A simple quality assurance test tool for the visual verification of light and radiation field congruent using electronic portal images device and computed radiography

Christopher F Njeh,Blas Caroprese,Pushkar Desai

doi:10.1186/1748-717x-7-49

Christopher F Njeh, Blas Caroprese + Show 1 more

Open Access

https://doi.org/10.1186/1748-717x-7-49

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Abstract

BackgroundThe radiation field on most megavoltage radiation therapy units are shown by a light field projected through the collimator by a light source mounted inside the collimator. The light field is traditionally used for patient alignment. Hence it is imperative that the light field is congruent with the radiation field.MethodA simple quality assurance tool has been designed for rapid and simple test of the light field and radiation field using electronic portal images device (EPID) or computed radiography (CR). We tested this QA tool using Varian PortalVision and Elekta iViewGT EPID systems and Kodak CR system.ResultsBoth the single and double exposure techniques were evaluated, with double exposure technique providing a better visualization of the light-radiation field markers. The light and radiation congruency could be detected within 1 mm. This will satisfy the American Association of Physicists in Medicine task group report number 142 recommendation of 2 mm tolerance.ConclusionThe QA tool can be used with either an EPID or CR to provide a simple and rapid method to verify light and radiation field congruence.

Highlights

The radiation field on most megavoltage radiation therapy units are indicated by a light field projected through the collimator by a light source mounted inside the collimator [1]
Images acquired on Varian electronic portal images device (EPID) using the single and double exposure technique are presented in Figures 2, 3, 4, 5
Images acquired on Kodak computed radiography (CR) using the single and double exposure technique are presented in Figures 8 and 9 As can be seen in Figure 5, the PortalVision image detection algorithm successfully detected the edges of the field which coincided with the first marker of the V-shaped markers designed

Summary

Introduction

The radiation field on most megavoltage radiation therapy units are shown by a light field projected through the collimator by a light source mounted inside the collimator. The radiation field on most megavoltage radiation therapy units are indicated by a light field projected through the collimator by a light source mounted inside the collimator [1]. With the drive toward film-less and chartless radiation therapy environment, there is a need to develop ways to carry out this important QA check To this effect, there have been proposed techniques to use computed radiography (CR) system [8,9], photodiodes [10], diodes arrays and electronic portal imaging devices (EPIDS). These approaches involve potential cost and in some cases access to the EPID software

Methods

Results

Conclusion