• Korean Journal of Radiology
• /
• v.2 no.1
• /
• pp.28-36
• /
• 2001

Objective: To provide a systematic overview of the effects of various parameters on contrast enhancement within the same population, an animal experiment as well as a computer-aided simulation study was performed. Materials and Methods: In an animal experiment, single-level dynamic CT through the liver was performed at 5-second intervals just after the injection of contrast medium for 3 minutes. Combinations of three different amounts (1, 2, 3 mL/kg), concentrations (150, 200, 300 mgI/mL), and injection rates (0.5, 1, 2 mL/sec) were used. The CT number of the aorta (A), portal vein (P) and liver (L) was measured in each image, and time-attenuation curves for A, P and L were thus obtained. The degree of maximum enhancement (Imax) and time to reach peak enhancement (Tmax) of A, P and L were determined, and times to equilibrium (Teq) were analyzed. In the computed-aided simulation model, a program based on the amount, flow, and diffusion coefficient of body fluid in various compartments of the human body was designed. The input variables were the concentrations, volumes and injection rates of the contrast media used. The program generated the time-attenuation curves of A, P and L, as well as liver-to-hepatocellular carcinoma (HCC) contrast curves. On each curve, we calculated and plotted the optimal temporal window (time period above the lower threshold, which in this experiment was 10 Hounsfield units), the total area under the curve above the lower threshold, and the area within the optimal range. Results: A. Animal Experiment: At a given concentration and injection rate, an increased volume of contrast medium led to increases in Imax A, P and L. In addition, Tmax A, P, L and Teq were prolonged in parallel with increases in injection time The time-attenuation curve shifted upward and to the right. For a given volume and injection rate, an increased concentration of contrast medium increased the degree of aortic, portal and hepatic enhancement, though Tmax A, P and L remained the same. The time-attenuation curve shifted upward. For a given volume and concentration of contrast medium, changes in the injection rate had a prominent effect on aortic enhancement, and that of the portal vein and hepatic parenchyma also showed some increase, though the effect was less prominent. A increased in the rate of contrast injection led to shifting of the time enhancement curve to the left and upward. B. Computer Simulation: At a faster injection rate, there was minimal change in the degree of hepatic attenuation, though the duration of the optimal temporal window decreased. The area between 10 and 30 HU was greatest when contrast media was delivered at a rate of 2 3 mL/sec. Although the total area under the curve increased in proportion to the injection rate, most of this increase was above the upper threshould and thus the temporal window was narrow and the optimal area decreased. Conclusion: Increases in volume, concentration and injection rate all resulted in improved arterial enhancement. If cost was disregarded, increasing the injection volume was the most reliable way of obtaining good quality enhancement. The optimal way of delivering a given amount of contrast medium can be calculated using a computer-based mathematical model.

• Journal of the Korean Society of Radiology
• /
• v.83 no.5
• /
• pp.1059-1070
• /
• 2022

Purpose To compare the sensitivity of tumor detection and inter-observer agreement between acquired diffusion-weighted imaging (aDWI) b2000 and computed DWI (cDWI) b2000 in patients with prostate cancer (PCa). Materials and Methods Eighty-eight patients diagnosed with PCa by radical prostatectomy and having undergone pre-operative 3 Tesla-MRI, including DWI (b, 0, 100, 1000, 2000 s/mm²), were included in the study. cDWI b2000 was obtained from aDWI b0, b100, and b1000. Two independent reviewers performed a review of the aDWI b2000 and cDWI b2000 images in random order at 4-week intervals. A region of interest was drawn for the largest tumor on each dataset, and a Prostate Imaging-Reporting and Data System (PI-RADS) score based on PI-RADS v2.1 was recorded. Histologic topographic maps served as the reference standard. Results The study population's Gleason scores were 6 (n = 16), 7 (n = 53), 8 (n = 9), and 9 (n = 10). According to the reviewers, the sensitivities of cDWI b2000 and aDWI b2000 showed no significant differences (for reviewer 1, both 94% [83/88]; for reviewer 2, both 90% [79/88]; p = 1.000, respectively). The kappa values of cDWI b2000 and aDWI b2000 for the PI-RADS score were 0.422 (95% confidence interval [CI], 0.240-0.603) and 0.495 (95% CI, 0.308-0.683), respectively. Conclusion cDWI b2000 showed comparable sensitivity with aDWI b2000, in addition to sustained moderate inter-observer agreement, in the detection of PCa.

• Journal of the Korean Society of Radiology
• /
• v.82 no.6
• /
• pp.1505-1523
• /
• 2021

Purpose Although chest CT has been discussed as a first-line test for coronavirus disease 2019 (COVID-19), little research has explored the implications of CT exposure in the population. To review chest CT protocols and radiation doses in COVID-19 publications and explore the number needed to diagnose (NND) and the number needed to predict (NNP) if CT is used as a first-line test. Materials and Methods We searched nine highly cited radiology journals to identify studies discussing the CT-based diagnosis of COVID-19 pneumonia. Study-level information on the CT protocol and radiation dose was collected, and the doses were compared with each national diagnostic reference level (DRL). The NND and NNP, which depends on the test positive rate (TPR), were calculated, given a CT sensitivity of 94% (95% confidence interval [CI]: 91%-96%) and specificity of 37% (95% CI: 26%-50%), and applied to the early outbreak in Wuhan, New York, and Italy. Results From 86 studies, the CT protocol and radiation dose were reported in 81 (94.2%) and 17 studies (19.8%), respectively. Low-dose chest CT was used more than twice as often as standard-dose chest CT (39.5% vs.18.6%), while the remaining studies (44.2%) did not provide relevant information. The radiation doses were lower than the national DRLs in 15 of the 17 studies (88.2%) that reported doses. The NND was 3.2 scans (95% CI: 2.2-6.0). The NNPs at TPRs of 50%, 25%, 10%, and 5% were 2.2, 3.6, 8.0, 15.5 scans, respectively. In Wuhan, 35418 (TPR, 58%; 95% CI: 27710-56755) to 44840 (TPR, 38%; 95% CI: 35161-68164) individuals were estimated to have undergone CT examinations to diagnose 17365 patients. During the early surge in New York and Italy, daily NNDs changed up to 5.4 and 10.9 times, respectively, within 10 weeks. Conclusion Low-dose CT protocols were described in less than half of COVID-19 publications, and radiation doses were frequently lacking. The number of populations involved in a first-line diagnostic CT test could vary dynamically according to daily TPR; therefore, caution is required in future planning.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.12 no.3
• /
• pp.125-132
• /
• 2007

We estimated the distribution of predator-prey interaction strengths for 12 species of herbivores (including amphipods, isopods, gastropods, and sea urchins) and made a regression model that may be applicable to other species. Laboratory experiments were used to determine per capita grazing rate (PCGR; g seaweeds/individual/day). Relationship between the biomass of individual grazers and fourth-root transformed PCGR was fitted to power curve ($y=0.2310x^{0.3290}$, r=0.8864). This finding supported that the grazing efficiency was not even as individual grazers increase in size (biomass). Therefore, the biomass-normalized PCGR was estimated and revealed that smaller size herbivores were more effective grazers. Grazing impact considering density of each taxon was calculated. The sea hare Aplysia kurodai had greatest grazing impact on the seaweed bed and the sea urchin Strongylocentrotus nudus and S. intermedius were ranked in descending order of the impact. The amount of seaweed grazed by the amphipod Elasmopus sp. (>4,000 $ind./m^2$) and Jassa falcata (>2,000 $ind./m^2$) were 3.435 and $1.697mg/m^2/day$ respectively. The combined grazing amount of herbivores was $5,045mg/m^2/day$ in the seaweed bed. Although sea hare and sea urchin had strong impacts on seaweeds, the effects of dense, smaller species could not be seen as negligible. Surprisingly, the calculated grazing potential of sea urchins with a mean density of 3 $ind./m^2$ exceeded the mean production of seaweed cultured in domestic coastal waters in Korea (ca., 5 ton/ha). Small crustaceans were also expected to consume up to 16% of the seaweed production if their densities were rising under weak predation conditions. Considering that the population density of herbivores are strongly controlled by fish, human interference like overfishing may have strong negative effects on persistence of seaweeds communities.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.13 no.1
• /
• pp.27-41
• /
• 2008

Distribution characteristics of phytoplankton community were investigated by HPLC and flow cytometry in Jeju Strait and the Northern East China Sea (NECS) in May 2004, in order to understand the relationship between physical environmental factors and distribution pattern of phytoplankton communities. Based on temperature and salinity data, three distinct water masses were identified; warm and saline Tsushima Warm Current (TWC), which is flowing from northwest of Jeju Island, warm and low saline water at the center of Jeju Strait, which is originated from China Coastal Water (CCW) and relatively cold and high saline water originated from Yellow Sea at the bottom of the Jeju Strait. At Jeju Strait, less saline water (<33 psu) of 15 km width occupied surface layer up to 20 m which located at 20 km offshore and strong thermal front between warm and saline water and cold and less saline water was found in the middle of the Jeju Strait. Vertical transect of temperature and salinity at the NECS also showed that low saline (<33 psu) water occupied the upper 20 m layer and cold and saline water was present at the eastern part. Chl a was measured as $0.06{\sim}3.07\;{\mu}g/L$. Spring bloom of phytoplankton was recognized by the high concentrations of Chl a at the low saline water masses influenced by the CCW and subsurface chlorophyll maximum layer appeared between $20{\sim}30\;m$ depth, which was at thermocline depth or below. Abundances of Synechococcus and picoeukaryote were $0.2{\sim}9.5{\times}10^4\;cells/mL$ and $0.43{\sim}4.3{\times}10^4\;cells/mL$, respectively. Dinoflagellate, diatom and prymnesiophyte were major groups and minor groups were chlorophyte+prasinophyte, chrysophyte, cryptophyte and cyanophyte. Especially high abundance of dinoflagellate was identified by high concentration (>1\;{\mu}g/L$) of peridinin at the bottom of the thermocline, which showed an outbreak of red tide by high density of dinoflagellates. Abundances of picoeukaryote in Jeju Strait were about $5{\sim}10$ times higher than abundance measured in Kuroshio water and showed a good correlation with Chl b (Pras+Viola), which implies the most of population of picoeukaryote was composed of prasinophytes. Prochlorococcus was not detected at all, which suggests that Kuroshio Current did not directly influenced on the study area. Based on the strong negative correlations between biomass of phytoplankton (Chl a) and temperature+salinity, the primary production and biomass of phytoplankton in the study area were controlled by the nutrients supply from CCW.

• Clinical and Experimental Pediatrics
• /
• v.52 no.4
• /
• pp.464-470
• /
• 2009

Purpose : This study assessed the incidence and outcome of congenital anomalies of the kidney and urinary tract (CAKUT) detected by prenatal ultrasonography Methods : There were 906 cases of CAKUT detected by prenatal ultrasonography and postnatally confirmed at the Asan Medical Center from October 1989 to October 2007. We investigated the incidence and outcome of these cases by reviewing medical records retrospectively. Results : The order of incidence was hydronephrosis, multicystic dysplastic kidney (MCDK), duplex kidney, vesico-ureteral reflux (VUR), single kidney, hydroureteronephrosis, ectopic kidney, polycystic kidney, ureterocele, and posterior urethral valve (PUV). There were 520 cases (57.4%) of hydronephrosis, and 20% of these needed an operation due to significant obstruction. MCDK was associated with other CAKUT in 25.4% of all cases. Approximately 57.9% of duplex kidney cases needed surgical treatment due to ureterocele and VUR. VUR had a male: female ratio of 10:1. Two out of seven cases of autosomal recessive polycystic kidney had progressed to chronic renal failure. Patients with PUV were relatively uncommon, and one out of nine cases progressed to end-stage renal disease. Conclusion : CAKUTs detected by prenatal ultrasonography were composed of various anomalies, and almost all of them had a good outcome without any intervention. However, in some cases, recurrent urinary tract infection or renal failure occurred, especially in bilateral cases. For further management, a long-term multicenter study is needed to investigate the precise incidence and outcome of each anomaly in the general population.

• Clinical and Experimental Pediatrics
• /
• v.48 no.4
• /
• pp.387-394
• /
• 2005

Purpose : We performed this study to compare the TSH and free $T_4$ levels according to gestational age and birth weight, and to reevaluate the cut-off values in the neonatal screening test for congenital hypothyroidism. Methods : Total 2,133 neonates(1,749 healthy newborns and 384 sick neonates) were screened in Dankook University Hospital from May 2000 to January 2003. Neonates with abnormal TSH values (higher than $20{\mu}IU/mL$) or abnormal free $T_4$ levels(lower than 1 ng/dL) were recalled to recheck the thyroid function test. At that time, physical examinations and history-taking regarding perinatal problem, medication history, and mother's illness were undertaken. Results : Serum TSH and free $T_4$ values revealed no significant difference according to sex, delivery type, and Apgar score. The free $T_4$ levels showed statistically significant differences, with gestational age or birth weight(P<0.01). The recall rate of neonates due to abnormal screening test was 7.48 percent. Compared with original cut-off values, the recall rate of the new cut-off values setted to TSH higher than $20{\mu}IU/mL$ or free $T_4$ lower than 0.64 ng/dL decreased from 7.48 percent to 4.8 percent in the healthy group. But, it compromised sensitivity when applied to the sick group. Conclusion : In this study, neonatal free $T_4$ levels were significantly different according to birth weight, gestational age, and the presence of compromised condition. Although the recall rate by TSH > $20{\mu}IU/mL$ or free $T_4$ <1 ng/dL was relatively high, it was impossible to set up new cut-off values without compromising sensitivity. We think studies including a larger study population will be required to change the cut-off values.

• Clinical and Experimental Pediatrics
• /
• v.50 no.1
• /
• pp.65-73
• /
• 2007

Purpose : Short stature is an important complication that impairs the quality of life in survivors of childhood brain tumors. We studied their final adult height (FAH) to evaluate risk factors for short stature. Methods : We reviewed the medical data of 95 survivors of childhood brain tumors (64 males and 31 females) who had been followed up from 1982 to 2006, reached FAH, and had a more than five year-disease-free survival. Results : Final adult height standard deviation score (FAHTSDS: $mean{\pm}SD$) of the patients was lower than those of general population ($-1.15{\pm}1.72$), HTSDS at diagnosis ($-0.13{\pm}1.57$), and target HTSDS ($-0.49{\pm}0.69$). FAHTSDS of craniopharyngioma patients did not decrease ($0.57{\pm}1.17$), but those of germ cell tumor and medulloblastoma patients were significantly reduced ($-1.20{\pm}1.45$, $-2.70{\pm}1.46$; P<0.05). The patients treated with craniospinal radiation or chemotherapy had lower FAHTSDS ($-1.93{\pm}1.58$, $-2.27{\pm}1.44$; P<0.01). In the spinal irradiation group, the younger the age at diagnosis was, the more the loss of FAH (r=0.442, P<0.01). Growth hormone replacement (GHR) didn't improve FAHTSDS, but starting GHR under 12 years was an independent factor for improving FAH once treatment methods were taken into account (P=0.01). Conclusion : The younger age at diagnosis, spinal radiation and chemotherapy were all important risk factors of height loss, and height gain was expected in patients who received GHR under the age of 12 years. Therefore, regular check-ups of growth and early intervention with growth hormones are needed for high risk groups to improve FAH.

• Clinical and Experimental Pediatrics
• /
• v.50 no.11
• /
• pp.1072-1077
• /
• 2007

Purpose : It has been described that the incidence of breastfeeding jaundice is 13% and that of breast milk jaundice is 2%. The incidence in Korea was believed to be higher, but there were no studies to prove this assumption. The purpose of this study was to investigate the incidence of jaundice of healthy breastfed full-term infants in Korea. Methods : 839 infants were enrolled who were admitted to the Postpartum Care Center of the Cheil General Hospital between January 1 and December 31, 2005, and were followed up for more than 7 days. Those infants were divided into 3 groups; Exclusive breastfeeding group; Partial breastfeeding group; Formula feeding group. If they became icteric, transcutaneous bilirubin (TcB) was measured by research nurses with JM-103 Jaundice meter (Konica Minolta sensing, Inc., Osaka, Japan). Using this method we investigated the incidence of breast milk jaundice of healthy breastfed full-term infants. Results : There were no significant differences in sex, birth weight, Apgar score, or obstetric risk factors among 3 groups but there were higher rates of vaginal delivery in the exclusive breastfeeding group. The incidence of breast milk jaundice was 10.8% in the exclusive breastfeeding group and 4.4% in the partial breastfeeding group. The incidence of breast milk jaundice in the breastfed infants was 6.3%. The incidence was significantly higher in the exclusive breastfeeding group than in the partial breastfeeding group. Conclusion : The incidence of breast milk jaundice of healthy breastfed full-term infants was 6.3%. It was found that the incidence of breast milk jaundice was higher in this study than in other countries. But it was not a population-based study, so further study with the large sample sizes is needed.

• Journal of Life Science
• /
• v.19 no.4
• /
• pp.472-478
• /
• 2009

The purpose of this study was to evaluate the levels of blood lead and cadmium in urban and rural populations. Blood samples were collected from 100 urban (Busan) residents and 150 rural residents (Jinju-84, Gijang-66) from July 1 to August 30, 2007. The blood lead and cadmium levels were analyzed using flameless atomic absorption spectrophotometry and were compared by age, gender and smoking status. The mean levels of blood lead in urban-Busan, rural-Jinju and rural-Gijang residents were $6.38{\pm}2.86{\mu}g/dl$, $5.41{\pm}2.16{\mu}g/dl$ and $4.50{\pm}2.87{\mu}g/dl$, respectively. There was a significant difference in the level of blood lead between urban-Busan residents and rural-Gijang residents. The mean levels of blood cadmium in urban-Busan, rural-Jinju and rural-Gijang residents were $0.85{\pm}0.44{\mu}g/l$, $1.57{\pm}0.78{\mu}g/l$ and $0.95{\pm}0.54{\mu}g/l$, respectively. There was a significant difference in the level of blood cadmium between urban-Busan residents and rural-Jinju residents. This study showed that the levels of blood lead and cadmium were significantly different between urban and rural populations. The level of blood lead was highest in urban-Busan residents, but the level of blood cadmium was highest in rural-Jinju residents. Further studies are needed to define the cause of high levels of blood lead and cadmium related to area of residence and personal habits.