• The Korean Journal of Nuclear Medicine
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• v.32 no.4
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• pp.325-331
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• 1998

Purpose: We evaluated the importance of redistribution and 24 hour reinjection images in T1-201 SPECT assessment of myocardial viability after acute myocardial infarction (AMI). Materials and Methods: We performed dipyridamole stress-4 hour redistribution-24 hour reinjection T1-201 SPECT in 43 patients with recent AMI (4-16 days). The myocardium was divided into 16 segments and perfusion grade was measured visually with 4 point score from 0 to 3 (absent uptake to normal uptake). A perfusion defect with stress score 2 was considered moderate. A defect was considered severe if the stress score was 0 or 1 (absent uptake or severe perfusion decrease). Moderate defect on stress image were considered viable and segments with severe defect were considered viable if they showed improvement of 1 score or more on redistribution or reinjection images. We compared the results of viability assessment in stress-redistribution and stress-reinjection images. Results: On visual analysis, 344 of 688 segments (50%) had abnormal perfusion. Fifty two (15%) had moderate perfusion defects and 292 (85%) had severe perfusion defects on stress image. Of 292 severe stress defects, 53 were irreversible on redistribution and reversible on reinjection images, and 15 were reversible on redistribution and irreversible on reinjection images. Two hundred twenty four of 292 segments (76.7%) showed concordant results on stress-redistribution and stress-reinjection images. Therefore 24 hour reinjection image changed viability status from necrotic to viable in 53 segments of 292 severe stress defect (18%). However, myocardial viability was underestimated in only 5% (15/292) of severe defects by 24 hour reinjection. Conclusion: The 24 hour reinjection imaging is useful in the assessment of myocardial viability. It is more sensitive than 4 hour redistribution imaging. However, both redistribution and reinjection images are needed since they complement each other.

• Journal of radiological science and technology
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• v.45 no.2
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• pp.135-143
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• 2022

In SPECT image, scatter count is the cause of quantitative count error and image quality degradation. This study is to evaluate the accuracy of CT based SC(CTSC) and energy window based SC(EWSC) as the comparison with existing Non SC. SPECT/CT images were obtained after filling air in order to acquire a reference image without the influence of scatter count inside the Triple line insert phantom setting hot rod(^99mTc 74.0 MBq) in the middle and each SPECT/CT image was obtained each separately after filling water instead of air in order to derive the influence of scatter count under the same conditions. For EWSC, 9 sub-energy windows were set additionally in addition to main energy window(140 keV, 20%) and then, images were acquired at the same time and five types of EWSC including DPW(dual photo-peak window)10%, DEW(dual energy window)20%, TEW(triple energy window)10%, TEW5.0%, TEW2.5% were used. Under the condition without fluctuations in primary count, total count was measured by drawing volume of interest (VOI) in the images of the two conditions and then, the ratio of scatter count of total counts was calculated as percent scatter fraction(%SF) and the count error with image filled with water was evaluated with percent normalized mean-square error(%NMSE) based on the image filled with air. Based on the image filled with air, %SF of images filled with water to which each SC method was applied is non scatter correction(NSC) 37.44, DPW 27.41, DEW 21.84, TEW10% 19.60, TEW5% 17.02, TEW2.5% 14.68, CTSC 5.57 and the scatter counts were removed the most in CTSC and %NMSE is NSC 35.80, DPW 14.28, DEW 7.81, TEW10% 5.94, TEW5% 4.21, TEW2.5% 2.96, CTSC 0.35 and the error in CTSC was found to be the lowest. In SPECT/CT images, the application of each scatter correction method used in the experiment could improve the quantitative count error caused by the influence of scatter count. In particular, CTSC showed the lowest %NMSE(=0.35) compared to existing EWSC methods, enabling relatively accurate scatter correction.

• The Korean Journal of Nuclear Medicine
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• v.25 no.2
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• pp.237-244
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• 1991

$^{99m}Tc-DMSA$ renal scan has been evaluated not only the renal functional cell mass but also some anatomical structures at a loss of the renal parenchymal function. The author classified a renal morphology of the posterior image of $^{99m}Tc-DMSA$ renal scan as the groups of symmetric and asymmetric morphology, the groups of the large, normal and small sized kidneys, the groups of the central photon defects (PD) which could be noted in a dilated pelvocalyceal system due to obstructive uropathy and the cortical photon defects (CD) due to focal parenchymal lesions or scars after a loss of function and the last groups of the single and multiple CD for a suggestion of the clinical usefulness. Regarding to measurement of normal renal size, the longest size of the kidneys were evaluated with 5 cm of a lead scale on the posterior renal image, and those were decided to the limits beteen 104.1 and 119.4 mm as comparison with the renal size of intravenous pyelogram (IVP) in 59 cases who were underwent $^{99m}Tc-DMSA$ and IVP concommitantly. Among 85 cases of PD in $^{99m}Tc-DMSA$ renal scan, the 61 (71.8%) were cases of a dilated pelvocalyceal system related with obstructive uropathy, meanwhile the 28 (27.0%) of 162 cases with CD were cases of obstructive and infectious uropathy. The probability of a presence of some uropathy in cases of CD were 99.3%, meanwhile that of the presence of CD in cases of some uropathy were 37.9%. Besides, there were some specific anatomical findings such as polycystic kidneys with symmetric enlarged kidneys with multiple CD and the kidneys of chronic renal failure and/or hypertension with symmetric small size in $^{99m}Tc-DMSA$ renal stan.

• The Korean Journal of Nuclear Medicine
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• v.27 no.2
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• pp.195-202
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• 1993

$^{123}Iodine$-metaiodobenzylguanidine (MIBG) which is a norepinephrine analogue, can be used to evaluate the sympathetic innervation of the heart. In this study, cardiac imaging with $^{123}I-MIBG$ was performed in patients with 9 dilated cardiomyopathy, 2 ischemic cardiomyopathy and 1 acute myocardial infarction to evaluate the sympathetic nervous function. $^{123}I-MIBG$ imaging showed multifocal defects (8), diffuse defect (2), near non-visualization (2). The defects of MIBG scans were found to be larger and more severe on 4 hours image than 30 minutes. Heart to lung, heart to mediastinum ratios were decreased at 4 hours than those at 30 minutes. Measured LVEF values were not correlated with the severity of MIBG uptake. $^{99m}Tc-MIBI$ imaging was also performed in all patients to find the relationship with $^{123}I-MIBG$ scan. $^{99m}Tc-MIBI$ scan showed multifocal defects in 9 patients, diffuse defects in 1 patient and no defect in 2 patients. The defects are similar in size, severity and extent, but more larger and severe on $^{123}I-MIBG$ imaging. Therefore, cardiac $^{123}I-MIBG$ imaging is a useful method to evaluate the sympathetic nervous function in cardiomyopathy.

• Journal of radiological science and technology
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• v.35 no.4
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• pp.353-360
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• 2012

Diverse designs of collimator have been applied to Single Photon Emission Computed Tomography (SPECT) according to the purpose of acquisition; thus, it is necessary to reflect geometric characteristic of each collimator for successive image reconstruction. This study carry out reconstruction algorithm for imaging system in nuclear medicine with pinhole collimator. Especially, we study to solve sampling problem which caused in the system model of pinhole collimator. System model for a maximum likelihood expectation maximization (MLEM) was developed based on the geometry of the collimator. The projector and back-projector were separately implemented based on the ray-driven and voxel-driven methods, respectively, to overcome sparse sampling problem. We perform phantom study for pinhole collimator by using geant4 application for tomographic emission(GATE) simulation tool. The reconstructed images show promising results. Designed iterative reconstruction algorithm with unmatched system model effective to remove sampling problem artefact. Proposed algorithm can be used not only for pinhole collimator but also for various collimator system of imaging system in nuclear medicine.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.2072-2077
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• 2020

The purpose of this study was to demonstrate the feasibility of sensing changes in a tumor during boron neutron capture therapy (BNCT) using a Monte Carlo simulation tool. In the simulation, an epi-thermal neutron source and a water phantom including boron uptake regions (BURs) were simulated. Moreover, this simulation also included a detector for positron emission tomography (PET) scanning and an adaptively-designed collimator (ADC) for PET. After the PET scanning of the water phantom, including the 511 keV source in the BUR, the ADC was positioned in the PET's gantry. Single prompt gamma rays were collected through the ADC during neutron irradiation. Then, single prompt gamma ray-based tomography images of different sized tumors were acquired by a four-step process. Both the signal-to-noise ratio (SNR) and tumor size were analyzed from each step image. From this analysis, we identified a decreasing trend of both the SNR and signal intensity as the tumor size decreased, which was confirmed in all images. In conclusion, we confirmed the feasibility of sensing changes in a tumor during BNCT using PET and an ADC through Monte Carlo simulation.

• 대한핵의학회:학술대회논문집
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• 2001.05a
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• pp.66-75
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• 2001

Although diverse mechanisms are involved in multidrug resistance for chemotherapeutic drugs, the development of cellular P-glycoprotein(Pgp) and multidrug-resistance associated protein (MRP) are important factors in the chemotherapy failure to cancer. Various detection assays provide information about the presence of drug efflux pumps at the mRNA and protein levels. However these methods do not yield information about dynamic function of Pgp and MRP un vivo. Single photon emission tomography (SPECT) and positron emission tomography (PET) are available for the detection of Pgp and MRP-mediated transport. $^{99m}Tc$-sestaMIBl and other $^{99m}Tc$-radiopharmaceuticals are substrates for Pgp and MRP, and have been used in clinical studies for tumor imaging, and to visualize blockade of Pgp-mediated transport after modulation of Pgp pump. Colchicine, verapamil and daunorubicin labeled with $^{11}C$ have been evaluated for the quantification of Pgp-mediated transport with PET in vivo and reported to be feasible substrates with which to image Pgp function in tumors. Leukotrienes are specific substrates for MRP and N-$[^{11}C]$acetyl-leukotriene E4 provides an opportunity to study MRP function non-invasively in vivo. Results obtained from recent publications are reviewed to confirm the feasibility of using SPECT and PET to study the functionality of MDR transporters in vivo.

• The Korean Journal of Nuclear Medicine Technology
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• v.19 no.1
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• pp.17-29
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• 2015

Purpose For nuclear medicine technologists, it is difficult to stay away from or to separate from radiation sources comparing with workers who are using radiation generating devices. Nuclear medicine technologists work is recognized as an optimized way when they are familiar with work practices. The aims of this study are to measure radiation exposure of technologists working in PET and to evaluate the occupational radiation dose after implementation of strategies to lower exposure. Materials and Methods We divided into four working types by QC for PET, injection, scan and etc. in PET scan procedure. In QC of PET, we compared the radiation exposure controlling next to $^{68}Ge$ cylinder phantom directly to controlling the table in console room remotely. In injection, we compared the radiation exposure guiding patient in waiting room before injection to after injection. In scan procedure of PET, we compared the radiation exposure moving the table using the control button located next to the patient to moving the table using the control button located in the far distance. PERSONAL ELECTRONIC DOSEMETER (PED), Tracerco$^{TM}$ was used for measuring exposed radiation doses. Results The average doses of exposed radiation were $0.27{\pm}0.04{\mu}Sv$ when controlling the table directly and $0.13{\pm}0.14{\mu}Sv$ when controlling the table remotely while performing QC. The average doses of exposed radiation were $0.97{\pm}0.36{\mu}Sv$ when guiding patient after injection and $0.62{\pm}0.17{\mu}Sv$ when guiding patient before injection. The average doses of exposed radiation were $1.33{\pm}0.54{\mu}Sv$ when using the control button located next to the patient and $0.94{\pm}0.50{\mu}Sv$ when using the control button located in far distance while acquiring image. As a result, there were statistically significant differences(P<0.05). Conclusion: From this study, we found that how much radiation doses technologists are exposed on average at each step of PET procedure while working in PET center and how we can reduce the occupational radiation dose after implementation of strategies to lower exposure. And if we make effort to seek any other methods to reduce technologist occupational radiation, we can minimize and optimize exposed radiation doses in department of nuclear medicine. Conclusion From this study, we found that how much radiation doses technologists are exposed on average at each step of PET procedure while working in PET center and how we can reduce the occupational radiation dose after implementation of strategies to lower exposure. And if we make effort to seek any other methods to reduce technologist occupational radiation, we can minimize and optimize exposed radiation doses in department of nuclear medicine.

• The Korean Journal of Nuclear Medicine
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• v.34 no.4
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• pp.344-352
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• 2000

Purpose: Re-188-Hydroxyethylidene diphosphonate (HEDP) is a new cost-effective agent for systemic radioisotope therapy of metastatic bone pain. We investigated the influence of carrier for labeling and biodistribution of Re-188-HEDP using HEDP kit with or without carrier ($KReO_4$). Materials and Methods: The kits (HEDP 15 mg, gentisic acid 4 mg and $SnCl_2.2H_2O_2$ 4.5 mg) with or without carrier ($KReO_4$ 0.1 mg) were labeled with Re-188 solution, made available from an in-house generator by boiling for 15 min. We compared the labeling efficiency and stability of carrier-added and carrier-free preparations of Re-188-HEDP Biodistribution and imaging studies of each preparation were performed in ICR mice ($1.85{\sim}3.7MBq/0.1ml$) and SD rats ($74.1{\sim}85.2MBq/0.5ml$). Results: The carrier-added preparation showed high labeling efficiency (95% at pH 5) and high stability in serum (88%, 3 hr). However, the carrier-free preparation showed low labeling efficiency (59% at pH 5) and low stability (43%, 3 hr). The carrier-added preparation showed high uptake in bone and low uptake in stomach and kidneys. However, the carrier-free preparation showed lower uptake in bone and higher uptake in both stomach and kidneys, which is supposed to be due to released perrhenate. The carrier-added preparation also showed better images with higher skeletal accumulation, lower uptake in other organs and lower soft tissue uptake than the carrier-free preparation. Conclusion: The results of these studies clearly demonstrate that addition of carrier perrhenate is required for high labeling efficiency, stability, bone uptake and good image quality of Re-188-HEDP.

• The Korean Journal of Nuclear Medicine
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• v.26 no.2
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• pp.274-279
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• 1992

Clinical role of $^{99m}Tc-MIBI$ myocardial scintigraphy in the diagnosis of coronary artery disease (CAD) is now well accepted, however, the role of it in the identification of viable myocardium in patients with chronic CAD has not yet been clarified. To determine the usefulness of rest-injected $^{99m}Tc-MIBI$ scan as a marker of myocardial viability, the regional uptake of this agent at rest was compared with that of $^{201}Tl$ on reinjection and 24 hours after reinjection images. Subject patients were 13 chronic CAD patients who showed irreversible perfusion defect(s) on standard pharmacologic (dipyridamole) stress-redistribution images. Immediately after the redistribution images were obtained, 37 MBq thallium was injected at rest, and images were reacquired at 10 minutes and 24 hours after reinjection. After then 740 MBq $^{99m}Tc-MIBI$ was injected, and 1 hour later rest MIBI myocardial imaging was performed. Five sets of imagestress, redistribution, reinjection, delayed images of thallium, and rest image of MIBI) were then analyzed qualitatively and quantitatively. Left ventricle was arbitrarily divided into 9 segments (apex, basal and apical portions of anterior, septal, inferior, and lateral walls). Seven patients and 30 regions showed a fixed perfusion defect on the stress-redistribution images. Among 30 regions, 15 showed positive uptakes and 6 showed negative uptakes on both $^{201}Tl$ reinjection/delayed images and $^{99m}Tc-MIBI$ rest images. Five regions showed only thallium uptake and were regarded as viable clinically. Of four regions which showed only $^{99m}Tc-MIBI$ uptake, two were regarded as viable, while the other two were regarded as a nonviable scar tissue clinically. In conclusion, $^{201}Tl$ reinjection technique was more reliable in the identification of viable myocardium. However, the role of $^{99m}Tc-MIBI$ in identification of viable myocardium was still remained to be clarified because 2 of 9 regions showed only $^{99m}Tc-MIBI$ uptake and were regarded as viable tissues.