title: Design and assessment of a novel SPECT system for desktop open-gantry imaging of small animals: A simulation study.
abstract: OBJECTIVE
  Given increasing efforts in biomedical research utilizing molecular imaging methods, development of dedicated high-performance small-animal SPECT systems has been growing rapidly in the last decade. In the present work, we propose and assess an alternative concept for SPECT imaging enabling desktop open-gantry imaging of small animals.
  
  
  METHODS
  The system, PERSPECT, consists of an imaging desk, with a set of tilted detector and pinhole collimator placed beneath it. The object to be imaged is simply placed on the desk. Monte Carlo (MC) and analytical simulations were utilized to accurately model and evaluate the proposed concept and design. Furthermore, a dedicated image reconstruction algorithm, finite-aperture-based circular projections (FABCP), was developed and validated for the system, enabling more accurate modeling of the system and higher quality reconstructed images. Image quality was quantified as a function of different tilt angles in the acquisition and number of iterations in the reconstruction algorithm. Furthermore, more complex phantoms including Derenzo, Defrise, and mouse whole body were simulated and studied.
  
  
  RESULTS
  The sensitivity of the PERSPECT was 207 cps/MBq. It was quantitatively demonstrated that for a tilt angle of 30°, comparable image qualities were obtained in terms of normalized squared error, contrast, uniformity, noise, and spatial resolution measurements, the latter at ∼0.6 mm. Furthermore, quantitative analyses demonstrated that 3 iterations of FABCP image reconstruction (16 subsets/iteration) led to optimally reconstructed images.
  
  
  CONCLUSIONS
  The PERSPECT, using a novel imaging protocol, can achieve comparable image quality performance in comparison with a conventional pinhole SPECT with the same configuration. The dedicated FABCP algorithm, which was developed for reconstruction of data from the PERSPECT system, can produce high quality images for small-animal imaging via accurate modeling of the system as incorporated in the forward- and back-projection steps. Meanwhile, the developed MC model and the analytical simulator of the system can be applied for further studies on development and evaluation of the system.
authors.affiliation: Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran 1419733141, Iran.
authors.forename: Navid
authors.initials: N
authors.lastname: Zeraatkar
authors.affiliation: Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran 1419733141, Iran.
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Farahani
authors.affiliation: Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21287 and Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218.
authors.forename: Arman
authors.initials: A
authors.lastname: Rahmim
authors.affiliation: Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran 1417613151, Iran and Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, Tehran 1419733141, Iran.
authors.forename: Saeed
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran 1419733141, Iran and Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran 1417613151, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Ay
mesh_terms: D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D004867:Equipment Design; D007091:Image Processing, Computer-Assisted / Q000379:methods; D051379:Mice; D008953:Models, Anatomic; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation* / Q000379:methods*