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QA of treatment planning equipment: teletherapy and brachytherapy

Introduction

Quality assurance of a treatment planning system (TPS) concerns tests of the anatomical description of a patient, the beam description and the dose calculations. The first task for the physicist is to understand in detail how the treatment planning software functions. It must be clear from the documentation accompanying the software package as well as from the literature how the various steps in the dose calculation of a specific treatment technique are performed.In the past some irradiation accidents happened, which were related to the misuse of treatment planning equipment. Good training, as well as the availability of well-documented quality assurance procedures, have a huge impact in preventing planning errors.

Important Principles

Efforts should concentrate on testing those aspects relevant for the treatment techniques applied in a specific institution. The overall accuracy of the 3D dose calculation in an irradiated patient is determined by the accuracy of the imaging (patient) information, the beam description and the dose calculation algorithm. The QA of a 3D TPS to be used for IMRT not only consists of verifying the algorithms in the system, but is a combination of testing simultaneously the planning and delivery of IMRT. Such an IMRT QA programme depends very much on the local situation and requires a lot of effort in addition to other QA tests of a 3D TPS. Specific QA tests of a TPS for brachytherapy include verification of the data describing these sources in the planning system and checking the calculated dose distributions against an atlas.

Introduction to References

Several reports exist that provide a comprehensive set of QA tests of a 3D TPS including IAEA Report TRS 430, ESTRO Booklet No. 7 and NCS Report no. 15. These tests concern both dosimetric as well as non-dosimetric issues such as verification of anatomy description. ESTRO Booklets No. 8 and No. 9 discuss many aspects of brachytherapy and IMRT, respectively, including QA of treatment planning systems for these types of radiotherapy.