• Journal of Biomedical Engineering Research
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• v.20 no.6
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• pp.515-521
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• 1999

Scintillator crystal is an important part and detcrmines performance characteristics of the gamma camera. We investigated the offects of scintillation crystal surface treatment on gamma camera imaging. Nal(TI) and Csl(Tl) scintillators. 20 mm diameter and 10 mm thickness, applied with two different surface treatments, white and black reflcetors, were applied to Nal(Tl) and Csl(Ti). The optical properties of generated scintillation light were evaluated by Monte Carlo simulation method and by actual measurement using a position sensitive photomultiplier tube (PSPMT). We measured sensitivity, energy resolution and spatial resolution of gamma camera with the various scintillators coupled to a PSPMT. In the simulation. Nal(Tl)-white prosented the best sensitivity. In the measurements, the sensitivities and the intrinsic spatial resolutions of Nal(Tl)-white, Nal(Tl)-black. CsI(Tl)-white, CsI(Tl)-black were 2920, 2322, 1754, 1401 cps/$\mu$ci and 5.2, 4.5, 7.0, 6.3 mm FWHM. respectively. Their intrinsic energy resolutions were mesured 12.5, 23.5, 20.5, 33.3% FWHM at 140 keV Tc-99m. In this study, we investigated the offects of a side surface treatment of the scintillator on the gamma camera imaging. Simulation and measurement prescnted similat trends. Based on the results, we concluded that the surface of th NaI(Tl)seintillator must be treated by absorptive materials in order to develop the gamma camera having good spatial resolution.

• Journal of Radiation Protection and Research
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• v.44 no.1
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• pp.1-7
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• 2019

Background: To monitor proton beam in proton therapy, prompt gamma imaging systems are being developed by several research groups, and these systems are expected to improve the quality of the treatment and the patient safety. To apply the prompt gamma imaging systems into spot scanning proton therapy, the systems should be able to monitor the proton beam range of a spot with a small number of protons ( <$10^8$ protons), which is quite often not the case due to insufficient prompt gamma statistics. Materials and Methods: In the present study, we propose to improve prompt gamma statistics by merging the prompt gamma distributions of several individual spots into a new distribution. This proposal was tested by Geant4 Monte Carlo simulations for a multi-slit prompt gamma camera which has been developed to measure the proton beam range in the patient. Results and Discussion: The results show that the proposed method clearly enhance the statistical precision of beam range measurement. The accuracy of beam range verification is improved, within ~1.4 mm error, which is not achievable before applying the developed method. Conclusion: In this study, we tried to improve the statistics of the prompt gamma statistics by merging the prompt gamma distributions of multiple spots, and it was found that the merged distribution provided sufficient prompt gamma statistics and the proton beam range was determined accurately.

• Journal of Biomedical Engineering Research
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• v.17 no.4
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• pp.443-448
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• 1996

Sequential brain SPECT imaging has been used to assess the cerebral perfusion reserve(CPR) in cerebrovascular diseases(UD). We have realized parametric images of CPR using deadtime correction of gamma camera and normalized difference ratio. For the anatomical localization of CPR, the parametric images were registered to the contours of the cerebral regions using optimal threshold method, which showed to reflect the CPR more reliably and distinctively than the simple subtraction. We conclude that the quantitative estimation of CPR using normalized difference ratio image could be useflll for the diagnosis and prognostic assessment of CVD.

• Journal of radiological science and technology
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• v.24 no.2
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• pp.35-40
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• 2001

Performance of SPECT imaging systems which use a rotating gamma camera, are affected by characteristics of the detector-collimator assembly, the data acquisition method, and the filter used in imaging reconstruction. The purpose of this study Is to examine image qualifies of SPECT with different types of low energy collimators. The SPECT imaging system in this study is a digital gamma camera system GCA-901A(Toshiba) and a data processing unit Scintipac-700(Shimadzu). The four types of collimators compared are UHR(ultra high resolution), LEHR(low energy high resolution), LEGP(low energy general purpose), and I-123 PAR(Parallel), with 0.27, 0.66, 1.00, and 2.06 relative sensitivity, respectively. In this case of the same collimators, the spatial resolutions measured in the slice plane showed a slight difference in the FWHM values(mean values of UHR, LEHR, LEGP, and I-123 PAR were 11.3 mm, 13.6 mm, 15.8 mm, and 20.4 mm, respectively) between the center and the circumference of the field of view, in the radial direction, but a large difference in the tangential direction, with lower FWHM values(values of UHR, LEHR, LEGP, and I-123 PAR were 8.4 mm, 8.7 mm, 9.3 mm, and 10.8 mm at 12 cm from the center, respectively). In comparison of SPECT images with the four types of collimators, except for the I-123 PAR collimator, image qualities of UHR, LEHR, and LEGP collimators showed only a slight difference. From the point of for, it is expected that the LEGP collimator would be suitable for SPECT imaging with $^{99m}Tc$.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.216-219
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• 1997

We are developing a portable multipurpose gamma counting and imaging probe that will be useful for many applications in nuclear medicine including radioimmunoguided surgery in the detection and treatment of malignant tumors. Any diagnostic information provided by CT, MRI, PET, SPECT or gamma camera imaging prior to surgery obviously is very important, but current techniques are limited in many instances. To overcome some of these limitations, the portable multipurpose gamma probe is being developed. The gamma probe consists of NaI(Tl) crystal with 1" dia $\times$ 0.5" thick and singlechannel photomultiplier tube (SC-PMT) for counting, and 3" dia $\times$ 0.375" and multichannel photomultiplier tube (MC-PMT) for imaging, nuclear instrument module (NIM), position circuits, interface, and PC. The energy resolution using Tc-99m was measured as 14% and the spatial resolution using 3mm dia green LED was measured as 2.9mm. These priliminary results indicate that the currently developing probe is very promising and could be very useful for many applications in nuclear medicine.

• Korean Journal of Digital Imaging in Medicine
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• v.15 no.1
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• pp.55-59
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• 2013

Patients who had claustrophobia tend to feel fear when they were scanned by an MRI, CT, PET-CT, or using a gamma camera scan. In this paper, claustrophobic patients were tested to find effective ways by changing patient's positions. For this paper, PET-CT scan in patients who had claustrophobia were used in the prone position. Prone position helped to maintain stable position and to get a h0igh quality of inspection without failure. Thus, as claustrophobic patients were requested taking prone position, they could feel comfortable. In a confined space, prone position for the claustrophobic patients who had a fear of the PET-CT examination would be expected to reduce the failure rate of inspection.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.715-727
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• 2024

During fast neutron imaging, besides the dark current noise and readout noise of the CCD camera, the main noise in fast neutron imaging comes from high-energy gamma rays generated by neutron nuclear reactions in and around the experimental setup. These high-energy gamma rays result in the presence of high-density gamma white spots (GWS) in the fast neutron image. Due to the microscopic quantum characteristics of the neutron beam itself and environmental scattering effects, fast neutron images typically exhibit a mixture of Gaussian noise. Existing denoising methods in neutron images are difficult to handle when dealing with a mixture of GWS and Gaussian noise. Herein we put forward a deep learning approach based on the Swin Transformer UNet (SUNet) model to remove high-density GWS-Gaussian mixture noise from fast neutron images. The improved denoising model utilizes a customized loss function for training, which combines perceptual loss and mean squared error loss to avoid grid-like artifacts caused by using a single perceptual loss. To address the high cost of acquiring real fast neutron images, this study introduces Monte Carlo method to simulate noise data with GWS characteristics by computing the interaction between gamma rays and sensors based on the principle of GWS generation. Ultimately, the experimental scenarios involving simulated neutron noise images and real fast neutron images demonstrate that the proposed method not only improves the quality and signal-to-noise ratio of fast neutron images but also preserves the details of the original images during denoising.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.661-666
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• 2019

Diverging collimators is used to obtain reduced images of an object, or to detect a wide filed-of-view (FOV) using a small gamma camera. In the gamma camera using the diverging collimators, the block scintillator, and the pixel scintillator array, gamma rays are obliquely incident on the scintillator surface when the source is located the periphery of the FOV. Therefore, the spatial resolution is reduced because it is obliquely detected in depth direction. In this study, we designed a novel system to improve the spatial resolution in the periphery of the FOV. Using a tapered crystal array to configure the scintillation pixels to coincide with the angle of the collimator's hole allows imaging to one scintillation pixel location, even if events occur to different depths. That is, even if is detected at various points in the diagonal direction, the gamma rays interact with one crystal pixel, so resolution does not degrade. The resolution of the block scintillator and the tapered crystal array was compared and evaluated through Geant4 Application for Tomographic Emission (GATE) simulation. The spatial resolution of the obtained image was 4.05 mm in the block scintillator and 2.97 mm in the tapered crystal array. There was a 26.67% spatial resolution improvement in the tapered crystal array compared to the block scintillation.

• The Korean Journal of Nuclear Medicine
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• v.33 no.1
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• pp.65-75
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• 1999

Purpose: The aim of this study is to demonstrate the feasibility of 2-[fluorine-18] fluoro-2-deoxy-D-glucose (F-18-FDG) whole body scan (FDG W/B Scan) using dual-head gamma camera equipped with ultra high energy collimator in patients with various cancers, and compare the results with those of coincidence imaging. Materials and Methods: Phantom studies of planar imaging with ultra high energy and coincidence tomography (FDG CoDe PET) were performed. Fourteen patients with known or suspected malignancy were examined. F-18-FDG whole body scan was performed using dual-head gamma camera with high energy (511 keV) collimators and regional FDG CoDe PET immediately followed it Radiological, clinical follow up and histologic results were correlated with F-18-FDG findings. Results: Planar phantom study showed 13.1 mm spatial resolution at 10 cm with a sensitivity of 2638 cpm/MBq/ml. In coincidence PET, spatial resolution was 7.49 mm and sensitivity was 5351 cpm/MBq/ml. Eight out of 14 patients showed hypermetabolic sites in primary or metastatic tumors in FDG CoDe PET. The lesions showing no hypermetabolic uptake of FDG in both methods were all less than 1 cm except one lesion of 2 cm sized metastatic lymph node. The metastatic lymph nodes of positive FDG uptake were more than 1.5 cm in size or conglomerated lesions of lymph nodes less than 1cm in size. FDG W/B scan showed similar results but had additional false positive and false negative cases. FDG W/B scan could not visualize liver metastasis in one case that showed multiple metastatic sites in FDG CoDe PET. Conclusion: FDG W/B scan with specially designed collimators depicted some cancers and their metastatic sites, although it had a limitation in image quality compared to that of FDG CoDe PET. This study suggests that F-18-FDG positron imaging using dual-head gamma camera is feasible in oncology and helpful if it should be more available by regional distribution of FDG.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.597-607
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• 2016

Personalized medicine is tailored medical treatment that targets the individual characteristics of each patient. Theragnosis, combining diagnosis and therapy, plays an important role in selecting appropriate patients. Noninvasive in vivo imaging can trace small molecules, antibodies, peptides, nanoparticles, and cells in the body. Recently, imaging methods have been able to reveal molecular events in cells and tissues. Molecular imaging is useful not only for clinical studies but also for developing new drugs and new treatment modalities. Preclinical and early clinical molecular imaging shows biodistribution, pharmacokinetics, mechanisms of action, and efficacy. When therapeutic materials are labeled using radioisotopes, nuclear imaging with positron emission tomography or gamma camera can be used to treat diseases and monitor therapy simultaneously. Such nuclear medicine technology is defined as radiation theragnosis. We review the current development of drugs and technology for radiation theragnosis using peptides, albumin, nanoparticles, and cells.