Improved Volume Selective 1H MR Spectroscopic Imaging of the Prostate with Gradient Offset Independent Adiabaticity Pulses at 3 Tesla


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Abstract

Purpose:Volume selection in 1H MR spectroscopic imaging (MRSI) of the prostate is commonly performed with low-bandwidth refocusing pulses. However, their large chemical shift displacement error (CSDE) causes lipid signal contamination in the spectral range of interest. Application of high-bandwidth adiabatic pulses is limited by radiofrequency (RF) power deposition. In this study, we aimed to provide an MRSI sequence that overcomes these limitations.Methods:Measurements were performed at 3 T with an endorectal receive coil. A semi-LASER sequence was equipped with low RF power demanding gradient-modulated offset-independent adiabaticity (GOIA) refocusing pulses with WURST(16,4) modulation, with a 10 kHz bandwidth.Results:Simulations and phantom studies verified that the GOIA pulses select slices with a flat top and sharp edges and minimal CSDE. The sequence timing was tuned to an optimal citrate signal shape at an echo time of 88 ms. Patient studies (n = 10) demonstrated that high quality spectra with reduced lipid artifacts can be obtained from the whole prostate. Compared with PRESS acquisition at 145 ms the signal-to-noise ratio (SNR) of citrate is increased up to 2.6 and choline up to 1.3.Conclusion:An MRSI sequence of the prostate is presented with minimized spectral lipid contamination and improved SNR, to facilitate routine clinical acquisition of metabolic data. Magn Reson Med 74:915–924, 2015. © 2014 Wiley Periodicals, Inc.

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