title: Cone-beam CT based image-guidance for extracranial stereotactic radiotherapy of intrapulmonary tumors.
abstract: Cone-beam CT (CB-CT) based image-guidance was evaluated for extracranial stereotactic radiotherapy of intrapulmonary tumors. A total of 21 patients (25 lesions: prim. NSCLC n = 6; pulmonary metastases n = 19) were treated with stereotactic radiotherapy (1 to 8 fractions). Prior to every fraction a CB-CT was acquired in treatment position, errors between planned and actual tumor position were measured and corrected. Intra- and inter-observer variability of manual evaluation of tumor position error was investigated and this manual method was compared with automatic image registration. Based on CB-CTs from 66 fractions the discrepancy (3-D vector) between planned and actual tumor position was 7.7 mm +/-1.3 mm. Tumor position error relative to the bony anatomy was 5.3 mm +/-1.2 mm, the correlation between bony anatomy and tumor position was poor. Intra-observer and inter-observer variability of manual evaluation of tumor position error was 0.9 mm +/-0.8 mm and 2.3 mm +/-1.1 mm, respectively. Automatic image registration showed highly reproducible results (<1 mm). However, compared with manual registration a systematic error was found in direction of predominant tumor breathing motion (2.5 mm vs 1.4 mm). Image-guidance using CB-CT was validated for high precision radiotherapy of intrapulmonary tumors. It was shown that both the planning reference and the verification image study have to consider tumor breathing motion.
authors.affiliation: Department of Radiation Oncology, University of Wuerzburg, Wuerzburg, Germany. guckenberger_m@klinik.uni-wuerzburg.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Guckenberger
authors.forename: Juergen
authors.initials: J
authors.lastname: Meyer
authors.forename: Juergen
authors.initials: J
authors.lastname: Wilbert
authors.forename: Kurt
authors.initials: K
authors.lastname: Baier
authors.forename: Gerd
authors.initials: G
authors.lastname: Mueller
authors.forename: Joern
authors.initials: J
authors.lastname: Wulf
authors.forename: Michael
authors.initials: M
authors.lastname: Flentje
mesh_terms: D000368:Aged; D002277:Carcinoma / Q000556:secondary / Q000601:surgery; D002289:Carcinoma, Non-Small-Cell Lung / Q000601:surgery*; D015179:Colorectal Neoplasms / Q000473:pathology; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000556:secondary / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009038:Motion; D011786:Quality Control; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012119:Respiration; D025321:Surgery, Computer-Assisted / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*