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Analysis of Composite MVCT Planning Dosimetry with SBRT of Upper Peripheral Lung Cancer

C Yang*, K Doxsee , Y Chen , Monmouth Medical Center, Tinton Falls, NJ

Presentations

SU-E-T-40 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: Quantitatively evaluate and compare the final adaptive planning doses of upper peripherally located lung SBRT treated with Tomotherapy using 3rd party software tool.

Methods: With tumor located in the upper quadrant of lung, a 3rd party software tool was implemented to evaluate the Tomotherapy composite dosimetry created by adaptive fan beam MVCT images described by RTOG 0915 dose criteria (48 Gy / 4 fractions). The composite doses was then summarized with deformable registration in this package with corresponding target and critical structures. The final dosimetry variation, both for target and critical structures, were evaluated in a tabular format and isodose distribution comparisons.

Results: Composite SBRT treatment doses were evaluated with adaptive planning. The PTV and several critical structures were mapped/deformed into the package via DICOM from Tomotherapy after the final composite doses were created. Initial plan versus the final composite plan calculated from verification images were compared. The ITV defined by 4D CT and contoured on MVCT images were correlated in patient repositioning. Final composite dose calculated for PTV coverage has shown 0.1-0.17 cGy coverage (0.2-0.4% of prescription dose) variation. Total lung and cord were both less than 0.17 Gy which represented <0.4% difference. All other critical structure were within statistical significance. The adaptive plans justified/included the breathing and motion during the treatment process. Final 95% isotope line coverage from prescription has been met without issues.

Conclusions: With lung tumor location in the upper peripheral area, breathing control was not necessary required during SBRT treatment using Tomotherapy technique. Slow fan beam CT provides definitive ITV information and the adaptive composite plan for all fractions were suitable for final dose delivery. The final composite dose calculated with Tomotherapy adaptive tool indicated that the composite dosimetry justified the target location with SBRT delivery, safe with minimum margin of errors.

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