Markerless 3D tumor tracking during single-fraction free-breathing 10MV flattening-filter-free stereotactic lung radiotherapy. (November 2021)

• Record Type: Journal Article
• Authors: Remmerts de Vries, I.F.; Dahele, Max; Mostafavi, Hassan; Slotman, Ben; Verbakel, Wilko
• Is Part Of: Radiotherapy and oncology. Volume 164(2021)
• Page Start: 6
• Page End: 12
• Publication Date: 2021-11
• Subjects: Radiotherapy -- Markerless tracking -- Lung cancer -- SBRT -- Single fraction; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2021.08.025
• Languages: English
• ISSNs: 0167-8140

Abstract

Highlights: Continuous fluoroscopy during MV delivery allows for markerless real time tumor tracking. 3D lung tumor position monitoring was based on template matching and triangulation. Lung tumor tracking was possible for >70% of the time during single fraction 34Gy lung SBRT. Longitudinal, lateral and vertical position of the tumor was within 3 mm PTV margin 85.3% of the time. The total time from first set-up imaging to end of the last arc was 18.3–31.4 min (mean = 23.4, SD = 4.1). Abstract: Background and purpose: Positional verification during single fraction lung SBRT could increase confidence and reduce the chance of geographic miss. As planar 2DkV imaging during VMAT irradiation is already available on current linear accelerators, markerless tracking based on these images could offer widely available and low-cost verification. We evaluated treatment delivery data and template matching and triangulation for 3D-positional verification during free-breathing, single fraction (34 Gy), 10 MV flattening-filter-free VMAT lung SBRT. Methods and materials: Tumor tracking based on kV imaging at 7 frames/second was performed during irradiation in 6 consecutive patients (7 lesions). Tumor characteristics, tracking ability, comparison of tracking displacements with CBCT-based shifts, tumor position relative to the PTV margin, and treatment times are reported. Results: For all 7 lesions combined, 3D tumor position could be determined for, on average, 71% (51–84%) of the total irradiation time. Visually estimated tracked and automated match +/− manually-corrected CBCT-derived displacements generally agreed within 1 mm. During the tracked period, the longitudinal, lateral and vertical position of the tumor was within a 5 mm/3 mm PTV margin 95.5/85.3% of the time. The PTV was derived from the ITV including all tumor motion. The total time from first set-up imaging to end of the last arc was 18.3–31.4 min (mean = 23.4, SD = 4.1). Conclusion: 3D positional verification during irradiation of small lung targets with limited motion, was feasible. However, tumor position could not be determined for on average 29% of the time. Improvements are needed. Margin reduction may be feasible. Imaging and delivery of a single 34 Gy fraction was fast.