An intraperitoneal tuberculous abscess: Computed tomography (CT) findings and clinical course / 대한내과학회지

BACKGROUND/AIMS: Intraperitoneal tuberculous abscesses develop infrequently. Because of overlapping features it is difficult to differentiate a tuberculous abscess from carcinomatosis peritonei. The aim of this study was to define the computed tomography (CT) findings and clinical course of the intraperitoneal tuberculous abscess. METHODS: The study included 11 patients (3 males, 8 females, mean age 34.8 years) with a pathologically proven intraperitoneal tuberculous abscess. We analyzed the CT findings and reviewed the medical records retrospectively. RESULTS: Sixteen abscesses were found in 11 patients. The locations of the abscesses were in the right subphrenic space (n=1), right perihepatic space (n=4), left perihepatic space (n=4), left subphrenic space (n=2), perisplenic space (n=3), right lower abdominal space (n=1), and left lower abdominal space (n=1). Five patients were proven to have abdominal tuberculosis while six patients had paradoxical responses to antituberculosis therapy for tuberculous peritonitis. The abscess lesions presented on the CT scan as thin walled cystic enhancing lesions without calcification (n=16), a septated mass (n=12), with enlargement of lymph nodes (n=2), and peritoneal and omental haziness (n=3). The mean duration from commencement of treatment to onset of a paradoxical response was 88 days. All patients had antituberculosis therapy for 6 to 12 months and five patients underwent surgery. The mean follow-up was 15 months. CONCLUSIONS: The intraperitoneal tuberculous abscess appeared as an ovoid cystic lesion with a slightly enhanced thin wall in the upper abdomen, in the perihepatic space on the CT scan; such as lesion can be the primary lesion of abdominal tuberculosis or associated with the paradoxical response of tuberculous peritonitis.

Feasibility of an Ultrasonographic Categorical Reporting System for Thyroid Incidentaloma

PURPOSE: To evaluate the feasibility of an ultrasonographic category system for the proper management of incidentally found thyroid nodules. MATERIALS and METHODS: We retrospectively evaluated 2,688 patients who had thyroid nodules and underwent ultrasonography-guided fine needle aspiration biopsy. We made an ultrasonographic categorical reporting system by logistic regression analysis for comparison with the pathologic results of cytology and biopsy. RESULTS: The distribution of malignancy probability for benign nodules was 0.07 to 0.23 and for malignant nodules was 0.37 to 0.91 (95% confidence intervals). We stratified the distribution of the probability of malignancy of each nodule into 6 categories (category 0, no nodule; 1, highly suggestive of benignancy; 2, probably benign; 3, indeterminate; 4, probably malignant; and 5, highly suggestive of malignancy) and summarized the representative US findings. We compared the category of each nodule with the pathological results. In nodules with surgically proven pathologic diagnoses, benign lesions were 96.1% (348/361) in category 1 and malignant lesions were 98.6% (139/141) in category 5. CONCLUSION: We suggest that the ultrasonographic category system for thyroid incidentaloma may provide optimal strategies to manage incidentally found thyroid nodules.

Image Reconstruction of Eigenvalue of Diffusion Principal Axis Using Diffusion Tensor Imaging

PURPOSE: The objective of this work to construct eigenvalue maps that have information of magnitude of three primary diffusion directions using diffusion tensor images. MATERIALS AND METHODS: To construct eigenvalue maps, we used a 3.0T MRI scanner. We also compared the Moore-Penrose pseudo-inverse matrix method and the SVD (single value decomposition) method to calculate magnitude of three primary diffusion directions. Eigenvalue maps were constructed by calculating of magnitude of three primary diffusion directions. We did investigate the relationship between eigenvalue maps and fractional anisotropy map. RESULTS: Using Diffusion Tensor Images by diffusion tensor imaging sequence, we did construct eigenvalue maps of three primary diffusion directions. Comparison between eigenvalue maps and Fractional Anisotropy map shows what is difference of Fractional Anisotropy value in brain anatomy. Furthermore, through the simulation of variable eigenvalues, we confirmed changes of Fractional Anisotropy values by variable eigenvalues. And Fractional anisotropy was not determined by magnitude of each primary diffusion direction, but it was determined by combination of each primary diffusion direction. CONCLUSION: By construction of eigenvalue maps, we can confirm what is the reason of fractional anisotropy variation by measurement the magnitude of three primary diffusion directions on lesion of brain white matter, using eigenvalue maps and fractional anisotropy map.

Endovascular Management of Peripheral Lateral Posterior Choroidal Artery Aneurysm Associated with Moyamoya disease: Case Report and Review of the Literature / 신경중재치료의학

Cerebral aneurysms associated with moyamoya disease are often reviewed. When they occur, they generally are located around the circle of Willis and in the basal ganglia. Peripheral aneurysms in the lateral posterior choroidal artery are exceptionally rare and optimal treatment may be difficult. We describe a case of moyamoya disease with a thalamic hematoma and aneurysm in the distal LPChA unassociated with the thalamic hemorrhage. Endovascular treatment with glue was performed, resulting in an excellent anatomical and clinical outcome.

Simple Pulmonary Eosinophilia Detected at Low-dose CT for Lung Cancer Screening

PURPOSE: The aim of this study was to evaluate the frequency, radiologic findings and clinical significance of the simple pulmonary eosinophilia (SPE) that was diagnosed among the asymptomatic patients who underwent low-dose CT scans for the early detection of lung cancer. MATERIALS AND METHODS: From June 2003 to May 2005, 1,239 asymptomatic patients (1,275 examinations) who visited the health promotion center in our hospital and who underwent low-dose CT were enrolled in this study. SPE was defined as the presence of > 500 eosinophils per microliter of peripheral blood and the presence of abnormal parenchymal lesions such as nodules, airspace consolidation or areas of ground-glass attenuation (GGA) on CT, and there was spontaneous resolution or migration of the lesions on the follow-up examination. We analyzed the CT findings of SPE and we investigated the relationship between the occurrence of SPE and the season, smoking and the presence of parasite infestation. RESULTS: 36 patients were finally diagnosed as having SPE; this was 24% of the 153 patients who were diagnosed with parasite infestation and 2.8% of the total low-dose CT scans. These 36 patients consisted of 31 men and 5 women with a mean age 45.7 years. There was no significant relationship between SPE and the presence of parasite infestation, smoking or gender. Among the patients with peripheral blood eosinophilia, the eosinophil count was significantly higher in the patients with SPE than that in the patients without pulmonary infiltration (p < 0.05). SPE more frequently occurred in winter and spring than in summer and autumn (p < 0.05). The CT findings were single or multiple nodules in 18 patients, nodules and focal GGA in 9 patients and GGA only in 9 patients. Most of the nodules were less than 10 mm (88%, 49/56) in diameter and they showed an ill-defined margin (82%, n = 46); 30% of the nodules (n = 17) showed a halo around them. CONCLUSION: Simple pulmonary eosinophilia can be suggested as the cause if single or multiple ill-defined nodules or focal GGA are found on the low-dose CT performed in asymptomatic patients with peripheral blood eosinophilia. Short interval follow-up should be recommended to avoid invasive procedures or unnecessary aggressive treatment due to mistaking these lesions as lung cancer or metastatic malignancy.

The Magnetic Relaxation Properties of DTPA-bis(4-carboxycyclohexyl) amide Paramagnetic Gd-chelates

PURPOSE: To evaluate the NMR relaxation properties of newly developed high performance paramagnetic. MATERIALS AND METHODS: 4-aminomethylcyclohexane carboxylic acid (0.63 g, 4 mmol) was mixed with the suspension solution of DMF (15 mL) and DTPA-bis-anhydride (0.71 g, 2 mmol) to synthesize the ligand. The ligand was then mixed with Gd2O3 (0.18 g, 0.5 mmol) to synthesize Gd-chelate. For the measurement of magnetic relaxivity of paramagnetic compounds, the compounds were diluted to 1mM and then the relaxation times were measured at 1.5T(64 MHz). Inversion-recovery pulse sequence was employed for T1 relaxation measurement and CPMG(Carr-Purcell-Meiboon-Gill) pulse sequence was employed for T2 relaxation measurement. Using MATLAB(Version 7.1) program, T1 magnetic relaxation map, R1 map, T2 magnetic relaxation map and R2 map were developed to represent magnetic relaxation time and magnetic relaxivity as image. RESULTS: Compared to R1=4.9 mM(-1) sec(-1) and R2= 4.8 mM(-1) sec(-1) of Omniscan (Gadodiamide), which is commercially available paramagnetic MR agent, R1 of SUK090(Gd-C32H74N5O24) was 12.46 mM(-1) sec(-1) and R1 of SUK091(Gd-C34H78N5O24) was 12.77 mM(-1) sec(-1). However, R1 of SUK092(Gd-C30H56N5O17) was decreased to 2.09 mM(-1) sec(-1). In case of R2, SUK090(Gd-C32H74N5O24) was 8.76 mM(-1) sec(-1) and SUK091(Gd-C34H78N5O24) was 7.60 mM(-1) sec(-1) whereas SUK092(Gd-C30H56N5O17) CONCLUSION: Among three new paramagnetic complexes, SUK090(Gd-C32H74N5O24) and SUK091(Gd-C34H78N5O24) showed higher T1, T2 magnetic relaxation rates than that of commercially available paramagnetic MR agent and thus expected to have more contrast enhancement effect.

Learning Styles in Medical School / 한국의학교육

PURPOSE: The purpose of this study is to investigate the learning styles of students at Kyungpook National University(KNU) School of Medicine and to assess its implications on teaching-learning methods in medical school. METHODS: 571 students in all years of medical school were invited to complete a questionnaire via online. For this study, Felder's Index of Learning Styles(ILS) was used, which included 49 items. Felder's ILS measures the learner's relative preference for each of the five dichotomous learning style dimensions. RESULTS: 242(42.3%) students completed the questionnaire. More than 80% preferred sensitive information and more than 60% preferentially took in visual information. Both males and females preferred sensing and visual learning materials. On average, The students at KNU school of Medicine were reflective, sensing, visual, global and inductive. CONCLUSION: From these results, we suggested some effective methods of teaching-learning based on the students' preferences and some perspectives for future works.

Doppler Ultrasonographic Parameters for Predicting Cerebral Vascular Reserve in Patients with Acute Ischemic Stroke

PURPOSE: We investigated Doppler ultrasonographic (US) parameters of patients with acute stroke to predict the cerebral vascular reserve (CVR) measured by SPECT. MATERIALS and METHODS: We reviewed the flow velocity and cross-sectional area of the circular vessel at the common, external, and internal carotid arteries (ICA) and the vertebral arteries (VA) in 109 acute stroke patients who underwent SPECT. Flow volume (FV) of each artery was calculated as the product of the angle-corrected time-averaged flow velocity and cross-sectional area of the circular vessel. Total cerebral FV (TCBFV) was determined as the sum of the FVs of the right and left ICA and VA. We compared the Doppler US parameters between 44 cases of preserved and 65 cases of impaired CVR. RESULTS: In the preserved CVR group, ICA FV, anterior circulating FV (ACFV) and TCBFV were higher than in the impaired CVR group (p < 0.05, independent t-test). In the impaired CVR group, the ROC curves showed ACFV and TCBFV were suitable parameters to predict CVR (p < 0.05). CONCLUSION: Doppler US was helpful for understanding the hemodynamic state of acute stroke. FV measurement by Doppler US was useful for predicting CVR.

Preoperative Detection of Hepatic Metastases from the colorectal Cancers: Comparison of Dual-phase CT scan, Mn-DPDP enhanced MRI, and combination of CT and MRI

PURPOSE: To determine the usefulness of additional Mn-DPDP MRI for preoperative evaluation of the patients with colorectal cancers by comparison of dual-phase CT scan, Mn-DPDP enhanced MRI and combination of CT and MRI. MATERIALS AND METHODS: Fifty-three colorectal cancer patients with 92 metastatic nodules underwent dualphase (arterial and portal) helical CT scan and Mn-DPDP MRI prior to surgery. The indication of MRI was presence or suspected of having metastatic lesions at CT scan and/or increased serum carcinoembryonic antigen (CEA) levels (10 ng/mL or more). The diagnosis was established by the combination of findings at surgery, intraoperative ultrasonography, and histopathologic examination. Two radiologists interpreted CT, MRI, and combination of CT-MRI at discrete sessions and evaluated each lesion for location, size, and intrinsic characteristics. The lesions were divided into three groups according to their diameter; 1cm 2 cm. Diagnostic accuracy was evaluated using the alternative-free response receiver operating characteristic method. Detection and false positive rate were also evaluated. RESULTS: In the lesions smaller than 1 cm, detection rate of combined CT-MRI was superior to CT or MRI alone (82%, p = 0.036). The mean accuracy (Az values) of combined CT and MRI was significantly higher than that of CT in the lesions smaller than 2 cm (1 cm <, p=0.034; 1-2 cm, p=0.045). However, there was no significant difference between MRI and combined CT-MRI. The false positive rate of CT was higher than those of combined CT-MR in the lesions smaller than 1 cm (28 %, p=0.023). CONCLUSION: Additional MRI using Mn-DPDP besides routine CT scan was helpful in differentiating the hepatic lesions (< 2 cm) and could improve detection of the small hepatic metastases (< 1 cm) from colorectal carcinoma.

Histogram Analysis of Noise Performance on Fractional Anisotropy Brain MR Image with Different Diffusion Gradient Numbers

PURPOSE: We wished to analyze, qualitatively and quantitatively, the noise performance of fractional anisotropy brain images along with the different diffusion gradient numbers by using the histogram method. MATERIALS AND METHODS: Diffusion tensor images were acquired using a 3.0 T MR scanner from ten normal volunteers who had no neurological symptoms. The single-shot spin-echo EPI with a Stejskal-Tanner type diffusion gradient scheme was employed for the diffusion tensor measurement. With a b-valuee of 1000 s/mm2, the diffusion tensor images were obtained for 6, 11, 23, 35 and 47 diffusion gradient directions. FA images were generated for each DTI scheme. The histograms were then obtained at selected ROIs for the anatomical structures on the FA image. At the same ROI location, the mean FA value and the standard deviation of the mean FA value were calculated. RESULTS: The quality of the FA image was improved as the number of diffusion gradient directions increased by showing better contrast between the WM and GM. The histogram showed that the variance of FA values was reduced as the number of diffusion gradient directions increased. This histogram analysis was in good agreement with the result obtained using quantitative analysis. CONCLUSION: The image quality of the FA map was significantly improved as the number of diffusion gradient directions increased. The histogram analysis well demonstrated that the improvement in the FA images resulted from the reduction in the variance of the FA values included in the ROI.

Quantitative Evaluation of Liver Function with MRI Using Gd-EOB-DTPA

OBJECTIVE: Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) is a newly developed MR contrast agent. After intravenous injection, Gd-EOB-DTPA is gradually taken up by the hepatocytes and eventually excreted via the biliary pathway without any change to its chemical structure. Because of these characteristics, it can be used as a tracer for quantitative liver function testing. The purpose of this study is to develop a noninvasive method of quantitation of the hepatic function using Gd-EOB-DTPA through the deconvolution analysis. MATERIALS AND METHODS: Adult New Zealand white rabbits (n = 10, average body weight = 3.5 kg) were used in the present study. Hepatic injury was induced to by the intragastric administration of carbon tetrachloride (CCl4) three times a week for three weeks. Liver enzyme (aspartate aminotransferase, AST; alanine aminotransferase, ALT) levels and the plasma indocyanine green (ICG) retention rate 15 minutes after an intravenous injection of ICG (ICG R15), was checked before and after the three-week administration of CCl4. At the end of experimental period, an observer "blinded" to the treatment given the rabbits performed the histological examination. MRI studies were performed before and after the three-week administration of CCl4 on a 1.5 T scanner using a human extremity coil. After intravenous bolus injection of Gd-EOB-DTPA (0.3 mL of Gd-EOB-DTPA freshly prepared in 2.7 mL of normal saline) through the ear vein, the 250 axial single level dynamic MR images were obtained using a fast low angle shot (FLASH, TR/TE = 11/4.2 msec, flip angle = 15, acquisition time 1 second, slice thickness = 5 mm, matrix = 128x128, field of view = 120 mm) sequence with 1.5 sec time intervals. The time-intensity curves were obtained at the abdominal aorta and the liver parenchyma that was devoid of blood vessels. Deconvolution analysis of the aortic (input function) and hepatic parenchymal (output function) time-intensity curves was performed with a modified Fourier transform technique to calculate the hepatic extraction fraction (HEF). The presence and type of hepatic injury were determined by the histopathologic examination and statistical analysis of the changes of the hepatic enzyme levels, the ICG R15 and Gd-EOB-DTPA HEF values between the time before and after CCl4 administration with Wicoxon signed rank test. Correlation between the Gd-EOB-DTPA HEF and the change of the ICG R15 were analyzed with Pearson's correlation coefficient. RESULTS: Histopathologic examination showed findings that were compatible with hepatic fibrosis caused by chronic liver injury. The initial blood biochemical studies before the administration of carbon tetrachloride showed that the mean AST and ALT levels were 39.8+/-5.2 IU/L and 59.1+/-11.7 IU/L, respectively. The AST and ALT levels increased to 138.4+/-50.5 IU and 172.0+/-71.6 IU/L, respectively, after the three week administration of CCl4. The ALT and AST levels were significantly increased after the three weeks of CCl4 administration (p=0.018). The ICG R15 values were 4.47+/-2.08% and 19.43+/-3.98% before and after three-week administration of CCl4, respectively. The ICG R15 values were significantly increased after hepatic injury (p=0.018). After normalizing the HEF as 100% in each rabbit before CCl4 administration, the deconvoluted curve after CCl4 administration revealed less hepatocyte extraction efficiency with a mean value of 77.7+/-3.6. There was a significant correlation between the HEF and changes of the ICG R15 by the Pearson correlation coefficient assessment (correlation coefficient = -0.965, p=0.000). CONCLUSION: The Gd-EOB-DTPA HEF could be calculated from deconvolution analysis of aortic and hepatic parenchymal time-intensity curves obtained by dynamic MRI. The Gd-EOB-DTPA HEF was well correlated with changes of the ICG R15, which is the most common parameter used in the quantitative estimation of the hepatic function. The Gd-EOB-DTPA HEF is a direct, noninvasive technique for the quantitative evaluation of liver function. It could be a promising alternative for the determination of noninvasive hepatic function in those patients with liver disease.

Pneumothorax, Pneumomediastinum and Pneumopericardium: A Pictorial Review

Pneumothorax, pneumomediastinum and pneumopericardium usually develop during emergency situations and these conditions may result in cardiopulmonary compromise, so an early and accurate diagnosis is seen as crucial for proper treatment. For diagnosis of pneumothorax, pneumomediastinum and pneumopericardium, chest radiography is a primary modality and CT can help for diagnosing them earlier and detecting associated abnormalities. The purpose of this pictorial essay is to describe the pathophysiology, various radiographic signs and diagnostic pitfalls of pneumothorax, pneumomediastinum and peumopericardium on chest radiographs that are correlated with CTs, and to aid the physician in the radiographic diagnosis.

Multiple Thymoma in a Patient with Myasthenia Gravis: Case Report

A thymoma often occurs in patients with myasthenia gravis, but the development of multiple thymoma is very rare. The authors report the radiologic and pathologic findings of multiple invasive thymoma in a 59-year-old male with myasthenia gravis.

The Achievement of Medical Students Admitted after Baccalaureate Level / 한국의학교육

PURPOSE: Kyungpook National University School of Medicine initiated a pilot project to admit small number of qualified students who received BS degree or above in the field of sciences in 1996. This study was conducted to evaluate effectiveness of the pilot project. METHODS: Students' academic grades, outcome of their opinion surveys on adaptability to the school life, difficulties and problems from the classes of 1996 to 2001 were analyzed. RESULTS: A total of 57 students were admitted to this program over the past 7-year period, 54.8% of them from natural science major and 36.8% from engineering. Students admitted with BS degree were performing above average in the class by % rank. There was no significant difference in academic performance between the natural science and the engineering major. Of 20 graduated, only one took career in basic medical science (physiology). The students thought undergraduate education was helpful in maturing personal characters than in knowledge or skill attainment. CONCLUSION: The achievement of medical students admitted after baccalaureate level was comparable to that of students with two years of premedical education.

Imaging Features of Nontumorous Conditions Involving the Trachea and Main-stem Bronchi

A number of nontumorous diseases may affect the trachea and main-stem bronchi, and their nonspecific symptoms may include coughing, dyspnea, wheezing and stridor. The clinical course is often long-term and a misdiagnosis of bronchial asthma is common. The imaging findings of these nontumorous conditions are, however, relatively characteristic, and diagnosis either without or in conjunction with clinical information is often possible. For specific diagnosis, recognition of their imaging features is therefore of prime importance. In this pictorial essay, we illustrate the imaging features of various nontumorous conditions involving the trachea and main-stem bronchi.

Tracheal Involvement of Bronchus-Associated Lymphoid Tissue Lymphoma: A Case Report

Primary malignant tumors of the trachea are rare, the most prevalent histologies beeing squamous cell and adenoid cystic carcinoma. A review of the literature revealed only ten cases of primary tracheal or bronchial non-Hodgkin's lymphoma. We describe a case in which tracheal involvement of bronchus-associated lymphoid tissue lymphoma, a subtype of non-Hodgkin's lymphoma, occurred.

Multi-Component Relaxation Study of Human Brain Using Relaxographic Analysis

PURPOSE: To demonstrate that the relaxographic method provides additional information such as the distribution of relaxation times and water content which are poentially applicable to clinical medicine. MATERIALS AND METHODS: First, the computer simulation was performed with the generated relaxation data to verify the accuracy and reliablility of the relaxographic method (CONTIN). Secondly, in order to see how well the CONTIN quantifies and resolves the two different T1 environments, we calculated the oil to water peak area ratios and identified peak positions of T1-distribution curve of the phantom solutions, which consist of four centrifugal tubes (10ml) filled with the compounds of 0, 10, 20, 30% of corn oil and distilled water, using CONTIN. Finally, inversion recovery MR images for a volunteer are acquired for each TI ranged from 40 to 1160 msec with TR/TE=2200/20 msec. From the 3 different ROIs (GM, WM, CSF), CONTIN analysis was performed to obtain the T1-distribution curves, which gave peak positions and peak area of each ROI location. RESULTS: The simulation result shows that the errors of peak positions were less in the higher peak (centered T1=600 msec) than in the lower peak (centered T1=150 msec) for all SNR but the errors of peak areas were larger in the higher peak than in the lower peak. The CONTIN analysis of the measured relaxation data of phantoms revealed two peaks between 20 and 60 msec and between 500 and 700 msec. The analysis gives the peak area ratio as oil 10%: oil 20%: oil 30%=1:1.3:1.9, which is different from the exact ratio, 1:2:3. For human brain, in ROI 3 (CSF), only one component of -distributions was observed whereas in ROI 1 (GM) and in ROI 2 (WM) we observed two components of T1-distribution. For the WM and CSF there was great agreement between the observed T1-relaxation times and the reported values. CONCLUSION: we demonstrated that the relaxographic method provided additional information such as the distribution of relaxation times and water content, which were not available in the routine relaxometry and T1/T2 mapping techniques. In addition, these additional information provided by relaxographic analysis may have clinical importance.

Transcaval TIPS in Patients with Failed Revision of Occluded Previous TIPS

OBJECTIVE: To determine the feasibility of transcaval transjugular intrahepatic portosystemic shunt (TIPS) in patients with occluded previous TIPS. MATERIALS AND METHODS: Between February 1996 and December 2000 we performed five transcaval TIPS procedures in four patients with recurrent gastric cardiac variceal bleeding. All four had occluded TIPS, which was between the hepatic and portal vein. The interval between initial TIPS placement and revisional procedures with transcaval TIPS varied between three and 31 months; one patient underwent transcaval TIPS twice, with a 31-month interval. After revision of the occluded shunt failed, direct cavoportal puncture at the retrohepatic segment of the IVC was attempted. RESULTS: Transcaval TIPS placement was technically successful in all cases. In three, tractography revealed slight leakage of contrast materials into hepatic subcapsular or subdiaphragmatic pericaval space. There was no evidence of propagation of extravasated contrast materials through the retroperitoneal space or spillage into the peritoneal space. After the tract was dilated by a bare stent, no patient experienced trans-stent bleeding and no serious procedure-related complications occurred. After successful shunt creation, variceal bleeding ceased in all patients. CONCLUSION: Transcaval TIPS placement is an effective and safe alternative treatment in patients with occluded previous TIPS and no hepatic veins suitable for new TIPS.

(17)O NMR Study On Water Exchange Rate of Paramagnetic Contrast Agents

PURPOSE: The water exchange rate between bulk water and bound water is an important parameter in deciding the efficiency of paramagnetic contrast agents. In this study, we evaluated the water exchange rates of various Gd-chelates using oxygen-17 NMR technique. MATERIAL AND MEHTODS: The samples (Gd-DTPA, Gd-DTPA-BMA, Gd-DOTA, Gd-EOB-DTPA) were prepared by mixing 5% (17)O-enriched water (Isotech, USA). The pH of the samples was adjusted to physiological value (pH=7.0) by buffer solution. The variable temperature (17)O-NMR measurements were performed using Bruker-600 (14.1 T, 81.3 MHz) spectrometer. Bruker VT-1000 temperature control units were used to stabilize the temperature. The (17)O spin-spin relaxation times (T2) were measured using Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence with 24 echo trains. The variable temperature T2 relaxation data were then fitted into Solomon-Bloembergen equations using least square fit algorithm to estimate the water exchange times. RESULTS: From the measured (17)O-NMR relaxation rates, the determined water exchange rates at 300K are : 0.42 microsecond for Gd-DTPA, 1.99 microsecond for Gd-DTPA-BMA, 0.27 microsecond for Gd-DOTA, and 0.11 microsecond for Gd-EOB-DTPA. The Gd-DTPA-BMA showed slowest exchange whereas Gd-EOB-DTPA had fastest water exchange rate. In addition, it was found that the water exchange rates of all samples had exponential temperature dependence with different decay constant. CONCLUSION: (17)O-NMR relaxation rate measurements, when combined with variable temperature technique, provide a solid tool for studying water exchange rate, which is very important in investigating the detailed mechanism of relaxation enhancement effect of the paramagnetic contrast agents.

The Implementation of Problem-based Learning in Kyungpook National University School of Medicine and its Evaluation / 한국의학교육

The effectiveness of Problem-based Learning(PBL) in medical education has already been acclaimed widely. Representatives of the curriculum committee at Kyungpook National University School of Medicine paid a visit to McMaster University School of Medicine in Canada in May, 1994 in order to learn mechanics and effectiveness of PBL in its medical education and they were impressed by the efficacy of PBL. Soon after that the school launched a pilot PBL tutorial for two years from 1994 through 1996(4-semester) as a non-credit course for senior, junior and sophomore in medical school during one semester each, to introduce PBL to faculty members and students as well. After the pilot, opinion survey on PBL from both faculty and students revealed affirmative for PBL from 55.1% of seniors, 61.4% of juniors and 83.9% of faculty members. The faculty body at medical school was then encouraged by the pilot experience and decided to include the PBL as the part of medical education reform. During the fall semester in 1998, the senior at pre-medical course was given PBL experience to prepare for implementation of PBL at school of medicine. The PBL was implemented as an essential 2-credit-hour course in each semester commencing in 1999 to the freshmen class throughout the year; it was extended to the sophomore in 2000 and to the junior in 2001. Although there had been initial excitements of over expectations, confusion, and disappointments from faculty members and students, majority opinion of both parties on continuation of PBL was positive. The issues to be settled are preparation of study cases, students learning resources, and method of evaluating students' performance. The PBL was started as an essential course in medical school in 1999 after 4 years of preparation and on the basis of our interim evaluations the following conclusions were made: we have reached the following consensus that students seem to follow the objectives of PBL and new PBL tutorial has well been accepted by students; and enhancing the program by correcting currently known weaknesses, the PBL tutorials could further be expanded to be a major modality of teaching in our medical school.