SU-E-T-330: To Analyze the Calculation Error of Live Dose-Volume Indices Applying 4D-CT in Radiotherapy for PTVs Within the Liver Completely

Authors


Abstract

Purpose:

To study the variation rule of normal liver dose-volume indices calculation for the liver malignancy patients whose plan target volumes were in the liver completely in all breath phases.

Methods:

Ten patients who accepted radiotherapy for malignant tumor were selected in our study. All patients underwent 4D-CT simulation and 3D-CT simulation in free breathing(FB). 4D-CT was sorted into 10 series CT images according to breath phase, named CT0, CT10 to CT90, respectively. And GTVs were contoured on different CT series, and the individual target volume(ITV) was obtained by merging 10 GTVs from 4D-CT. The PTVs were obtained from ITV applying margins. The PTVs were not beyond the boundary of liver in all breath phase observed by dynamic 4D-CT. The radiotherapy plans were designed and irradiation dose was calculated on 3D-CT images, and the livers were contoured on different series CT images and mapped to 3D-CT images applying rigid registration. To compare the dose-volume difference of livers based on distinct CT images.

Results:

(1)The liver volumes were similar on 4D-CT and 3D-CT images(CTFB 1485±500cm3, CT0 1413±377cm3, CT10 1409±396cm3, CT20 1419±418cm3,CT30 1485±500cm3, CT40 1438±392cm3, CT50 1437±404cm3, CT60 1439±409cm3, CT70 1408±393cm3, CT80 1384±397cm3, CT90 1398±397cm3; F=0.064,p=1.00) (2) The PTVs volume were 30.17±14.62cm3;(3) The mean dose and V5 to V10 of liver were similar among 4D-CT different series CT images(p>0.05), and the indices varied less than ±4% refer to liver on CT50.

Conclusion:

The calculation affection of liver dose-volume indices induced by breath motion were not significant for the PTV within liver completely as estimation before. And more objective prediction indices for radiation induced l

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