In the context of high performance computing, new architectures, becoming more and more parallel, offer higher floating-point computing power. Efficient simulation programs that take benefit of this computing power are developed for medical imaging. Because of the higher level of parallelism and of the large number of floating-point operations, numerical validation of these programs becomes increasingly important. The aim of this seminar is a discussion about the numerical reliability of high performance simulations for medical imaging. New high performance algorithms for medical imaging will be presented, as topics related to numerical validation on high performance architectures such as numerical reproducibility or precision optimisation.