title: Markerless lung tumor tracking and trajectory reconstruction using rotational cone-beam projections: a feasibility study.
abstract: Algorithms for direct tumor tracking in rotational cone-beam projections and for reconstruction of phase-binned 3D tumor trajectories were developed. The feasibility of the algorithm was demonstrated on a digital phantom, a physical phantom and two patients. Tracking results were obtained by comparing reference templates generated from 4DCT to rotational cone-beam projections. The 95th percentile absolute errors (e(95)) in phantom tracking results did not exceed 1.7 mm in either imager dimension, while e(95) in the patients was 3.3 mm or less. Accurate phase-binned trajectories were reconstructed in each case, with 3D maximum errors of no more than 1.0 mm in the phantoms and 2.0 mm in the patients. This work shows the feasibility of a direct tumor tracking technique for rotational images, and demonstrates that an accurate 3D tumor trajectory can be reconstructed from relatively less accurate tracking results. The ability to reconstruct the tumor's average trajectory from a 3D cone-beam CT scan on the day of treatment could allow for better patient setup and quality assurance, while direct tumor tracking in rotational projections could be clinically useful for rotational therapy such as volumetric modulated arc therapy (VMAT).
authors.affiliation: Department of Radiation Oncology, University of California San Diego, La Jolla, CA 92093, USA.
authors.forename: John H
authors.initials: JH
authors.lastname: Lewis
authors.forename: Ruijiang
authors.initials: R
authors.lastname: Li
authors.forename: W Tyler
authors.initials: WT
authors.lastname: Watkins
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Lawson
authors.forename: W Paul
authors.initials: WP
authors.lastname: Segars
authors.forename: Laura I
authors.initials: LI
authors.lastname: Cerviño
authors.forename: William Y
authors.initials: WY
authors.lastname: Song
authors.forename: Steve B
authors.initials: SB
authors.lastname: Jiang
mesh_terms: D000465:Algorithms; D054893:Cone-Beam Computed Tomography / Q000379:methods* / Q000592:standards; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000532:radiotherapy; D009068:Movement; D019047:Phantoms, Imaging; D011786:Quality Control; D012015:Reference Standards; D012399:Rotation; D013997:Time Factors