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Assess Interfractional Tumor Motion in SBRT Lung Treatment Using 4D Cone-Beam CT

J Li

J Li*, Y Yu, Y Xiao, Thomas Jefferson Univ Hospital, Philadelphia, PA

SU-E-J-121 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The aim of the study was to assess interfractional tumor motion in SBRT lung treatment using 4D cone-beam computed tomography (CBCT) to check if tumor motion changes during treatment course.

Methods: 4D CBCT scans of eight SBRT lung patients were studied. Each patient had 3-6 fraction treatments. The patients were scanned on an Elekta XVI cone-beam imaging system with 4D acquisition module before each fraction treatment. Reconstructed 4D CBCT images were binned into 10 phases (frames). Tumor motion was assessed on the XVI system by measuring the maximum displacements of tumor border positions among 10 frame images, in superior-inferior (SI), anterior-posterior (AP), and lateral (LAT) directions. Interfactional tumor motion change was determined by calculating the difference of tumor motion of each fraction and that measured on planning 4DCT.

Results: The tumor motion changes were in the ranges of -0.5~0.4 cm, -0.3~0.2 cm, and -0.3~0.2 cm, in the SI, AP, and LAT directions, respectively.

Conclusion: 4D CBCT was used to assess interfractional tumor motions. The results showed that the tumor motion changes were clinically insignificant, with respect to the 1-cm margin used to generate planning target volume from internal target volume.

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