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J K Chung

Publications and source records attributed to J K Chung.

At least 37 records · Page 2Linked to original sources
PubMed2001

Blind separation of cardiac components and extraction of input function from H(2)(15)O dynamic myocardial PET using independent component analysis.

UNLABELLED: The independent component analysis (ICA) method is suggested to be useful for separation of the ventricles and the myocardium and for extraction of the left ventricular input function from the dynamic H(2)(15)O myocardial PET. The ICA-generated input function was validated with the sampling method, and the myocardial blood flow (MBF) calculated with this input function was compared with the microsphere results. METHODS: We assumed that the elementary activities of the ventricular pools and the myocardium were spatially independent and that the mixture of them composed dynamic PET image frames. The independent components were estimated by recursively minimizing the mutual information (measure of dependence) between the components. The ICA-generated input functions were compared with invasively derived arterial blood samples. Moreover, the regional MBF calculated using the ICA-generated input functions and single-compartment model was correlated with the results obtained from the radiolabeled microspheres. RESULTS: The ventricles and the myocardium were successfully separated in all cases within a short computation time (<15 s). The ICA-generated input functions displayed shapes similar to those obtained by arterial sampling except that they had a smoother tail than those obtained by sampling, which meant that ICA removed the statistical noise from the time--activity curves. The ICA-generated input function showed a longer time delay of peaks than those obtained by arterial sampling. MBFs estimated using the ICA-generated input functions ranged from 1.10 to approximately 2.52 mL/min/g at rest and from 1.69 to approximately 8.00 mL/min/g after stress and correlated well with those calculated with microspheres (y = 0.45 + 0.98x; r = 0.95, P < 0.000). CONCLUSION: ICA, a rapid and reliable method for extraction of the pure physiologic components, was a valid and useful method for quantification of the regional MBF using H(2)(15)O PET.

Animals↗
PubMed2000

Hypoglycemia-induced cerebellar dysfunction and quantitative positron emission tomography study.

OBJECTIVE: To describe an unusual case of hypoglycemia-induced bilateral cerebellar dysfunction. BACKGROUND: The cerebellum is known to be resistant to hypoglycemia, and selective cerebellar dysfunction caused by hypoglycemia has not been reported. Previous studies showed that the ratio between the rate constants for glucose uptake and phosphorylation (K1 and k3) is reversed in the cerebellum compared with the cerebral cortex; higher K1 in the cerebellum and higher k3 in the cerebral cortex. METHODS: Quantitative dynamic PET scanning with labeled fluorodeoxyglucose (18F-FDG) was performed to prove altered glucose kinetics in the cerebellum of a patient who presented with episodic cerebellar dysfunction associated with hypoglycemia. Four control subjects underwent the same study. RESULTS: The ratio between K1 and k3 was not reversed in the cerebellum of our patient (K1 = 0.082, k3 = 0.192). On the contrary, the ratio was reversed in the control subjects (mean K1 = 0.109, mean k3 = 0.080). In addition, the patient's cerebellar metabolic rate of glucose (rCMRglu = 27.9 micromol/100 g/minute) and the rate constant of glucose egress (k2 = 0.543) were relatively increased compared with those of control subjects (mean rCMRglu = 21.9 micromol/100 g/minute, mean k2 = 0.352). CONCLUSIONS: In a case of episodic bilateral cerebellar dysfunction caused by hypoglycemia, quantitative dynamic PET study demonstrated decreased glucose uptake-to-utilization ratio and increased leak of glucose in the cerebellum. The cerebellum is not invariably resistant to hypoglycemia.

Blood Glucose↗
PubMed2000

Inhibition of phospholipase D by amphiphysins.

Two distinct proteins inhibiting phospholipase D (PLD) activity in rat brain cytosol were previously purified and identified as synaptojanin and AP180, which are specific to nerve terminals and associate with the clathrin coat. Two additional PLD-inhibitory proteins have now been purified and identified as the amphiphysins I and II, which forms a heterodimer that also associates with the clathrin coat. Bacterially expressed recombinant amphiphysins inhibited both PLD1 and PLD2 isozymes in vitro with a potency similar to that of brain amphiphysin (median inhibitory concentration of approximately 15 nm). Expressions of either amphiphysin in COS-7 cells reduced activity of endogenous PLD as well as exogenously expressed PLD1 and PLD2. Coprecipitation experiments suggested that the inhibitory effect of amphiphysins results from their direct interaction with PLDs. The NH(2) terminus of amphiphysin I was critical for both inhibition of and binding to PLD. Phosphatidic acid formed by signal-induced PLD is thought to be required for the assembly of clathrin-coated vesicles during endocytosis. Thus, the inhibition of PLD by amphiphysins, synaptojanin, and AP180 might play an important role in synaptic vesicle trafficking.

Amino Acid Sequence↗
PubMed2000

Dosimetry of rhenium-188 diethylene triamine penta-acetic acid for endovascular intra-balloon brachytherapy after coronary angioplasty.

To examine the possibility of using rhenium-188 diethylene triamine penta-acetic acid (DTPA) for endovascular intra-balloon brachytherapy after angioplasty, dose distribution around the balloon was calculated and validated by film dosimetry. Medical internal radiation dosimetry (MIRD) was calculated assuming that the balloon had ruptured and that the contents had been released into the systemic circulation. 188Re-perrhenate eluate from the 188W/188Re generator was concentrated using an ion column and used to label DTPA. The dose distribution around the angioplasty balloon (20 mm length, 3 mm diameter cylinder) was estimated by Monte Carlo simulation using the EGS4 code. The time required for 17.6 Gy to be absorbed at 1 mm from the balloon's surface following application of 3700 MBq/ml of 188Re was found to be 278 s. Fifty percent of the energy was deposited in the first millimetre of the vessel wall from the balloon's surface. The calculated radiation absorbed dose agreed with that measured by film dosimetry, which was performed using a water phantom, with errors ranging from 9.4% to 17%. Upon balloon rupture the total amount of 188Re-DTPA was presumed to enter the systemic circulation. The resulting radiation absorbed dose was calculated using the MIRDOSE3 program and residence times obtained from dogs and amounted to 0.0056 mGy/MBq to the whole body and 4.56 mGy/MBq to the urinary bladder. The absorbed dose of 188Re-DTPA to the whole body was one-tenth of that of 188Re-perrhenate. A window-based program was developed to calculate the exposure time and the radiation dose absorbed as a function of the 188Re concentration and the arbitrary distance from the balloon to the surrounding tissues. We conclude that 188Re-DTPA is easy to prepare, safe to use and suitable for intra-balloon brachytherapy after coronary angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed2000

Comparative study of single-injection, single-acquisition 99mTc-MIBI gated SPET and stress-rest perfusion SPET for the evaluation of myocardial viability after bypass surgery in coronary artery disease.

In patients without previous myocardial infarction, the single-injection stress perfusion/rest function (SISPRF) approach using stress technetium-99m methoxyisobutylisonitrile (MIBI) gated single-photon emission tomography (SPET) can substitute for conventional stress-rest myocardial perfusion imaging for the assessment of myocardial viability. This study compared pre-operative single-injection, single-acquisition 99mTc-MIBI gated SPET and conventional stress-rest imaging for the prediction of myocardial viability in patients who underwent coronary artery bypass surgery (CABG). Rest thallium-201 SPET followed by stress 99mTc-MIBI gated SPET was performed in 20 patients [nine with previous myocardial infarction (MI) and 11 without previous MI). The study was performed before and 3 months after CABG, and viability assessment was validated by wall motion improvement after CABG. A four-point scoring system (0-3 for normal to absent tracer uptake) for 17 segments of the left ventricular myocardium was used for the assessment of stress and rest uptake. Wall motion, wall thickening and perfusion status were analysed by semi-quantitative visual assessment. On gated SPET, perfusion defect reversibility was considered present when a definite perfusion defect was observed and wall motion or thickening was normal or showed only a mild decrease. In patients with a previous MI, the left ventricular ejection fraction improved significantly after CABG (46% +/- 7% vs 42% +/- 11% before CABG, P < 0.05). In patients without previous MI, the ejection fraction improved significantly after CABG (50 +/- 12% vs 44% +/- 16% before CABG, P<0.05). In patients with previous MI, positive predictive values using the stress-rest reversibility and SISPRF approaches were 91% and 90%, respectively, and corresponding negative predictive values were 25% and 18%. In patients without previous MI, positive predictive values using the stress-rest and SISPRF approaches were 70% and 61%, respectively, and corresponding negative predictive values were 63% and 14%. It is concluded that SISPRF SPET study is of similar value to conventional stress-rest perfusion study in predicting wall motion improvement in patients with a previous MI, but that it is of limited value in predicting the myocardial viability of patients without previous MI, owing to a lower predictive value.

Aged↗
PubMed2000

Limited performance of quantitative assessment of myocardial function by thallium-201 gated myocardial single-photon emission tomography.

We investigated the reproducibility between thallium-201 and technetium-99m methoxyisobutylisonitrile (MIBI) gated single-photon emission tomography (SPET) for the assessment of indices of myocardial function such as end-diastolic and end-systolic volume (EDV, ESV), ejection fraction (EF) and wall motion. Rest 201Tl (111 MBq) gated SPET was sequentially performed twice in 20 patients. Rest 201Tl gated SPET and rest 99mTc-MIBI (370 MBq) gated SPET were performed 24 h apart in 40 patients. Wall motion was graded using the surface display of the Cedars quantitative gated SPET (QGS) software. EDV, ESV and EF were also measured using the QGS software. The reproducibility of functional assessment on rest 201Tl gated SPET was compared with that on 99mTc-MIBI gated SPET, and also with that between 201Tl gated SPET and 99mTc-MIBI gated SPET performed on the next day. The two standard deviation (2 SD) values for EDV, ESV and EF on the Bland-Altman plot were 29 ml, 19 ml and 12%, respectively, on repeated 201Tl gated SPET, compared with 14 ml, 11 ml and 5.3% on repeated 99mTc-MIBI gated SPET. The correlations were good (r=0.96, 0.97 and 0.87) between the two measurements of EDV, ESV and EF on repeated rest studies with 201Tl and 99mTc-MIBI gated SPET. However, Bland-Altman analysis revealed that the 2 SD values between the two measurements were 31 ml, 23 ml and 12%. We were able to score the wall motion in all cases using the 3D surface display of the QGS on 201Tl gated SPET. The kappa value of the wall motion grade on the repeated 201Tl study was 0.35, while that of the wall motion grade on the repeated 99mTc-MIBI study was 0.76. The kappa value was 0.49 for grading of wall motion on repeated rest studies with 201Tl and 99mTc-MIBI. In conclusion, QGS helped determine EDV, ESV, EF and wall motion on 201Tl gated SPET. Because the EDV, ESV and EF were less reproducible on repeated 201Tl gated SPET or on 201Tl gated SPET and 99mTc-MIBI gated SPET on the next day than on repeated 99mTc-MIBI gated SPET, functional measurement on 201Tl gated SPET did not seem to be interchangeable with that on 99mTc-MIBI gated SPET.

Coronary Disease↗
PubMed2000

Preparation of rhenium-188-tin colloid as a radiation synovectomy agent and comparison with rhenium-188-sulfur colloid.

As a generator-produced beta-emitting radionuclide, the importance of 188Re for radionuclide therapy is increasing rapidly. We prepared 188Re-tin colloid and compared its properties with 188Re-sulfur colloid. Labeling efficiencies reached >98% for tin colloid at 2 h and 89-94% for sulfur colloid at 3 h. All the preparations were stable for 72 h in water, serum, and synovial fluid. If labeled at higher temperature, the particle size of tin colloid increased. The residual radioactivity of 188Re-sulfur colloid in disposable polypropylene syringes after injecting mice was high (62.0+/-7.0%) due to its hydrophobic nature, while that of 188Re-tin colloid was low (2.9+/-1.6%). Although both 188Re-tin colloid and 188Re-sulfur colloid might be useful for radionuclide therapy, we conclude that 188Re tin colloid is more advantageous over 188Re sulfur colloid, due to higher labeling efficiency, control of the particle size, and lower residual activity in the injection syringes.

Animals↗
PubMed2000

Usefulness of 99Tcm-MDP knee SPET for pre-arthroscopic evaluation of patients with internal derangements of the knee.

The aim of this study was to ascertain whether knee SPET can localize lesion sites in patients with internal derangements of the knee. We performed knee SPET as a pre-arthroscopic examination in 63 consecutive patients. SPET imaging was performed with a triple-headed SPET camera 4 h after the injection of 99Tcm-methylene diphosphonate. Arthroscopic diagnoses were as follows: 28 medial meniscus injuries, 24 lateral meniscus injuries, 31 anterior cruciate ligament (ACL) injuries, three posterior cruciate ligament injuries and one medial collateral ligament injury. Of 30 patients with crescent-shaped increased activity at the medial tibial plateau, 22 had medial meniscus injuries (positive predictive value: PPV 73%); of 17 patients with crescent-shaped activity at the lateral tibial plateau, 13 had lateral meniscus injuries (PPV 76%). Of 18 patients with increased activity at ACL attachment sites (primary sign), 17 had ACL injuries (PPV 94%). Of 27 patients with increased activity at bone impaction sites of ACL injury (secondary sign), 22 had ACL injuries (PPV 81%). Of 32 patients who had either a primary or secondary sign, 26 had ACL injuries (PPV 81%). We conclude that knee SPET is very useful in the management of internal derangements of the knee, particularly in determining the need for arthroscopy by localizing lesion sites.

Adolescent↗
PubMed2000

Indirect signs of anterior cruciate ligament injury on SPET: comparison with MRI and arthroscopy.

Indirect signs of anterior cruciate ligament (ACL) injury on magnetic resonance imaging (MRI) include bony contusions in the lateral femoral condyle and the posterior portion of the lateral tibial plateau. This study was undertaken to assess the value of single photon emission tomography (SPET) in the diagnosis of ACL injury by examining the uptake pattern in the distal femur and the proximal tibia. Thirty-five patients were examined using SPET, MRI and arthroscopy. Seventeen patients were found to have ACL tears on arthroscopy. The duration of symptoms was 4 days to 10 years (mean 26.4 months). MRI and SPET images were analysed retrospectively without information from arthroscopic examination. Radionuclide uptake in the lateral femoral condyle and the posterior lateral tibial plateau was considered an indirect sign of ACL injury on SPET. We evaluated the diagnostic value of indirect signs of ACL injury obtained on SPET by comparing these findings with arthroscopic and MRI results. Fifteen of 17 patients with ACL injury showed indirect signs on SPET. The sensitivity, specificity, positive predictive value and negative predictive value for indirect signs of ACL injury were 88%, 56%, 65% and 83% on SPET and 59%, 94%, 91% and 71% on MRI, respectively. However, despite the higher sensitivity of indirect signs on SPET than on MRI, the overall diagnostic value of MRI is better than that of SPET. In the clinical setting, indirect signs of ACL injury may be of value in interpreting incidental findings on SPET.

Adult↗
PubMed2000

Reproducibility of assessment of myocardial function using gated 99Tc(m)-MIBI SPECT and quantitative software.

PURPOSE: We investigated the reproducibility of the quantification of left ventricular volumes and ejection fraction, and grading of myocardial wall motion and systolic thickening with gated myocardial single-photon emission computed tomography (SPECT) and Cedars quantification software. PATIENTS, MATERIALS AND METHODS: We performed post-stress gated myocardial SPECT in 33 consecutive patients twice sequentially in situ. Sixteen frames per cycle were used for gating. Using Cedars quantitative gated SPECT software ventricular volumes and ejection fraction (EF) were calculated. Wall motion and thickening was graded using 5- and 4-point scores, respectively. Coefficients of variation for re-examination of volumes and EF were calculated. Kappa values for assessing reproducibility of wall motion or wall thickening were calculated. RESULTS: Root mean square of errors was 5.0 ml for end-diastolic volume, 3.9 ml for end-systolic volume and 1.9% for EF. No bias or difference was found between the first and second acquisition by Bland-Altman analysis. Kappa values for wall motion and thickening of repeated acquisition was 0.76 and 0.87, respectively. The value of 2 SD from Bland-Altman analysis was 14.4 ml for EDV, 11.2 ml for ESV and 5.3% for EF. CONCLUSION: We conclude that quantification of functional indices and assessment of wall motion or thickening using gated 99Tc(m)-sestamibi (MIBI) SPECT was reproducible and we found that their ranges of physiological fluctuation were narrow enough.

Aged↗
PubMed2000

Localization of epileptogenic zones in F-18 FDG brain PET of patients with temporal lobe epilepsy using artificial neural network.

For an objective interpretation of cerebral metabolic pattern to find epileptogenic zones in patients with temporal lobe epilepsy (TLE), we developed a computer-aided classifier using an artificial neural network (ANN). We studied 261 epilepsy patients diagnosed as no abnormal findings (NA, n = 64), left TLE (n = 116), or right TLE (n = 81) on interictal brain F-18-fluorodeoxyglucose positron emission tomography (FDG PET) by the consensus of two expert physicians. Seventeen asymmetry indexes between the mean counts of the 34 mirrored regions were extracted from the spatially normalized images and used as input parameters. The three diagnoses of NA, left TLE, and right TLE were used as outputs of the ANN. The structure of the ANN was optimized with variable error goals and the number of hidden units. On the criteria of agreement of diagnoses with those of expert viewers, the best classifier was chosen, which yielded a maximum average agreement of 85% for the test set when we used an error goal of 20 (sum of squared error) and ten hidden units. We could devise an ANN that performed as well in diagnosing left or right TLE on FDG PET as human experts and could be used as a clinical decision support tool.

Adult↗
PubMed2000

Pulmonary tuberculoma evaluated by means of FDG PET: findings in 10 cases.

PURPOSE: To describe findings of pulmonary tuberculoma at 2-[fluorine 18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET). MATERIALS AND METHODS: Ten consecutive patients who underwent PET and subsequently were proved to have pulmonary tuberculoma were analyzed. Tuberculosis was proved histopathologically in eight by means of wedge resection or lobectomy (n = 7) or needle biopsy (n = 1) and in two by means of clinical follow-up for more than 2 years. PET scans were evaluated by using peak standardized uptake values. Computed tomographic (CT) and histopathologic findings also were reviewed. RESULTS: Nine of 10 tuberculomas showed FDG uptake at PET, and the mean peak standardized uptake value was 4.2 +/- 2.2 (SD). FDG uptake (range, 1. 9-3.7) in lesions adjacent to main abnormalities was demonstrated in four patients. On CT scans, the mean of the longest nodule diameters was 21 mm +/- 8, and there were some areas of branching linear opacities or satellite nodules that suggested pulmonary tuberculosis in seven patients. Histopathologic findings were chronic granulomatous inflammation with caseation necrosis (n = 7) and healed tuberculosis with aspergilloma (n = 1). CONCLUSION: Pulmonary tuberculoma commonly causes an increase in FDG uptake. These results suggest that in geographic regions with a high prevalence of granulomatous lesions, positive FDG PET results should be interpreted with caution in differentiating benign from malignant pulmonary abnormalities.

Adult↗
PubMed2000

Transient prolonged stunning induced by dipyridamole and shown on 1- and 24-hour poststress 99mTc-MIBI gated SPECT.

UNLABELLED: We investigated whether poststress gated SPECT, which was believed to show resting wall motion, revealed stunning induced by dipyridamole stress. METHODS: In 62 patients with coronary artery disease (n = 57) or chest pain (n = 5), dipyridamole stress gated 99mTc-hexakis-2-methoxyisobutyl isonitrile (MIBI) SPECT and rest 201Tl SPECT were performed on the first day; 24-h delayed 201Tl SPECT and rest gated 99mTc-MIBI SPECT were performed on the second day. Stress and rest gated 99mTc-MIBI SPECT was performed 1 h after injection. The myocardium was divided into 17 segments, and perfusion was scored on a 4-point scoring system (scores, 0-3 for normal to defect); wall motion during first-day poststress gated and second-day rest gated SPECT was also scored on another 4-point scale (scores, 0-3 for normal to dyskinesia). RESULTS: Thirty-one of 62 patients showed wall motion abnormality that was worse after stress than during resting. Three hundred eight (29%) of the total 1054 segments showed wall motion abnormality on poststress gated SPECT. In 198 of these segments, wall motion abnormality was the same on poststress and rest gated SPECT, and 106 segments showed wall motion that was worse on 1-h poststress than on rest gated SPECT. Perfusion was normal either during rest (n = 113) or after a 24-h delay (n = 18) in 131 segments with the poststress wall motion abnormality. Of these 131 segments, 69 showed the same wall motion abnormality between poststress and resting periods (persistent stunning). However, in 40 segments, abnormal wall motion on 1-h poststress gated SPECT normalized on rest gated SPECT (transient prolonged stunning). The other 20 segments showed improvement of wall motion during rest compared with the poststress period but still showed abnormal wall motion during the resting period (between transient prolonged stunning and persistent stunning). Stress perfusion decrease was more severe in transient prolonged stunning than in persistent stunning. Poststress wall motion abnormality was more severe in persistent stunning. CONCLUSION: Using gated 99mTc-MIBI SPECT, stunned myocardium was found on 1-h poststress SPECT compared with normal resting wall motion found on rest gated SPECT on the next day. We conclude that some myocardial walls did not show true resting wall motion on 1-h poststress gated SPECT; hence, caution is necessary when using wall motion on 1-h poststress gated SPECT to assess resting wall motion.

Coronary Disease↗
PubMed2000

Limited incremental diagnostic values of attenuation-noncorrected gating and ungated attenuation correction to rest/stress myocardial perfusion SPECT in patients with an intermediate likelihood of coronary artery disease.

UNLABELLED: Either gated myocardial perfusion SPECT or attenuation-corrected SPECT can be used to improve specificity in the diagnosis of coronary artery disease (CAD). We investigated whether attenuation-noncorrected gating and ungated attenuation correction could improve the diagnostic performance of rest/stress perfusion SPECT in patients having an intermediate pretest likelihood of CAD. METHODS: Sixty-eight patients (29 men, 39 women; mean age, 59 +/- 12 y) with coronary artery stenosis > or =70% (1 vessel, n = 13; 2 vessels, n = 18; 3 vessels, n = 8; normal, n = 29) underwent rest attenuation-corrected 201TI SPECT and dipyridamole stress gated attenuation-corrected 99mTc-methoxyisobutyl isonitrile SPECT with an ADAC vertex camera. Three physicians graded the post-test likelihood of CAD for each arterial territory using a 5-point scale (1, normal; 2, possibly normal; 3, equivocal; 4, possibly abnormal; 5, abnormal). The sensitivity, specificity, and areas under receiver-operating-characteristic curves were compared for each operator by 3 methods: attenuation-noncorrected rest/stress SPECT, gated poststress SPECT plus attenuation-noncorrected rest/stress SPECT, and attenuation-corrected rest/stress SPECT plus gated poststress SPECT plus attenuation-noncorrected rest/stress SPECT. RESULTS: When higher than grade 3 was used as the criterion for CAD, no differences in sensitivity and specificity were found among the 3 methods for each operator. Areas under receiver-operating-characteristic curves for the diagnosis of CAD and stenosis revealed no differences for each modality (P > 0.05 for each comparison). CONCLUSION: In patients with an intermediate risk of CAD, viewing attenuation-noncorrected gated poststress SPECT and ungated attenuation-corrected rest/stress SPECT images did not improve the diagnostic performance for CAD and stenosis.

Coronary Circulation↗
PubMed1999

Establishment and characterization of 12 human colorectal-carcinoma cell lines.

In this article, we describe the characteristics of 12 human colorectal-carcinoma cell lines established from 6 primary tumors and 6 metastatic sites of 11 Korean colorectal-carcinoma patients, including the morphology in vivo and in vitro and mutations of K-ras2, p15, p16, p53, APC, beta-catenin, hMLH1 and hMSH2 genes in vitro. No lines were contaminated with Mycoplasma or bacteria. All lines were proven to be unique by DNA-fingerprinting analysis. All lines expressed the surface carcino-embryonic antigen and secreted it into the supernatant fluid. The morphological correlation between the original tumors and cultured cells suggested that the original tumors showing mucinous adenocarcinoma correlated with floating aggregates in culture, and degree of desmoplasia in the original tumor correlated with attached growth in culture. Five of the cell lines showed mutations in the K-ras2 gene, and 6 of the cell lines showed mutations in the p53 gene. The p15 gene was deleted in 2 cell lines, and the p16 gene was hypermethylated in 3 cell lines. The mutation of mismatch-repair genes (hMLH1 and hMSH2) was found in 4 lines, the APC gene and beta-catenin gene were mutated in 9 and 2 lines respectively. These well-characterized colorectal-cancer cell lines should serve as useful tools for investigating the biological characteristics of colorectal cancer.

Adaptor Proteins, Signal Transducing↗