title: Accuracy of image guidance using free-breathing cone-beam computed tomography for stereotactic lung radiotherapy.
abstract: Movement of the target object during cone-beam computed tomography (CBCT) leads to motion blurring artifacts. The accuracy of manual image matching in image-guided radiotherapy depends on the image quality. We aimed to assess the accuracy of target position localization using free-breathing CBCT during stereotactic lung radiotherapy. The Vero4DRT linear accelerator device was used for the examinations. Reference point discrepancies between the MV X-ray beam and the CBCT system were calculated using a phantom device with a centrally mounted steel ball. The precision of manual image matching between the CBCT and the averaged intensity (AI) images restructured from four-dimensional CT (4DCT) was estimated with a respiratory motion phantom, as determined in evaluations by five independent operators. Reference point discrepancies between the MV X-ray beam and the CBCT image-guidance systems, categorized as left-right (LR), anterior-posterior (AP), and superior-inferior (SI), were 0.33 ± 0.09, 0.16 ± 0.07, and 0.05 ± 0.04 mm, respectively. The LR, AP, and SI values for residual errors from manual image matching were -0.03 ± 0.22, 0.07 ± 0.25, and -0.79 ± 0.68 mm, respectively. The accuracy of target position localization using the Vero4DRT system in our center was 1.07 ± 1.23 mm (2 SD). This study experimentally demonstrated the sufficient level of geometric accuracy using the free-breathing CBCT and the image-guidance system mounted on the Vero4DRT. However, the inter-observer variation and systematic localization error of image matching substantially affected the overall geometric accuracy. Therefore, when using the free-breathing CBCT images, careful consideration of image matching is especially important.
authors.affiliation: Department of Therapeutic Radiology, Nagoya University Graduate School of Medicine, Nagoya, Japan; Department of Radiation Oncology, Okayama Central Hospital, Okayama, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kamomae
authors.affiliation: Department of Radiation Oncology, Graduate School of Medical Science, Kinki University, Osaka, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Monzen
authors.affiliation: Division of Clinical Radiology Service, Okayama Central Hospital, Okayama, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Nakayama
authors.affiliation: Division of Clinical Radiology Service, Okayama Central Hospital, Okayama, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Mizote
authors.affiliation: Division of Clinical Radiology Service, Okayama Central Hospital, Okayama, Japan.
authors.forename: Yuuichi
authors.initials: Y
authors.lastname: Oonishi
authors.affiliation: Department of Radiation Oncology, Okayama Central Hospital, Okayama, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Kaneshige
authors.affiliation: Department of Radiation Oncology, Okayama Central Hospital, Okayama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sakamoto
mesh_terms: D054893:Cone-Beam Computed Tomography; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D061089:Radiotherapy, Image-Guided; D012119:Respiration