Fig. 1

A sub-structure of a system dynamics model capturing the preparatory steps of the RT process built in over seven RT preparatory tasks evaluating number of waiting patients from scenarios defined by various capacity settings, combined with actual patient volumes and corresponding capacity demands. Note that the flow starts at the top left of the graph and finishes at the top right. If the workflow in question does not include a certain operation, the patients flow through this task without any capacity demand; this never happens at the boundaries of the model (referral and ready to start treatment). Symbols: Rectangles = points in the flow where patients accumulate; blue thick lines with valve symbol = route for patients transferring through a capacity-restricted operation; red fine lines with arrow head = transfer of information held in the circular symbol to be utilized in a computation at the point of the arrowhead. At each capacity restricted operation, two variables are combined to determine what flows through, capacity for the operation and the variable PPRCT x, which determines the percentage of the waiting patients who will be requiring capacity in operation x. Abbreviations: CT=Computed Tomography, MRI=Magnetic Resonance Imaging, PET=Positron Emission Tomography, PPRCT=Percentage patients requiring capacity, QA=Quality Assurance, and RT=Radiotherapy