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Treatment delivery equipment: teletherapy

Introduction

Acceptance testing of teletherapy equipment assures that the mechanical and dosimetric specifications described in the purchase order are fulfilled, and that the equipment is free of electrical and radiation hazards to staff and patients. After acceptance of the equipment, treatment beam characteristics needed for clinical use are established during the commissioning process. These measurements include the determination of the beam characteristics needed to operate a treatment planning system for this particular type of equipment. A more strict definition of commissioning teletherapy equipment is the process of preparing QA procedures, protocols and other types of instructions for clinical service. Clinical use can only begin when the physicist responsible for acceptance testing and commissioning is satisfied with all aspects required for a safe treatment of patients and places therefore a heavy responsibility on the medical physicist for correct performance of these tests.

Important Principles

Acceptance tests are generally divided into mechanical checks, dosimetry measurements and safety checks, and are performed in the presence of a representative of the equipment manufacturer. Often some of the beam characteristics acquired during the acceptance testing procedures serve as baseline values to be checked relative to constancy during future dosimetric QA measurements.

Introduction to References

A number of national and international protocols exist to guide the physicist in the performance of acceptance testing and commissioning of teletherapy equipment. The AAPM Task Group 142 Report is an update of the TG-40 Report, specifying new tests and tolerances, and has added recommendations for not only the new ancillary delivery technologies but also for imaging devices that are part of the linear accelerator. Additional information can be found in the IAEA Radiation Oncology Physics Handbook.