title: Fast kilovoltage/megavoltage (kVMV) breathhold cone-beam CT for image-guided radiotherapy of lung cancer.
abstract: Long image acquisition times of 60-120 s for cone-beam CT (CBCT) limit the number of patients with lung cancer who can undergo volume image guidance under breathhold. We developed a low-dose dual-energy kilovoltage-megavoltage-cone-beam CT (kVMV-CBCT) based on a clinical treatment unit reducing imaging time to < or =15 s. Simultaneous kVMV-imaging was achieved by dedicated synchronization hardware controlling the output of the linear accelerator (linac) based on detector panel readout signals, preventing imaging artifacts from interference of the linac's MV-irradiation and panel readouts. Optimization was performed to minimize the imaging dose. Single MV-projections, reconstructed MV-CBCT images and images of simultaneous 90 degrees kV- and 90 degrees MV-CBCT (180 degrees kVMV-CBCT) were acquired with different parameters. Image quality and imaging dose were evaluated and compared to kV-imaging. Hardware-based kVMV synchronization resulted in artifact-free projections. A combined 180 degrees kVMV-CBCT scan with a total MV-dose of 5 monitor units was acquired in 15 s and with sufficient image quality. The resolution was 5-6 line pairs cm(-1) (Catphan phantom). The combined kVMV-scan dose was equivalent to a kV-radiation scan dose of approximately 33 mGy. kVMV-CBCT based on a standard linac is promising and can provide ultra-fast online volume image guidance with low imaging dose and sufficient image quality for fast and accurate patient positioning for patients with lung cancer under breathhold.
authors.affiliation: Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany. hansjoerg.wertz@umm.de
authors.forename: Hansjoerg
authors.initials: H
authors.lastname: Wertz
authors.forename: Dzmitry
authors.initials: D
authors.lastname: Stsepankou
authors.forename: Manuel
authors.initials: M
authors.lastname: Blessing
authors.forename: Michael
authors.initials: M
authors.lastname: Rossi
authors.forename: Chris
authors.initials: C
authors.lastname: Knox
authors.forename: Kevin
authors.initials: K
authors.lastname: Brown
authors.forename: Uwe
authors.initials: U
authors.lastname: Gros
authors.forename: Judit
authors.initials: J
authors.lastname: Boda-Heggemann
authors.forename: Cornelia
authors.initials: C
authors.lastname: Walter
authors.forename: Juergen
authors.initials: J
authors.lastname: Hesser
authors.forename: Frank
authors.initials: F
authors.lastname: Lohr
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012119:Respiration; D012399:Rotation; D013997:Time Factors