Evaluation of ImageGuidance Protocols for the Treatment of Head and Neck Cancers - PowerPoint PPT Presentation

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Evaluation of ImageGuidance Protocols for the Treatment of Head and Neck Cancers

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Evaluation of Image-Guidance Protocols for the Treatment of Head and Neck Cancers ... Meeks, Thomas Wagner, Twyla Willoughby, D. Wayne Jenkins, Patrick Kupelian ... – PowerPoint PPT presentation

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Title: Evaluation of ImageGuidance Protocols for the Treatment of Head and Neck Cancers


1
Evaluation of Image-Guidance Protocols for the
Treatment of Head and Neck Cancers
Omar Zeidan, Katja Langen, Sanford Meeks,
Thomas Wagner, Twyla Willoughby, D. Wayne
Jenkins, Patrick Kupelian M. D. Anderson
Cancer Center Orlando
Purpose To assess the residual setup error of
different image-guidance (IG) protocols in the
alignment of head and neck cancer patients. The
protocols differ in the percentage of treatment
fractions that are associated with
image-guidance. Using data from patients that
were treated with daily IG, the residual setup
errors for several different protocols are
retrospectively calculated. Materials and
Methods Alignment data from 24 patients (802
fractions) treated with daily IG on a helical
tomotherapy unit was analyzed. The difference
between the daily setup correction and the setup
correction that would have been made according to
a specific protocol was used to calculate the
residual setup errors for each protocol.
Results The different protocols are generally
effective in reducing systematic setup errors.
Random setup errors are generally not reduced for
fractions that are not image-guided. As a
consequence, if every other treatment is
image-guided, still about 11 of all treatments
(IG and not IG) are subject to three-dimensional
setup errors of at least 5 mm. This frequency
increases to about 29 if setup errors gt3 mm are
scored. For various protocols that require 15-31
of the treatments to be image guided, between
50-60 and 26-31 of all fractions are subject to
setup errors gt3 and gt5 mm, respectively.
The frequency of residual 3-dimensional setup
errors is shown for all protocols. Figures A and
B show results for all treatments and the non-IG
treatments. The non IG treatments are treatment
fractions that were not accompanied by image
guidance
x

Frequencies of the residual errors observed with
the different scenarios exceeding 3, 5, and 10
mm. The 3-D setup error is the vector calculated
from the remaining setup errors in the 3
directions. The data in this table are calculated
for all, i.e. image guided (IG) as well as non IG
treatments. The uncertainty in the results was
estimated by using the square root of N, where N
is the number of observations.

Conclusion Systematic errors throughout the
course of treatment can be reduced with protocols
that involve infrequent imaging. However, random
setup errors are not eliminated with any of the
imaging protocols investigated in the current
study. Protocols that use image guidance for
0-50 of all treatments have three-dimensional
residual setup errors of 5 mm or larger in 47-11
of all treatment. The acceptability of the
reduced setup accuracy and precision that is due
to infrequent use of image guidance depends on
treatment margins and the proximity of sensitive
structures. If target structures are in close
proximity to critical sensitive structure,
image-guidance should be used daily
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