• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.1-9
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• 2009

Many types of small animal imaging modalities, like micro-CT, micro-PET, and micro-SPECT, have been recently developed worldwide. Small animal imaging systems are now recognized as indispensable tools to validate efficacy and safety of new drugs or new therapeutic methods using the animal disease models. With increasing demands for small animal imaging in biomedical research, multimodal small animal imaging systems, like micro-PET/CT or micro PET/MRI, are now also being developed. Small animal imaging with spatial resolution and sensitivity comparable to human imaging is quite challenging since laboratory small animals are much smaller than human beings. Research activities in Korea on small animal imaging systems are reviewed in this paper. In the field of micro-CT and micro-PET, many world-class technologies have been developed successfully in Korea. It is expected that the developed animal imaging system technologies can be used in the development of clinical imaging systems in Korea in the near future.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.5
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• pp.324-329
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• 2015

A decreased number of readout method is investigated to provide precise pixel information for small-animal positron emission tomography (PET). Small-animal PET consists of eight modules, and each module is composed of a $6{\times}6$ array of $2{\times}2{\times}20mm^3$ lutetium yttrium orthosilicate (LYSO) crystals optically coupled to a $4{\times}4$ array of $3{\times}3mm^2$ silicon photomultipliers (SiPMs). The number of readout channels is reduced by one-quarter that of the conventional method by applying a simplified row and column matrix algorithm. The performance of the PET system and detector module was evaluated with Geant4 Application for Emission Tomography (GATE) 6.1 and DETECT2000 simulations. In the results, all pixels of the $6{\times}6$ LYSO array were decoded well, and the spatial resolution and sensitivity, respectively, of the PET system were 1.75 mm and 4.6% (@ center of field of view, energy window: 350-650 keV).

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2646-2651
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• 2021

A rectangular-shaped PET system with an adjustable gantry (AGPET) has been developed for imaging small animals. The AGPET system employs a new depth of interaction (DOI) method using a depth dependent reflector patterns and a new digital time pickoff method based on the pulse reconstruction method. To evaluate the performance of the AGPET, timing resolution, intrinsic spatial resolution and point source images were acquired. The timing resolution and intrinsic spatial resolution were measured using two detector modules and Na-22 gamma source. The PET images were acquired in two field of view (FOV) sizes, 30 mm and 90 mm, to demonstrate the characteristic of the AGPET. As a result of in the experiment results, the timing resolution was 0.9 ns using the pulse reconstruction method based on the bi-exponential model. The intrinsic spatial resolution was an average of 1.7 mm and the spatial resolution of PET images after DOI correction was 2.08 mm and 2.25 mm at the centers of 30 mm and 90 mm FOV, respectively. The results show that the proposed AGPET system provided higher sensitivity and resolution for small animal imaging.

• Journal of the Korea Society of Computer and Information
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• v.12 no.2 s.46
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• pp.123-130
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• 2007

The aim of this study was to propose a fusion and registration method with heterogeneous small animal acquisition system in small animal in-vivo study. After an intravenous injection of $^{18}F$-FDG through tail vain and 60 min delay for uptake, mouse was placed on an acryl plate with fiducial markers that were made for fusion between small animal PET (microPET R4, Concorde Microsystems, Knoxville TN) and Discovery LS CT images. The acquired emission list-mode data was sorted to temporally framed sinograms and reconstructed using FORE rebining and 2D-OSEM algorithms without correction of attenuation and scatter. After PET imaging, CT images were acquired by mean of a clinical PET/CT with high-resolution mode. The microPET and CT images were fusion and co-registered using the fiducial markers and segmented lung region in both data sets to perform a point-based rigid co-registration. This method improves the quantitative accuracy and interpretation of the tracer.

• The Journal of the Korea Contents Association
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• v.20 no.7
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• pp.392-403
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• 2020

The aim of this study was to identify the awareness of the animal registration system, as well as to determine if there is a difference according to the types of pet attachment of consumers raising companion dogs. For this purpose, 250 data were collected by conducting an online survey and analyzed the data using SPSS 24.0. As a result of the study, pet attachment was identified as a companion attachment and emotional attachment. According to the form of attachment to dogs, the consumer types were categorized into three groups: type of simple cohabitation(25.6%), type of close companion(30.4%), and type of strong bond(44.0%). It was found that there are statistically significant differences in the relationship between the recognition and registration of the animal registration system for each consumer type. In addition, there were statistically significant differences in the perception and preference of the animal registration system depending on the type of consumer. This study has significance in that it suggests the effective direction of developing the consumer-oriented animal registration system.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.44-44
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• 2003

As a basic measurement tool in the areas of animal models of human disease, gene expression and therapy, and drug discovery and development, small animal PET imaging is being used increasingly. An ideal small animal PET should have high sensitivity and high and uniform resolution across the field of view to achieve high image quality. However, the combination of long narrow pixellated crystal array and small ring diameter of small animal PET leads to the degradation of spatial resolution for the source located at off center. This degradation of resolution can be improved by determining the depth of interaction (DOI) in the crystal and by taking into account the information in sorting the coincident events. Among a number of 001 identification schemes, dual layer phsowich detector has been widely investigated by many research groups due to its practicability and effectiveness on extracting DOI information. However, the effects of each crystal length composing dual layer phoswich detector on DOI measurements and image qualities were not fully characterized. In order to minimize the DOI effect, the length of each layer of phoswich detector should be optimized. The aim of this study was to perform simulations using a simulation tool, GATE to design the optimum lengths of crystals composing a dual layer phoswich detector. The simulated small PET system employed LSO front layer LuYAP back layer phoswich detector modules and the module consisted of 8${\times}$8 arrays of dual layer crystals with 2 mm ${\times}$ 2 mm sensitive area coupled to a Hamamatsu R7600 00 M64 PSPMT. Sensitivities and variation of radial resolutions were simulated by varying the length of LSO front layer from 0 to 10 mm while the total length (LSO + LuYAP) was fixed to 20 mm for 10 cm diameter ring scanner. The radial resolution uniformity was markedly improved by using DOI information. There existed the optimal lengths of crystal layers to minimize the variation of radial resolutions. In 10 cm ring scanner configuration, the radial resolution was kept below 3.4 mm over 8 cm FOV while the sensitivity was higher than 7.4% for LSO 5 mm : LuYAP 15 mm phoswich detector. In this study, the optimal length of dual layer phoswich detector was derived to achieve high and uniform radial resolution.

• The Journal of the Korea Contents Association
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• v.15 no.4
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• pp.350-356
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• 2015

The aim of this study is to perform simulations to design the detector module with crystal array by Monte Carlo simulation. For this purpose, a small animal PET scanner, employing module with 1~8 crystal array discrimination scheme, was designed. The proposed scanner has an inner diameter of 100 mm with detector modules in crystal array. Each module is composed of a 5.0 mm LSO crystal with a $2.0{\times}2.0mm^2$ sensitive area with a pitch 2.1 mm and 10.0 mm thickness. The LSO crystals are attached to the SiPM which has a dimension of $2.0{\times}2.0mm^2$. The detector module with crystal array of the designed PET detector was simulated using the Monte Carlo code GATE(Geant4 Application for Tomographic Emission). The detector is enough compensation for the loss of data in sinogram due to gaps between modules. The results showed that the high sensitivity and effectively reduced the problem about the missing data were greatly improved by using the detector module with 1 crystal array.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1764-1773
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• 2018

A-PET is a quad-head PET scanner developed for use in small-animal imaging. The dimensions of its volumetric field of view (FOV) are $46.1{\times}46.1{\times}46.1mm^3$ and the gap between the detector modules has been minimized in order to provide a highly sensitive system. However, such a small FOV together with the quad-head geometry causes image quality degradation. The main factor related to image degradation for the quad-head PET is the mispositioning of events caused by the penetration effect in the detector. In this paper, we propose a precise method for modelling the system at the high spatial resolution of the A-PET using a LOR (line of response) based ML-EM (maximum likelihood expectation maximization) that allows for penetration effects. The proposed system model provides the detection probability of every possible ray-path via crystal sampling methods. For the ray-path sampling, the sub-LORs are defined by connecting the sampling points of the crystal pair. We incorporate the detection probability of each sub-LOR into the model by calculating the penetration effect. For comparison, we used a standard LOR-based model and a Monte Carlo-based modeling approach, and evaluated the reconstructed images using both the National Electrical Manufacturers Association NU 4-2008 standards and the Geant4 Application for Tomographic Emission simulation toolkit (GATE). An average full width at half maximum (FWHM) at different locations of 1.77 mm and 1.79 mm are obtained using the proposed system model and standard LOR system model, which does not include penetration effects, respectively. The standard deviation of the uniform region in the NEMA image quality phantom is 2.14% for the proposed method and 14.3% for the LOR system model, indicating that the proposed model out-performs the standard LOR-based model.

• Progress in Medical Physics
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• v.21 no.2
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• pp.145-152
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• 2010

Inveon PET is a recently developed preclinical PET system for small animal. This study was conducted to measure the performance of Inveon PET as recommended by the NEMA NU 4-2008. We measured the spatial resolution, the sensitivity, the scatter fraction and the NECR using a F-18 source. A 3.432 ns coincidence window was used. A $1\;mm^3$ sized F-18 point source was used for the measurement of spatial resolution within an energy window of 350~625 keV. PET acquisition was performed to obtain the spatial resolution from the center to the 5 cm offset toward the edge of the transverse FOV. Sensitivity, scatter fraction, and NECR were measured within an energy window of 350~750 keV. For measuring the sensitivity, a F-18 line source (length: 12.7 cm) was used with concentric 5 aluminum tubes. For the acquisition of the scatter fraction and the NECR, two NEMA scatter phantoms (rat: 50 mm in diameter, 150 mm in length; mouse: 25 mm in diameter, 70 mm in length) were used and the data for 14 half-lives (25.6 hr) was obtained using the F-18 line source (rat: 316 MBq, mouse: 206 MBq). The spatial resolution of the F-18 point source was 1.53, 1.50 and 2.33 mm in the radial, tangential and axial directions, respectively. The volumetric resolution was $5.43\;mm^3$ in the center. The absolute sensitivity was 6.61%. The peak NECR was 486 kcps @121 MBq (rat phantom), and 1056 kcps @128 MBq (mouse phantom). The values of the scatter fraction were 20.59% and 7.93% in the rat and mouse phantoms, respectively. The performances of the Inveon animal PET scanner were measured in this study. This scanner will be useful for animal imaging.

• The Journal of the Korea Contents Association
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• v.9 no.11
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• pp.262-270
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• 2009

$^{18}F$-mefway has been developed as radioligand for serotonin receptor 5-$HT_{1A}$. The object of this study was to obtain the mefway precursor with the higher yield than previous method and to identify whether $^{18}F$-mefway can bind to 5-$HT_{1A}$ or not. from microPET imaging of small animal brain. Precursor was prepared by a modification of the reported procedure then [$^{18}F$] labeling was performed by adding $^{18}F$ ion at $130^{\circ}C$ in the hot cell for 30min. After purification of reaction mixture using alumina Sep-pak and HPLC, microPET images of small animal brain were determined. The chemical yield of precursor was increased from 9% to 34% using oxalyl chloride and LAH/diethylether. We synthesized a precursor which was successfully labeled with no-carrier-added $^{18}F$-by new synthetic route. This research suggest that $^{18}F$-mefway will be used a radiopharmaceutical for evaluation of central nerve system disorder as imaging a gent for 5-$HT_{1A}$ receptor.