• Analytical Science and Technology
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• v.8 no.3
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• pp.221-227
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• 1995

The fiber optic fluorosensor that shows a specific selectivity for calcium ion is studied. This sensor employs protein Calmodulin(CaM) which forms a fluorescent chelate with $Ca^{2+}$. A dialysis membrane is used to entrap a fluorescein isothiocyanate-labeled CaM solution at the common end of a bifurcated fiber optic bundle. The sensing mechanism of this sensor is based on the shifts in the fluorescence spectrum of metal-calmodulin complexes which FCaM forms a chelate with $Ca^{2+}$. Upon binding with $Ca^{2+}$, CaM undergoes a conformational change which induces a change in the fluorescence of FCaM. This change in fluorescence signal which is measured by photomultiflier tube is related to the concentration of $Ca^{2+}$ for calibration curve. Detection limit for $Ca^{2+}$ and the interference effects by $Mg^{2+}$, $Eu^{3+}$ and $La^{3+}$ for this sensor are studied. Response time and life time for this fluorosensor are also investigated.

• Analytical Science and Technology
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• v.19 no.5
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• pp.389-393
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• 2006

The detector consisted of ZnS(Ag) scintillator and photomultiplier tube (PMT) is widely used as contamination monitor in the nuclear facilities. Such detectors are mainly manufactured by adhering the ZnS(Ag) powder onto the transparent plastic. In this study the preparation condition for ZnS(Ag) scintillator sheet using a simple method was established. The scintillator sheet was composed with a support polymer sheet and ZnS(Ag) scintillator layer. The base sheet was prepared by casting the polymer solution after solving the polymer with solvent and the scintillator layer was manufactured by printing the mixture solution with ZnS(Ag) and paste. It was found that the polysulfone(PSf) as a polymer for the base sheet and a cyano resin as a paste for adhering the ZnS(Ag) scintillator was suitable. Also, the prepared thin scintillator sheet had a sufficient mechanical strength, a optical transparency and an alpha-ray detection performance.

• Progress in Medical Physics
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• v.13 no.1
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• pp.37-43
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• 2002

Effect of scatter media materials and thickness, located between radioactivity and small gamma camera, on imaging characteristics was evaluated. The small gamma camera developed for breast imaging was consisted of collimator, NaI(T1) crystal(60$\times$60$\times$6 ㎣), PSPMT(position sensitive photomultimplier tube), NIMs and personal computer. Monte Carlo simulation was performed to evaluate the system sensitivity with different scatter media thickness(0~8 cm) and materials(air and acrylic) with parallel hole collimator and diverging collimator. The sensitivity and spatial resolution was measured using the small gamma camera with the same condition applied to the simulation. Counts was decreased by 10%(air) and 54%(acryl) with the parallel hole collimator and by 35%(air) and 63%(acryl) with the diverging collimator. Spatial resolution was decreased as increasing the thickness of scatter media. This study substantiate the importance of a gamma camera positioning and the minimization of the distance between detector and target lesion in the clinical application of a gamma camera.

• The Korean Journal of Nuclear Medicine
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• v.38 no.5
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• pp.338-343
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• 2004

Purpose: The purpose of this study was to develop a small animal PET using dual layer phoswich detector to minimize parallax error that degrades spatial resolution at the outer part of field-of-view (FOV). Materials and Methods: A simulation tool GATE (Geant4 Application for Tomographic Emission) was used to derive optimal parameters of small PET, and PET was developed employing the parameters. Lutetium Oxyorthosilicate (LSO) and Lutetium-Yttrium Aluminate-Perovskite(LuYAP) was used to construct dual layer phoswitch crystal. $8{\times}8$ arrays of LSO and LuYAP pixels, $2mm{\times}2mm{\times}8mm$ in size, were coupled to a 64-channel position sensitive photomultiplier tube. The system consisted of 16 detector modules arranged to one ring configuration (ring inner diameter 10 cm, FOV of 8 cm). The data from phoswich detector modules were fed into an ADC board in the data acquisition and preprocessing PC via sockets, decoder block, FPGA board, and bus board. These were linked to the master PC that stored the events data on hard disk. Results: In a preliminary test of the system, reconstructed images were obtained by using a pair of detectors and sensitivity and spatial resolution were measured. Spatial resolution was 2.3 mm FWHM and sensitivity was 10.9 $cps/{\mu}Ci$ at the center of FOV. Conclusion: The radioactivity distribution patterns were accurately represented in sinograms and images obtained by PET with a pair of detectors. These preliminary results indicate that it is promising to develop a high performance small animal PET.