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TBI lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections

This study compares lung dose distributions for two common techniques of total body photon irradiation (TBI) at extended source‐to‐surface distance calculated with, and without, tissue density correction (TDC). Lung dose correction factors as a function of lateral thorax separation are approximated...

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Autores principales: Bailey, Daniel W., Wang, Iris Z., Lakeman, Tara, Hales, Lee D., Singh, Anurag K., Podgorsak, Matthew B.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690074/
https://www.ncbi.nlm.nih.gov/pubmed/26103198
http://dx.doi.org/10.1120/jacmp.v16i2.5293
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author Bailey, Daniel W.
Wang, Iris Z.
Lakeman, Tara
Hales, Lee D.
Singh, Anurag K.
Podgorsak, Matthew B.
author_facet Bailey, Daniel W.
Wang, Iris Z.
Lakeman, Tara
Hales, Lee D.
Singh, Anurag K.
Podgorsak, Matthew B.
author_sort Bailey, Daniel W.
collection PubMed
description This study compares lung dose distributions for two common techniques of total body photon irradiation (TBI) at extended source‐to‐surface distance calculated with, and without, tissue density correction (TDC). Lung dose correction factors as a function of lateral thorax separation are approximated for bilateral opposed TBI (supine), similar to those published for anteroposterior–posteroanterior (AP–PA) techniques in AAPM Report 17 (i.e., Task Group 29). 3D treatment plans were created retrospectively for 24 patients treated with bilateral TBI, and for whom CT data had been acquired from the head to the lower leg. These plans included bilateral opposed and AP–PA techniques—each with and without — TDC, using source‐to‐axis distance of 377 cm and largest possible field size. On average, bilateral TBI requires 40% more monitor units than AP–PA TBI due to increased separation (26% more for 23 MV). Calculation of midline thorax dose without TDC leads to dose underestimation of 17% on average (standard deviation, 4%) for bilateral 6 MV TBI, and 11% on average (standard deviation, 3%) for 23 MV. Lung dose correction factors (CF) are calculated as the ratio of midlung dose (with TDC) to midline thorax dose (without TDC). Bilateral CF generally increases with patient separation, though with high variability due to individual uniqueness of anatomy. Bilateral CF are 5% (standard deviation, 4%) higher than the same corrections calculated for AP–PA TBI in the 6 MV case, and 4% higher (standard deviation, 2%) for 23 MV. The maximum lung dose is much higher with bilateral TBI (up to 40% higher than prescribed, depending on patient anatomy) due to the absence of arm tissue blocking the anterior chest. Dose calculations for bilateral TBI without TDC are incorrect by up to 24% in the thorax for 6 MV and up to 16% for 23 MV. Bilateral lung CF may be calculated as 1.05 times the values published in Table 6 of AAPM Report 17, though a larger patient pool is necessary to better quantify this trend. Bolus or customized shielding will reduce lung maximum dose in the anterior thorax. PACS numbers: 87.55.D, 87.55.Dk, 87.55.Ne, 87.56.Bd, 87.57.Qp
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spelling pubmed-56900742018-04-02 TBI lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections Bailey, Daniel W. Wang, Iris Z. Lakeman, Tara Hales, Lee D. Singh, Anurag K. Podgorsak, Matthew B. J Appl Clin Med Phys Radiation Oncology Physics This study compares lung dose distributions for two common techniques of total body photon irradiation (TBI) at extended source‐to‐surface distance calculated with, and without, tissue density correction (TDC). Lung dose correction factors as a function of lateral thorax separation are approximated for bilateral opposed TBI (supine), similar to those published for anteroposterior–posteroanterior (AP–PA) techniques in AAPM Report 17 (i.e., Task Group 29). 3D treatment plans were created retrospectively for 24 patients treated with bilateral TBI, and for whom CT data had been acquired from the head to the lower leg. These plans included bilateral opposed and AP–PA techniques—each with and without — TDC, using source‐to‐axis distance of 377 cm and largest possible field size. On average, bilateral TBI requires 40% more monitor units than AP–PA TBI due to increased separation (26% more for 23 MV). Calculation of midline thorax dose without TDC leads to dose underestimation of 17% on average (standard deviation, 4%) for bilateral 6 MV TBI, and 11% on average (standard deviation, 3%) for 23 MV. Lung dose correction factors (CF) are calculated as the ratio of midlung dose (with TDC) to midline thorax dose (without TDC). Bilateral CF generally increases with patient separation, though with high variability due to individual uniqueness of anatomy. Bilateral CF are 5% (standard deviation, 4%) higher than the same corrections calculated for AP–PA TBI in the 6 MV case, and 4% higher (standard deviation, 2%) for 23 MV. The maximum lung dose is much higher with bilateral TBI (up to 40% higher than prescribed, depending on patient anatomy) due to the absence of arm tissue blocking the anterior chest. Dose calculations for bilateral TBI without TDC are incorrect by up to 24% in the thorax for 6 MV and up to 16% for 23 MV. Bilateral lung CF may be calculated as 1.05 times the values published in Table 6 of AAPM Report 17, though a larger patient pool is necessary to better quantify this trend. Bolus or customized shielding will reduce lung maximum dose in the anterior thorax. PACS numbers: 87.55.D, 87.55.Dk, 87.55.Ne, 87.56.Bd, 87.57.Qp John Wiley and Sons Inc. 2015-03-08 /pmc/articles/PMC5690074/ /pubmed/26103198 http://dx.doi.org/10.1120/jacmp.v16i2.5293 Text en © 2015 The Authors. This is an open access article under the terms of the Creative Commons Attribution (http://creativecommons.org/licenses/by/3.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Radiation Oncology Physics
Bailey, Daniel W.
Wang, Iris Z.
Lakeman, Tara
Hales, Lee D.
Singh, Anurag K.
Podgorsak, Matthew B.
TBI lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections
title TBI lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections
title_full TBI lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections
title_fullStr TBI lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections
title_full_unstemmed TBI lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections
title_short TBI lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections
title_sort tbi lung dose comparisons using bilateral and anteroposterior delivery techniques and tissue density corrections
topic Radiation Oncology Physics
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690074/
https://www.ncbi.nlm.nih.gov/pubmed/26103198
http://dx.doi.org/10.1120/jacmp.v16i2.5293
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