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To Study the Feasibility of Contouring the Planning Organ at Risk Volume for Heart Based On KV-CBCT Images

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G Gong

G Gong*, C Liu, Y Yin, shandong cancer hospitalJinan

SU-E-I-15 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To study the feasibility of contouring heart planning organ at risk volume (PRV) on KV -Cone-beam CT images,and measure the margins for the PRV of heart based on planning CT images.

Methods:15 early stage non-small cell lung cancer (NSCLC) patients accepted radiotherapy in our hospital were selected. For every case,KV-CBCT scan was achieved before every fraction treatment to correct the setup error,and the first 10 serious CBCT images were selected in present research. After contouring the heart on CBCT images according to the same standard,compared the differences of heart between CT and KV-CBCT,analyzed the reproducibility of contouring the heart on different serious CBCT images,measured the margins in different axial direction from heart on planning CT to CBCT.

Results:The heart volume of planning CT was smaller than CBCTs with statistical difference (p<0.05), and the volumes based on different serious CBCT images were similar for every patient (p>0.05). The coincidence of the hearts region on the same anatomical section between the first serious CBCT and others serious could reach to (0.985±0.020) without statistical significant difference (p>0.05). The mean margins for heart from planning CT to CBCT was (10.5 ± 2.8mm) in left direction, (5.9 ± 2.8mm) in right direction, (2.2 ± 1.6mm) in head direction, (3.3 ± 2.2mm) in foot direction, (6.7 ± 1.1mm) in the anterior direction, (4.5mm ± 2.5mm) less in the posterior direction; respectively.

Conclusion:The PRV of heart contouring based on KV-CBCT was feasible with good reproducibility. If there were no CBCT,11mm in left direction,6mm in right direction,3mm in head-foot direction,7mm in the anterior direction, and 5mm in posterior direction should be applied to obtain the PRV of heart.

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