title: Resolution at oblique incidence angles of a flat panel imager for breast tomosynthesis.
abstract: Oblique incidence of x rays on an imaging detector causes blurring that reduces spatial resolution. For simple projection imaging this effect is small and often ignored. However, for breast tomosynthesis, the incidence angle can be larger (>20 degrees), leading to increased blur for some of the projections. The modulation transfer function (MTF) is measured for a typical phosphor-coupled flat-panel detector versus angular incidence of the x-ray beam for two x-ray spectra: 26 kV Mo/Mo and 40 kV Rh/Al. At an incidence angle of 40 degrees the MTF at 5 mm(-1) falls by 35% and 40% for each spectrum, respectively (and 65%/80% at 8 mm(-1)). Increasing the detector absorber thickness to achieve improved quantum efficiency will cause the blurring effect due to beam obliquity to become greater. The impact of this blur is likely to cause misregistration and increased relative noise in tomosynthesis reconstructed images.
authors.affiliation: Imaging Research, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario, Canada M4N 3M5.
authors.forename: James G
authors.initials: JG
authors.lastname: Mainprize
authors.forename: Aili K
authors.initials: AK
authors.lastname: Bloomquist
authors.forename: Michael P
authors.initials: MP
authors.lastname: Kempston
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Yaffe
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D021621:Imaging, Three-Dimensional / Q000295:instrumentation*; D008327:Mammography / Q000295:instrumentation*; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014963:X-Ray Intensifying Screens