This post describes a reimplementation of the method described by Caruyer et al. (2013). If you already know what this is about, you can skip the information below and simply grab the code on GitHub: multishell.py. If you don't know, a good place to start is Tuch et al. (2004). Background When we plan a magnetic resonance imaging protocol, we often have to balance what we would like to have in terms of quantity and quality of images, versus what can realistically be obtained within limited time slots (e.g., 30 minutes or 1 hour) while minimizing discomfort to the research participants, most of whom would rather not spend more than an hour in a somewhat uncomfortable MRI exam table.