| dc.description.abstract |
<p>The need for clinically intuitive metrics for patient-specific quality assurance
in radiation therapy has been well-documented (Zhen, Nelms et al. 2011). A novel
transform method has shown to be effective at converting full-density 3D dose measurements
made in a phantom to dose values in the patient geometry, enabling comparisons using
clinically intuitive metrics such as dose-volume histograms (Oldham et al. 2011).
This work investigates the transform method and compares its calculated dose-volume
histograms (DVHs) to DVH values calculated by a Delta4 QA device (Scandidos), marking
the first comparison of a true 3D system to a semi-3D device using clinical metrics.
Measurements were made using Presage 3D dosimeters, which were readout by an in-house
optical-CT scanner. Three patient cases were chosen for the study: one head-and-neck
VMAT treatment and two spine IMRT treatments. The transform method showed good agreement
with the planned dose values for all three cases. Furthermore, the transformed DVHs
adhered to the planned dose with more accuracy than the Delta4 DVHs. The similarity
between the Delta4 DVHs and the transformed DVHs, however, was greater for one of
the spine cases than it was for the head-and-neck case, implying that the accuracy
of the Delta4 Anatomy software may vary from one treatment site to another. Overall,
the transform method, which incorporates data from full-density 3D dose measurements,
provides clinically intuitive results that are more accurate and consistent than the
corresponding results from a semi-3D Delta4 system.</p>
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