title: Differential impact of multi-focus fan beam collimation with L-mode and conventional systems on the accuracy of myocardial perfusion imaging: Quantitative evaluation using phantoms.
abstract: OBJECTIVE
  A novel IQ-SPECT™ method has become widely used in clinical studies. The present study compares the quality of myocardial perfusion images (MPI) acquired using the IQ-SPECT™ (IQ-mode), conventional (180° apart: C-mode) and L-mode (90° apart: L-mode) systems. We assessed spatial resolution, image reproducibility and quantifiability using various physical phantoms.
  
  
  METHODS
  SPECT images were acquired using a dual-headed gamma camera with C-mode, L-mode, and IQ-mode acquisition systems from line source, pai and cardiac phantoms containing solutions of (99m)Tc. The line source phantom was placed in the center of the orbit and at ± 4.0, ± 8.0, ± 12.0, ± 16.0 and ± 20.0 cm off center. We examined quantifiability using the pai phantom comprising six chambers containing 0.0, 0.016, 0.03, 0.045, 0.062, and 0.074 MBq/mL of 99m-Tc and cross-calibrating the SPECT counts. Image resolution and reproducibility were quantified as myocardial wall thickness (MWT) and %uptake using polar maps.
  
  
  RESULTS
  The full width at half maximum (FWHM) of the IQ-mode in the center was increased by 11% as compared with C-mode, and FWHM in the periphery was increased 41% compared with FWHM at the center. Calibrated SPECT counts were essentially the same when quantified using IQ-and C-modes. IQ-SPECT images of MWT were significantly improved (P<0.001) over L-mode, and C-mode SPECT imaging with IQ-mode became increasingly inhomogeneous, both visually and quantitatively (C-mode vs. L-mode, ns; C-mode vs. IQ-mode, P<0.05).
  
  
  CONCLUSIONS
  Myocardial perfusion images acquired by IQ-SPECT were comparable to those acquired by conventional and L-mode SPECT, but with significantly improved resolution and quality. Our results suggest that IQ-SPECT is the optimal technology for myocardial perfusion SPECT imaging.
authors.affiliation: Program in Health and Welfare, Graduate on School of Comprehensive Scientific Research, Prefectural University of Hiroshima; Program in Biological System Sciences, Graduate on School of Comprehensive Scientific Research, Prefectural University of Hiroshima.
authors.forename: Hideo
authors.initials: H
authors.lastname: Onishi
authors.affiliation: Department of Radiology, Kurashiki Central Hospital.
authors.forename: Norikazu
authors.initials: N
authors.lastname: Matsutomo
authors.affiliation: Program in Biological System Sciences, Graduate on School of Comprehensive Scientific Research, Prefectural University of Hiroshima.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Kangai
authors.affiliation: Program in Health and Welfare, Graduate on School of Comprehensive Scientific Research, Prefectural University of Hiroshima.
authors.forename: Tatsunori
authors.initials: T
authors.lastname: Saho
authors.affiliation: Department of Nursing, Hyogo University of Health Sciences.
authors.forename: Hizuru
authors.initials: H
authors.lastname: Amijima
keywords: Acquisition mode; Collimator; Image quality; Multi-focus fan beam