Implementation and Clinical Use of Portal Imaging

  • Cynthia L. Thomason
Part of the Cancer Treatment and Research book series (CTAR, volume 93)


Although introduced recently, on-line electronic portal imaging devices (EPIDs) are beginning to have an impact on radiation therapy, primarily in geometric verification of treatment fields. Using an EPID, a digital electronic portal image (EPI) can be obtained within a few seconds and be available for immediate review prior to completion of treatment. With the advent of more sophisticated techniques, such as conformal therapy and three-dimensional (3D) localization and treatment planning using computed tomography (CT) and magnetic resonance imaging (MRI), patient setup verification is perhaps the weak link in the planning and treatment process. Accuracy and precision of patient positioning is crucial to ensure delivery of the maximum dose to the target volume while avoiding normal and critical structures. Electronic portal imaging (EPIG) has the potential to strengthen that link at a lower cost than could be achieved with film. While it may not be possible to totally eliminate setup errors, effective use of an EPID will minimize both random and systematic errors, which may result in the reduction of the dose to the target volume and/or an overdose to normal critical structures.


Reference Image Setup Error Portal Image Electronic Portal Imaging Device Patient Setup 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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© Springer Science+Business Media New York 1998

Authors and Affiliations

  • Cynthia L. Thomason

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