On the accuracy of dose prediction near metal fixation devices for spine SBRT

The metallic fixations used in surgical procedures to support the spine mechanically usually consist of high‐density materials. Radiation therapy to palliate spinal cord compression can include prophylactic inclusion of potential tumor around the site of such fixation devices. Determination of the c...

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Bibliographic Details
Published in:Journal of applied clinical medical physics 2016-05, Vol.17 (3), p.475-485
Main Authors: Cheng, Zhangkai J., Bromley, Regina M., Oborn, Brad, Carolan, Martin, Booth, Jeremy T.
Format: Article
Language:English
Subjects:
Accuracy
Algorithms
Cancer therapies
Computer Simulation
dose calculation accuracy
Dosimetry
Humans
Metals - chemistry
Monte Carlo Method
Patients
Phantoms, Imaging
Prostheses
Radiation Measurements
Radiation therapy
Radiosurgery - instrumentation
Radiosurgery - methods
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted - methods
Radiotherapy, Intensity-Modulated - methods
Spinal cord
Spinal Neoplasms - surgery
spine SBRT
Studies
Titanium alloys
Tomography, X-Ray Computed
Transplants & implants
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Summary:The metallic fixations used in surgical procedures to support the spine mechanically usually consist of high‐density materials. Radiation therapy to palliate spinal cord compression can include prophylactic inclusion of potential tumor around the site of such fixation devices. Determination of the correct density and shape of the spine fixation device has a direct effect on the dose calculation of the radiation field. Even with the application of modern computed tomography (CT), under‐ or overestimation of dose, both immediately next to the device and in the surrounding tissues, can occur due to inaccuracies in the dose prediction algorithm. In this study, two commercially available dose prediction algorithms (Eclipse AAA and ACUROS), EGSnrc Monte Carlo, and GAFchromic film measurements were compared for a clinical spine SBRT case to determine their accuracy. An open six‐field plan and a clinical nine‐field IMRT plan were applied to a phantom containing a metal spine fixation device. Dose difference and gamma analysis were performed in and around the tumor region adjacent to the fixation device. Dose calculation inconsistency was observed in the open field plan. However, in the IMRT plan, the dose perturbation effect was not observed beyond 5 mm. Our results suggest that the dose effect of the metal fixation device to the spinal cord and the tumor volume is not observable, and all dose calculation algorithms evaluated can provide clinically acceptable accuracy in the case of spinal SBRT, with the tolerance of 95% for gamma criteria of 3%/3 mm. PACS number(s): 87.53.bn, 87.53.Ly, 87.55.kd
ISSN:1526-9914
1526-9914
DOI:10.1120/jacmp.v17i3.5536