Biomedical subjects

J K Lee

Publications and source records attributed to J K Lee.

At least 19 recordsLinked to original sources

PubMed2007

Serum prostate-specific antigen as a predictor of prostate volume in Korean men with lower urinary tract symptoms.

The aim of the study was to assess the utility of prostate-specific antigen (PSA) as a predictor of prostate volume indexes (total prostate volume (TPV), transition zone volume and transition zone index) in Korean men with lower urinary tract symptoms (LUTS). From September 2003 to April 2006, 3431 patients with LUTS were included in the study; they had a median age of 63.8 years, a median prostate volume of 22.6 ml and a median serum PSA of 1.04 ng/ml. Men with a baseline PSA of >10 ng/ml were excluded, to reduce the likelihood of including occult prostate cancer. Prostate volume indexes and serum PSA levels had an age-dependent log-linear relationship. Receiver operating characteristic curve analysis showed that PSA had good predictive value for various prostate volume indexes thresholds. The approximate age-specific criteria for detecting men with a TPV of >40 ml are PSA levels of 1.20, 1.44 and 1.72 ng/ml for men with LUTS in their sixth, seventh and eighth decades, respectively. The results show that serum PSA identifies Korean men with large prostates reasonably well. Korean men may produce and/or release more PSA per unit prostate volume than white men. The cutoffs for PSA and prostate volume to response to LUTS therapy should be determined in this population.

Aged↗

PubMed2006

Specific absorbed fraction for Korean adult voxel phantom from internal photon source.

Absorbed fraction (AF) and specific absorbed fraction (SAF) are crucial values for the calculation of radionuclide S-values and consequently for internal dose estimates. The formalism of the Medical Internal Radiation Dose (MIRD) committee of the Society of Nuclear Medicine (SNM) has been utilised as a standard in the calculation of individual organ doses for biologically distributed radionuclides and for different types of radiation. Although those quantities are highly sensitive to individual anatomical difference, the SAF dataset calculated by Caucasian-based stylised phantoms have been applied to Korean population until now. This study was intended to calculate the SAFs by using realistic Korean voxel phantom and Monte Carlo transport technique for the first time and compare the results with those of the existing Caucasian-based data and the Korean stylised phantom published recently. The up-to-date realistic Korean voxel phantom, KTMAN-2, which was developed from computed tomography (CT) images of an average Korean adult male, was employed for Monte Carlo calculation using EGSnrc user-code, developed for the purpose of this study. The SAFs for 32 target organs and tissues from the photon source, uniformly deposited in a total of 37 source organs and tissues, were calculated from KTMAN-2. The results were compared with those for an adult phantom of Oak Ridge National Laboratory (ORNL) and Korean adult stylised phantom. Two major reasons of discrepancy were analysed: (1) racial difference between the Korean and the Caucasian and (2) anatomical difference between stylised and voxel phantoms. When the source organ was identical to the target organ, difference in SAF caused by the difference in target-organ mass between the Korean and the Caucasian phantoms was mainly observed. When the source and target organs were not identical, significant difference in SAF was observed which was mainly attributed to the difference in inter-organ distance and organ shape between voxel and stylised phantoms.

Body Burden↗

PubMed2006

Endothelial progenitor cells in pterygium pathogenesis.

PURPOSE: The pathogenesis of pterygium is not well known, and controversy exists about the cell origins and the nature of initial trigger required for its development. We investigated whether endothelial progenitor cells (EPCs) are involved in pathogenesis of pterygium and the mechanism underlying the selective recruitment of EPCs during this process. METHODS: We studied 13 normal controls and 28 pterygium patients (primary (n=15), recurrent (n=13)). Substance-P, vascular endothelial growth factor (VEGF), and stem cell factor (SCF) were measured in plasma and tears using ELISA, and circulating CD34(+) and c-kit(+) mononuclear cells (MNCs) by flow cytometry. Anterior segment fluorescein angiography (FAG) was performed to evaluate hypoxic conditions in the early stage of pterygium. Surgically removed pterygial tissues were analyzed immunohistochemically using the progenitor cell markers, CD34, c-kit, VEGFR-1, and VEGFR-2. RESULTS: Anterior segment FAG findings showed an increase in non-perfusion areas and attenuated vessels in the nasal limbus during early-stage pterygium. Circulating CD34(+) MNCs and c-kit(+) MNCs were increased in pterygium groups compared with normal controls. Systemic and local cytokines including SP, VEGF, and SCF in pterygium groups were also elevated and showed positive correlations with CD34(+) and c-kit(+) MNC numbers. Immunohistochemical analysis of pterygium showed strong progenitor cell marker immunoreactivities. CONCLUSIONS: EPCs might be involved in pterygium development, and ocular hypoxia triggers this neovascularization by recruiting EPCs derived from the bone marrow via the production of systemic and local cytokines.

Age Distribution↗

PubMed2006

Monte Carlo simulation of the photon beam characteristics from medical linear accelerators.

The MCNPX code has been employed on a personal computer to calculate the dosimetric characteristics of the photon beams from the 6 MV Siemens MX2 and the 10 MV Varian Clinac 2100C linear accelerators. A model of the treatment head includes the major geometric structure within the beam path. The model was used to calculate the energy spectra of the photon beam, percentage depth dose and the dose profiles. The accuracy of the calculated results is examined by comparing them with the measured dose distributions for the two machines. The computed and measured depth dose curves agree to within 2% for all the depths beyond the build-up region for both treatment machines. The calculations agree to within 2% of the measured profiles within the 100-50% dose level. It has been found that the MCNPX code is an effective tool for simulating the clinical photon beam.

Body Burden↗

PubMed2006

Development of a Korean adult male computational phantom for internal dosimetry calculation.

A Korean adult male computational phantom was constructed based on the current anthropometric and organ volume data of Korean average adult male, and was applied to calculate internal photon dosimetry data. The stylised models of external body, skeleton, and a total of 13 internal organs (brain, gall bladder, heart, kidneys, liver, lungs, pancreas, spleen, stomach, testes, thymus, thyroid and urinary bladder) were redesigned based on the Oak Ridge National Laboratory (ORNL) adult phantom. The height of trunk of the Korean phantom was 8.6% less than that of the ORNL adult phantom, and the volumes of all organs decreased up to 65% (pancreas) except for brain, gall bladder wall and thymus. Specific absorbed fraction (SAF) was calculated using the Korean phantom and Monte Carlo code, and compared with those from the ORNL adult phantom. The SAF of organs in the Korean phantom was overall higher than that from the ORNL adult phantom. This was caused by the smaller organ volume and the shorter inter-organ distance in the Korean phantom. The self SAF was dominantly affected by the difference in organ volume, and the SAF for different source and target organs was more affected by the inter-organ distance than by the organ volume difference. The SAFs of the Korean stylised phantom differ from those of the ORNL phantom by 10-180%. The comparison study of internal dosimetry will be extended to tomographic phantom and electron source in the future.

Adult↗

PubMed2006

Spinal metastasis from cranial meningeal hemangiopericytomas.

Spine metastasis from cranial meningeal hemangiopericytomas are extremely rare, with five surgically verified cases. We describe a case of a 55-year-old female diagnosed with metastatic hemangiopericytoma to the cervical spine 78 months after the first operation. Because of the long latency period, aggressive spinal surveillance should be advocated along with repeated bone scintigraphy and MRI.

Cervical Vertebrae↗

PubMed2006

Prostate activity and prostate cancer in spinal cord injury.

In addition to androgen, autonomic nerves may be involved in prostatic function. As patients with spinal cord injury (SCI) have impaired innervation of the prostate, the prostate volume and prostate-specific antigen (PSA) level in patients with SCI may be different from those of healthy men. Experiments in rats with SCI indicate that neurogenic factors play an important role in prostate growth and function but the same phenomena may not occur in men with SCI because the current animal models differ from clinical results in humans in several respects. Although many of studies indicate the importance of intact peripheral innervation on the secretory function of the prostate, the effect of more central denervation such as occurs in complete SCI at the cervical, thoracic, or lumbar levels on prostatic function is unclear. In addition, the impact of central nervous system injury on prostatic secretory activity, and consequently on serum PSA levels, is also not clear. Furthermore, the impact of hormonal changes on prostate cancer development and prognosis observed in patients with SCI may also be affected by the level of injury and patient age at the time of injury, which have not been studied. In this article, we review prostate activity and prostate cancer in SCI and discuss how they may relate to neurogenic factors.

Adolescent↗

PubMed2006

Physical phantom of typical Korean male for radiation protection purpose.

Dose distribution within a human body can be measured using physical anthropomorphic phantoms. In an effort to establish reference Korean physical model, the first Korean physical phantom of average Korean adult male was constructed using computed tomography (CT) images of a healthy volunteer. The body dimension of the subject was close to that of average Korean male. The source images were obtained using fusion positron emission tomography machine at Radiation Health Research Institute in Korea, and ported into rapid prototyping process. The physical phantom was composed of three tissue-equivalent materials: epoxy resin, urethane foam and polyurethane representing bone, lungs and soft tissues, respectively. The densities of the tissue-equivalent materials were close to those recommended by the International Commission on Radiation Units and measurements. To facilitate dose mapping, the phantom was sliced into 2 cm sections. Hole grids for thermoluminescence (TL) dosemeter chips were drilled. To verify the appropriateness of the physical phantom, organ doses of selected organs were measured for reference photon beam, and compared with those computed by tomographic model constructed from the same CT images. Absorbed doses converted from TL relative response showed good agreement within 7% with those calculated.

Body Burden↗

PubMed2006

Intraductal papillary mucinous tumour of the pancreas: differentiation of malignancy and benignancy by CT.

AIM: To retrospectively identify signs predictive of malignant intraductal papillary mucinous tumour (IPMT) of the pancreas on computed tomography (CT) images. MATERIALS AND METHODS: Thirty-four benign and 21 malignant pancreatic IPMTs were evaluated. Preoperative helical CT images in these 55 cases of pathologically proven pancreatic IPMT were reviewed by two radiologists unaware of the histological grading. Tumour morphological types, locations, numbers and sizes of cystic lesions, maximum main pancreatic duct diameters, the presence of septa, mural nodule, wall thickening, and calcification in cysts, communication with the main pancreatic duct, peripancreatic haziness, protrusion of duodenal papilla, pancreatic atrophy, lymphadenopathy and distant metastasis were analysed using univariate and multivariate analysis. RESULTS: Main duct IPMTs were more likely to be malignant (71%) than branch duct (23%) or combined type IPMTs (28%; p=0.002). Among the branch duct type and combined types, large cystic lesion (p=0.018), the presence of a mural nodule (p=0.018), a thickened wall (p=0.009), and peripancreatic haziness (p=0.039) were found to predict malignancy. CONCLUSION: CT is helpful in the preoperative differentiation of malignant and benign pancreatic IPMT. The presence of a dilated main pancreatic duct, mural nodules, thickened wall and peripancreatic haziness may be used as independent predictive signs of malignancy.

Adult↗

PubMed2006

Influence of bladder management on epididymo-orchitis in patients with spinal cord injury: clean intermittent catheterization is a risk factor for epididymo-orchitis.

STUDY DESIGN: Retrospective study, based on cases of spinal cord injury (SCI). OBJECTIVES: To establish hazard ratios for risk of epididymo-orchitis in SCI. SETTING: South Korea. METHODS: A total of 140 male patients injured before 1987 were eligible for this investigation and have been followed up on a yearly basis from January 1987 to December 2003. RESULTS: The average age at which the lesion occurred was 24.8 years old (range, 18-53). The average time since SCI was 16.9 years (range, 1-37). A total of 34 lesions (24.3%) were complete and 106 (75.7%) were incomplete. Over the 17 years, 39 patients (27.9%) were diagnosed with epididymo-orchitis. Epididymo-orchitis was more common for patients with a history of urethral stricture (66.7 versus 25.2%, P=0.014). We also found that epididymo-orchitis was more common for patients on clean intermittent catheterization (CIC) than with indwelling urethral catheterization (42.2% versus 8.3%, P=0.030). In multivariate analysis, patients on CIC had a 7.0-fold higher risk (odds ratio, 6.96; 95% confidence interval, 1.26-38.53; P=0.026); however, a history of urethral stricture lost statistical significance (P=0.074). For other variables, no positive association with epididymo-orchitis was observed. CONCLUSIONS: In this study, CIC was an independent risk factor for the development of epididymo-orchitis in patients with SCI. In addition, our findings suggest that urethral stricture may be a contributing factor for the development of epididymo-orchitis in these patients. Correct instructions about CIC are of utmost importance.

Adolescent↗

PubMed2006

Clinical utility of multislice computed tomographic angiography for detection of cerebral vasospasm in acute subarachnoid hemorrhage.

Digital subtraction angiography (DSA) has been used as the standard method for detecting cerebral vasospasm after subarachnoid hemorrhage (SAH). Multislice computed tomographic angiography (CTA) is a relatively recent method used for evaluating the vasculature of the intracranial arteries. The purpose of this study was to compare multislice CTA and DSA for the detection and quantification of cerebral vasospasm after SAH, and to analyze the usefulness of multislice CTA. Eight patients with SAH underwent initial CTA with DSA within 72 hours after the onset of symptoms and follow-up multislice CTA and DSA 8 to 48 days after SAH. Five arterial locations were established in the A1 and A2 segments of the anterior cerebral artery, the M1 and M2 segments of the middle cerebral artery and the posterior cerebral artery (PCA) on both multislice CTA and DSA images. Vasospasm was classified as none, mild (up to 30% reduction in luminal diameter), moderate (31-60% reduction), and marked (at least 60% reduction) using the scale of Schneck and Kricheff. The multislice CT system used the following parameters: 1.25 mm collimation and 3.75 pitch with a 4-channel system. The degree of vasospasm revealed by the multislice CTA was significantly correlated with the degree of vasospasm revealed by DSA. In general, most discrepancies between CTA and DSA were in the detection of mild and moderate vasospasm. We found that the consistency between multislice CTA and DSA was greater for mild (100%, n=3) or moderate (100%, n=3) vasospasm than none (n=1) or marked vasospasm (n=1). However, it was unclear whether multislice CTA was more specific for a proximal location (A1, M1, PCA) or distal location (A2, M2) for evaluation of cerebral arteries. Multislice CTA can detect angiographic vasospasm after SAH with an accuracy similar to that of DSA. Multislice CTA is highly sensitive, specific and accurate in detecting mild and moderate cerebral vasospasm. It is less accurate for detecting no vasospasm and marked vasospasm. Therefore, the authors propose that multislice CTA be considered as a useful tool for the detection and management of intracranial vasospasm after SAH.

Aged↗

PubMed2006

Molecular analysis of Staphylococcus aureus isolates associated with staphylococcal food poisoning in South Korea.

AIMS: To investigate the molecular epidemiological study of Staphylococcus aureus from staphylococcal food poisoning (SFP) incidents in South Korea. METHODS AND RESULTS: Three hundred and thirty-two strains isolated from ten provinces between June 1999 and January 2002 were characterized by staphylococcal enterotoxin genes, toxic shock syndrome toxin 1 (tst) gene, and exfoliative toxin genes. Toxin genotypes were sea-seh (n=197), sea (n=51), sea-seg-sei (n=14), seg-sei (n=10), seb (n=10), seb-sed-seg-sei-sej (n=3), sea-seg-seh-sei (n=1), sea-seb (n=1), sea-sec (n=1), seg-sei plus eta (n=4), and sea-seg-sei plus tst (n=40). Most of the strains could be classified into three clusters of pulsed-field gel electrophoresis (PFGE) types A and B with coagulase type VII and type E with coagulase type IV. Of the ten sequence types (ST), ST1, ST59, and ST30 were frequently showed by multilocus sequence typing. CONCLUSIONS: The strain belonging to PFGE pattern A with sea-seh gene, coagulase VII, and ST1 was the most epidemic clone of SFP incidents in Korea.

Coagulase↗

PubMed2006

Incomplete discoid glenoid labrum combined with a ganglion cyst of the spinoglenoid notch.

In a 41-year-old man, right-sided infraspinatus muscle weakness was associated with compression of the suprascapular nerve caused by a spinoglenoid ganglion cyst. The lesion was confirmed using electromyography and MRI. In addition, arthroscopy showed an incomplete discoid labrum. The free inner edge of the labrum was removed as in a meniscectomy of a discoid meniscus in the knee joint. Arthroscopic decompression of the cyst was performed through a juxtaglenoid capsulotomy which was left open. Neurological function recovered completely.

Adult↗

PubMed2006

A novel method for gene expression mapping of metastatic competence in human bladder cancer.

Expression profiling by DNA microarray analysis has provided insights into molecular alterations that underpin cancer progression and metastasis. Although differential expression of microarray-defined probes can be related to numerical or structural chromosomal alterations, it is unclear if such changes are also clustered in distinct chromosomes or genomic regions and whether chromosomal alterations always reflect changes in gene expression. Here we apply the dChip algorithm and a novel technique to test the hypothesis that expression changes occurring as a function of tumor progression and metastasis are nonrandomly distributed. Expression profiling of a human xenograft model of lung metastasis phenotype indicates that chromosomes 2, 11, and 20 contain higher percentages of differentially expressed genes (P < .05). Furthermore, we show that a number of differentially expressed probes mapped to chromosome 17q, defining the existence of an expression "hot spot" corresponding to an area of gain determined by comparative genomic hybridization (CGH). Interestingly, other areas of gains detected by CGH were not associated with expression hot spots. In summary, we show that gene expression changes during bladder cancer lung metastasis occur nonrandomly in specific chromosomes and intrachromosomal locations.

Algorithms↗

PubMed2006

Thallium-201 scan in evaluating thyroid nodules following equivocal fine-needle aspiration cytology.

UNLABELLED: The AIM of this prospective study was to evaluate the usefulness of the thallium-201 ( (201) Tl) thyroid scan in the detection of malignancy in cold thyroid nodules whose status was equivocal following palpation fine-needle aspiration cytology (FNAC). PATIENTS, METHODS: Fifty-one patients with clinically palpable solitary cold thyroid nodules classified as non-diagnostic or suspicious following biopsy underwent (201) Tl thyroid scans. Each scan was performed 15 min (early scan) and 3 h (delayed scan) after an intravenous administration of 74 MBq (201) Tl. Thallium uptake in the nodules was visually assessed and scored on a three point scale, with a grade of three defining malignancy. All patients underwent surgery and the histopathology of nodule tissues were compared with results of the scans. RESULTS: Fifty-one nodules were examined. Forty were benign and 11 were malignant. For early scans, the diagnostically relevant parameters were: sensitivity (100%), specificity (75%), and accuracy (80%). Corresponding findings for the delayed scan were: 91%, 98%, and 96%. CONCLUSION: The (201) Tl scan is useful for detecting malignancy in cold thyroid nodules classified as nondiagnostic or suspicious lesions by FNAC.

Biopsy, Fine-Needle↗

PubMed2006

An Internet-based surveillance system for tuberculosis in Korea.

SETTING: The Korea Tuberculosis Surveillance (KTBS) network includes 248 health centres throughout the country, as well as other public and private health institutions. OBJECTIVE: To develop a web-based surveillance system for tuberculosis (TB) and to monitor implementation of the National TB Control Programme (NTP) on an ongoing basis. DESIGN: A TB notification form was developed with new case definitions, and standardised to obtain uniform essential information of the cases with ease and speed. Data collection, compilation, analysis and feedback were made available at every level of the health authority via the Internet without restrictions of time and space. RESULTS: The Internet-based surveillance system was successfully implemented across the country, providing real-time national figures of TB using different variables-patient, time, area, site and type of disease--and facilitating on-line evaluation of NTP implementation. CONCLUSION: The web-based surveillance system has been well established within the existing health infrastructure, providing real-time figures on the TB burden. However, it requires continued improvement of the quality of information and of case reporting activities.

Adolescent↗

PubMed2005

In vivo organ mass of Korean adults obtained from whole-body magnetic resonance data.

In vivo organ mass of the Korean adult, male and female were presented for the purpose of radiation protection. A total of 121 healthy volunteers (66 males and 55 females), whose body dimensions were close to that of average Korean adults, were recruited for this study. Whole-body magnetic resonance (MR) images were obtained, and contours of 15 organs (brain, eye, gall bladder, heart, kidney, liver, lung, pancreas, stomach, spleen, testes, thymus, thyroid, urinary bladder and uterus) and 9 bones (femur, tibia + fibula, humerus, radius + ulna, pelvis, cervical spine, thoracic and lumber spine, skull and clavicle) were segmented for organ volume rendering by anatomists using commercial software. Organ and bone masses were calculated by multiplying the Asian reference densities of the corresponding organs and bones by the measured volumes. The resulting organ and bone masses were compared with those of the International Commission of Radiological Protection (ICRP) and the Asian reference data. Significantly large standard deviation was shown in the moving organs of the respiratory and circulatory systems and in the alimentary and urogenital organs that are variable in volume in a single person. Gall bladder and pancreas showed unique Korean organ masses compared with those of ICRP and the Asian reference adults. Different from anatomical data based on autopsy, the in vivo volume and mass in this study can more exactly describe the organ volume of a living human subject for radiation protection. A larger sample size would be required for obtaining statistically more reliable results. It is also needed to establish the reference organ mass of younger age groups for which it is difficult to recruit volunteers and to immobilise the subjects for long-time MR scanning. At present, the data from this study will contribute to the establishment of a Korean reference database.

Adult↗

PubMed2005

Demonstration of a multiwave coherent holographic beam combiner in a polymeric substrate.

We demonstrate an efficient coherent holographic beam combiner (CHBC) that uses angle multiplexing of gratings in a thick polymeric substrate. Our experimental results compare well with the theoretical model based on the coupled-wave theory of multiwave mixing in a passive medium. A CHBC of this type may prove useful in producing a high-power laser by combining amplified beams produced by splitting a master oscillator. Furthermore, the ability to angle multiplex a large number of beams enables a CHBC to be used in multiple-beam interferometry applications as a high-precision surface sensor.

Journal Article↗