• The Korean Journal of Nuclear Medicine Technology
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• v.24 no.1
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• pp.15-19
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• 2020

Purpose Generative Adversarial Network(GAN) is one of deep learning technologies. This is a way to create a real fake image after learning the real image. In this study, after acquiring artificial intelligence images through GAN, We were compared and evaluated with real scan time images. We want to see if these technologies are potentially useful. Materials and Methods 30 patients who underwent ¹⁸F-FDG Brain PET/CT scanning at Severance Hospital, were acquired in 15-minute List mode and reconstructed into 1,2,3,4,5 and 15minute images, respectively. 25 out of 30 patients were used as learning images for learning of GAN and 5 patients used as verification images for confirming the learning model. The program was implemented using the Python and Tensorflow frameworks. After learning using the Pix2Pix model of GAN technology, this learning model generated artificial intelligence images. The artificial intelligence image generated in this way were evaluated as Mean Square Error(MSE), Peak Signal to Noise Ratio(PSNR), and Structural Similarity Index(SSIM) with real scan time image. Results The trained model was evaluated with the verification image. As a result, The 15-minute image created by the 5-minute image rather than 1-minute after the start of the scan showed a smaller MSE, and the PSNR and SSIM increased. Conclusion Through this study, it was confirmed that AI imaging technology is applicable. In the future, if these artificial intelligence imaging technologies are applied to nuclear medicine imaging, it will be possible to acquire images even with a short scan time, which can be expected to reduce artifacts caused by patient movement and increase the efficiency of the scanning room.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.1
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• pp.54-60
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• 2010

Purpose: Nuclear medicine manufacturers provide various softwares which shorten imaging time using their own image processing techniques such as UlatraSPECT, ASTONISH, Flash3D, Evolution, and nSPEED. Seoul National University Hospital has introduced softwares from Siemens and Philips, but it was still hard to understand algorithm difference between those two softwares. Thus, the purpose of this study was to figure out the difference of two softwares in planar images and research the possibility of application to images produced with high energy isotopes. Materials and Methods: First, a phantom study was performed to understand the difference of softwares in static studies. Various amounts of count were acquired and the images were analyzed quantitatively after application of PIXON, Siemens and ASTONISH, Philips, respectively. Then, we applied them to some applicable static studies and searched for merits and demerits. And also, they have been applied to images produced with high energy isotopes. Finally, A blind test was conducted by nuclear medicine doctors except phantom images. Results: There was nearly no difference between pre and post processing image with PIXON for FWHM test using capillary source whereas ASTONISH was improved. But, both of standard deviation(SD) and variance were decreased for PIXON while ASTONISH was highly increased. And in background variability comparison test using IEC phantom, PIXON has been decreased over all while ASTONISH has shown to be somewhat increased. Contrast ratio in each spheres has also been increased for both methods. For image scale, window width has been increased for 4~5 times after processing with PIXON while ASTONISH showed nearly no difference. After phantom test analysis, ASTONISH seemed to be applicable for some studies which needs quantitative analysis or high contrast, and PIXON seemed to be applicable for insufficient counts studies or long time studies. Conclusion: Quantitative values used for usual analysis were generally improved after application of the two softwares, however it seems that it's hard to maintain the consistency for all of nuclear medicine studies because result images can not be the same due to the difference of algorithm characteristic rather than the difference of gamma cameras. And also, it's hard to expect high image quality with the time shortening method such as whole body scan. But it will be possible to apply to static studies considering the algorithm characteristic or we can expect a change of image quality through application to high energy isotope images.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.3
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• pp.203-206
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• 2009

Nuclear cardiac imaging has been widely used to assess viable myocardium in patients with ischemic heart disease, The assessment of viable myocardium is important in selecting patients who will be benefit from revascularization. Although revascularization is indicated in patients with sufficient myocardium, patients with scar tissue should be treated medically. Nuclear imaging methods including myocardial perfusion SPECT and FDG PET have been shown to be effective modalities for identifying viable myocardium.

• Journal of the Korean Society of Radiology
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• v.5 no.5
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• pp.295-302
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• 2011

To n the field of nuclear medicine, with regard to checking regular patients, from the moment they register up to the doctor's diagnosis, the person in charge of the checks can find errors in the diagnosis, reexamine, reanalyze the results or save images to PACS. Through this process, the results obtained from the readings are delayed due to checks and additional tests which occur in hospitals, causing patient satisfaction and affected reliability. Accordingly, the purpose is to include visual inspection of the results to minimize error, improve efficiency and increase patient satisfaction. Nuclear medicine and imaging tests from examines at Asan Medical Center, Seoul, from March 2008 to December 2008, were analyzed for errors. The first stage, from January 2009 to December 2009, established procedures and know-how. The second stage from January 2010 until June 2010 conducted Pre-and Post-filtering assessment, and the third stage from July 2010 until October 2010 consisted of cross-checks and attaching stickers and comparing error cases. Of 92 errors, the 1st, 2nd and 3rd stage had 32 cases, and there were 46 cases after the 4th stage, with the overall errors reduced by 74.3% from 94.6%. In the field of general nuclear medicine, where various kinds of checks are performed according to the patient's needs, analysis, image composition, differing images in PACS, etc, all have the potential for mistakes to be made. In order to decrease error rates, the image can continuously Cross-Check and Confirm diagnosis.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.5
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• pp.468-477
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• 2009

Purpose: Hydrodynamic-based procedure is a simple and effective gene delivery method to lead a high gene expression in liver tissue. Non-invasive imaging reporter gene system has been used widely with herpes simplex virus type 1 thymidine kinase (HSV1-tk) and its various substrates. In the present study, we investigated to image the expression of HSV1-tk gene with 5-(2-iodovinyD-2'-deoxyuridine (IVDU) in mouse liver by the hydrodynamicbased procedure. Materials and Methods: HSV1-tk or enhanced green fluorescence protein (EGFP) encoded plasmid DNA was transferred into the mouse liver by hydrodynaminc injection. At 24 h post-injection, RT-PCR, biodistribution, fluorescence imaging, nuclear imaging and digital wholebody autoradiography (DWBA) were performed to confirm transferred gene expression. Results: In RT-PCR assay using mRNA from the mouse liver, specific bands of HSV1-tk and EGFP gene were observed in HSV1-tk and EGFP expressing plasmid injected mouse, respectively. Higher uptake of radiolabeled IVDU was exhibited in liver of HSV1-tk gene transferred mouse by biodistribution study. In fluorescence imaging, the liver showed specific fluorescence signal in EGFP gene transferred mouse. Gamma-camera image and DWBA results showed that radiolabeled IVDU was accumulated in the liver of HSV1-tk gene transferred mouse. Conclusion: In this study, hydrodynamic-based procedure was effective in liver-specific gene delivery and it could be quantified with molecular imaging methods. Therefore, co-expression of HSV1-tk reporter gene and target gene by hydrodynamic-based procedure is expected to be a useful method for the evaluation of the target gene expression level with radiolabeled IVDU.

• The Korean Journal of Nuclear Medicine
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• v.35 no.6
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• pp.378-388
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• 2001

Purpose: In this study, we developed a new method for the determination of renal depth with anterior and posterior renal scintigrams in a dual-head gamma camera, considering the attenuation factor $e^{-{\mu}x}$ of the conjugate-view method. Material and Method: We developed abdomen and kidney phantoms to perform experiments using Technetium-99m dimercaptosuccinic acid ($^{99m}Tc$-DMSA). The phantom images were obtained by dual-head gamma camera equipped with low-energy, high-resolution, parallel-hole collimators (ICONf, Siemens). The equation was derived from the linear integration of omission ${\gamma}$-ray considering attenuation from the posterior abdomen to the anterior abdomen phantom surface. The program for measurement was developed by Microsoft Visual C++ 6.0. Results : Renal depths of the phantoms were derived from the derived equations and compared with the exact geometrical values. Differences between the measured and the calculated values were the range of 0.1 to 0.7 cm ($0.029{\pm}0.15cm,\;mean{\pm}S.D.$). Conclusion: The present study showed that the use of the derived equations for renal depth measurements, combined with quantitative planar imaging using dual-head gamma camera, could provide more accurate results for individual variation than the conventional method.

• Progress in Medical Physics
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• v.12 no.2
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• pp.103-112
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• 2001

Purpose: The purpose of this study was to investigate the current status of performing nuclear medicine quality control in korea and to test selected protocols of quality control of nuclear medicine counting system and gamma camera. Materials and Methods: Fifty three hospitals were included to investigate the current status of nuclear medicine quality control in korea. The precision of dose calibrator and thyroid uptake system was measured with Tc-99m 35.52 MBq for 2 minuets and Tc-99m 5.14 MBq for 10 sec every one minute, respectively. The sensitivity of CeraSPECT$^{TM}$ with low energy high resolution parallel hole collimator was measured using two cylindrical phantoms with 15 cm in diameter and 12 cm and 30 cm in heights containing Tc-99m. The correction factor for sensitivity of CeraSPECT$^{TM}$ was calculated using phantom data. The system planar sensitivity, uniformity, count rate and spatial resolution were measured for Varicam gamma camera with low energy high resolution parallel hole collimator using 140 keV centered 20% energy window, 256$\times$256 or 512$\times$512 matrix sizes. Results: The quality control of dose calibrator and well counter were showed poor performance status. On the other hand, The quality control of gamma camera and other systems were showed relatively good performance status. The results of precision of dose calibrator and thyroid uptake system was $\pm$1.4%(<$\pm$5%) and chi^2=29.7(>16.92), respectively. It showed that the sensitivity of CeraSPECT$^{TM}$ was higher in center slices compared with the edge slices. After correction of nonuniform sensitivities for patient data, it showed better results compare with prior to correction. System planar sensitivity of Varicam gamma camera was 4.39 CPM/MBq. The observed count rate at 20% loss was 102,407 counts/sec (head 1), 113,427 counts/sec (head 2), when input count rate was 81,926 counts/sec (head 1), 90,741 counts/sec (head 2). The spatial resolution without scatter medium were 8.16 mm of FWHM and 14.85 mm of FWTM. The spatial resolution with scatter medium were 8.87 mm of FWHM and 18.87 mm of FWTM. Conclusion: It is necessary to understand the importance of quality control and to perform quality control of nuclear medicine devices.vices.

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.1
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• pp.90-93
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• 2011

Purpose: A Pixelated BSGI gamma camera has features to enhance resolution and sensitivity and minimize the distance between detector and organs by narrow FOV. Therefore, it is known as useful device to examine small organs such as thyroid, parathyroid and gall bladder. In general, when we would like to enlarge the size of images and obtain high resolution images by gamma camera in nuclear medicine study, we use pinhole collimator. The purpose of this study is to evaluate the usefulness of Pixelated BSGI gamma camera and to compare to it using pinhole collimator in thyroid scan which is a study of typical small organs. Materials and methods: (1) The evaluation of sensitivity and spatial resolution: We measured sensitivity and spatial resolution of Pixelated BSGI with LEHR collimator and Infinia gamma camera with pinhole collimator. The sensitivity was measured by point source sensitivity test recommended by IAEA. We acquired images considering dead time in BSGI gamma camera for 100 seconds and used $^{99m}TcO4-\;400{\mu}Ci$ line source. (2) The evaluation of thyroid phantom: The thyroid phantom was filled with $^{99m}TcO4-$. After set 300 sec or 100 kcts stop conditions, we acquired images from both pixelated BSGI gamma camera and Infinia gamma camera with LEHR collimator. And we performed all thyroid studies in the same way as current AMC's procedure. Results: (1) the result of sensitivity: As a result, the sensitivity and spatial resolution of pixelated BSGI gamma camera were better than Infinia's. The sensitivities of pixelated BSGI and Infinia gamma camera were $290cps/{\mu}Ci$ and $350cps/{\mu}Ci$ respectively. So, the sensitivity of pixelated BSGI was 1.2 times higher than Infinia's (2) the result of thyroid phantom: Consequently, we confirmed that images of Pixelated BSGI gamma camera were more distinguishable between hot and cold spot compared with Infinia gamma camera. Conclusion: A pixelated BSGI gamma camera is able to shorten the acquisition time. Furthermore, the patients are exposed to radiation less than before by reducing amount of radiopharmaceutical doses. Shortening scan time makes images better by minimizing patient's breath and motion. And also, the distance between organ and detector is minimized because detector of pixelated BSGI gamma camera is small and possible to rotate. When patient cannot move at all, it is useful since device is feasible to move itself. However, although a pixelated BSGI gamma camera has these advantages, the effect of dead time occurs over 2000 cts/s since it was produced only for breast scan. So, there were low concentrations in organ. Therefore, we should consider that it needs to take tests to adjust acquisition time and amount of radiopharmaceutical doses in thyroid scan case with a pixelated BSGI gamma camera.

• The Korean Journal of Nuclear Medicine
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• v.30 no.3
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• pp.344-350
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• 1996

Purpose : Noninvasive imaging of tumor cell proliferation could be helpful in the evaluation of tumor growth potential and could provide an early assessment of treatment response. Radiolabeled thymidine, uridine and adenosine have been used to evaluate tumor cell proliferation. These nucleoside analogs are incorporated into DNA during proliferation. Iodine-131-Iodomethyluridine, an analog of Iodine-131-Iododeoxyuridine, is also involved in DNA/RNA synthesis. The purpose of this study was to develop Iodine-131-Iodomethylurdine and image tumor proliferation using Iodine-131-Iodomethyluridine. Materials and Methods : Radiosynthesis of Iodine-131-5-Iodo-2'-O-methyluridine (Iodine-131-Iodomethyluridine) was prepared from 10 mg of 2'-O-methyluridine(Sigma chemical Co., St. Louis, Missouri) and 2.1 mCi(SP. 10Ci/mg) of Iodine-131-labeled sodium iodide in $100{\mu}l$ of water using iodogen reaction. Female Fischer 344 rats were inoculated in the thigh area with breast tumor cells(13765 NF, $10^5$ cells/rat S.C.). After 14 days, the Iodine-131-Iodomethyluridine $10{\mu}Ci$ was injected to three groups of rats(3/group). The percent of injected dose per gram of tissue weight was determined at 0.5-hours, 2-hours, 4-hours, and 24-hours respectively. Tumor bearing rats after receiving Iodine-131-Iodomethyluridine($50{\mu}Ci$ IV) were euthanized at 2 hours after injection. Autoradiography was done using freeze-dried $50{\mu}m$ coronal section. After injection of Iodine-131- Iodomethyluridine ($10{\mu}Ci$/rat, IV) in three breast tumor-bearing rats, planar scintigraphy was taken at 45 minutes, 90 minutes and 24 hours. Results : Iodine-131-Iodomethyluridine was conveniently synthesized using iodogen reaction. The biodistribution showed fast blood clearance and the tumor-to-tissue uptake ratios showed that optimal imaging time was at 2 hours postinjection. Autoradiogram and planar scintigram indicated that tumor could be well visualized. Conclusion : The findings suggest that Iodine-131-Iodomethyluridine, a new radio-iodinated nucleoside, has potential use for evaluation of active regions of tumor growth.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.38-40
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• 2010

Purpose: This study was performed to find the current problems of PET/CT data from other hospitals. Materials and Methods: The subjects were acquired from 64 hospitals referred to our department for image interpretation. The formats and contents of PET/CT data were reviewed and the phone questionnaire survey about these were performed. Results: PET/CT data from 39 of 64 hospitals (61%) included all transaxial CT and PET images with DICOM (Digital Imaging Communications in Medicine) standard format which were required for authentic interpretation. PET/CT data from the others included only secondary capture images or fusion PET/CT images. Conclusion: The majority of hospitals provided limited PET/CT data which could be inadequate for accurate interpretation and clinical decision making. It is necessary to standardize the format of PET/CT data to transfer including all transaxial CT and PET images with DICOM standard format.