title: Basic performance and stability of a CdTe solid-state detector panel.
abstract: OBJECTIVE
  We have developed a prototype gamma camera system (R1-M) using a cadmium telluride (CdTe) detector panel and evaluated the basic performance and the spectral stability.
  
  
  METHODS
  The CdTe panel consists of 5-mm-thick crystals. The field of view is 134 x 268 mm comprising 18,432 pixels with a pixel pitch of 1.4 mm. Replaceable small CdTe modules are mounted on to the circuit board by dedicated zero insertion force connectors. To make the readout circuit compact, the matrix read out is processed by dedicated ASICs. The panel is equipped with a cold-air cooling system. The temperature and humidity in the panel were kept at 20 degrees C and below 70% relative humidity. CdTe polarization was suppressed by the bias refresh technique to stabilize the detector. We also produced three dedicated square pixel-matched collimators: LEGP (20 mm-thick), LEHR (27 mm-thick), and LEUHR (35 mm-thick). We evaluated their basic performance (energy resolution, system resolution, and sensitivity) and the spectral stability in terms of short-term (several hours of continuous acquisition) and long-term (infrequent measurements over more than a year) activity.
  
  
  RESULTS
  The intrinsic energy resolution (FWHM) acquired with Tc-99m (140.5 keV) was 6.6%. The spatial resolutions (FWHM at a distance of 100 mm) with LEGP, LEHR, and LEUHR collimators were 5.7, 4.9, and 4.2 mm, and the sensitivities were 71, 39, and 23 cps/MBq, respectively. The energy peak position and the intrinsic energy resolution after several hours of operation were nearly the same as the values a few minutes after the system was powered on; the variation of the peak position was <0.2%, and that of the resolution was about 0.3%. Infrequent measurements conducted over a year showed that the variations of the energy peak position and the intrinsic energy resolution of the system were at a similar level to those described above.
  
  
  CONCLUSIONS
  The basic performance of the CdTe-gamma camera system was evaluated, and its stability was verified. It was shown that the camera could be operated daily for several months without calibration.
authors.affiliation: Medical Systems Research Department, Life Science Research Center, Central Research Laboratory, Hitachi, Ltd., 7-2-1 Omika-cho, Hitachi, Ibaraki, 319-1221, Japan. katsutoshi.tsuchiya.bs@hitachi.com
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: Isao
authors.initials: I
authors.lastname: Takahashi
authors.forename: Tsuneaki
authors.initials: T
authors.lastname: Kawaguchi
authors.forename: Kazuma
authors.initials: K
authors.lastname: Yokoi
authors.forename: Yuuichi
authors.initials: Y
authors.lastname: Morimoto
authors.forename: Takafumi
authors.initials: T
authors.lastname: Ishitsu
authors.forename: Atsurou
authors.initials: A
authors.lastname: Suzuki
authors.forename: Yuuichirou
authors.initials: Y
authors.lastname: Ueno
authors.forename: Keiji
authors.initials: K
authors.lastname: Kobashi
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging; D019187:Cadmium Compounds; D003080:Cold Temperature; D006358:Hot Temperature; D016014:Linear Models; D019047:Phantoms, Imaging; D011877:Radionuclide Imaging / Q000295:instrumentation / Q000379:methods*; D013691:Tellurium; D013997:Time Factors
chemical_list: D019187:Cadmium Compounds; D013691:Tellurium; C028337:cadmium telluride