Visualization of treatment response in tumors by use of dynamic contrast-enhanced magnetic resonance imaging

Our goal in this study was to present a method for generating functional parametric maps of hemodynamic parameters in tumors and a visualization method for assessing treatment response by use of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). A total of 13 patients with musculoskeletal tumors were included in this study. First, tumor blood flow (F(T)) maps were generated from DCE-MRI data by use of deconvolution analysis, and K(1), k(2), and f were obtained from a two-compartment model, where K(1) and k(2) denote the rate constant for the transfer of contrast agent from blood to tissue and from tissue to blood, respectively, and f is the fraction of the blood volume. Images were generated by application of the linear least squares method pixel by pixel. Furthermore, the images of the distribution volume (V(d)) and permeability-surface area product (PS) were obtained from the relations V(d) = K(1)/k(2) and PS = -F(T) x ln(1 - K(1)/(F(T)), respectively. Second, two-dimensional (2D) plots were generated with V(d) and K(1) placed on the x- and y-axes, and three-dimensional (3D) plots were generated by the addition of PS on the z-axis. In the case of good responders whose biopsied specimens revealed tumor necrosis greater than 90%, both 2D and 3D plots gradually approached the origin after an increasing number of treatments. On the other hand, in the case of non-responders whose biopsied specimens showed little chemotherapeutic effect, large changes were not observed in either plot. In conclusion, our method will be promising for evaluating the treatment response in tumors visually.