Abstract
Imaging techniques are a combination of a contrast mechanism, exogenous or endogenous, and an instrument to exploit that contrast. This final chapter of these two special issues of this journal points to possible ways to improve the ability of imaging systems to exploit markers of cancer in the early detection of that disease. The aim not only is to find cancer at an earlier, more treatable stage, but to determine whether the disease discovered is dangerous and to indicate the possibilities for successful treatment. These topics are explored for each imaging system, with an emphasis on directions for future improvements.