Fast kilovoltage/megavoltage (kVMV) breathhold cone-beam CT for image-guided radiotherapy of lung cancer

• Published in: Physics in medicine & biology Vol. 55; no. 15; pp. 4203 - 4217
• Main Authors: Wertz, Hansjoerg, Stsepankou, Dzmitry, Blessing, Manuel, Rossi, Michael, Knox, Chris, Brown, Kevin, Gros, Uwe, Boda-Heggemann, Judit, Walter, Cornelia, Hesser, Juergen, Lohr, Frank, Wenz, Frederik
• Format: Journal Article
• Language: English
• Published: England 07.08.2010
• Subjects: Cone-Beam Computed Tomography - instrumentation; Cone-Beam Computed Tomography - methods; Humans; Lung Neoplasms - diagnostic imaging; Lung Neoplasms - physiopathology; Lung Neoplasms - radiotherapy; Phantoms, Imaging; Radiation Dosage; Respiration; Rotation; Time Factors
• ISSN: 1361-6560
• DOI: 10.1088/0031-9155/55/15/001

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.