Abstract: It is presented a computer-implemented method for estimating narrowings in arteries of a heart based on a sample myocardial perfusion imaging (S-MPI) data set using an artificial neural network (ANN). The method comprises receiving, in a data processing apparatus, the S-MPI data and a request, determining, in the data processing apparatus, an estimate quantitative coronary angiography (E-QCA) data set based on the S-MPI data set using the ANN, wherein the ANN is trained using a reference MPI (R-MPI) data set, a reference quantitative coronary angiography (R-QCA) data set and a reference invasive measurement (R-IM) data set, wherein each record in the R-MPI data set has a corresponding record in the R-QCA data set and a corresponding record in the R-IM data set, respectively, and transmitting, from the data processing apparatus, the E-QCA data set in response to the request.