title: Optimization of dual-energy subtraction chest radiography by use of a direct-conversion flat-panel detector system.
abstract: We aimed to optimize the exposure conditions in the acquisition of soft-tissue images using dual-energy subtraction chest radiography with a direct-conversion flat-panel detector system. Two separate chest images were acquired at high- and low-energy exposures with standard or thick chest phantoms. The high-energy exposure was fixed at 120 kVp with the use of an auto-exposure control technique. For the low-energy exposure, the tube voltages and entrance surface doses ranged 40-80 kVp and 20-100 % of the dose required for high-energy exposure, respectively. Further, a repetitive processing algorithm was used for reduction of the image noise generated by the subtraction process. Seven radiology technicians ranked soft-tissue images, and these results were analyzed using the normalized-rank method. Images acquired at 60 kVp were of acceptable quality regardless of the entrance surface dose and phantom size. Using a repetitive processing algorithm, the minimum acceptable doses were reduced from 75 to 40 % for the standard phantom and to 50 % for the thick phantom. We determined that the optimum low-energy exposure was 60 kVp at 50 % of the dose required for the high-energy exposure. This allowed the simultaneous acquisition of standard radiographs and soft-tissue images at 1.5 times the dose required for a standard radiograph, which is significantly lower than the values reported previously.
authors.affiliation: Division of Radiology, Department of Medical Technology, Osaka University Hospital, 2-15, Yamadaoka, Suita, Osaka, 565-0871, Japan, m_shimada@hp-rad.med.osaka-u.ac.jp.
authors.forename: Mari
authors.initials: M
authors.lastname: Fukao
authors.forename: Kiyosumi
authors.initials: K
authors.lastname: Kawamoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsuzawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Honda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Iwaki
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Doi
mesh_terms: D000465:Algorithms; D005260:Female; D006801:Humans; D008875:Middle Aged; D055613:Multiple Pulmonary Nodules / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011786:Quality Control; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013902:Radiography, Thoracic / Q000295:instrumentation* / Q000379:methods*