Development of 1H-31P Animal RF Coil for pH Measurement Using a Clinical MR Scanner

Abstract

Purpose : To establish a pH measurement system for a mouse tumor study using a clinical scanner, to develop the 1H and 31P radio frequency (RF) coil system and to test pH accuracy with phantoms.

Materials and Methods: The 1H and the 31P 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 1H decoupled 31P 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 1H image was greater than 300. The high resolution in vivo mice images were acquired using a 31P -decoupled 1H coil. The pH values calculated from the 1H -decoupled 31P spectrum correlated well with the values measured by pH meter (R2 =0.97).

Conclusion: Accurate pH values can be acquired using a 1H -decoupled 31P RF coil with a clinical scanner. This two-surface coil system could be applied to other nuclear MRS or MRI.