SemiSPECT: A small-animal single-photon emission computed tomography (SPECT) imager based on eight cadmium zinc telluride (CZT) detector arrays

Hyunki Kim, Lars R. Furenlid, Michael J. Crawford, Donald W. Wilson, H. Bradford Barber, Todd E. Peterson, William C.J. Hunter, Zhonglin Liu, James M. Woolfenden, Harrison H. Barrett

Research output: Contribution to journalArticlepeer-review

103 Scopus citations


The first full single-photon emission computed tomography (SPECT) imager to exploit eight compact high-intrinsic-resolution cadmium zinc telluride (CZT) detectors, called SemiSPECT, has been completed. Each detector consists of a CZT crystal and a customized application-specific integrated circuit (ASIC). The CZT crystal is a 2.7 cm X 2.7 cm X ∼0.2 cm slab with a continuous top electrode and a bottom electrode patterned into a 64 X 64 pixel array by photolithography. The ASIC is attached to the bottom of the CZT crystal by indium-bump bonding. A bias voltage of -180 V is applied to the continuous electrode. The eight detectors are arranged in an octagonal lead-shielded ring. Each pinhole in the eight-pinhole aperture placed at the center of the ring is matched to each individual detector array. An object is imaged onto each detector through a pinhole, and each detector is operated independently with list-mode acquisition. The imaging subject can be rotated about a vertical axis to obtain additional angular projections. The performance of SemiSPECT was characterized using 99mTc. When a 0.5 mm diameter pinhole is used, the spatial resolution on each axis is about 1.4 mm as estimated by the Fourier crosstalk matrix, which provides an algorithm-independent average resolution over the field of view. The energy resolution achieved by summing neighboring pixel signals in a 3 X 3 window is about 10% full-width-at-half-maximum of the photopeak. The overall system sensitivity is about 0.5 × 10-4 with the energy window of ±10% from the photopeak. Line-phantom images are presented to visualize the spatial resolution provided by SemiSPECT, and images of bone, myocardium, and human tumor xenografts in mice demonstrate the feasibility of preclinical small-animal studies with SemiSPECT.

Original languageEnglish (US)
Pages (from-to)465-474
Number of pages10
JournalMedical physics
Issue number2
StatePublished - Feb 2006


  • Cadmium zinc telluride (CZT)
  • Single-photon emission computed tomography (SPECT)
  • Small-animal imaging

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging


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