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Accuracy of Dose-Volume Metric Calculation for Small Volume Radiosurgery Targets

D Stanley1*, H Liu2, D Bridges1, E Thomas1, R Cardan1,J Fiveash1, R Popple1, (1) The University of Alabama at Birmingham, Birmingham, AL, (2) Thomas Jefferson University, Philadelphia, PA

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: For stereotactic radiosurgery (SRS), accurate evaluation of dose-volume metrics for small structures is important. The purpose of this study was to compare the DVH metric capabilities of three commercial dose-volume analysis tools (Eclipse, MIM, and Velocity).


Methods: DICOM dose and structure set files created using MATLAB were imported and evaluated in each of the tools. Each structure set consisted of 50 randomly placed spherical targets. The dose distributions were created on a 1 mm grid using an analytic model such that the dose-volume metrics of the spheres was known. Structure sets were created for 5, 10, 15, 20 mm diameter spheres. The reported structure volume, V100%[cc], and V50%[cc], and the RTOG conformity index, were compared with the analytical values.


Results: MIM and Velocity, the average difference in the structure volume from the analytical volume was 0.0% and < 0.6% for all sphere diameters, respectively. For Eclipse, the average difference was -9.6%, -2.2%, -0.9%, and -0.4% for the 5, 10, 15, 20 mm spheres, respectively. For V100%[cc], the average difference from the analytical volume for the 5 mm sphere diameter was -3.4%, -3.6%, -1.4% for MIM, Velocity, and Eclipse, respectively, and < 0.5% for diameters 10, 15, and 20 mm. For V50%[cc], the average difference from the analytical volume was < 0.6%. The analytical CI was 1. For MIM and Velocity, the average CI was 0.97 for the 5 mm sphere diameter and 1.00 for diameters 10, 15, and 20 mm. For Eclipse, the average CI was 1.09, 1.02, 1.01, and 1.01 for the 5, 10, 15, 20 mm spheres, respectively.


Conclusion: underestimated the volume for the smallest spheres, resulting in overestimation of the conformity index. Work is underway to extend this investigation to additional tools used for evaluation of SRS dose-volume metrics.

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Keywords

Stereotactic Radiosurgery, Dose Volume Histograms

Taxonomy

TH- External Beam- Photons: extracranial stereotactic/SBRT

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