title: Evaluating performance of a pixel array semiconductor SPECT system for small animal imaging.
abstract: OBJECTIVE
  Small animal imaging has recently been focused on basic nuclear medicine. We have designed and built a small animal SPECT imaging system using a semiconductor camera and a newly designed collimator. We assess the performance of this system for small object imaging.
  
  
  METHODS
  We employed an MGC 1500 (Acrorad Co.) camera including a CdTe semiconductor. The pixel size was 1.4 mm/pixel. We designed and produced a parallel-hole collimator with 20-mm hole length. Our SPECT system consisted of a semiconductor camera with the subject holder set on an electric rotating stage controlled by a computer. We compared this system with a conventional small animal SPECT system comprising a SPECT-2000H scanner with four Anger type cameras and pinhole collimators. The count rate linearity for estimation of the scatter was evaluated for a pie-chart phantom containing different concentrations of 99mTc. We measured the FWHM of the 99mTc SPECT line source along with scatter. The system volume sensitivity was examined using a flood source phantom which was 35 mm long with a 32-mm inside diameter. Additionally, an in vivo myocardial perfusion SPECT study was performed with a rat.
  
  
  RESULTS
  With regards to energy resolution, the semiconductor camera (5.6%) was superior to the conventional Anger type camera (9.8%). In the count rate linearity evaluation, the regression lines of the SPECT values were y = 0.019x + 0.031 (r2 = 0.999) for our system and y = 0.018x + 0.060 (r2 = 0.997) for the conventional system. Thus, the scatter count using the semiconductor camera was less than that using the conventional camera. FWHMs of our system and the conventional system were 2.9 +/- 0.1 and 2.0 +/- 0.1 mm, respectively. Moreover, the system volume sensitivity of our system [0.51 kcps/(MBq/ ml)/cm] was superior to that of the conventional system [0.44 kcps/(MBq/ml)/cm]. Our system provided clear images of the rat myocardium, sufficient for practical use in small animal imaging.
  
  
  CONCLUSIONS
  Our SPECT system, utilizing a semiconductor camera, permits high quantitative analysis by virtue of its low scatter radiation and high sensitivity. Therefore, this system may contribute to molecular imaging of small animals and basic medical research.
authors.affiliation: Department of Health Sciences, School of Medicine, Hokkaido University, Kita 12 Nishi 5, Kita-ku, Sapporo 060-0812, Japan. naoki@cme.hokudai.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Kubo
authors.forename: Songji
authors.initials: S
authors.lastname: Zhao
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fujiki
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Kinda
authors.forename: Nobutoku
authors.initials: N
authors.lastname: Motomura
authors.forename: Chietsugu
authors.initials: C
authors.lastname: Katoh
authors.forename: Tohru
authors.initials: T
authors.lastname: Shiga
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Kawashima
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kuge
authors.forename: Nagara
authors.initials: N
authors.lastname: Tamaki
mesh_terms: D000818:Animals; D004867:Equipment Design; D019544:Equipment Failure Analysis; D051379:Mice; D019047:Phantoms, Imaging; D051381:Rats; D015203:Reproducibility of Results; D012666:Semiconductors; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation* / Q000662:veterinary*; D014159:Transducers