Background and purpose
Proof of tumor position during stereotactic body radiotherapy (SBRT) delivery is desirable. We investigated if cone-beam CT (CBCT) scans reconstructed from (collimated) fluoroscopic kV images acquired during irradiation could show the dominant tumor position.
Materials and methods
Full-arc CBCT scans were reconstructed using FDK filtered back projection from 38 kV fluoroscopy datasets (16 patients) continuously acquired during volumetric modulated spine SBRT. CBCT-CT match values were compared to the average spine offset values found using template matching + triangulation of the individual kV images. Multiple limited-arc CBCTs were reconstructed from fluoroscopic images acquired during lung SBRT of an anthropomorphic thorax phantom using 20–180° arc lengths and for 3 breath-hold lung SBRT patients.
Differences between 3D CBCT-CT match results and average spine offsets found using template matching + triangulation were 0.1 ± 0.1 mm for all directions (range: 0.0–0.5 mm). For limited-arc CBCTs of the thorax phantom, the automatic 3D CBCT-CT match results for arc lengths of 80–180° were ≤1 mm. 20° CBCT reconstruction still allowed for positional verification in 2D.
(Limited-arc) CBCT reconstructions of kV images acquired during irradiation can identify the dominant position of the tumor during treatment delivery.
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Published online: May 19, 2017
Accepted: April 29, 2017
Received in revised form: April 26, 2017
Received: October 28, 2016
© 2017 Elsevier B.V. All rights reserved.