Optimizing Lung SBRT Delivery: Role of Multiple Cbcts in Managing Intra-Fraction Motion
Recommended Citation
Huang-Vredevoogd JY, Zhao B, Riess JA, Gallagher I, Doemer AJ, Thind KS. Optimizing Lung SBRT Delivery: Role of Multiple Cbcts in Managing Intra-Fraction Motion. Med Phys 2025; 52(10):673.
Document Type
Conference Proceeding
Publication Date
9-30-2025
Publication Title
Med Phys
Keywords
adult, cone beam computed tomography, conference abstract, controlled study, female, four dimensional computed tomography, human, lung cancer, major clinical study, male, motion, radiosurgery, radiotherapy, retrospective study, stereotactic body radiation therapy, workflow
Abstract
Purpose: Stereotactic body radiation therapy (SBRT) is commonly used for early-stage lung cancer. While pre-treatment CT captures some tumor motion, it may not fully represent intra-fraction motion during treatment. This study evaluates the need for increased intra-fraction imaging frequency in lung SBRT by identifying patients with greater than average motion. Methods: A retrospective study was performed on 100 SBRT lung patients treated with 45∼60Gy in 5 fractions from 09/2022 to 08/2024. Internal target volume (ITV) was constructed from free-breathing 4DCT, and PTV included the ITV plus a patient-specific margin of 0.3∼0.8cm. Cone-beam CT (CBCT) was used for image guidance for all treatments. The treatment workflow included an initial CBCT (CBCTi) followed by a verification CBCT (CBCTv). Additionally, at 1st fraction and the discretion of treatment team at subsequent fractions, 280 out of the 500 fractions had mid-treat CBCT (CBCTm). Any deviation observed by the CBCTs at the target was corrected. The additional deviation at CBCTv or CBCTm, and time between successive CBCTs was recorded. Results: The correction at CBCTv was 0.13±0.21cm (N=500). While majority patients did not have intra-fraction correction ≥0.5cm at CBCTv, deviation ≥0.5cm was observed in 1 fraction on 9 patients, 2 fractions on 4 patients, 3 fractions on 3 patients, and 4 fractions on 1 patient. Of the 280 fractions that had both CBCTv and CBCTm, intra-fraction corrections decreased from 0.17±0.21cm at CBCTv to 0.10±0.16cm at CBCTm, with a 90th percentile of 0.46 and 0.28cm, correspondingly. The time between CBCTi and CBCTv, and between CBCTv and CBCTm, was 5.8±2.1 and 6.5±1.9min, respectively. Conclusion: A small percentage of SBRT lung patients had more intra-fraction motion than normal. Multiple CBCTs can identify such patients and potentially mitigate the impact of any intra-fraction motion. .
Volume
52
Issue
10
First Page
673
