Evaluation of quantitative accuracy in CZT-based pre-clinical SPECT for various isotopes

Abstract

In vivo pre-clinical single-photon emission computed tomography (SPECT) is a valuable tool for functional small animal imaging, but several physical factors, such as scatter radiation, limit the quantitative accuracy of conventional scintillation crystal-based SPECT. Semiconductor detectors such as CZT overcome these deficiencies through superior energy resolution. To our knowledge, little scientific information exists regarding the accuracy of quantitative analysis in CZT-based pre-clinical SPECT systems for different isotopes. The aim of this study was to assess the quantitative accuracy of CZT-based pre-clinical SPECT for four isotopes: 201 Tl, 99m Tc, 123 I, and 111 In. The quantitative accuracy of the CZT-based Triumph X-SPECT (Gamma-Medica Ideas, Northridge, CA, U.S.A.) was compared with that of a conventional SPECT using GATE simulation. Quantitative errors due to the attenuation and scatter effects were evaluated for all four isotopes with energy windows of 5%, 10%, and 20%. A spherical source containing the isotope was placed at the center of the air-or-water-filled mouse-sized cylinder phantom. The CZT-based pre-clinical SPECT was more accurate than the conventional SPECT. For example, in the conventional SPECT with an energy window of 10%, scatter effects degraded quantitative accuracy by up to 11.52%, 5.10%, 2.88%, and 1.84% for 201 Tl, 99m Tc, 123 I, and 111 In, respectively. However, with the CZT-based pre-clinical SPECT, the degradations were only 9.67%, 5.45%, 2.36%, and 1.24% for 201 Tl, 99m Tc, 123 I, and 111 In, respectively. As the energy window was increased, the quantitative errors increased in both SPECT systems. Additionally, the isotopes with lower energy of photon emissions had greater quantitative error. Our results demonstrated that the CZT-based pre-clinical SPECT had lower overall quantitative errors due to reduced scatter and high detection efficiency. Furthermore, the results of this systematic assessment quantifying the accuracy of these SPECT for various isotopes will provide valuable reference information for the design of CZT-based preclinical SPECT system imaging protocols.

Head-to-head comparison of lung perfusion with dual-energy CT and SPECT-CT

“…This new technique has demonstrated greater sensitivity, specificity, reproducibility, and lower indeterminate rate of perfusion defects than planar scintigraphy with stronger correlation with clinical outcome after lobe volume reduction surgery (19)(20)(21). In addition, cadmium zinc telluride (CZT) gamma cameras provide greater sharpness, contrast, and quantitative accuracy for 99m Tc by comparison with analog cameras (22,23). Second, DECT systems with dual-layer scintillator detectors do not require acquisition parameter adjustment permitting retrospective reconstruction of a data set for spectral imaging purposes (24); such systems have demonstrated great in vitro quantification capabilities for minimal iodine concentrations using low and up to 7 mGy radiation doses (24)(25)(26).…”

Hybrid Pixel-Waveform (HPWF) Enabled CdTe Detectors for Small Animal Gamma-Ray Imaging Applications

“…The selection of these detectors yields a potential combination of excellent energy and spatial resolution combined with adequate detection efficiency for numerous single photon emitters. In recent years, several groups have evaluated the use of small pixel CZT/CdTe based imaging detectors as a potential replacement for scintillation detectors for high-resolution SPECT imaging applications [10-13]. Extensive effort towards building future PET based on CZT and CdTe detectors has been explored as well [14-20].…”