title: Real-time 2D/3D registration using kV-MV image pairs for tumor motion tracking in image guided radiotherapy.
abstract: Intra-fractional respiratory motion during radiotherapy leads to a larger planning target volume (PTV). Real-time tumor motion tracking by two-dimensional (2D)/3D registration using on-board kilo-voltage (kV) imaging can allow for a reduction of the PTV though motion along the imaging beam axis cannot be resolved using only one projection image. We present a retrospective patient study investigating the impact of paired portal mega-voltage (MV) and kV images on registration accuracy. Material and methods. We used data from 10 patients suffering from non-small cell lung cancer (NSCLC) undergoing stereotactic body radiation therapy (SBRT) lung treatment. For each patient we acquired a planning computed tomography (CT) and sequences of kV and MV images during treatment. We compared the accuracy of motion tracking in six degrees-of-freedom (DOF) using the anterior-posterior (AP) kV sequence or the sequence of kV-MV image pairs. Results. Motion along cranial-caudal direction could accurately be extracted when using only the kV sequence but in AP direction we obtained large errors. When using kV-MV pairs, the average error was reduced from 2.9 mm to 1.5 mm and the motion along AP was successfully extracted. Mean registration time was 188 ms. Conclusion. Our evaluation shows that using kV-MV image pairs leads to improved motion extraction in six DOF and is suitable for real-time tumor motion tracking with a conventional LINAC.
authors.affiliation: Center for Medical Physics and Biomedical Engineering, Medical University Vienna , Vienna , Austria.
authors.forename: Hugo
authors.initials: H
authors.lastname: Furtado
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Steiner
authors.forename: Markus
authors.initials: M
authors.lastname: Stock
authors.forename: Dietmar
authors.initials: D
authors.lastname: Georg
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Birkfellner
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D009068:Movement; D009367:Neoplasm Staging; D011379:Prognosis; D011829:Radiation Dosage; D016634:Radiosurgery; D061089:Radiotherapy, Image-Guided; D012119:Respiration; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed