• Investigative Magnetic Resonance Imaging
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• v.10 no.2
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• pp.98-107
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• 2006

Magnetization Transfer (MT) imaging generates contrast dependent on the phenomenon of magnetization exchange between free water proton and restricted proton in macromolecules. In biological materials in knee, MT or cross-relaxation is commonly modeled using two spin pools identified by their different T2 relaxation times. Two models for cross-relaxation emphasize the role of proton chemical exchange between protons of water and exchangeable protons on macromolecules, as well as through dipole-dipole interaction between the water and macromolecule protons. The most essential tool in medical image manipulation is the ability to adjust the contrast and intensity. Thus, it is desirable to adjust the contrast and intensity of an image interactively in the real time. The proton density (PD) and T2-weighted SE MR images allow the depiction of knee structures and can demonstrate defects and gross morphologic changes. The PD- and T2-weighted images also show the cartilage internal pathology due to the more intermediate signal of the knee joint in these sequences. Suppression of fat extends the dynamic range of tissue contrast, removes chemical shift artifacts, and decreases motion-related ghost artifacts. Like fat saturation, phase sensitive methods are also based on the difference in precession frequencies of water and fat. In this study, phase sensitive methods look at the phase difference that is accumulated in time as a result of Larmor frequency differences rather than using this difference directly. Although how MT work was given with clinical evidence that leads to quantitative model for MT in tissues, the mathematical formalism used to describe the MT effect applies to explaining to evaluate knee disorder, such as anterior cruciate ligament (ACL) tear and meniscal tear. Calculation of the effect of the effect of the MT saturation is given in the magnetization transfer ratio (MTR) which is a quantitative measure of the relative decrease in signal intensity due to the MT pulse.

• Investigative Magnetic Resonance Imaging
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• v.8 no.2
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• pp.94-99
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• 2004

Purpose : To investigate the signal enhancement ratio by NOE effect on in vivo $^{31}P$ MRS in human heart muscle and liver. we also evaluated the enhancement ratios of different phosphorus metabolites, which are important in 31P MRS for each organ. Materials and Methods : Ten normal subjects (M:F = 8:2, age range = 24-32 yrs) were included for in vivo $^{31}P$ MRS measurements on a 1.5 T whole-body MRI/MRS system using $^1H-^{31}P$ dual tuned surface coil. Two-dimensional Chemical Shift Imaging (2D CSI) pulse sequence for $^{31}P$ MRS was employed in all $^{31}P$ MRS measurements. First, $^{31}P$ MRS performed without NOE effect and then the same 2D CSI data acquisitions were repeated with NOE effect. After postprocessing the MRS raw data in the time domain, the signal enhancements in percent were estimated from the major metabolites. Results : The calculated NOE enhancement for liver $^{31}P$ MRS were $\alpha-ATP\;(7\%),\;\beta-ATP\;(9\%),\;\gamma-ATP\;(17\%),\;Pi\;(1\%),\;PDE\;(19\%)$ and $PME\;(31\%)$. Because there is no creatine kinase activity in liver, PCr signal is absent. For cardiac $^{31}P$ MRS, whole body coil gave better scout images and thus better localization than surface coil. In $^{31}P$cardiac multi-voxel spectra, DPG signal increased from left to right according to the amount of blood included. The calculated enhancement for cardiac $^{31}P$ MRS were : $\alpha-ATP\;(12\%),\;\beta-ATP\;(19\%),\;\gamma-ATP\;(30\%),\;PCr\;(34\%),\;Pi\;(20\%),\;(PDE)\;(51\%),\;and\;DPG\;(72\%)$. Conclusion : Our results revealed that the NOE effect was more pronounced in heart muscle than in liver with different coupling to 1H spin system and thus different heteronuclear cross-relaxation.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.13 no.2
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• pp.146-153
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• 2010

Purpose: Recent studies have reported an increase in the incidence of community-acquired Clostridium difficile-associated disease (CA-CDAD) among children. There is an overall lack of information on CA-CDAD in the pediatric population. The aim of our study was to compare the epidemiologic and clinical features between CA-CDAD and hospital-acquired C. difficile-associated disease (HA-CDAD) in children. Methods: We retrospectively reviewed the medical records of all patients who were diagnosed with C. difficile-associated disease (CDAD) at Gil Hospital between April 2008 and March 2009. The diagnosis of CDAD was made when patients with gastrointestinal symptoms had positive results for C. difficile toxins A and B assay or stool culture. Results: Sixty-one (male, 32 and female, 29) patients were included. The mean age was 3.79${\pm}$4.54 years. Of the 61 patients, 22 (36.1%) were <1 year of age. Twenty-three patients (37.7%) had a history of antibiotic exposure in the previous 3 months. Forty-one patients (67.2%) were diagnosed with CA-CDAD. There were no significant differences in age, gender, symptoms, laboratory findings, recovery period, complications, and recurrence between the CA-CDAD and HA-CDAD groups. On the other hand, exposure to antibiotics was significantly more frequent among patients in the HA-CDAD group (p=0.005). Conclusion: This study suggests that the occurrence of CA-CDAD is increasing in the pediatric population, especially in younger children with no history of exposure to antibiotics and in outpatients. Awareness of the increasing incidence of CA-CDAD and prompt investigation of C. difficile in susceptible patients is needed to avoid misdiagnosis and for appropriate therapy.

• Pediatric Infection and Vaccine
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• v.10 no.1
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• pp.102-113
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• 2003

Purpose : Acute respiratory tract infections are the most common illnesses in children. The great majority of these infections involving lower respiratory tracts infections(LRTI) are caused by respiratory viruses such as respiratory syncytial virus(RSV), parainfluenza virus (PIV), influenza virus(INF), adenovirus(ADV), etc. Our purpose of this study was to examine the seasonal occurrence, clinical and laboratory features of each viral infections. Methods : Nasopharyngeal aspirates(NPA) were collected from 913 hospitalized children on the first day of admission. They were all admitted to Hangang Sacred Heart hospital and diagnosed as LRTIs. The study period was from September 1998 to August 2002. Specimens were inoculated onto HEp-2 cell, LLC-MK2 cell and MDCK cell. Viruses were detected by immunofluorescent method performed at day 10 postinoculation. Respiratory viruses were detected in 251(27%) cases. Medical records of 208 cases diagnosed as acute LRTIs were all taken reviewed and analyzed. Results : The identified pathogens were RSV 122 cases(58%), PIV 30 cases(14%), INFA 20 cases(10%), INFB 21 cases(11%) and ADV 15 cases(7%) during the study period. Outbreaks of RSV infections occurred every year but mostly on December, 1998 and November, 1999. LRTIs by PIV and ADV occurred during all seasons of the year. INFA was isolated moslty on March, 1999 and January, 2000. INFB infections occurred largely on April, 2002. The clinical diagnoses were bronchiolitis 88 cases(43%), pneumonia 87 cases(42%), croup 19 cases(9%) and tracheobronchitis 14 cases(6%). Common symptoms and signs were cough, rhinorrhea, sputum and fever. WBC counts in peripheral blood showed normal findings in 123 cases(59%). Each viral infections also showed some differences in auscultatory findings and chest X-ray findings. Conclusion : We learned that viruses are one of the major and important etiologic agents of acute LRTIs of children in Korea. However, we still need to find out more about its characteristic clinical features and continue studying on their seasonal occurrence to focus on their management and also prevention.

• Pediatric Infection and Vaccine
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• v.18 no.1
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• pp.31-39
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• 2011

Purpose : This study was performed for the purpose of finding causative organisms and clinical features of septic arthritis or acute osteomyelitis in children. Methods : The study involved a retrospective review of the medical records of 63 microbiologically confirmed cases of acute pyogenic arthritis and osteomyelitis. All of the cases were brought about by community-associated infections and managed at the Seoul National University Children's Hospital or Seoul National University Bundang Hospital from June 2003 to July 2009. Results : The median age of all cases was 60 months and there were 35 males and 28 females. Major involved joints included the hip joint (15 cases), knee joint (7 cases), shoulder joint (4 cases), and elbow joint (4 cases). Also, major involved bones included the femur (20 cases), tibia (13 cases), humerus (7 cases), and radius (7 cases). Staphylococcus aureus was the most commonly identified causative organism, accounting for 49 cases (77.8%). Of the 49 isolates of S. aureus, methicillin-resistant S. aureus (MRSA) accounted for 8 cases (16.3%). Group B streptococcus spp. (GBS) and Salmonella spp. accounted for 3 cases, respectively. Nafcillin or cefazolin was often prescribed as an initial empirical antibiotic. There were 9 cases that were managed by a regimen that included vancomycin as the first choice. Fifty four cases (85.7%) recovered without any complications. Methicillin-sensitive S. aureus (MSSA), responsible for 41 cases, caused chronic complications in 3 cases. Of 8 cases caused by MRSA, 1 case showed chronic complication. There were no fatal cases. Conclusion : S. aureus remains the most common organism causing acute pyogenic arthritis and osteomyelitis of childhood acquired in the community. The high prevalence of methicillin resistance among S. aureus should be considered carefully in the selection of initial empirical antibiotics.

• Pediatric Infection and Vaccine
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• v.22 no.2
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• pp.63-68
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• 2015

Purpose: This study analyzed a small outbreak of measles at a single hospital located in northern Gyeonggi-do in 2013. Methods: We reviewed the medical records of measles patients at The Catholic University of Korea Uijeongbu St. Mary's Hospital from August to October, 2013. Results: Fifteen children were confirmed to have measles by RT-PCR and serum IgM test; 1 neonate, 11 infants, and 3 toddlers. None of the patients had received Measles-Mumps-Rubella vaccination. All patients showed B3 type in viral genotyping. Nine children (60%) had been exposed to measles during treatment for other diseases in the pediatric ward. Incubation period was between 8 and 15 days. Fever started at a median 10 days after exposure and persisted for a median of 8 days. Rash showed at a median 13 days after exposure. Respiratory complications were observed in 40% of patients. Diarrhea developed in 53% of patients. Conclusion: Although measles has been well-controlled due to the high rate of vaccination coverage, it is possible to have an outbreak at any given time, especially in infants. We must learn from this outbreak, and remain fully aware of the possibility of reemergence and provide proper management, including vaccination or immune globulin administration, to infants exposed to measles. Reevaluation of serum IgG titer of neonates, infants, and pregnant women may be the first step to prevent further outbreaks.

• Pediatric Infection and Vaccine
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• v.21 no.1
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• pp.43-52
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• 2014

Purpose: This study aimed to evaluate the disease severity of children suffering from gastroenteritis using different scales. The results are compared and subsequently classified on the basis of the type of virus causing the disease in order to investigate the differences in clinical characteristics and disease severity according to pathogen. Method: This study was conducted prospectively with patients under 5 years of age diagnosed with acute gastroenteritis and hospitalized at 9 medical institutions in 8 regions across the Republic of Korea. Disease severity was evaluated using the Vesikari Scale, the Clark Scale, and the modified Flores Scale. Fecal samples collected from patients were used to detect rotavirus and enteric adenovirus by enzyme immunoassay, and for RT-PCR of norovirus, astrovirus, and sapovirus. Results: There were a total of 214 patients with a male : female ratio of 1.58 : 1, of which 35 were under the age of 6 months (16.4%), 105 were aged 6-23 months (49.1%), and 74 were aged 24-59 months (34.5%). The rate of concordance between the Vesikari and Clark Scales was 0.521 (P<0.001) and, in severe cases, the Vesikari Scale was 60.7% and Clark Scale was 2.3%, indicating that the Clark Scale was stricter in the evaluation of severe cases. Conclusions: In children with gastroenteritis, there were differences in disease severity based on the scale used. Therefore, to achieve consistent results among researchers, either only a single scale or a measure of all scales should be used to determine disease severity.

• Childhood Kidney Diseases
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• v.10 no.2
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• pp.152-161
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• 2006

Purpose : In Korea, the school urine screening program is a useful tool for screening urine abnormalities. It is particularly useful in early detection of membranoproliferative glomerulonephritis(MPGN) I, which frequently progresses to chronic renal failure. In this study, we studied the medical history, laboratory findings, and histologic findings of MPGN to gain helpful information on early detection and treatment. Methods : The subjects were 19 children, who were diagnosed with MPGN from kidney biopsies that were performed in ten nationwide university hospitals because of abnormal urine findings from school urine screening programs conducted from July 1999 to April 2004. We divided the patients into 2 groups, a nephrotic range proteinuria group(n=8) and a non-nephrotic proteinuria group(n=11), and retrospectively analyzed the clinical features, laboratory findings, histologic findings, treatment, and clinical course. Results : The mean age at the first abnormal urinalysis was $10.6{\pm}2.2$ years in the nephrotic proteinuria group and $9.6{\pm}3.2$ years in the non-nephrotic proteinuria group. The mean age at the time of kidney biopsy was $11.3{\pm}2.3$ years in the nephrotic range proteinuria group and $10.4{\pm}3.2$ years in the non-nephrotic proteinuria group respectively. There was no significant difference in the mean age and sex between the two groups. In the nephrotic proteinuria group, 6 children had a low plasma C3 level and in the non-nephrotic proteinuria group, 8 children had a low plasma C3 level, but there was no significant difference between the 2 groups. There was no significant difference in the laboratory test results(including WBC count, RBC count, platelet count and other serologic tests) between the 2 groups except for 24 hour urine protein secretion. There was no difference between the 2 groups with regard to the acute and chronic changes in the glomerulus on light microscopic findings, IgG, IgA, Ig M, C1q, C3, C4, fibrogen deposition on immunofluoroscence findings, and mesangial deposits, subendothelial deposits, and subepithelial deposits on electron microscopic findings. The children were treated with corticosteroids, ACE(angiotensin-converting enzyme) inhibitors, dipyridamole and other immunosuppressive agents. During the course of treatment, there were no children whose clinical condition worsened. Among 19 children, 3 children went into remission(2 in the nephrotic proteinuria group, 1 in the non-nephrotic proteinuria group) and 9 children went into a partial remission(4 in the nephrotic proteinuria group, 5 in the non-nephrotic proteinuria group) on urinalysis. There was no significant difference in the treatment results between the two groups. Conclusion : The 73.7% of children who were incidentally diagnosed with MPGN by the school urine screening program had reduced C3. 42.1% of the children had nephrotic range proteinuria. There were no significant differences in clinical features, laboratory test results, light microscopic, immunofluorescence microscopic, and electron microscopic findings between the nephrotic proteinuria group and the non-nephrotic proteinuria group except for the 24 hour urine protein secretion. Therefore, for early detection of MPGN during the school urine screening program, we strongly recommend a kidney biopsy if children have abnormal urine findings such as persistent proteinuria and persistent hematuria, or if the serum C3 is reduced.

• Childhood Kidney Diseases
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• v.13 no.2
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• pp.229-234
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• 2009

Purpose : The aim of this study was evaluating the efficacy of endoscopic $Deflux^{(R)}$ submucosal injection in children with primary vesicoureteral reflux (VUR). Methods : Retrospective analysis of medical record was conducted on 38 children (59 ureters) who underwent endoscopic $Deflux^{(R)}$ injection due to primary VUR. Data were collected from March 2000 to February 2006. Mean infused amount of $Deflux^{(R)}$ was 0.77 cc. After $Deflux^{(R)}$ injection, patients were reassessed by voiding cystourethrogram (VCUG) 6 months later. Results : The success rate of endoscopic $Deflux^{(R)}$ submucosal injection 6 months later by VCUG was 100% for grade 1 VUR, 87.5% for grade 2, 60% for grade 3, 26.6% for grade 4, 16.6% for grade 5, respectively and there was negatively significant correlation between success rate and grade of VUR (P<.01). Degree of improvement of VUR by endoscopic $Deflux^{(R)}$ submucosal injection was not related to age at diagnosis, time to operation, existence of voiding dysfunction or constipation and infused amount of $Deflux^{(R)}$. However, group with anticholinergics medication had significantly lower success rate than non-medication group (P<0.047). Conclusion : Endoscopic $Deflux^{(R)}$ submucosal injection is effective therapy in patient with primary VUR, especially low grade VUR. It can be not only a useful substitute for prophylaxis with antibiotics, but also an effective management prior to ureteroneocystostomy in children with primary VUR.

• Childhood Kidney Diseases
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• v.13 no.2
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• pp.215-221
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• 2009

Purpose : Thymus is a lymphoproliferative organ that changes size in various physiological states in addition to some pathological conditions. Thymus is susceptible to involution, and shows a dramatic response to severe stress. Thymic measurements may be helpful in various diseases. UTI (urinary tract infection) is most common bacterial infection in infants and VUR (vesicoureteral reflux) is a common abnormality associated with UTI. In our study, the size of thymus was compared on the premise that a greater stress is exerted on the body when UTI is accompanied by VUR, than when occurs on its own. Methods : Thymic size was measured on standard chest anteroposterior radiographs and expressed as the ratio between the transverse diameter of the cardiothymic image at the level of the carina and that of the thorax (CT/T). The medical records of 99 febrile urinary tract infection infants without other genitourinary anomalies except VUR were reviewed retrospectively. Results : Among 99 patients with febrile UTIs, 25 were febrile UTI without VUR and 74 with VUR. For the UTI with VUR group, there was a significant decrease in the thymic size compared to the those without VUR group ($0.382{\pm}0.048$ vs $0.439{\pm}0.079$, P<0.05). However, there were no differences in the duration of fever and WBC, CRP between the UTI with VUR and UTI without VUR. In addition, there were no differences in the cardiothymic/thoracic ratios between renal defects and renal scars in febrile UTI patients. Conclusion : The results of this study show that the shirinkage of thymus was more frequently found in the UTI patients with VUR. Therefore, awareness of the risks associated with thymic size is important for the appropriate work up and management of UTI patients.