IMPROVED SPACIAL LOCALIZATION FOR SPECTROSCOPIC IMAGING

Brigham And Women'S Hospital, Boston MA

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Abstract

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Project Summary Grant Number: Project Official Start: 09-MAY-2005 Project Start: 09-MAY-2008 Project End: 28-FEB-2011 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 and 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. A new hybrid spatial encoding method is being developed. The method, called PSF-Choice, maintains the simplicity of standard Fourier encoding while including the flexibility of non-Fourier encoding to shape the point-spread-function (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. Benefits to NCIGT MR spectroscopic imaging is becoming a common modality used in the IGT program for diagnosis of prostate cancer. Unfortunately, as some studies show, the spectra in many voxels of a patient exam are corrupted by lipid leakage and the spectra are not of diagnostic quality. In some patients this may be as many as 90 percent of the voxels. The PSF-Choice offers the possibility of eliminating this kind of contamination and, thus, greatly improving the diagnostic quality of the MRSI exams. The method is being programmed based on the PROSE sequence which is used by other groups for prostate spectroscopy. The benefit to the resource of this collaboration is that, if the project is successful, a much improved spectroscopic sequence will be available to the prostate program and can also be disseminated to external groups. Benefits to the Project The IGT resource provides an essential support to the R21 project. The programming environment for development of the sequence is maintained (in part) through support from the imaging core of the resource. In addition, a training fellow attached to the IGT resource, Joe Roebuck, who is both a radiologist and an spectroscopist, is participating in the experimental work of the R21 project. He is able to give clinical focus to the project as well as expert advice on matters pertaining to spectroscopy - in particular, processing of the spectroscopic data. He has built a prostate spectroscopic phantom for use by the project. Finally, the resource provides an essential clinical environment in which the method developed can be validated. Once technical development is completed, a feasibility study will be conducted using patients recruited through collaborations withing the IGT resource.