• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.5124-5130
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• 2014

Dilution of the contrast agent by analyzing the change in the signal intensity during MR angiography in accordance with the viscosity and osmotic pressure minimizes the side effects, and improves the image quality. The contrast agent molarity changes by the dilution of the contrast agent in the blood, as it is injected, which leads to a change in signal intensity. Based on this principle, a phantom was prepared and experiments were performed. After the phantom experiment, a clinical experiment was conducted using the results of the phantom experiment. From November 2013 to January 2014, a group of patients were classified into diluted contrast agent (30 persons) and undiluted (30 persons), and the signal intensity of the cerebral vessels was compared. The signal intensity of the phantom according to the molarity of the contrast agent increased sharply from 0.0125 mmol, reached a peak at 20 mmol, and achieved equilibrium from 200 mmol. Based on the study results, the signal intensity of the blood vessels in the brain through were compared in a clinical experiment. All the brain vessels in the imaging range with diluting a high content of the gadolinium contrast agent showed high signal intensity. This result supports the phantom experiment and means that using the 500mmol diluted contrast agent is better than using 1000mmol undiluted contrast agent because it is easier to approach the 20mmol level needed to achieve the highest signal intensity. This study has significance in that it can minimize the high viscosity and osmotic pressure, which can cause side effects and improve the image quality using the method of the dilution rate.

• Pediatric Infection and Vaccine
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• v.6 no.2
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• pp.194-202
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• 1999

Background : Group B ${\beta}$-hemolytic Streptococcus(GBS) has been the major pathogen of neonatal sepsis in western country. In contrast, GBS has played little role in neonatal sepsis in Korea. But recently, neonatal GBS infections are encountered more frequently. It is important to characterize the clinical and epidemiological features of GBS infection in Korean children. Methods: We reviewed retrospectively the medical records of twenty-seven infants and children with GBS infection experienced at the Seoul National University Children's Hospital during 14 year-period from June, 1985 to June, 1999. Fourteen strains isolated from blood and cerebrospinal fluid were serotyped. Minimum inhibitory concentrations of 10 strains were determined by agar dilution method for penicillin, ampicillin, ampicillin with sulbactam, cefarolin, cefuroxime, and cefuiaxone. Results: The numbers of cases with GBS infection increased in 1990s. Among twenty seven cases, twenty-five cases were under three months of age and both of two cases with underlying disease occurred at three years of age. All neonatal infections were late-onset type and meningitis predominated. Serotypes were III(6 strain), Ib(4), Ia(l) and V(2). All of the strain were susceptible to all of the antibiotics tested. Conclusion: GBS infections in infants were increasingly recognized. GBS should be considered as an etiological agent of neonatal sepsis or meningitis in Korea. Maternal screening and prophylactic antibiotic therapy may be considered.