In-vivo MR proton spectroscopy has been shown to be clinically valuable for assessing and localizing tumors in the prostate. However, due to the inherently low signal-to-noise ratio (SNR) in MR spectroscopic imaging (MRSI), measurement times can be very long. Thus, to be practical for clinical prostate MRSI, these times must be reduced, with the inevitable result that data quality suffers. In particular, spatial resolution is generally very low. A significant problem in MRSI, related to low-resolution data acquisition, is that there can be significant ringing, i.e., a kind of bleeding of signal contamination into the voxel-of-interest, from neighboring and even distant voxels. Contamination from unsuppressed lipid or water signal can be especially problematic, in some cases, rendering prostate spectra useless for diagnosis. An important advantage of non-Fourier encoding over standard Fourier encoding, is that ringing artifact can be eliminated because of the ability to arbitrarily shape the imaging point-spread-function, or PSF. A new hybrid spatial encoding method is proposed. The method, called PSF-Choice, maintains the simplicity of Fourier encoding while including the flexibility of non-Fourier encoding to shape the PSF. With this method, practical spectroscopic imaging of the prostate that is free from lipid contamination can be achieved with no additional cost in imaging time or loss in resolution or SNR. Core technical development and validation in phantom studies, along with a feasibility testing for prostate MRSI in an initial group of cancer patients will be completed in the R21 phase of this project. In the R33 phase of the project, a much larger clinical validation study is planned with the aim to demonstrate that the new method will significantly enhance the power of MR spectroscopy as a diagnostic tool for prostate cancer diagnosis. In addition, the R33 phase will feature further enhancements to the method along with a plan for integration into a very active program in MR image-guided therapy.
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