title: Multipinhole SPECT helical scan parameters and imaging volume.
abstract: OBJECTIVE
  The authors developed SPECT imaging capability on an animal PET scanner using a multiple-pinhole collimator and step-and-shoot helical data acquisition protocols. The objective of this work was to determine the preferred helical scan parameters, i.e., the angular and axial step sizes, and the imaging volume, that provide optimal imaging performance.
  
  
  METHODS
  The authors studied nine helical scan protocols formed by permuting three rotational and three axial step sizes. These step sizes were chosen around the reference values analytically calculated from the estimated spatial resolution of the SPECT system and the Nyquist sampling theorem. The nine helical protocols were evaluated by two figures-of-merit: the sampling completeness percentage (SCP) and the root-mean-square (RMS) resolution. SCP was an analytically calculated numerical index based on projection sampling. RMS resolution was derived from the reconstructed images of a sphere-grid phantom.
  
  
  RESULTS
  The RMS resolution results show that (1) the start and end pinhole planes of the helical scheme determine the axial extent of the effective field of view (EFOV), and (2) the diameter of the transverse EFOV is adequately calculated from the geometry of the pinhole opening, since the peripheral region beyond EFOV would introduce projection multiplexing and consequent effects. The RMS resolution results of the nine helical scan schemes show optimal resolution is achieved when the axial step size is the half, and the angular step size is about twice the corresponding values derived from the Nyquist theorem. The SCP results agree in general with that of RMS resolution but are less critical in assessing the effects of helical parameters and EFOV.
  
  
  CONCLUSIONS
  The authors quantitatively validated the effective FOV of multiple pinhole helical scan protocols and proposed a simple method to calculate optimal helical scan parameters.
authors.affiliation: Department of Nuclear Medicine, State University of New York at Buffalo, Buffalo, New York 14214.
authors.forename: Rutao
authors.initials: R
authors.lastname: Yao
authors.affiliation: Department of Nuclear Medicine, State University of New York at Buffalo, Buffalo, New York 14214.
authors.forename: Xiao
authors.initials: X
authors.lastname: Deng
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Qingyang
authors.initials: Q
authors.lastname: Wei
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Tiantian
authors.initials: T
authors.lastname: Dai
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Tianyu
authors.initials: T
authors.lastname: Ma
authors.affiliation: Department of Nuclear Medicine and Radiobiology, Sherbrooke Molecular Imaging Center, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada.
authors.forename: Roger
authors.initials: R
authors.lastname: Lecomte
mesh_terms: D000818:Animals; D003198:Computer Simulation; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D012399:Rotation; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation* / Q000379:methods*