In-vivo 3T and ex-vivo 7T diffusion tensor imaging of prostate cancer : correlation with histology

Diffusion Tensor Imaging has been successfully applied in prostate cancer diagnosis (Kozlowski et al., 2010). It has been well established that the water Apparent Diffusion Coefficient has a lower value in the prostate carcinomas when compared to normal prostatic tissue (Bashar, 2002; Gürses et al., 2008; Kozlowski et al., 2010; Manenti et al., 2007; Pickles et al., 2005; Sato et al., 2005; Xu et al., 2009). However, fractional anisotropy values in prostatic carcinoma have been reported to be higher (Gürses et al., 2008), lower (Manenti et al., 2007), and unchanged(Xu et al., 2009) when compared to the prostate’s normal peripheral zone. Preliminary data from a study involving diffusion tensor imaging measurements in prostate glands, in-vivo and ex-vivo following radical prostatectomy, is presented. Histology whole mount slides were registered to T2 weighted images and diffusion parametric maps using a mutual information voxel intensity registration algorithm using software developed in-house. Regions of interest which included the normal peripheral zone, the normal peripheral zone with enlarged glands, and tumours were taken into account for this study. The tumours were highlighted and graded with the Gleason score grading system by a specialized pathologist. Values of the apparent diffusion coefficient and the fractional anisotropy parameters were calculated. Monte-Carlo simulations of the behaviour of the fractional anisotropy with respect to the value of the apparent diffusion coefficient, the signal to noise ratio, and the b-value of the Stejskal-Tanner equation were performed. The results show lower values of the apparent diffusion coefficient for regions of tumours for the ex-vivo and in-vivo cases. Values of the fractional anisotropy in the prostate carcinomas are slightly higher ex-vivo than in-vivo, which may be explained by the dependence of the fractional anisotropy on partial volume effects and noise. These preliminary results show that the fractional anisotropy does not show significant differences between normal and cancerous tissue, strongly suggesting that it is not likely to contribute significantly to the diagnostic capabilities of diffusion tensor imaging in prostate cancer.Science, Faculty ofPhysics and Astronomy, Department ofGraduat