title: Image guided respiratory gated hypofractionated Stereotactic Body Radiation Therapy (H-SBRT) for liver and lung tumors: Initial experience.
abstract: To evaluate our initial experience with image guided respiratory gated H-SBRT for liver and lung tumors. The system combines a stereoscopic x-ray imaging system (ExacTrac X-Ray 6D) with a dedicated conformal stereotactic radiosurgery and radiotherapy linear accelerator (Novalis) and ExacTrac Adaptive Gating for dynamic adaptive treatment. Moving targets are located and tracked by x-ray imaging of implanted fiducial markers defined in the treatment planning computed tomography (CT). The marker position is compared with the position in verification stereoscopic x-ray images, using fully automated marker detection software. The required shift for a correct, gated set-up is calculated and automatically applied. We present our acceptance testing and initial experience in patients with liver and lung tumors. For treatment planning CT and Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET) as well as magnetic resonance imaging (MRI) taken at free breathing and expiration breath hold with internal and external fiducials present were used. Patients were treated with 8-11 consecutive fractions to a dose of 74.8-79.2 Gy. Phantom tests demonstrated targeting accuracy with a moving target to within +/-1 mm. Inter- and intrafractional patient set-up displacements, as corrected by the gated set-up and not detectable by a conventional set-up, were up to 30 mm. Verification imaging to determine target location during treatment showed an average marker position deviation from the expected position of up to 4 mm on real patients. This initial evaluation shows the accuracy of the system and feasibility of image guided real-time respiratory gated H-SBRT for liver and lung tumors.
authors.affiliation: Department of Radiation Oncology, Charité Campus Mitte, Charité-Universitätsmedizin Berlin, Germany. Reinhard.Wurm@charite.de
authors.forename: R E
authors.initials: RE
authors.lastname: Wurm
authors.forename: F
authors.initials: F
authors.lastname: Gum
authors.forename: S
authors.initials: S
authors.lastname: Erbel
authors.forename: L
authors.initials: L
authors.lastname: Schlenger
authors.forename: D
authors.initials: D
authors.lastname: Scheffler
authors.forename: D
authors.initials: D
authors.lastname: Agaoglu
authors.forename: R
authors.initials: R
authors.lastname: Schild
authors.forename: B
authors.initials: B
authors.lastname: Gebauer
authors.forename: P
authors.initials: P
authors.lastname: Rogalla
authors.forename: M
authors.initials: M
authors.lastname: Plotkin
authors.forename: K
authors.initials: K
authors.lastname: Ocran
authors.forename: V
authors.initials: V
authors.lastname: Budach
mesh_terms: D000368:Aged; D002277:Carcinoma / Q000601:surgery*; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000601:surgery*; D008175:Lung Neoplasms / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D019047:Phantoms, Imaging; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D012119:Respiration; D025321:Surgery, Computer-Assisted / Q000379:methods*