Detection and estimation of membrane diffusion during exocytosis in TIRFM image sequences

Assessing the dynamics of plasma membrane diffusion processes in live cell fluorescence microscopy is of paramount interest to understand cell mechanisms. We propose a new method to detect vesicle fusion events, and estimate the associated diffusion coefficients in image sequences of total internal reflection fluorescence microscopy (TIRFM). In contrast to usual approaches, a diffusion coefficient is locally estimated for each detected fusing vesicle. We first detect the membrane fusion events and then select the diffusion configurations among them with a correlation test. To estimate the diffusion coefficient, a geometric model is fitted to the detected spot directly in the 2D+t subvolume. Quantitative results demonstrate the accuracy of the proposed method.