As cancer leads to increasing mortality worldwide, early detection is essential to patient survival. Nevertheless, the natural contrasts of magnetic resonance imaging (MRI) is often insufficient in order to discriminate between healthy and cancerous tissues. Therefore, contrast agents are frequently used, most commonly to increase T1 and T2 divergence between various tissues. However, the invasive and expensive method may not be tolerated by some patients. On the other hand, it is noticeable that the diffusivity of fluids in tissues may be anisotropic. Diffusion Tensor Imaging (DTI) is suited to evaluate Fractional Anisotropy (FA) in each voxel1,2 , which has larger contrast than Relative Anisotropy (RA)3 . FA had triple degradation within cyst as compared to healthy tissues1, which makes it a candidate for robust cancer detection without contrast agents.
Anisotropic structures has been studied by two-dimensional NMR Diffusion-Diffusion COrrelation SpectroscopY (DDCOSY)4,5,6, providing a promising approach for obtaining similar parameters as compared to DTI. To this extend DDCOSY experiments were performed on bulk water, water in 20 μm diameter aligned capillaries and in biological tissue. After data processing, isotropic and anisotropic features can be identified by diagonal and off-diagonal peaks, respectively. Furthermore, for preliminarily testing the feasibility of DDCOSY, carrot was chosen as a biological phantom7 before using human tissues, confirming anisotropic features in the obtained two dimentional correlation maps. Subsequently, the eigenvalues of the diffusion tensor can be extracted from the orthogonal apparent diffusion coefficients by applying three-shot DDCOSY experiments, the ratio of which can be calculated as an indicator for tissue anisotropy. Furthermore, we compare DTI and DDCOSY, and discuss their common features both mathematically and experimentally. All the experiments were performed on Avance 400MHz Bruker spectrometer.