An Attempt to Integrate Diffusion Weighted and Dynamic Contrast Enhanced MRI.
In cancer studies of several organs functional imaging can give useful information for better quantify the staging. In particular, Diffusion Weighted Imaging and Dynamic Contrast Enhanced MRI are becoming increasingly adopted in clinical practice.
DWI can give information about the microstructure organisation of the tissue. In fact, tumors have an increased cellularity leading to reduced water diffusion. Isotropic diffusion can be modeled using Intra-Voxel Incoherent Motion which depends on a few parameters: perfusion fraction f, ‘slow’ diffusion Ds, ‘fast’ diffusion Df. Diffusion constants are measured in mm2/s.
DCE provides information on the capillary wall permeability. This latter increases in cancer because of leaky vessels associated to the fast grow induced by VEGF. One of the most commonly employed models is the Extended Tofts-Kety model includes the following parameters: vascular plasma fraction, transfer constant from plasma to extra-vascular-extra-cellular space Ktrans, transfer constant from EES to plasma kep. Transfer constant are mesured in min-1.
Both models parameters are typically estimated from measured DCE and DWI data. Due to noise the estimated parameters can inaccurate and imprecise. Following the suggestion by LeBihan et al in this study we hypothesized that perfusion fraction in IVIM and plasma volume fraction should be equal and might be used for improving the estimation of parameters attainable with DWI and DCE. It seems reasonable that a larger number of b-values might improve DWI fitting alone and consequently also the combined fitting.
Radiol Open J. 2016; 1(1): 31-34. doi: 10.17140/ROJ-1-105