Comparative Cardiac Phantom Study Using Tc-99m/I-123 and Tl-201/I-123 Tracers with Cadmium-Zinc-Telluride Detector-Based Single-Photon Emission Computed Tomography
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A recently introduced single-photon emission computed tomography (SPECT), based on cadmium-zinc-telluride (CZT) detectors (D-SPECT), supports high energy resolution for cardiac imaging. Importantly, the high energy resolution may allow simultaneous dual-isotope (SDI) imaging (e.g., using Tc-99m and I-123). We quantitatively evaluated Tc-99m/I-123 SDI imaging by D-SPECT in comparison with conventional T1-201/I-123.
Materials and Methods
Energy resolution was measured as a percentage of the full width at half maximum (FWHM) for Tc-99m, I-123, and Tl-201. The impact of cross-talk and reconstructed image contrast were quantified by measuring the contrast-to-noise ratio (CNR), and the transmural defect contrast in the left ventricle wall (CTD) induced by a difference in energy, for combinations of Tc-99m/I-123 or Tl-201/I-123, using an RH-2 cardiac phantom. Corresponding measurement was also carried out in Anger SPECT (A-SPECT).
The energy resolution of the D-SPECT system was 5.4%/5.1% for Tc-99m/I-123 and 5.4%/5.3% for Tl-201/I-123, which was approximately two times higher than the A-SPECT. No notable difference was confirmed in the CNRs of the two systems, but T1-201/I-123 showed overall higher value than Tc-99m/I-123. Compared to A-SPECT, CTD of D-SPECT significantly increased with both Tc-99m/I-123 and T1-201/I-123 (p < 0.05). In DSPECT, the combination of Tc-99m/I-123 had a slightly better CTD than T1-201/I-123. In addition, CTD of Tc-99m/I-123 was improved with scatter correction at both nuclides (p < 0.05), but in Tl-201/I-123, no significant improvement was confirmed in I-123 (p > 0.05).
D-SPECT was considered to be capable of performing high-quality SDI imaging using Tc-99m/I-123.
KeywordsCZT detector Energy resolution Simultaneous dual-isotope SPECT Cardiac imaging
The authors would like to acknowledge the assistance, support, and advice of the engineers of Spectrum Dynamics and the staff of Biosensors Japan. They also acknowledge the advice of M. Sugumi and the EIZO Corporation for the measurements of contrast-to-noise ratio, and the transmural defect contrast in the left ventricle wall.
Compliance with Ethical Standards
Conflict of Interest
Takanaga Niimi, Mamoru Nanasato, Mitsuo Sugimoto, and Hisatoshi Maeda declare that they have no conflict of interest.
This study was approved by the institutional review board of the hospital on October 25, 2016 and has been performed in accordance with the ethical standards laid down in the Helsinki Declaration of 1964 and later revision.
All subjects in the study gave written informed consent or the institutional review board waived the need to obtain informed consent.
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