title: Reduced exposure using asymmetric cone beam processing for wide area detector cardiac CT.
abstract: The purpose of this study was to estimate dose reduction after implementation of asymmetrical cone beam processing using exposure differences measured in a water phantom and a small cohort of clinical coronary CTA patients. Two separate 320 × 0.5 mm detector row scans of a water phantom used identical cardiac acquisition parameters before and after software modifications from symmetric to asymmetric cone beam acquisition and processing. Exposure was measured at the phantom surface with Optically Stimulated Luminescence (OSL) dosimeters at 12 equally spaced angular locations. Mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at the center plus four peripheral locations in the water phantom. To assess image quality, mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at five points within the water phantom. Retrospective evaluation of 64 patients (37 symmetric; 27 asymmetric acquisition) included clinical data, scanning parameters, quantitative plus qualitative image assessment, and estimated radiation dose. In the water phantom, the asymmetric cone beam processing reduces exposure by approximately 20% with no change in image quality. The clinical coronary CTA patient groups had comparable demographics. The estimated dose reduction after implementation of the asymmetric approach was roughly 24% with no significant difference between the symmetric and asymmetric approach with respect to objective measures of image quality or subjective assessment using a four point scale. When compared to a symmetric approach, the decreased exposure, subsequent lower patient radiation dose, and similar image quality from asymmetric cone beam processing supports its routine clinical use.
authors.affiliation: Applied Imaging Science Laboratory, Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Arash
authors.initials: A
authors.lastname: Bedayat
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Rybicki
authors.forename: Kanako
authors.initials: K
authors.lastname: Kumamaru
authors.forename: Sara L
authors.initials: SL
authors.lastname: Powers
authors.forename: Jason
authors.initials: J
authors.lastname: Signorelli
authors.forename: Michael L
authors.initials: ML
authors.lastname: Steigner
authors.forename: Chloe
authors.initials: C
authors.lastname: Steveson
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Soga
authors.forename: Kimberly
authors.initials: K
authors.lastname: Adams
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Mitsouras
authors.forename: Melvin
authors.initials: M
authors.lastname: Clouse
authors.forename: Richard T
authors.initials: RT
authors.lastname: Mather
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001900:Boston; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation; D017023:Coronary Angiography / Q000295:instrumentation / Q000379:methods*; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012189:Retrospective Studies