The influence of air humidity on an unsealed ionization chamber in a linear accelerator

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Abstract

The safe and accurate delivery of the prescribed absorbed dose is the central function of the dose monitoring and beam stabilization system in a medical linear accelerator. The absorbed dose delivered to the patient during radiotherapy is often monitored by a transmission ionization chamber. Therefore it is of utmost importance that the chamber behaves correctly. We have noticed that the sensitivity of an unsealed chamber in a Philips SL linear accelerator changes significantly, especially during and after the summer season. The reason for this is probably a corrosion effect of the conductive plates in the chamber due to the increased relative humidity during hot periods. We have found that the responses of the different ion chamber plates change with variations in air humidity and that they do not return to their original values when the air humidity is returned to ambient conditions.

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Subject classification (UKÄ) – MANDATORY

  • Radiology, Nuclear Medicine and Medical Imaging
Original languageEnglish
Pages (from-to)2541-2548
JournalPhysics in Medicine and Biology
Volume41
Issue number11
Publication statusPublished - 1996
Publication categoryResearch
Peer-reviewedYes