• Progress in Medical Physics
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• v.19 no.3
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• pp.191-199
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• 2008

PTV considered for the energy, dose distribution exposed to lung and spinal cord, and the characteristic of DVH(Dose Volume Histogram) were compared and investigated by planning the intensity modulated radiation therapy (IMRT) using the photon energies of 6 MV and 10 MV according to tumor location like as the anterior, middle, and posterior regions of lung, and the mediastinum region in lung cancer patients. Our institution installed the linear accelerator (Varian 21 EX-s, USA) equipped with 120 multileaf collimator for lung cancer patients, which is producing the photon energies of 6 MV and 10 MV, and radiation therapy planning was performed with ECLIPSE system (Varian, SomaVision 6.5, USA), which support inverse treatment planning. The tomographic images of 3 mm slice thickness for lung cancer patients were acquired using planning CT, and acquired tomographic images were sent to the Varis system, and then treatment planning was performed in the ECLIPSE system. The radiation treatment planning of the IMRT was processed from various angles according to the regions of the tumor, and using various beam lines according to the size and location of the tumor. The investigation of the characteristic of dose distributions for the energy of 6 MV and 10 MV according to tumor locations in lung cancer patients resulted that the maximum dose of 10 MV energy was 1.2% less than that of 6 MV energy without depending on the tumor location of lung cancer, and the reduction effects of MU were occurred from 10 to 25 MU. Radiation dose exposed to the lung satisfied the less 30% of V20, however radiation dose in 6 MV energy was from 0.1% to 0.5% less than that in 10 MV energy. Radiation dose exposed to the spinal cord for 6 MV energy was from 0.6% to 2.1% less than that for 6 MV energy.

• Journal of Gastric Cancer
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• v.6 no.3
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• pp.161-166
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• 2006

Purpose: Recently, the incidence of early gastric cancer (EGC) patients is rapidly increased in Korea. However, they're often not perceptible by surgical palpation or inspection. The aim of this study is 1) to develope a software that can locate the tumor and measure the mucosal distance from an anatomic landmark to the tumor using CT gastrography and 2) to compare the distance measured by the developed software with the distance measured by the pathologic findings. Materials and Methods: Between January 2004 and September 2005, sixty patients (male=45, female=15, mean 57.8 years old) estimated for EGC with preoperative CT scans and undergone gastrectomies in Kyungpook National University Hospital were enrolled in this study. Preoperative CT scans were performed after insufflations of room air via 5 Fr NG tube. The scans included the following parameters: (slice thickness/reconstruction interval: 0.625 mm, kVp: 120, mAs: 200). 3D volume rendering and measurement of the surface distance from the pylorus to the EGC were performed using the developed software. Results: The average difference between the lesion to pylorus distances measured from pathologic specimens and CT gastrography was $5.3{\pm}2.9\;mm(range,\;0{\sim}23\;mm)$. The lesion to pylorus distance measured from CT gastrography was well correlated with that measured from the pathologic specimens (r=0.9843, P<0.001). Conclusion: These results suggest that the surface distance from an anatomic landmark to the EGC can be measured accurately by CT gastrography. This technique could be used for preoperative localization of early gastric carcinomas to determine the optimal extent of surgical resection.

• The Journal of Korean Medicine
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• v.27 no.3 s.67
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• pp.187-200
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• 2006

Objectives: Acupuncture has been applied in Asia for thousands of years, especially to rehabilitation after stroke. It has been reported that acupuncture increased cerebral blood supply and stimulated the functional activity of brain nerve cells shown by using brain imaging techniques. This study was to evaluate the effect of GB 34-GB 39 electro-acupuncture (EA) on regional cerebral blood flow (rCBF) in stroke patients and normal volunteers using single photon emission computed tomography (SPECT). Methods: The study procedure was divided into two parts: patients and volunteers studies. For the patients study, ten ischemic stroke patients (3 males, 7 females, mean age $68.5{\pm}8.9$ years old) were selected. Baseline brain SPECT was done with triple head gamma camera (MultiSPECT3, Siemens, USA) after intravenous administration of 1,110 MBq of $^{99m}Tc-ECD$. Fifteen-minute EA at GB 34 and GB 39 were applied on the affected limb. The same dose of $^{99m}Tc-ECD$ was injected during the EA, and the second set of SPECT images wasobtained. Using the computer software (ICON 7.1, Siemens, USA), 3 SPECT slices (upper, middle, lower) surrounding the brain lesion were selected and each slice was divided into 10-16 brain regions. Asymmetry indexes (AI) were analyzed in each brain region. We regarded over 10% changes of AI between before and after EA as significance. For the volunteers study, 10 healthy human volunteers (5 males, 5 females, mean age $28.1{\pm}6$ years old) were selected. In the resting state, $^{99m}Tc-ECD$ brain SPECT scans were performed. On the 7th day after the resting examination, 15 minute EA was applied at GB 34 and GB 39 on the right side of the subjects. Immediately after EA, the second SPECT images were obtained inthe same manner as the resting state. Significant increases and decreases of rCBF after EA were estimated by comparing their SPECT images with those of the resting state using paired t statistics at every voxel, which were analyzed by statistical parametric mapping with a threshold of p = 0.01, uncorrected (extent threshold: k=100 voxels). Results: In stroke patients, six of the eight (75%) had significantly increased perfusion in post-acupuncture scans compared to their baseline state. In normal volunteers, GB 34-GB GB EA increased rCBF in both hemispheres including right ventral posterior cingulate (Brodmann area (BA) 23), left superior temporal, anterior transverse temporal (BA 22, 41), left parastriate, peristriate (BA 18, 19), right occipitotemporal, angular (BA 37, 39), left rostral postcentral, caudal postcentral and preparietal (BA 2, 3, 5). However GB 34-GB 39 EA decreased rCBF in the right hemisphere including triangular and middle frontal lobes. Conclusions: The results demonstrated that OB 34-GB 39 EA increased cerebral perfusion in ischemic stroke patients and increased rCBF grossly in temporal lobes of normal volunteers. It is also suggested that there may be a correlation between the GB meridian and the territory of the middle cerebral artery.

• Investigative Magnetic Resonance Imaging
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• v.5 no.2
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• pp.138-148
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• 2001

Purpose : Within a clinically acceptable time frame, we obtained the high resolution MR images of the human brain, knee, foot and wrist from 3T whole-body MRI system which was equipped with the world first 37 active shield magnet. Materials and Methods : Spin echo (SE) and Fast Spin Echo (FSE) images were obtained from the human brain, knee, foot and wrist of normal subjects using a homemade birdcage and transverse electromagnetic (TEM) resonators operating in quadrature and tuned to 128 MHz. For acquisition of MR images of knee, foot and wrist, we employed a homemade saddle shaped RF coil. Topical common acquisition parameters were as follows: matrix=$512{\times}512$, field of view (FOV) =20 cm, slice thickness = 3 mm, number of excitations (NEX)=1. For T1-weighted MR images, we used TR = 500 ms, TE = 10 or 17.4 ms. For T2-weighted MR images, we used TR=4000 ms, TE = 108 ms. Results : Signal to noise ratio (SNR) of 3T system was measured 2.7 times greater than that of prevalent 1.5T system. MR images obtained from 3T system revealed numerous small venous structures throughout the image plane and provided reasonable delineation between gray and white matter. Conclusion The present results demonstrate that the MR images from 3T system could provide better diagnostic quali\ulcorner of resolution and sensitivity than those of 1.5T system. The elevated SNR observed in the 3T high field magnetic resonance imaging can be utilized to acquire images with a level of resolution approaching the microscopic structural level under in vivo conditions. These images represent a significant advance in our ability to examine small anatomical features with noninvasive imaging methods.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.12 no.2
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• pp.256-262
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• 2001

Objective：The enlargement of the lateral ventricle is well established finding in adult-onset schizophrenia, but in the patients with early-onset psychotic disorder(EOPD) is still controversal. To identify structural abnormalities of the lateral ventricle in patients with EOPD and difference of the brain developmental course in EOPD group, planimetrical assessment of the lateral ventricle was conducted by means of retrospective quantitative neuroimaging. Methods：The brain MR images of 14 patients with EOPD(mean age $14.0{\pm}2.1$ years) who met the DSM-III-R diagnostic criteria for schizophrenia and bipolar disorder and 24 control subjects with simple headache(mean age $10.0{\pm}2.1$ years) were collected. Single best view for the lateral ventricle, one axial slice was selected for analysis. MR images were redigitalized with flatbed scanner and data were analyzed with NIH IMAGE software. Results：In the patients with EOPD, there were significant correlations between aging and lateral ventricular sizes and between aging and ventricular brain ratio(VBR). The statistical significance of normal asymmetry of the lateral ventricle was not observed for the EOPD group. The EOPD group had larger lateral ventricular sizes and VBR than control group, but these results were not statistically significant. Conclusion：These findings suggest that the brain abnormalities in patients with EOPD progress from the earlier course of the disorders and the course of brain development in EOPD group is different from control group.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.29-34
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• 2012

Purpose : Presently, hardwares and softwares for reducing radiation exposure are continually developed for PET/CT examination. Purpose of this study is to evaluate effectiveness of reducing radiation exposure dose of CT and SUV changes of PET when applied each kernel to ACCT (Attenuation Correction Computed Tomography) according to adopted IRIS (Iterative Reconstruction in Image Space) software. Materials and Methods : Biograph mCT (Siemens, Germany) was used as a PET/CT scanner. Using AAPM CT performance phantom, from standard (120 kVp, 100 mAs), 7 scans were conducted by reducing 15 mAs each. After image reconstruction by FBP (Filtered Back Projection) and IRIS, noise and spatial resolution were evaluated. The same method was applied to anthropomorphic chest phantom and acquired images were compared. NEMA IEC body phantom was used for SUV evaluation. Injected dose rate for hot sphere (hot) and background cylinder (BKG) were 1:8. CT dose condition (120 kVp, 50 mAs) was the same for each scan and PET scan durations were 1, 2, 3 and 4min. After scanning, each kernel of IRIS was applied to ACCT. And PET images were reconstructed by ACCT adopted IRIS for comparing SUV changes. Results : AAPM phantom test for noise evaluation, SD for FBP 100 mAs, IRIS 55 mAs were 8.8 and 8.9. FBP 85 mAs, IRIS 40 mAs were 9.5 and 9.7. FBP 70 mAs, IRIS 25 mAs were 11.9 and 11.1. Above mAs condition for FBP and IRIS, SD showed similar values. And for spatial resolution test, there was no significant difference. For chest phantom test, when applied the same mAs and kernel to both of FBP and IRIS, every applied kernels showed reduced noise. Lower mAs and higher kernel value showed higher noise reduction. There was no considerable difference only except for I70 very sharp kernel for SUV comparison using NEMA IEC body phantom. Conclusion : In this study, low mAs (55 mAs) applied IRIS and standard mAs (100 mAs) applied FBP showed similar noise. And only except for I70 kernel, there was no significant SUV changes. It is possible to reduce needless radiation exposure and acquire better image quality than FBP's through applying appropriate kernel of IRIS to PET/CT.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.68-80
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• 2012

Purpose : More recently, combined PET/MR scanners have been developed in which the MR data can be used for both anatometabolic image formation and attenuation correction of the PET data. For quantitative PET information, correction of tissue photon attenuation is mandatory. The attenuation map is obtained from the CT scan in the PET/CT. In the case of PET/MR, the attenuation map can be calculated from the MR image. The purpose of this study was to assess the quantitative differences between MR-based and CT-based attenuation corrected PET images. Materials and Methods : Using the uniform cylinder phantom of distilled water which has 199.8 MBq of $^{18}F$-FDG put into the phantom, we studied the effect of MR-based and CT-based attenuation corrected PET images, of the PET-CT using time of flight (TOF) and non-TOF iterative reconstruction. The images were acquired from 60 minutes at 15-minute intervals. Region of interests were drawn over 70% from the center of the image, and the Scanners' analysis software tools calculated both maximum and mean SUV. These data were analyzed by one way-anova test and Bland-Altman analysis. MR images are segmented into three classes(not including bone), and each class is assigned to each region based on the expected average attenuation of each region. For clinical diagnostic purpose, PET/MR and PET/CT images were acquired in 23 patients (Ingenuity TF PET/MR, Gemini TF64). PET/CT scans were performed approximately 33.8 minutes after the beginnig of the PET/MR scans. Region of interests were drawn over 9 regions of interest(lung, liver, spleen, bone), and the Scanners' analysis software tools calculated both maximum and mean SUV. The SUVs from 9 regions of interest in MR-based PET images and in CT-based PET images were compared. These data were analyzed by paired t test and Bland-Altman analysis. Results : In phantom study, MR-based attenuation corrected PET images generally showed slightly lower -0.36~-0.15 SUVs than CT-based attenuation corrected PET images (p<0.05). In clinical study, MR-based attenuation corrected PET images generally showed slightly lower SUVs than CT-based attenuation corrected PET images (excepting left middle lung and transverse Lumbar) (p<0.05). And percent differences were -8.01.79% lower for the PET/MR images than for the PET/CT images. (excepting lung) Based on the Bland-Altman method, the agreement between the two methods was considered good. Conclusion : PET/MR confirms generally lower SUVs than PET/CT. But, there were no difference in the clinical interpretations made by the quantitative comparisons with both type of attenuation map.

• Tuberculosis and Respiratory Diseases
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• v.66 no.1
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• pp.20-26
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• 2009

Background: $^{18}F$-Fluorodeoxyglucose positron emission tomography (FDG-PET) is widely used for the diagnosis and staging of non-small cell lung cancer (NSCLC). The aim of this study is to determine whether the bone marrow hypermetabolism seen on FDG-PET predicts a response to chemotherapy in patients with NSCLC. Methods: We evaluated the patients with advanced NSCLC and who were treated with combination chemotherapy. For determination of the standardized uptake value (SUV) of the bone marrow (BM SUV) on FDG-PET, regions of interest (ROIs) were manually drawn over the lumbar vertebrae (L1, 2, 3). ROIs were also drawn on a homogenous transaxial slice of the liver to obtain the bone marrow/ liver SUV ratio (BM/L SUV ratio). The response to chemotherapy was evaluated according to the Response Evaluation Criteria in Solid Tumor (RECIST) criteria after three cycles of chemotherapy. Results: Fifty-nine NSCLC patients were included in the study. Multivariate analysis was performed using a logistic regression model. The BM SUV and the BM/L SUV ratio on FDG-PET were not associated with a response to chemotherapy in NSCLC patients (p=0.142 and 0.978, respectively). Conclusion: The bone marrow hypermetabolism seen on FDG-PET can not predict a response to chemotherapy in NSCLC patients.

• The Korean Journal of Nuclear Medicine
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• v.35 no.2
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• pp.100-112
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• 2001

Purpose: The purpose of this study was to establish optimal imaging acquisition conditions for the GE $Advance^{TM}$ PET imaging system by performing the acceptance tests designed by National Electrical Manufacturers Association (NEMA) protocol and General Electric Medical Systems (GEMS) test procedures. Materials and Methods: Performance tests were carried out with $^{18}FDG$ radioactivity source and phantoms by using a standard acquisition mode. Transaxial resolution and scatter traction tests were performed with a line source and axial resolution with a point source, respectively. A cylindrical phantom made of polymethylmethacrylate (PMMA) was used to measure sensitivity, count rate losses and randoms, uniformity correction, and attenuation inserts were added to measure remaining tests. The test results were acquired in a diagnostic acquisition mode and analyzed mainly on high sensitivity mode. Results: Transaxial resolution and axial resolution were measured as average of 4.65 mm and 3.98 mm at 0 cm, and 6.02 mm and 6.71 mm at 20 cm on high sensitivity mode, respectively. Average scatter fraction was 9.87%, and sensitivity was $225.8kcps/{\mu}Ci/cc$ of trues. Activity at 50% deadtime was $4.6{\mu}Ci/cc$, and the error of count rate correction at that activity was from 1.49% to 3.83%. Average nonuniformity for total slice w3s 8.37%. The accuracy of scatter correction was -0.95%. The accuracies of attenuation correction were 5.68% for air, 0.04% for water and -6.51% for polytetrafluoroethylene (PTFE). Conclusion: The results satisfied most acceptance criteria, indicating that the GE $Advance^{TM}$ PET system can be optimally used for clinical applications.

• Journal of Broadcast Engineering
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• v.22 no.2
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• pp.193-206
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• 2017

In this paper, we propose a rate control method based on the $R-{\lambda}$ model that supports a parallel encoding structure in GOP levels or IDR period levels for 4K UHD input video in real-time. For this, a slice-level bit allocation method is proposed for parallel encoding instead of sequential encoding. When a rate control algorithm is applied in the GOP level or IDR period level parallelism, the information of how many bits are consumed cannot be shared among the frames belonging to a same frame level except the lowest frame level of the hierarchical B structure. Therefore, it is impossible to manage the bit budget with the existing bit allocation method. In order to solve this problem, we improve the bit allocation procedure of the conventional ones that allocate target bits sequentially according to the encoding order. That is, the proposed bit allocation strategy is to assign the target bits in GOPs first, then to distribute the assigned target bits from the lowest depth level to the highest depth level of the HEVC hierarchical B structure within each GOP. In addition, we proposed a processing method that is used to improve subjective image qualities by allocating the bits according to the coding complexities of the frames. Experimental results show that the proposed bit allocation method works well for frame-level parallel HEVC software encoders and it is confirmed that the performance of our rate controller can be improved with a more elaborate bit allocation strategy by using the preprocessing results.