title: Characterization and evaluation of 2.5 MV electronic portal imaging for accurate localization of intra- and extracranial stereotactic radiosurgery.
abstract: 2.5 MV electronic portal imaging, available on Varian TrueBeam machines, was characterized using various phantoms in this study. Its low-contrast detectability, spatial resolution, and contrast-to-noise ratio (CNR) were compared with those of conventional 6 MV and kV planar imaging. Scatter effect in large patient body was simulated by adding solid water slabs along the beam path. The 2.5 MV imaging mode was also evaluated using clinically acquired images from 24 patients for the sites of brain, head and neck, lung, and abdomen. With respect to 6 MV, the 2.5 MV achieved higher contrast and preserved sharpness on bony structures with only half of the imaging dose. The quality of 2.5 MV imaging was comparable to that of kV imaging when the lateral separation of patient was greater than 38 cm, while the kV image quality degraded rapidly as patient separation increased. Based on the results of patient images, 2.5 MV imaging was better for cranial and extracranial SRS than the 6 MV imaging.
authors.affiliation: Radiation Oncology; Texas Oncology. kwanghyun.song@usoncology.com.
authors.forename: Kwang Hyun
authors.initials: KH
authors.lastname: Song
authors.forename: Karen Chin
authors.initials: KC
authors.lastname: Snyder
authors.forename: Jinkoo
authors.initials: J
authors.lastname: Kim
authors.forename: Haisen
authors.initials: H
authors.lastname: Li
authors.forename: Wen
authors.initials: W
authors.lastname: Ning
authors.forename: Robert
authors.initials: R
authors.lastname: Rusnac
authors.forename: Paul
authors.initials: P
authors.lastname: Jackson
authors.forename: James
authors.initials: J
authors.lastname: Gordon
authors.forename: Salim M
authors.initials: SM
authors.lastname: Siddiqui
authors.forename: Indrin J
authors.initials: IJ
authors.lastname: Chetty
mesh_terms: D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods