Megavoltage quality control, resources and demand: a pragmatic review.

OBJECTIVE: Satisfactory radiotherapy treatment requires quality control (QC) of the equipment as well as patient-specific checks. Increased complexity and extended use of equipment plus greater demand for complex treatment has brought pressure on QC resources. The benefits of integrating patient-specific checks and QC and the efficient use of resources is examined. METHODS: A non-linear model for the probability of undetected machine failure is proposed which enables the comparative efficiency of resource to be assessed. Benefits of adopting an integrated view of patient-specific and treatment machine QC is considered, considering performance tolerance levels in the context of measurement uncertainty and patient-specific tolerances. RESULTS: Essential, machine-only QC is identified. A realistic approach to equipment-only QC is identified for 70% efficient use of resources and a relationship established to determine resource required for a QC programme. Integration of patient-specific and equipment QC is shown to half the resource required for equipment QC. CONCLUSION: Increasing benefit from QC requires greater resource, working at lower efficiency. A pragmatic approach is having guaranteed checks supplemented with additional, non-guaranteed checks performed within an integrated approach to machine- and patient-specific QC, bearing in mind the occasions when machine-only QC is essential. ADVANCES IN KNOWLEDGE: The work reveals on a quantitative basis a rational approach to accommodating the QC requirements for safe and effective treatment.