title: Investigation of imaging properties for submillimeter rectangular pinholes.
abstract: OBJECTIVE
  Recently, a multipinhole collimator with inserts that have both rectangular apertures and rectangular fields of view (FOVs) has been proposed for SPECT imaging since it can tile the projection onto the detector efficiently and the FOVs in transverse and axial directions become separable. The purpose of this study is to investigate the image properties of rectangular-aperture pinholes with submillimeter apertures sizes.
  
  
  METHODS
  In this work, the authors have conducted sensitivity and FOV experiments for 18 replicates of a prototype insert fabricated in platinum/iridium (Pt/Ir) alloy with submillimeter square-apertures. A sin(q)θ fit to the experimental sensitivity has been performed for these inserts. For the FOV measurement, the authors have proposed a new formula to calculate the projection intensity of a flood image on the detector, taking into account the penumbra effect. By fitting this formula to the measured projection data, the authors obtained the acceptance angles.
  
  
  RESULTS
  The mean (standard deviation) of fitted sensitivity exponents q and effective edge lengths we were, respectively, 10.8 (1.8) and 0.38 mm (0.02 mm), which were close to the values, 7.84 and 0.396 mm, obtained from Monte Carlo calculations using the parameters of the designed inserts. For the FOV measurement, the mean (standard deviation) of the transverse and axial acceptances were 35.0° (1.2°) and 30.5° (1.6°), which are in good agreement with the designed values (34.3° and 29.9°).
  
  
  CONCLUSIONS
  These results showed that the physical properties of the fabricated inserts with submillimeter aperture size matched our design well.
authors.affiliation: The Department of Radiology, The University of Chicago, Chicago, Illinois 60637.
authors.forename: Dan
authors.initials: D
authors.lastname: Xia
authors.affiliation: Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Moore
authors.affiliation: Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: Mi-Ae
authors.initials: MA
authors.lastname: Park
authors.affiliation: Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: Morgan
authors.initials: M
authors.lastname: Cervo
authors.affiliation: The Department of Radiology, The University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Metzler
mesh_terms: D002138:Calibration; D003198:Computer Simulation; D004867:Equipment Design; D007495:Iridium; D009010:Monte Carlo Method; D010984:Platinum; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation* / Q000379:methods
chemical_list: C077763:platinum-iridium alloy; D007495:Iridium; D010984:Platinum