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Title: SU-E-T-352: Effects of Skull Attenuation and Missing Backscatter On Brain Dose in HDR Treatment of the Head with Surface Applicators

Abstract

Purpose: To calculate the effect of lack of backscatter from air and attenuation of bone on dose distributions in brachytherapy surface treatment of head. Existing treatment planning systems based on TG43 do not account for heterogeneities, and thus may overestimate the dose to the brain. While brachytherapy generally has rapid dose falloff, the dose to the deeper tissues (in this case, the brain) can become significant when treating large curved surfaces. Methods: Applicator geometries representing a range of clinical cases were simulated in MCNP5. An Ir-192 source was modeled using the energy spectrum presented by TG-43. The head phantom was modeled as a 7.5-cm radius water sphere, with a 7 -mm thick skull embedded 5-mm beneath the surface. Dose values were calculated at 20 points inside the head, in which 10 of them were on the central axis and the other 10 on the axis connecting the central of the phantom with the second to last source from the applicator edge. Results: Central and peripheral dose distributions for a range of applicator and head sizes are presented. The distance along the central axis at which the dose falls to 80% of the prescribed dose (D80) was 7 mm for amore » representative small applicator and 9 mm for a large applicator. Corresponding D50 and D30 for the same small applicator were 17 mm and 32 mm respectively. D50 and D30 for the larger applicator were 32 mm and 60 mm respectively. These results reflect the slower falloff expected for larger applicators on a curved surface. Conclusion: Our results can provide guidance for clinicians to calculate the dose reduction effect due to bone attenuation and the lack of backscatter from air to estimate the brain dose for the HDR treatments of surface lesions.« less

Authors:
; ; ;  [1]; ;  [2]
  1. Brigham and Women’s Hospital, Harvard Medical School, Boston, MA (United States)
  2. University of Massachusetts Lowell, Lowell, MA (United States)
Publication Date:
OSTI Identifier:
22548402
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ATTENUATION; BRACHYTHERAPY; BRAIN; ENERGY SPECTRA; HEAD; IRIDIUM 192; PHANTOMS; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; SIMULATION; SKULL

Citation Formats

Cifter, F, Dhou, S, Lewis, J, Cormack, R, Altundal, Y, and Sajo, E. SU-E-T-352: Effects of Skull Attenuation and Missing Backscatter On Brain Dose in HDR Treatment of the Head with Surface Applicators. United States: N. p., 2015. Web. doi:10.1118/1.4924713.
Cifter, F, Dhou, S, Lewis, J, Cormack, R, Altundal, Y, & Sajo, E. SU-E-T-352: Effects of Skull Attenuation and Missing Backscatter On Brain Dose in HDR Treatment of the Head with Surface Applicators. United States. https://doi.org/10.1118/1.4924713
Cifter, F, Dhou, S, Lewis, J, Cormack, R, Altundal, Y, and Sajo, E. 2015. "SU-E-T-352: Effects of Skull Attenuation and Missing Backscatter On Brain Dose in HDR Treatment of the Head with Surface Applicators". United States. https://doi.org/10.1118/1.4924713.
@article{osti_22548402,
title = {SU-E-T-352: Effects of Skull Attenuation and Missing Backscatter On Brain Dose in HDR Treatment of the Head with Surface Applicators},
author = {Cifter, F and Dhou, S and Lewis, J and Cormack, R and Altundal, Y and Sajo, E},
abstractNote = {Purpose: To calculate the effect of lack of backscatter from air and attenuation of bone on dose distributions in brachytherapy surface treatment of head. Existing treatment planning systems based on TG43 do not account for heterogeneities, and thus may overestimate the dose to the brain. While brachytherapy generally has rapid dose falloff, the dose to the deeper tissues (in this case, the brain) can become significant when treating large curved surfaces. Methods: Applicator geometries representing a range of clinical cases were simulated in MCNP5. An Ir-192 source was modeled using the energy spectrum presented by TG-43. The head phantom was modeled as a 7.5-cm radius water sphere, with a 7 -mm thick skull embedded 5-mm beneath the surface. Dose values were calculated at 20 points inside the head, in which 10 of them were on the central axis and the other 10 on the axis connecting the central of the phantom with the second to last source from the applicator edge. Results: Central and peripheral dose distributions for a range of applicator and head sizes are presented. The distance along the central axis at which the dose falls to 80% of the prescribed dose (D80) was 7 mm for a representative small applicator and 9 mm for a large applicator. Corresponding D50 and D30 for the same small applicator were 17 mm and 32 mm respectively. D50 and D30 for the larger applicator were 32 mm and 60 mm respectively. These results reflect the slower falloff expected for larger applicators on a curved surface. Conclusion: Our results can provide guidance for clinicians to calculate the dose reduction effect due to bone attenuation and the lack of backscatter from air to estimate the brain dose for the HDR treatments of surface lesions.},
doi = {10.1118/1.4924713},
url = {https://www.osti.gov/biblio/22548402}, journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}