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3 D Dose Delivery Verification Using Megavoltage CT for Stereotactic Body Radiotherapy of NSCLC

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J Gu

J Gu1*, (1) Shandong Cancer Hospital Affiliated to Shandong University, Jinan, Shandong


WE-RAM2-GePD-TT-1 (Wednesday, August 2, 2017) 10:00 AM - 10:30 AM Room: Therapy ePoster Theater

Purpose: Using megavoltage CT (MVCT) image to investigate fraction 3D dose verification for NSCLC patients treated with stereotactic body radiotherapy (SBRT) by helical tomotherapy.

Methods: MVCT scans were made for patients positioning and dose reconstruction by Planed Adaptive Station (version5.0.0.172).Merging MVCT images and planning CT images, recontour the OARs and planning target volume (PTV) copy from planning image. Calculate the actual dose that was delivered for a single treatment fraction. The planned and delivered dose distributions were compared for 5 patients and 25 treatments fractions using dose-volume histograms.

Results: Compared with planning dose distribution, the PTV was acquired higher dose: the values of D2%、D98%、D50% and volume of prescription dose were higher than planning dose(3.3±1.5%、1.4±1.7%、2.0±0.7%、1.1±1.2%,P=0.058,0.01,0.01,0.007). The volume of lungs receiving at least 5 Gy (V5) and 1Gy (V1) were evaluated. For ipsilateral lung, the delivered V5 was higher than planned(1.30±0.48%、p=0.01),but the V1 of ipsilateral lung were lower than planned(0.3±1.1%、p=0.358). Compared to planned dose, the delivered maximum dose of bone, esophagus, and major vessels were increased (3.90±1.59%, 3.79±1.61%, 5.40±3.72%, 3.01±1.92%; P=0.058, 0.01, 0.01, 0.007). However, the major airway maximum dose was reduced (0.7±1.6%, P=0.213).

Conclusion: For NSCLC patients treated with SBRT by helical tomotherapy, the PTV of each treatment fraction received higher dose than planned. The study indicated that verifying each treatment fraction through MVCT images might be novel correction strategy applied in adaptive radiotherapy for NSCLC.

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