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Treatment delivery equipment: brachytherapy

Introduction

Acceptance testing and commissioning of brachytherapy equipment are generally part of a regular brachytherapy QA programme. These tests concern the various safety systems and physical parameters including source calibration, radioactive decay, linear uniformity of wire sources, source positioning accuracy and timer consistency.

Important Principles

Source commissioning should include wipe tests for any contamination both on the package surface and of an individual encapsulated source. Furthermore radiation levels should be measured and recorded both at the package surface and at 1 m distance. The uniformity of the distribution of the radioactive material within an encapsulated source should be checked. Brachytherapy sources should have their source strength calibration traceable to a national standards laboratory. Re-entrant or well type ionization chambers are convenient for calibration of either high or low strength sources. Cylindrical ionization chambers in air or in a solid phantom may also be used for the measurement of high strength sources. These procedures are different for the various types of sources used in brachytherapy.

Introduction to References

In ESTRO Booklet No. 8 separate quality control procedures are given for High dose rate (HDR), Pulsed dose rate (PDR) and Low dose rate (LDR) and permanent implants. IAEA TECDOC-1272 deals with standardization of calibration of the most commonly used brachytherapy sources, including both photon and beta emitting sources. Additional information can be found in the IAEA Radiation Oncology Physics Handbook.