Automated injection system disclosed in this application advantageously provides physicians with a simplified interface for selecting fluid sources, such as saline, contrast, or a mixture of both, to inject at high pressures. The injector system may comprise a multi-use subassembly, a single-use subassembly, a fitting to fluidly connect the multi-use and single-use subassemblies, a hand held controller, a user interface, and an injector housing.