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Title: SU-E-T-404: Evaluation of the Effect of Spine Hardware for CyberKnife Spinal Stereotactic Radiosurgery

Abstract

Purpose: Spine hardware made of high-Z materials such as titanium has the potential to affect the dose distribution around the metal rods in CyberKnife spinal stereotactic radiosurgery (SRS) treatments. The purpose of this work was to evaluate the magnitude of such effect retrospectively for clinical CyberKnife plans. Methods: The dose calculation was performed within the MultiPlan treatment planning system using the ray tracing (RT) and Monte Carlo (MC) method. A custom density model was created by extending the CT-to-Density table to titanium density of 4.5 g/cm3 with the CT number of 4095. To understand the dose perturbation caused by the titanium rod, a simple beam setup (7.5 mm IRIS collimator) was used to irradiate a mimic rod (5 mm) with overridden high density. Five patient spinal SRS cases were found chronologically from 2010 to 2015 in our institution. For each case, the hardware was contoured manually. The original plan was re-calculated using both RT and MC methods with and without rod density override without changing clinical beam parameters. Results: The simple beam irradiation shows that there is 10% dose increase at the interface because of electron backscattering and 7% decrease behind the rod because of photon attenuation. For actual clinicalmore » plans, the iso-dose lines and DVHs are almost identical (<2%) for calculations with and without density override for both RT and MC methods. However, there is a difference of more than 10% for D90 between RT and MC method. Conclusion: Although the dose perturbation around the metal rods can be as large as 10% for a single beam irradiation, for clinical treatments with complex beam composition the effect of spinal hardware to the PTV and spinal dose is minimal. As such, the MC dose algorithm without rod density override for CyberKnife spinal SRS is acceptable.« less

Authors:
; ; ; ; ; ;  [1]
  1. University Hospitals Case Medical Center, Cleveland, OH (United States)
Publication Date:
OSTI Identifier:
22548450
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; ALGORITHMS; BACKSCATTERING; BEAMS; COMPUTERIZED TOMOGRAPHY; DISTURBANCES; EVALUATION; MONTE CARLO METHOD; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIOTHERAPY; SURGERY; TITANIUM; VERTEBRAE

Citation Formats

Yuan, J, Zhang, Y, Zheng, Y, Wessels, B, Machtay, M, Yao, M, and Lo, S. SU-E-T-404: Evaluation of the Effect of Spine Hardware for CyberKnife Spinal Stereotactic Radiosurgery. United States: N. p., 2015. Web. doi:10.1118/1.4924765.
Yuan, J, Zhang, Y, Zheng, Y, Wessels, B, Machtay, M, Yao, M, & Lo, S. SU-E-T-404: Evaluation of the Effect of Spine Hardware for CyberKnife Spinal Stereotactic Radiosurgery. United States. doi:10.1118/1.4924765.
Yuan, J, Zhang, Y, Zheng, Y, Wessels, B, Machtay, M, Yao, M, and Lo, S. Mon . "SU-E-T-404: Evaluation of the Effect of Spine Hardware for CyberKnife Spinal Stereotactic Radiosurgery". United States. doi:10.1118/1.4924765.
@article{osti_22548450,
title = {SU-E-T-404: Evaluation of the Effect of Spine Hardware for CyberKnife Spinal Stereotactic Radiosurgery},
author = {Yuan, J and Zhang, Y and Zheng, Y and Wessels, B and Machtay, M and Yao, M and Lo, S},
abstractNote = {Purpose: Spine hardware made of high-Z materials such as titanium has the potential to affect the dose distribution around the metal rods in CyberKnife spinal stereotactic radiosurgery (SRS) treatments. The purpose of this work was to evaluate the magnitude of such effect retrospectively for clinical CyberKnife plans. Methods: The dose calculation was performed within the MultiPlan treatment planning system using the ray tracing (RT) and Monte Carlo (MC) method. A custom density model was created by extending the CT-to-Density table to titanium density of 4.5 g/cm3 with the CT number of 4095. To understand the dose perturbation caused by the titanium rod, a simple beam setup (7.5 mm IRIS collimator) was used to irradiate a mimic rod (5 mm) with overridden high density. Five patient spinal SRS cases were found chronologically from 2010 to 2015 in our institution. For each case, the hardware was contoured manually. The original plan was re-calculated using both RT and MC methods with and without rod density override without changing clinical beam parameters. Results: The simple beam irradiation shows that there is 10% dose increase at the interface because of electron backscattering and 7% decrease behind the rod because of photon attenuation. For actual clinical plans, the iso-dose lines and DVHs are almost identical (<2%) for calculations with and without density override for both RT and MC methods. However, there is a difference of more than 10% for D90 between RT and MC method. Conclusion: Although the dose perturbation around the metal rods can be as large as 10% for a single beam irradiation, for clinical treatments with complex beam composition the effect of spinal hardware to the PTV and spinal dose is minimal. As such, the MC dose algorithm without rod density override for CyberKnife spinal SRS is acceptable.},
doi = {10.1118/1.4924765},
journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 42,
place = {United States},
year = {2015},
month = {6}
}