title: Use of a compact pixellated gamma camera for small animal pinhole SPECT imaging.
abstract: OBJECTIVE
  Pinhole SPECT which permits in vivo high resolution 3D imaging of physiological functions in small animals facilitates objective assessment of pharmaceutical development and regenerative therapy in pre-clinical trials. For handiness and mobility, the miniature size of the SPECT system is useful. We developed a small animal SPECT system based on a compact high-resolution gamma camera fitted to a pinhole collimator and an object-rotating unit. This study was aimed at evaluating the basic performance of the detection system and the feasibility of small animal SPECT imaging.
  
  
  METHODS
  The gamma camera consists of a 22 x 22 pixellated scintillator array of 1.8 mm x 1.8 mm x 5 mm NaI(Tl crystals with 0.2-mm gap between the crystals coupled to a 2" flat panel position-sensitive photomultiplier tube (Hamamatsu H8500) with 64 channels. The active imaging region of the camera was 43.8 mm x 43.8 mm. Data acquisition is controlled by a personal computer (Microsoft Windows) through the camera controller. Projection data over 360 degrees for SPECT images are obtained by synchronizing with the rotating unit. The knife-edge pinhole collimators made of tungsten are attached on the camera and have 0.5-mm and 1.0-mm apertures. The basic performance of the detection system was evaluated with 99mTc and 201Tl solutions. Energy resolution, system spatial resolution and linearity of count rate were measured. Rat myocardial perfusion SPECT scans were sequentially performed following intravenous injection of 201TlCl. Projection data were reconstructed using a previously validated pinhole 3D-OSEM method.
  
  
  RESULTS
  The energy resolution at 140 keV was 14.8% using a point source. The system spatial resolutions were 2.8-mm FWHM and 2.5-mm FWHM for 99mTc and 201Tl line sources, respectively, at 30-mm source distance (magnification factor of 1.3) using a 1.0-mm pinhole. The linearity between the activity and count rate was good up to 10 kcps. In a rat study, the left ventricular walls were clearly visible in all scans.
  
  
  CONCLUSIONS
  We developed a compact SPECT system using compact gamma camera for small animals and evaluated basic physical performances. The present system may be of use for quantitation of biological functions such as myocardial blood flow in small animals.
authors.affiliation: Department of Investigative Radiology, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, Osaka, Japan. zeniya@ri.ncvc.go.jp
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Zeniya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watabe
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Aoi
authors.forename: Kyeong Min
authors.initials: KM
authors.lastname: Kim
authors.forename: Noboru
authors.initials: N
authors.lastname: Teramoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Takeno
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Ohta
authors.forename: Takuya
authors.initials: T
authors.lastname: Hayashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mashino
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ota
authors.forename: Seiichi
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Iida
mesh_terms: D000818:Animals; D004867:Equipment Design; D019544:Equipment Failure Analysis; D015902:Gamma Cameras; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008904:Miniaturization; D019047:Phantoms, Imaging; D051381:Rats; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation* / Q000379:methods / Q000662:veterinary*