title: Three-pinhole collimator to improve axial spatial resolution and sensitivity in pinhole SPECT.
abstract: OBJECTIVE
  The aim of this study was to improve the uniformity of the axial spatial resolution and sensitivity in pinhole single-photon emission computed tomography (SPECT) and to extend the axial field of view, by using a dedicated three-pinhole collimator.
  
  
  METHODS
  A rectangular tungsten plate with three pinhole apertures of 1.5 mm diameter was designed to image a cylindrical field of view of 55 mm diameter and 160 mm axial length using a clinical gamma camera. To evaluate the non-uniformity of spatial resolution and noise, a multiple-disk phantom was built. The phantom was filled with Tc-99m, and data were acquired using a circular orbit and reconstructed with a dedicated iterative reconstruction algorithm. The axial spatial resolution together with the noise was measured in each disk. These measurements were compared to a single-pinhole system using an identical acquisition geometry and reconstruction.
  
  
  RESULTS
  At the central slice, a spatial resolution of 2.7 mm was observed for both the three-pinhole and single-pinhole geometries. At 17.5 mm from the central slice, the axial spatial resolution deteriorated to 10.3 mm when using a single pinhole, while the spatial resolution remained 2.7 mm for the three-pinhole system. In the central slice, 19% noise was observed for both geometries. At 31.5 mm from this central slice, the noise remained 19% for the three-pinhole geometry, while it increased to 32% using a single pinhole.
  
  
  CONCLUSIONS
  The presented three-pinhole collimator improves the uniformity of the axial spatial resolution and sensitivity in pinhole SPECT and consequently extends the axial field of view, a requirement for whole-body small-animal imaging.
authors.affiliation: Nuclear Medicine Department, University Hospital Brussels, Brussels, Belgium. Christian.Vanhove@uzbrussel.be
authors.forename: Christian
authors.initials: C
authors.lastname: Vanhove
authors.forename: Michel
authors.initials: M
authors.lastname: Defrise
authors.forename: Tony
authors.initials: T
authors.lastname: Lahoutte
authors.forename: Axel
authors.initials: A
authors.lastname: Bossuyt
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation*