SU‐E‐J‐22: Measurement‐Based Cross‐Scatter Correction in Dual Detector Cone‐Beam CT
Purpose: A dual detector cone‐beam CT (CBCT) system could potentially allow for dual energy CBCT and dual‐view DTS. However, image quality in this system is severely degraded by the presence of scatter between the two imaging chains, i.e. cross‐scatter. The aim of this work is to develop a measurement‐based method for correcting cross‐scatter without increasing scan‐time or exposure and without adding additional hardware. Methods: The dual detector CBCT imaging system has two tube/detector pairs mounted orthogonally; each 40×30 cm detector has an anti‐scatter grid. The cross‐scatter distribution was measured at a certain angular intervals by firing a single x‐ray tube and reading out both detectors. Cross‐scatter at intermediate angles was estimated by cubic spline interpolation. The cross‐scatter estimates were subtracted from the projections prior to reconstruction. The angular interval between cross‐scatter measurements was optimized for an anthropomorphic pelvic phantom. Accuracy of scatter interpolation was evaluated by comparing to directly measured cross‐scatter. Effectiveness of scatter correction was evaluated by measures of contrast and contrast‐to‐noise ratio (CNR) in reconstructions of an image quality phantom from projection data acquired with and without cross‐scatter. Results: For the pelvic phantom and an angular interval of 11 degrees, interpolated cross‐scatter distributions were within 2.5% of measured cross‐scatter distributions. This error remained constant as the angular interval decreased below 11 degrees and rose sharply to about 90% as the angular interval increased to 34 degrees. The contrast was 58.0%, 70.8% and 70.8%, in the uncorrected, corrected, and cross‐scatter free reconstructions and similarly the CNR was 23.6, 22.8 and 24.9. Conclusions: This measurement‐based method effectively corrects for cross‐scatter without any additional hardware or imaging dose. This work is partially supported by a research grant from Varian Medical Systems. © 2011, American Association of Physicists in Medicine. All rights reserved.
Giles, W; Bowsher, J; li, H; Yin, F
Volume / Issue
Start / End Page
International Standard Serial Number (ISSN)
Digital Object Identifier (DOI)