• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.59-60
• /
• 2015

High resolution, multi-wavelength images from the Dutch Open Telescope were used to study the detailed mechanisms that might be involved in the multiple layer solar atmosphere observed in high cadence multi-wavelength observations. With the exceptional data observed for active region NOAA 10789 on 2005 July 13th, we study the changing pattern of the fibril using multi-wavelength tomography of the $H{\alpha}$ line center and blue wing, Ca II H, and the G Band. It is believed that a long fibril that is rooted in the umbra, with longer apparent periodicity, may be due to morphological changes. To determine this, we conduct phase difference and coherency analysis between points along the fibril to understand how the wave propagates.

• Imaging Science in Dentistry
• /
• v.33 no.3
• /
• pp.137-141
• /
• 2003

Purpose: To evaluate the precision of measurements taken of dental implants in bucco-lingually sectioned views of the maxilla by linear tomograms of the panorama and to assess the visibility of the inferior wall of the maxillary sinus. Materials and Methods : Eighty sites prepared with implants of gutta percha cone in the sockets of the upper premolars and molars of 10 dry skulls were radiographically examined using linear tomograms of panorama, and scanned coronally and axially by computed tomography. The differences in mm between the measurements in bucco-lingually sectioned images of maxillary alveolar bone and the true length and width of the implanted gutta percha cones were compared as mean values (mean) and standard deviations (SD) for each radiographic technique. Linear tomography of panorama was compared with computed tomography for visualization of the relationship between the inferior wall of maxillary sinus and the end of each implant. Results: The deviations between the actual implant length and the measured values taken from the linear tomograms (0.44±0.39 mm) was significantly less than the measured values from the multiplanar reconstructed images of the axially scanned computed tomogram (1.21 ± 0.90 mm). There was statistically significant difference (p < 0.05) between two techniques in the differences between the measurements and true implant length. The relationship of the inferior border of maxillary sinus with end of implant was worse identified with the linear tomogram of panorama (68%) than the multiplanar reconstructed image of axially scanned computed tomogram (99%). Conclusion: We could not find any differences in the accuracy of length measurement between the linear tomogram of panorama and computed tomogram, but computed tomogram allowed for a better visualization of the inferior wall of the maxillary sinus than the linear tomogram.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.3
• /
• pp.161-169
• /
• 1999

In order to investigate the validity of acoustic tomography for current measurement, an experiment of reciprocal sound transmission was conducted in April, 1997 in the southern water of Koje island. This experiment was attempted as a preliminary field study on coastal ocean acoustic tomography for construction of real-time current observation system. Examining the physical oceanography environments, the current data obtained by travel time difference of reciprocal sound wave was compared with the data of Acoustic Doppler Current Profiler (ADCP). The result shows the correlation coefficient of 0.943, very good relation between the two data, and therefore the ocean acoustic tomography could be a useful method for current measurement in the coastal area.

• Journal of Trauma and Injury
• /
• v.22 no.1
• /
• pp.44-50
• /
• 2009

Purpose: The purpose of this study was to evaluate the causes of blow-out fractures, the computed tomography findings, and the associated facial bone fractures in aged patients. Methods: This study was performed by conducting a chart review. From January 2004 to December 2007, the patients who visited the emergency room of Asan Medical Center and were diagnosed as having a blow-out fracture were included in the study population. Patients 60 years of age or older were grouped as the aged group while patients younger than 60 years of age were grouped as the control group. Results: Between the aged group and the control group, there was a difference in the causes of blow-out fractures. The most common cause of blow-out fracture was a slip down in the aged group and violence in the control group (p<0.05). There were no differences in associated symptoms. Extraocular muscle herniation was the only statistically different computed tomography findings. In associated facial bone fractures, the most common fractures were the zygoma in the aged group and the nasal bone in the control group (p<0.05). Conclusion: In patients 60 years of age or older, the most common cause of blow-out fracture was a slip down, and the most common associated facial bone fracture was a zygomatic fracture.

• Restorative Dentistry and Endodontics
• /
• v.23 no.1
• /
• pp.391-400
• /
• 1998

The aim of this study was to determine the shaping ability of stainless-steel K file (S-S K file), nickel-titanium K file (Ni-Ti K file) and engine driven nickel-titanium file (Quantec file) in resin simulated root canal. Computed tomography was used to evaluate the change of the root canal morphology. Thirty nine resin simulated root canal were divided into four groups (A:12, B:12, C:12, D:3). Resin simulated canals were scanned by computed tomography before instrumentation (1st C-T scan). Canals were instrumented using step back preparation technique with S-S K file in group A and Ni-Ti K file in group B. Group C was prepared with engine driven Ni-Ti file. Group D was uninstrumented to compare the 1st C-T scan images with 2nd C-T scan images of root canal. Instrumented canals were again scanned using computed tomography (2nd C-T scan), and reformated images of the uninstrumented canals were compared with images of the instrumented canals. In the sections of 2mm and 6mm from the apex, Quantec file caused significantly less canal transportation than S-S K file and Ni-Ti K file (p<0.05). Quantec file produced more centered than S-S K file and Ni-Ti K file in the sections of 2mm and 4mm from the apex (p<0.05). There was no significant difference in the removed volume of canals among the each groups (p>0.05). However the removed canal volume from the apex to 5mm were significantly higher than them from 5mm to 1mm (p<0.05) in each groups. Under the conditions of this study, preparation with Quantec file was more effective and produce more appropriate canal shapes than S-S K file and Ni-Ti K file.

• Imaging Science in Dentistry
• /
• v.49 no.1
• /
• pp.59-63
• /
• 2019

Purpose: This study evaluated the prevalence and characteristics of maxillary antroliths using cone-beam computed tomography (CBCT) scans performed for maxillofacial diagnostic purposes. Materials and Methods: CBCT scans of 13,946 patients over the age of 20 were reviewed for maxillary antroliths, and prevalence according to sex, age, and the side of the jaw was calculated. The relationships of single or multiple antroliths with sex, side, and the degree of sinus inflammation were evaluated. The shape and dimension of antroliths were also assessed. The data were analyzed using descriptive statistics, the chi-square or Fisher exact tests, and Kendall's tau-b. Results: A total of 138 (0.99%) of the 13,946 patients showed an antrolith in at least 1 sinus. Only 18 patients presented a bilateral manifestation, which brought the total number of sinuses containing an antrolith to 156 (0.56%). Multiple antroliths were observed in 36 sinuses, and the total number of antroliths was 207: 110 punctate, 65 linear, and 32 amorphous. The antrolith dimensions varied from $1mm^2$ to $91mm^2$ (average, $10.2{\pm}15.5mm^2$). No statistically significant differences were found according to sex, side, and age group (P>0.05). However, there was a statistically significant difference between the multiplicity of antrolith and the degree of sinus inflammation (P<0.05). Conclusion: Cone-beam computed tomography is an effective modality for the detection of incidental antroliths. Maxillary antroliths were found to be very rare and were usually asymptomatic. Dentists should have a comprehensive understanding of their diagnosis and treatment in light of possible associated dental problems.

• Journal of Radiopharmaceuticals and Molecular Probes
• /
• v.7 no.2
• /
• pp.99-103
• /
• 2021

In this study, the initial in vivo pharmacokinetic changes according to the routes of drug administration were investigated using bioimaging techniques. The purpose of this study was to quantify the degree of distribution of each major organ in normal mice over time by acquiring Positron Emission Tomography/Computed Tomography images while administering routes F-18 fluorodeoxyglucose such as intravenous, intraperitoneal and per oral, a representative diagnostic radiopharmaceutical. Dynamic Positron Emission Tomography images were acquired for 90 minutes after drug administration. Radioactivity uptake was calculated for major organs using the PMOD program. In the case of intravenous administration, it was confirmed that it spread quickly and evenly to major organs. Compared to intravenous administration, intraperitoneal administration was about three times more absorbed and distributed in the liver and intestine, and it was showed that the amount excreted through the bladder was more than twice. In the case of oral administration, most stayed in the stomach, and it was showed that it spread slowly throughout the body. In comparison with intravenous administration, it was presented that the distribution of kidneys was more than 9 times and the distribution of bladder was 66% lower. Since there is a difference in the initial in vivo distribution and excretion of each administration method, we confirmed that the determination of the administration route is important for in vivo imaging evaluation of new drug candidates.

• Imaging Science in Dentistry
• /
• v.53 no.4
• /
• pp.325-333
• /
• 2023

Purpose: The objective of this study was to evaluate and compare the accuracy and image quality of root surface area (RSA) measurements obtained with various cone-beam computed tomography (CBCT) protocols, relative to the gold standard of micro-computed tomography (CT), in an in vitro setting. Materials and Methods: Four dry human skulls were scanned using 8 different protocols, with voxel sizes of 0.15 mm, 0.3 mm, and 0.4 mm. Three-dimensional models of the selected teeth were constructed using CBCT and microCT protocols, and the RSA was automatically measured by the image-processing software. The absolute difference in the percentage of the RSA(%ΔRSA) was calculated and compared across the 8 CBCT protocols using repeatedmeasures analysis of variance. Finally, image quality scores of the RSA measurements were computed and reported in terms of percent distribution. Results: No significant differences were observed in the %ΔRSA across the 8 protocols (P>0.05). The deviation in %ΔRSA ranged from 1.51% to 4.30%, with an increase corresponding to voxel size. As the voxel size increased, the image quality deteriorated. This decline in quality was particularly noticeable at the apical level of the root, where the distribution of poorer scores was most concentrated. Conclusion: Relative to CBCT protocols with voxel sizes of 0.15mm and 0.3mm, the protocols with a voxel size of 0.4 mm demonstrated inferior image quality at the apical levels. In spite of this, no significant discrepancies were observed in RSA measurements across the different CBCT protocols.

• Korean Journal of Radiology
• /
• v.21 no.12
• /
• pp.1355-1366
• /
• 2020

Objective: We aimed to evaluate the diagnostic value and prognostic relevance of FDG positron emission tomography/computed tomography (PET-CT) in extrahepatic cholangiocarcinoma patients. Materials and Methods: This study included 234 extrahepatic cholangiocarcinoma patients who underwent FDG PET-CT between June 2008 and February 2016. The diagnostic performance of FDG PEG-CT was compared to that of contrast-enhanced multidetector row CT (MDCT) and MRI. Independent prognosticators for poor survival were also assessed. Results: The sensitivity of FDG PET-CT for detecting primary tumor and regional lymph node metastases was lower than that of MDCT or MRI (p < 0.001), whereas the specificity and positive predictive value for detecting regional lymph nodes metastases was significantly better in FDG PET-CT compared to MDCT and MRI (all p < 0.001). There was no significant difference in the diagnostic yield of distant metastases detection among three diagnostic imaging techniques. In a multivariate analysis, maximum standardized uptake values (SUV_max) of the primary tumor (adjusted hazard ratio [HR], 1.75; 95% confidence interval [CI], 1.13-2.69) and of the metastatic lesions ≥ 5 (adjusted HR, 8.10; 95% CI, 1.96-33.5) were independent contributors to poor overall survival in extrahepatic cholangiocarcinoma patients. In a subgroup analysis of 187 patients with periductal infiltrating type of cholangiocarcinoma, an SUV_max of the primary tumor ≥ 5 was associated with an increased risk of regional lymph node (adjusted odds ratio [OR], 1.60; 95% CI, 0.55-4.63) and distant metastases (adjusted OR, 100.57; 95% CI, 3.94-2567.43) at diagnosis as well as with poor overall survival (adjusted HR, 1.81; 95% CI, 1.04-3.15). Conclusion: FDG PET-CT showed lower sensitivity for detecting primary tumor and regional lymph node involvement than MDCT and MRI. However, the SUV_max of primary tumors and metastatic lesions derived from FDG PET-CT could have significant implications for predicting prognoses in extrahepatic cholangiocarcinoma patients.

• Geophysics and Geophysical Exploration
• /
• v.9 no.1
• /
• pp.30-36
• /
• 2006

Japan's first pilot-scale $CO_2$ sequestration experiment has been conducted in Nagaoka, where 10400 t of $CO_2$ have been injected in an onshore aquifer at a depth of about 1100 m. Among various measurements conducted at the site for monitoring the injected $CO_2$, we conducted time-lapse crosswell seismic tomography between two observation wells to determine the distribution of $CO_2$ in the aquifer by the change of P-wave velocities. This paper reports the results of the crosswell seismic tomography conducted at the site. The crosswell seismic tomography measurements were carried out three times; once before the injection as a baseline survey, and twice during the injection as monitoring surveys. The velocity tomograms resulting from the monitoring surveys were compared to the baseline survey tomogram, and velocity difference tomograms were generated. The velocity difference tomograms showed that velocity had decreased in a part of the aquifer around the injection well, where the injected $CO_2$ was supposed to be distributed. We also found that the area in which velocity had decreased was expanding in the formation up-dip direction, as increasing amounts of $CO_2$ were injected. The maximum velocity reductions observed were 3.0% after 3200 t of $CO_2$ had been injected, and 3.5% after injection of 6200 t of $CO_2$. Although seismic tomography could map the area of velocity decrease due to $CO_2$ injection, we observed some contradictions with the results of time-lapse sonic logging, and with the geological condition of the cap rock. To investigate these contradictions, we conducted numerical experiments simulating the test site. As a result, we found that part of the velocity distribution displayed in the tomograms was affected by artefacts or ghosts caused by the source-receiver geometry for the crosswell tomography in this particular site. The maximum velocity decrease obtained by tomography (3.5%) was much smaller than that observed by sonic logging (more than 20%). The numerical experiment results showed that only 5.5% velocity reduction might be observed, although the model was given a 20% velocity reduction zone. Judging from this result, the actual velocity reduction can be more than 3.5%, the value we obtained from the field data reconstruction. Further studies are needed to obtain more accurate velocity values that are comparable to those obtained by sonic logging.