PURPOSE: To establish a pH measurement system for a mouse tumor study using a clinical scanner, to develop the (1)H and (31)P radio frequency (RF) coil system and to test pH accuracy with phantoms. MATERIALS AND METHODS: The (1)H and the (31)P surface coils were designed to acquire signals from mouse tumors. Two coils were positioned orthogonally for geometric decoupling. The pH values of various pH phantoms were calculated using the (1)H decoupled (31)P MR spectrum with the Henderson-Hasselbalch equation. The calculated pH value was compared to that of a pH meter. RESULTS: The mutual coil coupling was shown in a standard S12. Coil coupling (S12) were -73.0 and -62.3 dB respectively. The signal-to-noise ratio (SNR) obtained from the homogeneous phantom (1)H image was greater than 300. The high resolution in vivo mice images were acquired using a (31)P-decoupled (1)H coil. The pH values calculated from the (1)H-decoupled (31)P spectrum correlated well with the values measured by pH meter (R(2)=0.97). CONCLUSION: Accurate pH values can be acquired using a (1)H-decoupled (31)P RF coil with a clinical scanner. This two-surface coil system could be applied to other nuclear MRS or MRI.
Animals* ; Hydrogen-Ion Concentration* ; Magnetic Resonance Imaging ; Mice ; Signal-To-Noise Ratio