title: Comprehensive assessment of the slice sensitivity profiles in breast tomosynthesis and breast CT.
abstract: OBJECTIVE
  This study experimentally evaluated the slice sensitivity profile (SSP) and its relationship between acquisition angle, object size, and cone angle. The sensitivity profile metric was used to characterize a breast tomosynthesis system's resolution in the z-axis. The SSP was also measured on a prototype breast computed tomography (bCT) system.
  
  
  METHODS
  The SSP was measured using brass disks placed within adipose tissue-equivalent breast phantoms. The digital tomosynthesis system (Selenia Dimensions, Hologic Corporation, Bedford, MA) acquires projection images over a 15° angular range and the bCT scanner acquires projection images over a 360° angular range. Angular ranges between 15° and 360° were studied by using a subset of the projection images acquired on the bCT scanner. The SSP was determined by measuring a background-corrected mean gray scale value as a function of the z-position (axis normal to the plane of the detector).
  
  
  RESULTS
  The results show that SSP improves when the angular acquisition range is increased and the SSP approaches a delta function for angles greater than 180°. Smaller objects have a narrower SSP and the SSP is not significantly dependent on the cone angle. For a 2.5, 5, 10 mm disk, the full width at half maximum of the SSP was 35, 61, 115 mm, respectively, on the tomosynthesis system (at 15°) and was 0.5 mm for all disk diameters on the bCT scanner (at 360°).
  
  
  CONCLUSIONS
  The SSP is dependent on object size and angular acquisition range. These dependencies are overcome once the angular acquisition range is increased beyond 180°.
authors.affiliation: Department of Radiology, University of California, Davis, CA 95817, USA.
authors.forename: Anita
authors.initials: A
authors.lastname: Nosratieh
authors.forename: Kai
authors.initials: K
authors.lastname: Yang
authors.forename: Shadi
authors.initials: S
authors.lastname: Aminololama-Shakeri
authors.forename: John M
authors.initials: JM
authors.lastname: Boone
mesh_terms: D005260:Female; D006801:Humans; D008327:Mammography / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*