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Comparison of Dose Difference of Heart Based On KV-CBCT and Planning CT in the Stereotactic Body Radiotherapy (SBRT) of Early Stage Non-Small Cell Lung Cancer (NSCLC)

Y Yin*, J Chen, Shandong Cancer Hospital, Jinan, Shandong

SU-E-J-195 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To compare the difference in evaluating the heart irradiation dose based on different heart rang contoured on KV-CBCT and planning CT images in the stereotactic body radiotherapy (SBRT) of early stage non-small cell lung cancer (NSCLC).

Methods: 15 early 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 used to research. Contour the heart rang on CBCT and planning CT images, analyze the volume and dose-volume indices differences.

Results: (1)The heart volume on first CBCT (717±103 cm3) was larger than planning CT (588±90 cm3) with statistical difference (p<0.05). (2) The relative dose-volume indices obtained on CBCT images were larger than planning CT with statistical difference(p<0.05): V10Gy-R(18.9±11.7%vs17.4±11.8%), V15Gy-R(14.4±10.2%vs 2.8±10.4%), V20Gy-R(10.5±9.0%vs9.0±8.9%), V25Gy-R(6.6±2.8%vs4.5±2.3%), V30Gy-R(4.2±2.2%vs2.5±1.6%), V35Gy-R(3.2±1.8%vs1.7±1.3%), expect for V5Gy-R(47.7±16.4% vs 49.0±16.0%,P>0.05); (3)The absolute dose-volume indices obtained on CBCT images were larger than planning CT: V5Gy-A (333±78.4vs 282±61.7cm3), V10Gy-A (133±68.6 vs 246±68.4 cm3), V15Gy-A (102±62.6 vs101±59.0 cm3), V20Gy-A (74±55.8vs 52.5±46.4 cm3), V25Gy-A (46±16.9 vs 27±12.0 cm3), V30Gy-A (30±14.4 vs 15±8.7 cm3), V35Gy-A (24±12.0 vs 10±7.0 cm3), and all differences were statistical significant (P<0.05). (4) The dose of certain heart volume Dmean, Dmax based on CBCT images
were larger than CT images and differed statistically significantly: D50cm3(19.9±7.7vs17.1±6.3 Gy), D100cm3 (15.3±6.2vs12.8±5.7Gy), D150cm3 (11.8±5.5 vs 9.2±3.4Gy), D200cm3 (8.2±2.0 vs 6.8±1.5), D250cm3 (6.4±1.7 vs5.2±2.0Gy), Dmean(7.0±2.8vs 6.5±2.4Gy) and Dmax(45.7±13.1vs 45.1±13.5Gy) .

Conclusion:The more accurate and objective dose-volume indices could be obtained applying KV-CBCT in SBRT of NSCLC.

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