title: Resolution-recovery-embedded image reconstruction for a high-resolution animal SPECT system.
abstract: The small-animal High-Resolution SPECT (HiReSPECT) is a dedicated dual-head gamma camera recently designed and developed in our laboratory for imaging of murine models. Each detector is composed of an array of 1.2 × 1.2 mm(2) (pitch) pixelated CsI(Na) crystals. Two position-sensitive photomultiplier tubes (H8500) are coupled to each head's crystal. In this paper, we report on a resolution-recovery-embedded image reconstruction code applicable to the system and present the experimental results achieved using different phantoms and mouse scans. Collimator-detector response functions (CDRFs) were measured via a pixel-driven method using capillary sources at finite distances from the head within the field of view (FOV). CDRFs were then fitted by independent Gaussian functions. Thereafter, linear interpolations were applied to the standard deviation (σ) values of the fitted Gaussians, yielding a continuous map of CDRF at varying distances from the head. A rotation-based maximum-likelihood expectation maximization (MLEM) method was used for reconstruction. A fast rotation algorithm was developed to rotate the image matrix according to the desired angle by means of pre-generated rotation maps. The experiments demonstrated improved resolution utilizing our resolution-recovery-embedded image reconstruction. While the full-width at half-maximum (FWHM) radial and tangential resolution measurements of the system were over 2 mm in nearly all positions within the FOV without resolution recovery, reaching around 2.5 mm in some locations, they fell below 1.8 mm everywhere within the FOV using the resolution-recovery algorithm. The noise performance of the system was also acceptable; the standard deviation of the average counts per voxel in the reconstructed images was 6.6% and 8.3% without and with resolution recovery, respectively.
authors.affiliation: Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, 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, Iran.
authors.forename: Salar
authors.initials: S
authors.lastname: Sajedi
authors.affiliation: Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran; Parto Negar Persia Co, Tehran, Iran.
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Farahani
authors.affiliation: Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran; Parto Negar Persia Co, Tehran, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Arabi
authors.affiliation: Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran; Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Saeed
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Chronic Respiratory Diseases Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran; PET/CT and Cyclotron Center, Masih Daneshvari Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Pardis
authors.initials: P
authors.lastname: Ghafarian
authors.affiliation: Department of Radiology, Johns Hopkins University, Baltimore, MD, USA; Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Arman
authors.initials: A
authors.lastname: Rahmim
authors.affiliation: Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran; Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran. Electronic address: mohammadreza_ay@sina.tums.ac.ir.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Ay
mesh_terms: D000465:Algorithms; D000818:Animals; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D051379:Mice; D019047:Phantoms, Imaging; D012399:Rotation; D013669:Technetium Tc 99m Medronate; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation*
chemical_list: D013669:Technetium Tc 99m Medronate
keywords: H8500; HiReSPECT; Parallel-hole; Resolution recovery; SPECT; Small-animal