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DOI http://dx.doi.org/10.1016/S0360-3016(97)80926-1
Title Standard off-cord lung oblique fields do not include the entire mediastinum: a computerized tomography simulator study
Creator/Author Di Biase, Steven J. ; Wasik, Maria Werner ; Croce, Raymond ; Sweet, John ; Yang Xie ; Curran, Walter J
Publication Date1997 Jul 01
OSTI IdentifierOSTI ID: 20423398
Other Number(s)ISSN 0360-3016; IOBPD3 ; TRN: US03R3963007071
Resource TypeJournal Article
Resource RelationInternational Journal of Radiation Oncology, Biology and Physics ; VOL. 39 ; ISSUE: 2,suppl.1 ; PII: S0360301697809261; Copyright (c) 1997 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); PBD: 1997
Subject62 RADIOLOGY AND NUCLEAR MEDICINE ; BRONCHI; CARCINOMAS; CAT SCANNING; LUNGS; MEDIASTINUM; PATIENTS; SIMULATORS; SPINAL CORD
Description/Abstract BACKGROUND: The routinely recommended target volume for off-cord lung oblique fields in the treatment of postoperative bronchogenic carcinoma includes the entire mediastinum, as defined by coverage of the contralateral mainstrem bronchus and subcarinal space. However, this may be difficult to accomplish with the suggested field angles of 20 - 40 degrees recommended in the recently completed Intergroup Trial (RTOG 91-05). This project was undertaken to define the oblique angle necessary to encompass the entire mediastinum as determined by computerized tomography (CT) simulator verification. METHODS: Axial CT simulation images of 25 patients with thoracic malignancies were used in this study. Sites of disease included bronchogenic carcinoma (n=23) and other (n=2). Five patients received prior resection as part of their management. The contralateral mainstem bronchus (CMB), subcarinal space (SS), and the spinal cord (SC) were each contoured as separate volumes. The length of the CMB was defined as extending from the carina to the bifurcation of the lobar bronchi. The SS was defined as a rectangular space (in coronal plane) with the carina at the apex, the mainstem bronchi superiorly, and a horizontal line 5 cm below the carina as the base of the triangle. The smallest angle (SA) to encompass the CMB and SS, and to exclude the spinal cord was determined for each patient. The contoured volumes did not have additional margin added. The position of the carina was scored as 'midline' if located in the mid-sagittal plane, or 'off-midline' if deviated to either side from midline. Midline deviation (MD) was determined at the level of the carina in order to evaluate possible anatomic distortion relating to the tumor or prior surgery, and its effect on the SA was assessed. RESULTS: The median SA measured was 45 degrees (range: 28-65 degrees) for the entire group, and in 64% of those evaluated, this oblique angle was significantly greater than 40 degrees recommended in RTOG guidelines (p=0.017). In patients without MD (n=19), the median SA was 45 degrees (range: 28-60), and in patients with MD (n=6), it was determined to be 44 degrees (range: 27-65), with no statistical difference noted between the two groups (p=NS). Although MD was present in two patients previously resected (n=5), the above relationship remained unchanged. CONCLUSION: Based on CT simulation verification, off-cord oblique field angles of 20-40 degrees do not adequately cover the entire mediastinum in most patients. To adequately encompass the entire mediastinum as defined in the Intergroup Trial (RTOG 91-05) with off-cord oblique fields, treatment angles greater than 40 degrees are necessary. Whether the potential increase in lung volume exposed to radiation from these larger angles results in a poorer therapeutic ratio requires further investigation.
Country of PublicationUnited States
LanguageEnglish
Formatpage(s) 320
System Entry Date2004 Feb 23

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