Convolution-based Gamma Knife planning from ICON CBCT: Three-level stepwise electron density assignment versus Hounsfield Unit curve.
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All Authors
Fallows, PB.
Wright, G.
LTHT Author
Fallows, Peter
Wright, Gavin
Wright, Gavin
LTHT Department
Oncology
Leeds Cancer Centre
Medical Physics & Engineering
Leeds Cancer Centre
Medical Physics & Engineering
Non Medic
Clinical Scientist
Clinical Scientist
Clinical Scientist
Publication Date
2025
Item Type
Journal Article
Language
Subject
Subject Headings
Abstract
Aims: To assess the suitability of CBCT images for dose calculation using the convolution algorithm.
Methods: A CT to electron density curve was produced for the Gamma Knife ICON CBCT scanner. A three-level stepwise curve with fixed electron densities for air, brain tissue and bone was also produced. For 10 patients, the beam on time for shots in 11 locations within the brain was calculated using each of these curves and compared to beam on times calculated using the TMR10 algorithm, and the convolution algorithm with CT images.
Results: The ratios of the average beam on time for convolution versus TMR10 were 1.058, 1.216 and 1.052 for CT images, CBCT images (Hounsfield unit electron density curve) and CBCT images (three-level stepwise curve with fixed electron densities) respectively.
Conclusions: Using ICON CBCT images for dose calculation can result in an underestimation of the dose compared to convolution using CT images. However, using CBCT images along with a three-level stepwise electron density curve with fixed electron densities can provide good agreement with doses calculated using convolution with CT images.
Journal
Journal of Radiosurgery and SBRT