title: Truncation correction of fan beam transmission data for attenuation correction using parallel beam emission data on a 3-detector SPECT system.
abstract: BACKGROUND
  When the simultaneous transmission computed tomography (TCT)/single photon emission CT (SPECT) acquisition protocol is applied to myocardial studies using a 3-detector SPECT, the narrow effective field of view of a fan beam collimator used for TCT acquisition may cause truncation artifacts on TCT images. In this paper, we propose a new method of correcting for the truncation of TCT.
  
  
  METHODS
  The truncated parts of the TCT projection data are corrected using quadratic functions, based on the properties that the integral of non-truncated TCT projection data is constant at any projection angle and the position of the centre of gravity is focused on a fixed point. The usefulness of our method was investigated in phantom and human studies using a 3-detector SPECT equipped with one cardiac fan beam collimator for TCT and two parallel beam collimators for SPECT. We used Tl as a tracer for SPECT and Tc as an external source for TCT.
  
  
  RESULTS
  The phantom and human studies showed that our method can adequately correct for the truncation of TCT data acquired using a fan beam collimator in a 3-detector SPECT, as long as there is no truncation in SPECT data.
  
  
  CONCLUSIONS
  Our method appears to be useful for improving the SPECT images obtained using simultaneous TCT/SPECT acquisition in a 3-detector SPECT. However, further studies will be necessary to establish the clinical usefulness of this method.
authors.affiliation: Department of Medical Engineering, Osaka University Graduate School of Medicine, Japan. takahashi.yasuyuki@pref.ehime.jp
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Kenya
authors.initials: K
authors.lastname: Murase
authors.forename: Teruhito
authors.initials: T
authors.lastname: Mochizuki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Higashino
authors.forename: Nobutoku
authors.initials: N
authors.lastname: Motomura
mesh_terms: D000465:Algorithms; D016477:Artifacts; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation / Q000379:methods*