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Purpose: To demonstrate in vivo magnetic resonance spectroscopic imaging (MRSI) of the human prostate at 4.0T using a transmit/receive endorectal coil and a pulse sequence designed specifically for this application., Materials and Methods: A solid, reusable endorectal probe was designed for both radiofrequency transmission and reception. Finite difference time domain (FDTD) simulations were performed to characterize the coil's electric field distribution, and temperature measurements were performed in a beef tissue phantom to determine the coil's safe operating limit. The localization by selective adiabatic refocusing (LASER) pulse sequence was implemented using six gradient modulated offset independent adiabatic (GOIA) pulses for very sharp, B(1)-insensitive voxel localization., Results: Based on the simulations and temperature measurements, the coil's safe operating limit was conservatively estimated to be 1.0W for 15 minutes. The transition width of the GOIA pulse selection profiles was only 6% of the bandwidth, compared with 22% for a specific absorption rate (SAR)-matched conventional adiabatic pulse. Using the coil and pulse sequence described here, MRSI data were successfully acquired from a patient with biopsy-proven prostate cancer, with a nominal voxel size of 0.34 cc in a scan time of 15 minutes., Conclusion: This work demonstrates the safe and effective use of a transmit/receive endorectal coil for in vivo MRSI of the prostate., ((c) 2009 Wiley-Liss, Inc.)

Purpose: To design and apply a method to quantitatively evaluate the MR compatibility of electroencephalographic (EEG) scalp electrodes based on pulse sequence-independent metrics., Materials and Methods: Three types of electrodes (constructed primarily of brass, silver, and conductive plastic, respectively) were tested. B0 field distortions, B1 shielding, and heat induction was measured in adjacent agarose and oil phantoms at 4 T. B0 field maps were corrected for distortions caused by the measurement apparatus and passive shim heating, and projections perpendicular to the surfaces of the electrodes were fit, generating cubic coefficients representing the electrode distortion severity. Signal loss in T2-weighted images was used to determine B1 shielding by the electrodes. Temperature measurements were recorded during the application of a high-power pulse sequence., Results: Significantly different B0 distortions were observed in the three types of electrodes. The B1 shielding detected in all three electrodes is minimal for most human MRI, and no significant heating was detected in the electrodes or adjacent phantom., Conclusion: The three types of electrodes were successfully differentiated in terms of MR compatibility based on pulse sequence-independent B0 field distortions., (Copyright (c) 2007 Wiley-Liss, Inc.)