A delivery transfer function (DTF) analysis for helical tomotherapy

The previous theoretical work of a delivery transfer function (DTF) in radiotherapy is expanded to include the unique intensity modulation method of helical tomotherapy. In addition to the collimation of each beamlet, and the Gaussian scatter convolution spreading of the dose that other radiotherapy...

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Bibliographic Details
Published in:Physics in medicine & biology 2007-05, Vol.52 (9), p.2355-2365
Main Authors: Kissick, Michael W, Mackie, Thomas Rockwell, Jeraj, Robert
Format: Article
Language:English
Subjects:
Algorithms
Radiotherapy Planning, Computer-Assisted - methods
Radiotherapy, Intensity-Modulated - instrumentation
Radiotherapy, Intensity-Modulated - methods
Tomography, Spiral Computed - methods
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Summary:The previous theoretical work of a delivery transfer function (DTF) in radiotherapy is expanded to include the unique intensity modulation method of helical tomotherapy. In addition to the collimation of each beamlet, and the Gaussian scatter convolution spreading of the dose that other radiotherapy units have, helical tomotherapy uses 51 small arcs of varying lengths to adjust the intensity. The blurring from these arcs is not taken into account during treatment planning. A theoretical DTF is constructed, and a calculation is performed which includes this unique source motion in relation to the other DTF components. Various typical delivery parameters are used to generate resolution maps for a constant intensity projection. Near the isocenter, the transverse (to a given beam direction) blurring is small but at larger radii (>6 cm), the source blurring dominates over leaf size. For most clinical situations, this inherent source motion blurring is expected to be negligible.
ISSN:0031-9155
1361-6560
DOI:10.1088/0031-9155/52/9/002