Cascade analysis for medical imaging detectors with stages involving both amplification and dislocation processes

Cascade analysis is a powerful tool which can be used to calculate the signal and noise properties of medical imaging detectors. It involves the conceptual separation of the imaging chain into stages which consist of either pure amplification or pure dislocation stages. It is, however, not always possible to break the physical processes down to these elementary stages. In this work we derive a new cascade equation which is applicable to any stage which involves multiple amplifications and dislocations. The equation simplifies to the known equations for pure amplification and pure dislocation stages in the appropriate limits, and can be numerically calculated using Monte Carlo techniques for more complicated situations. We demonstrate the use of this equation with an example: we derive an expression for the DQE of a metal/phosphor detector for megavoltage imaging with our formalism, and evaluate the expression with Monte Carlo techniques. We have found that there is excellent agreement between theory and experimental results, and believe that the formalism could be useful for other applications where the amplification and dislocation processes cannot be divided into elementary stages.