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Set-up errors analyses in IMRT treatments for nasopharyngeal carcinoma to evaluate time trends, PTV and PRV margins

Abstract

Introduction. The aims of this study were to analyze the systematic and random interfractional set-up errors during Intensity Modulated Radiation Therapy (IMRT) in 20 consecutive nasopharyngeal carcinoma (NPC) patients by means of Electronic Portal Images Device (EPID), to define appropriate Planning Target Volume (PTV) and Planning Risk Volume (PRV) margins, as well as to investigate set-up displacement trend as a function of time during fractionated RT course. Material and methods. Before EPID clinical implementation, an anthropomorphic phantom was shifted intentionally 5 mm to all directions and the EPIs were compared with the digitally reconstructed radiographs (DRRs) to test the system's capability to recognize displacements observed in clinical studies. Then, 578 clinical images were analyzed with a mean of 29 images for each patient. Results. Phantom data showed that the system was able to correct shifts with an accuracy of 1 mm. As regards clinical data, the estimated population systematic errors were 1.3 mm for left-right (L-R), 1 mm for superior-inferior (S-I) and 1.1 mm for anterior-posterior (A-P) directions, respectively. Population random errors were 1.3 mm, 1.5 mm and 1.3 mm for L-R, S-I and A-P directions, respectively. PTV margin was at least 3.4, 3 and 3.2 mm for L-R, S-I  More>>
Authors:
Mongioj, Valeria; [1]  Orlandi, Ester; [2]  Palazzi, Mauro [3] 
  1. Dept. of Medical Physics, Fondazione IRCCS Istituto Nazionale Tumori, Milan (Italy)
  2. Dept. of Radiotherapy, Fondazione IRCCS Istituto Nazionale Tumori, Milan (Italy)
  3. Dept. of Radiotherapy, A.O. Niguarda Ca'Granda, Milan (Italy); and others
Publication Date:
Jan 15, 2011
Product Type:
Journal Article
Resource Relation:
Journal Name: Acta Oncologica (Stockholm) (online); Journal Volume: 50; Journal Issue: 1; Other Information: 10.3109/0284186X.2010.509108
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; RADIOTHERAPY; NEOPLASMS; FRACTIONATED IRRADIATION; PHANTOMS; PHARYNX; NOSE; ACCURACY
OSTI ID:
1004329
Country of Origin:
Sweden
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 1651-226X; TRN: SE1108025
Availability:
Available from DOI: http://dx.doi.org/10.3109/0284186X.2010.509108
Submitting Site:
SWDN
Size:
page(s) 61-71
Announcement Date:
Feb 07, 2011

Citation Formats

Mongioj, Valeria, Orlandi, Ester, and Palazzi, Mauro. Set-up errors analyses in IMRT treatments for nasopharyngeal carcinoma to evaluate time trends, PTV and PRV margins. Sweden: N. p., 2011. Web. doi:10.3109/0284186X.2010.509108.
Mongioj, Valeria, Orlandi, Ester, & Palazzi, Mauro. Set-up errors analyses in IMRT treatments for nasopharyngeal carcinoma to evaluate time trends, PTV and PRV margins. Sweden. doi:10.3109/0284186X.2010.509108.
Mongioj, Valeria, Orlandi, Ester, and Palazzi, Mauro. 2011. "Set-up errors analyses in IMRT treatments for nasopharyngeal carcinoma to evaluate time trends, PTV and PRV margins." Sweden. doi:10.3109/0284186X.2010.509108. https://www.osti.gov/servlets/purl/10.3109/0284186X.2010.509108.
@misc{etde_1004329,
title = {Set-up errors analyses in IMRT treatments for nasopharyngeal carcinoma to evaluate time trends, PTV and PRV margins}
author = {Mongioj, Valeria, Orlandi, Ester, and Palazzi, Mauro}
abstractNote = {Introduction. The aims of this study were to analyze the systematic and random interfractional set-up errors during Intensity Modulated Radiation Therapy (IMRT) in 20 consecutive nasopharyngeal carcinoma (NPC) patients by means of Electronic Portal Images Device (EPID), to define appropriate Planning Target Volume (PTV) and Planning Risk Volume (PRV) margins, as well as to investigate set-up displacement trend as a function of time during fractionated RT course. Material and methods. Before EPID clinical implementation, an anthropomorphic phantom was shifted intentionally 5 mm to all directions and the EPIs were compared with the digitally reconstructed radiographs (DRRs) to test the system's capability to recognize displacements observed in clinical studies. Then, 578 clinical images were analyzed with a mean of 29 images for each patient. Results. Phantom data showed that the system was able to correct shifts with an accuracy of 1 mm. As regards clinical data, the estimated population systematic errors were 1.3 mm for left-right (L-R), 1 mm for superior-inferior (S-I) and 1.1 mm for anterior-posterior (A-P) directions, respectively. Population random errors were 1.3 mm, 1.5 mm and 1.3 mm for L-R, S-I and A-P directions, respectively. PTV margin was at least 3.4, 3 and 3.2 mm for L-R, S-I and A-P direction, respectively. PRV margins for brainstem and spinal cord were 2.3, 2 and 2.1 mm and 3.8, 3.5 and 3.2 mm for L-R, A-P and S-I directions, respectively. Set-up error displacements showed no significant changes as the therapy progressed (p>0.05), although displacements >3 mm were found more frequently when severe weight loss or tumor nodal shrinkage occurred. Discussion. These results enable us to choose margins that guarantee with sufficient accuracy the coverage of PTVs and organs at risk sparing. Collected data confirmed the need for a strict check of patient position reproducibility in case of anatomical changes}
doi = {10.3109/0284186X.2010.509108}
journal = {Acta Oncologica (Stockholm) (online)}
issue = {1}
volume = {50}
place = {Sweden}
year = {2011}
month = {Jan}
}