Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2008 Apr;33(2):49-53.
doi: 10.4103/0971-6203.41192.

Verification of setup errors in external beam radiation therapy using electronic portal imaging

K Krishna Murthy  1 , Zakiya Al-Rahbi, S S Sivakumar, C A Davis, R Ravichandran, Kamal El Ghamrawy
Affiliations

Verification of setup errors in external beam radiation therapy using electronic portal imaging

K Krishna Murthy et al. J Med Phys. 2008 Apr.

Abstract

The objective of this study was to conduct an audit on QA aspects of treatment delivery by the verification of the treatment fields' position on different days to document the efficiency of immobilization methods and reproducibility of treatment. A retrospective study was carried out on 60 patients, each 20 treated for head and neck, breast, and pelvic sites; and a total of 506 images obtained by electronic portal imaging device (EPID) were analyzed. The portal images acquired using the EPID systems attached to the Varian linear accelerators were superimposed on the reference images. The anatomy matching software (Varian portal Vision. 6.0) was used, and the displacements in two dimensions and rotation were noted for each treated field to study the patient setup errors. The percentages of mean deviations more than 3 mm in 'lateral (X) and longitudinal (Y)' directions were 17.5%, 11.25%, and 7.5% for breast, pelvis, and head and neck cases respectively. In all cases, the percentage of mean deviation with more than 5 mm error was 0.83%. The maximum average mean deviation in all the cases was 1.87. The average mean SD along X and Y directions in all the cases was less than 2.65. The results revealed that the ranges of setup errors are site specific and immobilization methods improve reproducibility. The observed variations were well within the limits. The study confirmed the accuracy and quality of treatments delivered to the patients.

Keywords: Anatomy matching software; electronic portal imaging device; immobilization casts; setup error; tumor control probability.

PubMed Disclaimer

Conflict of interest statement

Conflict of Interest: None declared.

Figures

Figure 1
Figure 1
Systematic errors in breast cases without Orfit. Graph shows the number of average mean deviations <3 mm, between 3 and 5 mm, and >5 mm in X and Y directions
Figure 2
Figure 2
Systematic errors in breast cases with Orfit. Graph shows the number of average mean deviations <3 mm, between 3 and 5 mm, and >5 mm in X and Y directions
Figure 3
Figure 3
Systematic errors in pelvis cases without Orfit. Graph shows the number of average mean deviations <3 mm, between 3 and 5 mm, and >5 mm in X and Y directions
Figure 4
Figure 4
Systematic errors in pelvis cases with Orfit. Graph shows the number of average mean deviations <3 mm, between 3 and 5 mm, and >5 mm in X and Y directions
Figure 5
Figure 5
Systematic errors in head and neck cases with Orfit. Graph shows the number of average mean deviations <3 mm, between 3 and 5 mm, and >5 mm in X and Y directions
See this image and copyright information in PMC

References

    1. Hunt MA, Schultheiss TE, Desobry GE, Hakki M, Hanks GE. An evaluation of setup uncertainties for patients treated to pelvic sites. Int J Radiat Oncol Biol Phys. 1995;32:227–33. - PubMed
    1. Goitein M, Busse J. Immobilization errors: Some theoretical considerations. Radiology. 1975;117:407–12. - PubMed
    1. Marks JE, Haus AG, Sutton H, Griem ML. The value of frequent verification films in reducing localization errors on irradiation of complex fields. Cancer. 1976;37:2755–761. - PubMed
    1. Bentel GC, Marks LB, Sherouse GW, Spencer BP, Anscher MS. Effectiveness of immobilization during prostate irradiation. Int J Radiat Oncol Biol Phys. 1995;31:143–8. - PubMed
    1. Bentel GC, Marks LB, Hendren K, Brizel DM. Comparison of two head and immobilization systems. Int J Radiat Oncol Biol Phys. 1997;38:867–73. - PubMed