Temperature monitoring of internal body heating induced by decoupling pulses in animal 13C‐MRS experiments

A temperature monitoring method to promote safety with regard to tissue heating induced by RF irradiation during MRI procedures, especially carbon‐13 magnetic resonance spectroscopy (13C‐MRS), is proposed. The method is based on the temperature dependence of the water proton chemical shift (−0.01 ppm/°C) combined with phase mapping. Using this method, temperature changes were measured in rats (n = 4) employing practical 1H‐decoupled 13C‐MRS pulse sequences for 1D projections (TR = 1000 ms, acquisition time = 15 ms, matrix = 256, spatial resolution = 0.2 mm) and 2D images (TR = 1500 ms, acquisition time = 840 ms, matrix = 128 × 32, spatial resolution = 0.8 × 1.5 mm). Measurement error was 0.18°C (SD) for 1D acquisition and 0.39°C (SD) for 2D acquisition, demonstrating the feasibility of this temperature mapping method. Further studies should be conducted in human subjects to monitor patient safety and to optimize the pulse sequences employed. Magn Reson Med 43:796–803, 2000. © 2000 Wiley‐Liss, Inc.

[1]  C J Hardy,et al.  Proton‐decoupled, overhauser‐enhanced, spatially localized carbon‐13 spectroscopy in humans , 1989, Magnetic resonance in medicine.

[2]  F. Shellock,et al.  Physiologic responses to an MR imaging procedure performed at a specific absorption rate of 6.0 W/kg. , 1994, Radiology.

[3]  N. Müller.  Concerning Structural Models for Water and Chemical‐Shift Data , 1965 .

[4]  Yasutoshi Ishihara,et al.  Temperature mapping using water proton chemical shift obtained with 3D‐MRSI: Feasibility in vivo , 1996, Magnetic resonance in medicine.

[5]  Y. Ishihara,et al.  A precise and fast temperature mapping method using water proton chemical shift , 1992 .

[6]  J. Schenck,et al.  Estimating radiofrequency power deposition in body NMR imaging , 1985, Magnetic resonance in medicine.

[7]  J V Hajnal,et al.  An evaluation of the effects of susceptibility changes on the water chemical shift method of temperature measurement in human peripheral muscle , 1996, Magnetic resonance in medicine.

[8]  R. Shulman,et al.  Detection of metabolites in rabbit brain by 13C NMR spectroscopy following administration of [1‐13C]glucose , 1986, Magnetic resonance in medicine.

[9]  T F Budinger,et al.  Nuclear Magnetic Resonance (NMR) In Vivo Studies: Known Thresholds for Health Effects , 1981, Journal of computer assisted tomography.

[10]  K. Kuroda,et al.  A precise and fast temperature mapping using water proton chemical shift , 1995, Magnetic resonance in medicine.

[11]  W. G. Schneider,et al.  Proton Magnetic Resonance Chemical Shift of Free (Gaseous) and Associated (Liquid) Hydride Molecules , 1958 .

[12]  N. Müller,et al.  Temperature Dependence of Chemical Shifts of Protons in Hydrogen Bonds , 1965 .

[13]  G. Adriany,et al.  Broadband decoupled, 1H‐localized 13C MRS of the human brain at 4 tesla , 1996, Magnetic resonance in medicine.

[14]  J. Hindman,et al.  Proton Resonance Shift of Water in the Gas and Liquid States , 1966 .

[15]  C A Cuenod,et al.  Temperature changes induced in human muscle by radio-frequency H-1 decoupling: measurement with an MR imaging diffusion technique. Work in progress. , 1992, Radiology.

[16]  N. Beckmann.  Carbon-13 NMR spectroscopy of biological systems , 1995 .