Kp. Mcgee et al., THE VALUE OF SETUP PORTAL FILMS AS AN ESTIMATE OF A PATIENTS POSITIONTHROUGHOUT FRACTIONATED TANGENTIAL BREAST IRRADIATION - AN ONLINE STUDY, International journal of radiation oncology, biology, physics, 37(1), 1997, pp. 223-228
Citations number
22
Categorie Soggetti
Oncology,"Radiology,Nuclear Medicine & Medical Imaging
Purpose: To determine if portal setup films are an accurate representa
tion of a patient's position throughout the course of fractionated tan
gential breast irradiation. Methods and Materials: Thirteen patients u
ndergoing external beam irradiation for T1-T2 infiltrating ductal carc
inoma of the breast following excisional biopsy and axillary dissectio
n were imaged using an on-line portal imaging device attached to a 6 M
V linear accelerator, Medial and lateral tangential fields were imaged
and a total of 139 fractions, 225 portal fields, and 4450 images were
obtained, Interfractional and intrafractional variations for anatomic
al parameters including the central lung distance (CLD), central flash
distance (CFD), and inferior central margin (ICM) were calculated fro
m these images, A pooled estimate of the random error associated with
a given treatment was determined by adding the interfractional and int
rafractional standard deviations in quadrature, A 95% confidence level
assigned a value of two standard deviations of the random error estim
ate, Central lung distance, CFD, and ICM distances were then measured
for all portal setup films, Significant differences were defined as oc
curring when the simulation-setup difference was greater than the 95%
confidence value. Results: Differences between setup portal and simula
tion films were less than their 95% confidence values in 70 instances
indicating that in 90% of the time these differences are a result of r
andom differences in daily treatment positioning. Conclusions: In 90%
of cases tested, initial portal setup films are an accurate representa
tion of a patients daily treatment setup. Copyright (C) 1997 Elsevier
Science Inc.