MR Diffusion Tensor Imaging of Prostate Cancer

University Of California, San Francisco, San Francisco CA

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Abstract

The goal of this study is to develop and evaluate MR diffusion tensor imaging to improve the delineation and characterization of prostate cancer. Our initial studies indicate that this technique has clear potential to greatly improve current prostate MR exams. Diffusion tensor imaging (DTI) has demonstrated great research and clinical value for brain applications, but due to technical limitations has been of little utility outside of the head. Recent diffusion MRI studies of prostate cancer have demonstrated significant differences in water diffusivity between cancer and normal prostatic tissues. The initial studies used echo- planar imaging (EPI) techniques similar to those typically used in the brain, but this technique suffers from susceptibility-induced spatial distortions and limited compatibility with endorectal coils used clinically for prostate MR exams. In this project we will use a DTI sequence based on single-shot fast spin-echo method (SSFSE), which due to rf refocusing negates the spatial distortions inherent in EPI. In our preliminary results, we demonstrate the feasibility of this technique for high quality diffusion imaging of the prostate that can be directly compared to anatomic locations with negligible spatial distortions. Its compatibility with endorectal coils allows both easy incorporation into routine clinical MR protocols and the advantage of the great ~10fold SNR advantage of endorectal coils over external coils. Our preliminary results demonstrated significant differences in mean diffusivity <D>and fractional anisotropy (FA) between cancer and normal and BPH tissues. In this project we aim to validate SSFSE-DTI of the prostate, define normal diffusion variations due to zonal anatomy and age-related changes in age-matched controls, and correlate diffusion values in pre- prostatectomy patients with post-surgical step-sectioned histopathologic studies. In addition to measuring the DTI parameters corresponding to specific histologically-defined tissue types, we will investigate the accuracy of DTI cancer volume measurements, the ability of SSFSE-DTI to detect small volume cancers and the improvement in sensitivity and specificity for cancer localization provided by this method. Our multidisciplinary research team has extensive experience in both the development and the validation studies required to translate the exciting preliminary findings into a valuable research and clinical imaging protocol for prostate cancer characterization.