Optimization of acquisition parameters and accuracy of target motion trajectory for four-dimensional cone-beam computed tomography with a dynamic thorax phantom

• Published in: Radiological physics and technology 2015-01, Vol.8 (1), p.97-106
• Main Authors: Shimohigashi, Yoshinobu, Araki, Fujio, Maruyama, Masato, Nakaguchi, Yuji, Nakato, Kengo, Nagasue, Nozomu, Kai, Yudai
• Format: Article
• Language: English
• Subjects: Algorithms; Cone-Beam Computed Tomography - methods; Four-Dimensional Computed Tomography - methods; Humans; Image Processing, Computer-Assisted - methods; Image Processing, Computer-Assisted - standards; Imaging; Medical and Radiation Physics; Medicine; Medicine & Public Health; Movement; Nuclear Medicine; Phantoms, Imaging; Radiology; Radiotherapy; Radiotherapy Planning, Computer-Assisted - standards; Respiration; Thorax - anatomy & histology
• ISSN: 1865-0333; 1865-0341
• DOI: 10.1007/s12194-014-0296-8

Our purpose in this study was to evaluate the performance of four-dimensional computed tomography (4D-CBCT) and to optimize the acquisition parameters. We evaluated the relationship between the acquisition parameters of 4D-CBCT and the accuracy of the target motion trajectory using a dynamic thorax phantom. The target motion was created three dimensionally using target sizes of 2 and 3 cm, respiratory cycles of 4 and 8 s, and amplitudes of 1 and 2 cm. The 4D-CBCT data were acquired under two detector configurations: “small mode” and “medium mode”. The projection data acquired with scan times ranging from 1 to 4 min were sorted into 2, 5, 10, and 15 phase bins. The accuracy of the measured target motion trajectories was evaluated by means of the root mean square error (RMSE) from the setup values. For the respiratory cycle of 4 s, the measured trajectories were within 2 mm of the setup values for all acquisition times and target sizes. Similarly, the errors for the respiratory cycle of 8 s were