chemical shift values of pairs of ¹H resonances provides a temperature sensitivity of about 1.6 ppm/°C. The technique is demonstrated in live rats undergoing ultrasound-induced hyperthermia therapy. Copyright © 2000 John Wiley & Sons, Ltd. Abbreviations used: CSI chemical shift imaging TmDOTP⁵⁻ thulium 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetrakis(methylene phosphonate)

NMR thermometry has previously suffered from poor thermal resolution owing to the relatively weak dependence of chemical shift on temperature in diamagnetic molecules. In contrast, the shifts of nuclear spins near a paramagnetic center exhibit strong temperature dependencies. The chemical shifts of the thulium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylene phosphonate) complex (TmDOTP5−) have been studied as a function of temperature, pH, and Ca2+concentration over ranges which may be encounteredin vivo.The results demonstrate that the1H and31P shifts in TmDOTP5−are highly sensitive to temperature and may be used for NMR thermometry with excellent accuracy and resolution. A new technique is also described which permits simultaneous measurements of temperature and pH changes from the shifts of multiple TmDOTP5−spectral lines.