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Lowe, Tristan,Azough, Feridoon,Freer, Robert The Korean Ceramic Society 2003 한국세라믹학회지 Vol.40 No.4
Ceramics of xCaTiO$_3$-(1-x)Li$_{0.5}$Nd$_{0.5}$TiO$_3$(xCT-(1-x)LNT) series have been prepared by the mixed oxide route. Powders were calcined at 110$0^{\circ}C$ ; cylindrical specimens were fired at temperatures in the range 1300-150$0^{\circ}C$. Sintered products were typically 90-95% dense. The microstructures were dominated by angular grains typically 1.3${\mu}{\textrm}{m}$ to 3.5 ${\mu}{\textrm}{m}$ in size. Twinning in the microstructures was analysed using Electron Back Scattered Diffraction (EBSD). Microwave dielectric properties of xCT-(1-x)LNT at 2.1 GHz ($\varepsilon$$_{r}$, Qxf, and $\tau$r) were 170,3800 GHz and 744 ppm/$^{\circ}C$ for pure CaTiO$_3$ and 80,2000 GHz and -240 ppm/$^{\circ}C$ for LNT. The $\tau$r decreases almost linearly from 744 for pure CaTiO$_3$ to -240 for pure LNT.LNT.T.
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Respiratory Motion Detection and Correction in ECG-Gated SPECT: a New Approach
Ahmad Bitarafan,Hossein Rajabi,Bernhard Gruy,Feridoon Rustgou,Hasan Firoozabady,Nahid Yaghoobi,Hadi Malek,Christian Pirich,Werner Langesteger,Mohsen Beheshti 대한영상의학회 2008 Korean Journal of Radiology Vol.9 No.6
Objective: Gated myocardial perfusion single-photon emission computed tomography (GSPECT) has been established as an accurate and reproducible diagnostic and prognostic technique for the assessment of myocardial perfusion and function. Respiratory motion is among the major factors that may affect the quality of myocardial perfusion imaging (MPI) and consequently the accuracy of the examination. In this study, we have proposed a new approach for the tracking of respiratory motion and the correction of unwanted respiratory motion by the use of respiratory-cardiac gated-SPECT (RC-GSPECT). In addition, we have evaluated the use of RC-GSPECT for quantitative and visual assessment of myocardial perfusion and function. Materials and Methods: Twenty-six patients with known or suspected coronary artery disease (CAD)-underwent two-day stress and rest 99mTc-Tetrofosmin myocardial scintigraphy using both conventional GSPECT and RC-GSPECT methods. The respiratory signals were induced by use of a CT real-time position management (RPM) respiratory gating interface. A PIO-D144 card, which is transistor-transistor logic (TTL) compatible, was used as the input interface for simultaneous detection of both ECG and respiration signals. Results: A total of 26 patients with known or suspected CAD were examined in this study. Stress and rest myocardial respiratory motion in the vertical direction was 8.8-16.6 mm (mean, 12.4 ± 2.9 mm) and 7.8-11.8 mm (mean, 9.5 ± 1.6 mm), respectively. The percentages of tracer intensity in the inferior, inferoseptal and septal walls as well as the inferior to lateral (I/L) uptake ratio was significantly higher with the use of RC-GSPECT as compared to the use of GSPECT (p < 0.01). In a left ventricular ejection fraction (LVEF) correlation analysis between the use of rest GSPECT and RC-GSPECT with echocardiography, better correlation was noted between RC-GSPECT and echocardiography as compared with the use of GSPECT (y = 0.9654x + 1.6514; r = 0.93, p < 0.001 versus y = 0.8046x + 5.1704; r = 0.89, p < 0.001). Nineteen (19/26) patients (73.1%) showed abnormal myocardial perfusion scans with reversible regional myocardial defects; of the 19 patients, 14 (14/26) patients underwent coronary angiography. Conclusion: Respiratory induced motion can be successfully corrected simultaneously with the use of ECG-gated SPECT in MPI studies using this proposed technique. Moreover, the use of ECG-gated SPECT improved image quality, especially in the inferior and septal regions that are mostly affected by diaphragmatic attenuation. However, the effect of respiratory correction depends mainly on the patient respiratory pattern and may be clinically relevant in certain cases. Objective: Gated myocardial perfusion single-photon emission computed tomography (GSPECT) has been established as an accurate and reproducible diagnostic and prognostic technique for the assessment of myocardial perfusion and function. Respiratory motion is among the major factors that may affect the quality of myocardial perfusion imaging (MPI) and consequently the accuracy of the examination. In this study, we have proposed a new approach for the tracking of respiratory motion and the correction of unwanted respiratory motion by the use of respiratory-cardiac gated-SPECT (RC-GSPECT). In addition, we have evaluated the use of RC-GSPECT for quantitative and visual assessment of myocardial perfusion and function. Materials and Methods: Twenty-six patients with known or suspected coronary artery disease (CAD)-underwent two-day stress and rest 99mTc-Tetrofosmin myocardial scintigraphy using both conventional GSPECT and RC-GSPECT methods. The respiratory signals were induced by use of a CT real-time position management (RPM) respiratory gating interface. A PIO-D144 card, which is transistor-transistor logic (TTL) compatible, was used as the input interface for simultaneous detection of both ECG and respiration signals. Results: A total of 26 patients with known or suspected CAD were examined in this study. Stress and rest myocardial respiratory motion in the vertical direction was 8.8-16.6 mm (mean, 12.4 ± 2.9 mm) and 7.8-11.8 mm (mean, 9.5 ± 1.6 mm), respectively. The percentages of tracer intensity in the inferior, inferoseptal and septal walls as well as the inferior to lateral (I/L) uptake ratio was significantly higher with the use of RC-GSPECT as compared to the use of GSPECT (p < 0.01). In a left ventricular ejection fraction (LVEF) correlation analysis between the use of rest GSPECT and RC-GSPECT with echocardiography, better correlation was noted between RC-GSPECT and echocardiography as compared with the use of GSPECT (y = 0.9654x + 1.6514; r = 0.93, p < 0.001 versus y = 0.8046x + 5.1704; r = 0.89, p < 0.001). Nineteen (19/26) patients (73.1%) showed abnormal myocardial perfusion scans with reversible regional myocardial defects; of the 19 patients, 14 (14/26) patients underwent coronary angiography. Conclusion: Respiratory induced motion can be successfully corrected simultaneously with the use of ECG-gated SPECT in MPI studies using this proposed technique. Moreover, the use of ECG-gated SPECT improved image quality, especially in the inferior and septal regions that are mostly affected by diaphragmatic attenuation. However, the effect of respiratory correction depends mainly on the patient respiratory pattern and may be clinically relevant in certain cases.
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