H. Alasti et al., Portal imaging for evaluation of daily on-line setup errors and off-line organ motion during conformal irradiation of carcinoma of the prostate, INT J RAD O, 49(3), 2001, pp. 869-884
Citations number
38
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Onconogenesis & Cancer Research
Journal title
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS
Purpose: To use portal imaging to measure daily on-line setup error and off
-line prostatic motion in patients treated with conformal radiotherapy to d
etermine an optimum planning target volume (PTV) margin incorporating both
setup error and organ motion,
Results: A total of 2549 portal images from 33 patients were acquired over
the course of the study. Of these patients, 23 were analyzed for setup erro
rs while the remaining 10 were analyzed for prostatic motion, Setup errors
were characterized by standard deviations of 1.8 mm in the anterior-posteri
or (AP) direction and 1.4 mm in the superior-inferior (SI) direction, Displ
acements due to prostatic motion, with standard deviations of 5.8 mm AP and
3.3 mm SI, were found to be more significant than setup errors,
Conclusions: Taking into account both setup errors and target organ motion,
optimum PTV margins to ensure 95% coverage are 10.0 mm AP and 5.9 mm SI. T
he portal imaging protocol established in this study allows radiation thera
pists to accept or adjust a treatment setup based upon daily on-line image
matching results. The successful localization of radiopaque fiducial marker
s on a significant number of portal images acquired in the study gives hope
that more accurate on-line targeting verification mag soon be possible thr
ough the visualization of the prostate itself as opposed to the surrounding
bony structures of the pelvis, (C) 2001 Elsevier Science Inc.