title: [Optimization of exposure conditions for amorphous selenium direct conversion DR-based mammography system].
abstract: A new direct-conversion detector for DR mammography has improved the detectability of microcalcifications and masses. Each optimized exposure condition (target/filter combination and tube voltage) was defined through comparison of physical values and visual evaluation on breast specimens using the innovative DR mammography. The contrast-to-noise-ratios (CNRs) of PMMA phantoms of various thicknesses were obtained under a variety of exposure conditions whose average glandular doses (AGDs) were made consistent. Fifty breast specimens were irradiated under these combinations. Visual evaluation was conducted on the images, whose histograms were controlled for consistency. In the phantoms with thicknesses of 20 mm or more, tungsten/rhodium had the highest CNRs of the targets/filters such as molybdenum/molybdenum and molybdenum/rhodium. For visualizing microcalcifications and masses on breast specimens of thicknesses of 35 mm and below, molybdenum/molybdenum was the best. Nevertheless, to obtain better image quality, molybdenum/rhodium was superior for 35-55 mm thickness, and tungsten/rhodium was superior for 55 mm and above under the same AGD, enabling accurate and efficient diagnosis. The study showed that the exposure conditions differ for obtaining the highest CNR using phantoms and those under which breast specimen images allow the most accurate and efficient diagnosis. In addition, image evaluations of the breast specimens allowed optimization of exposure conditions that are closer to those of the actual diagnosis using mammography.
authors.affiliation: Department of Advanced Diagnosis, Clinical Research Center, National Hospital Organization Nagoya Medical Center.
authors.forename: Tokiko
authors.initials: T
authors.lastname: Endo
authors.forename: Misaki
authors.initials: M
authors.lastname: Shiraiwa
authors.forename: Mikinao
authors.initials: M
authors.lastname: Oiwa
authors.forename: Chikako
authors.initials: C
authors.lastname: Nishida
authors.forename: Takako
authors.initials: T
authors.lastname: Morita
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yoshikawa
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Sato
authors.forename: Takako
authors.initials: T
authors.lastname: Hayashi
authors.forename: Shu
authors.initials: S
authors.lastname: Ichihara
authors.forename: Suzuko
authors.initials: S
authors.lastname: Moritani
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Hirofuji
authors.forename: Takuya
authors.initials: T
authors.lastname: Wakayama
mesh_terms: D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D005374:Filtration; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D008327:Mammography / Q000295:instrumentation* / Q000379:methods; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012542:Scattering, Radiation; D012643:Selenium
chemical_list: D012643:Selenium