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Biomedical subjects

H C Song

Publications and source records attributed to H C Song.

At least 19 recordsLinked to original sources
PubMed2003

Improvement in matched field processing using the CLEAN algorithm.

Adaptive matched field processing such as the minimum variance distortionless processor (MV) provides excellent sidelobe (or ambiguity) suppression capability in source localization given a perfect knowledge of the ocean environment. Unfortunately, this processing is very sensitive to sources of mismatch and robust adaptive algorithms are then employed such as a white noise constraint (WNC) often at the expense of insufficient sidelobe control. The CLEAN algorithm was introduced in radio astronomy [Astron. Astrophys. Suppl. Ser. 15, 417-426 (1974)] to produce a high quality image of the sky by reducing sidelobe-induced artifacts. In this paper, the CLEAN concept is extended to matched field processing. Numerical simulations and experimental data demonstrate that matched field processing combined with the CLEAN algorithm can improve performance, especially when a weak source is masked by sidelobes from a much stronger source.

Journal Article↗
PubMed2003

Robust time reversal focusing in the ocean.

Recent time-reversal experiments with high-frequency transmissions (3.5 kHz) show that stable focusing is severely limited by the time-dependent ocean environments. The vertical focal structure displays dynamic variations associated with focal splitting and remerging resulting in large changes in focal intensity. Numerical simulations verify that the intensity variation is linked to the focal shift induced by phase changes in acoustic waves resulting from sound speed fluctuations due to internal waves. A relationship between focal range shift, frequency shift, or channel depth changes is illustrated using waveguide-invariant theory. Based on the analysis of experimental data and numerical simulations, methods for robust time-reversal focusing are developed to extend the period of stable focusing.

Journal Article↗
PubMed2002

Time reversed reverberation focusing in a waveguide.

Time reversal mirrors have been applied to focus energy at probe source locations and point scatterers in inhomogeneous media. In this paper, we investigate the application of a time reversal mirror to rough interface reverberation processing in a waveguide. The method is based on the decomposition of the time reversal operator which is computed from the transfer matrix measured on a source-receiver array [Prada et al., J. Acoust. Soc. Am. 99, 2067-2076 (1996)]. In a similar manner, reverberation data collected on a source-receiver array can be filtered through an appropriate temporal window to form a time reversal operator. The most energetic eigenvector of the time reversal operator focuses along the interface at the range corresponding to the filter delay. It is also shown that improved signal-to-noise ratio measurement of the time reversal operator can be obtained by ensonifying the water column with a set of orthogonal array beams. Since these methods do not depend upon a priori environmental information, they are applicable to complex shallow water environments. Numerical simulations with a Pekeris waveguide demonstrate this method.

Journal Article↗
PubMed2002

Null-broadening in a waveguide.

Null-broadening, introduced in plane wave beamforming, is extended to an ocean waveguide in the context of matched field processing. The method is based on the minimum variance processor with white noise constraint and the distribution of fictitious sources using the theory of waveguide invariants. The proposed method is demonstrated in simulation as well as with data collected during the SWellEx-96 experiment. As another application, it is shown that the width of a null can be controlled in an adaptive time reversal mirror with a source-receive array.

Acoustics↗
PubMed2001

Effects of Korean red ginseng and its mixed prescription on the high molecular weight dextran-induced blood stasis in rats and human platelet aggregation.

This study was undertaken to evaluate the antithrombotic effects of Korean Red Ginseng (KRG) and its new prescription (KRGP) consisting of five herbs such as Korean red ginseng, Ganoderma, Cinnamomi Cortex, Glycyrrhizae Radix and Laminaria. In rats with blood stasis induced by high molecular weight dextran, KRG and KRGP significantly restored not only the number of platelets and fibrinogen, but also suppressed the fibrin degradation products (FDP) to normal range. In platelet aggregation assay with human platelet rich plasma (PRP), KRG and KRGP significantly inhibited thrombin and collagen-induced platelet aggregation. The IC(50) values of KRG and KRGP were >2 and 0.23+/-0.01 mg/ml for thrombin, 0.32+/-0.01 and 0.17+/-0.02 mg/ml for collagen and 0.72+/-0.25 and >2 mg/ml for ADP, respectively. In coagulation assay, KRG and KRGP significantly prolonged activated partial prothrombin time (APPT) and prothrombin time (PT) as compared with control data. KRGP was found to be more effective than KRG alone on antithrombotic activity. These results suggest that KRGP may exert its antithrombotic activity due to inhibition of platelet aggregation and coagulation activity more than KRG.

Animals↗
PubMed2001

Study on second harmonic generation of 10-hydrocarbylacridones.

Values of second-order polarizabilities (beta(xxx)), the composite magnitude (beta(CT microg)) of molecular hypersusceptibilities and the second harmonic generation (SHG) of microcrystal were used to characterize and evaluate the second-order nonlinear optical performance of 10-hydrocarbylacridones. Using Nd:YAG as a laser source, the SHG values of these compounds in powder as compared with urea powder were obtained, compared with the calculated values of beta(CT microg) and beta(xxx) found by solvatochromic method. The results showed that the SHG values of compounds 1, 2, and 5 are larger than that of urea. Compound 5 has a highest beta(CT microg) value among the 12 compounds. Although the different electronegativities of hydrocarbyl (R) attached to nitrogen atom should have an effect on the extent of intralmolecular charge-transfer and further influence SHG, beta(CT microg) or beta(xxx) values, the relationships between electronegativity of R and SHG, beta(CT microg) or beta(xxx) could not be found. But it is found that the bigger the donating-electron ability of R, the longer the maximum absorption wavelength of 10-hydrocarbylacridone molecules.

Acridines↗
PubMed2001

Study on second harmonic generation of 9-benzylidene-substituted-10-methyl-9,10-dihydroacridines.

Eight 9-benzylidene-substituted-10-methyl-9,10-dihydroacridine derivatives were synthesized from acridine as starting material and were characterized by 1H-NMR, 13C-NMR, Ms and elemental analysis. The second harmonic generation (SHG) values of these compounds were determined in powder using Nd:YAG as a laser source, as compared with urea powder, and the values of second-order polarizabilities (betaxxx), the values of the composite magnitude (betaCTmicrog) of molecular hypersusceptibilities and their moment of these compounds were obtained by the solvatochromic method under ground state for everyone. The results showed that SHG value of 10 is higher than that of urea; the betaCTmicrog of 5 (107.8 x 10(-30) esu) is lower than that of 4-nitro-N,N-dimethylaniline (30 x 10(-30) esu); the betaCTmicrog of 7 (350.8 x 10(-30) esu) and 10 (244.6 x 10(-30) esu) are higher than that of 4-nitro-N,N-dimethylaniline; the betaCTmicrog of 8 (3553 x 10(-30) esu), 11 (1187 x 10(-30) esu) and 12 (1163 x 10(-30) esu) are much more higher than that of 4-nitro-N,N-dimethylaniline. The results demonstrated that this series of compounds possesses good second-order nonlinear optical (NLO) property. The regular relationship could not be obtained between electronegativity of substituents (R) attached to benzylidene ring and SHG values or betaCTmicrog values although the Rs are different in electronegativity and should make an effect on the extent of intramolecular electron-transfer and would consequently influence SHG or betaCTmicrog. The electron-withdrawing ability of R from benzylidene ring played an important role on lambdamax of these compounds.

Acridines↗
PubMed2001

Improvement of SO2 removal by the solubility change of Ca(OH)2 in the spray dryer system.

Experiments were carried out to verify the effect of the solubility change of the Ca(OH)2 sorbent on the removal of SO2 in a lab-scale spray dryer system. First, to identify the solubility effect, HNO3 was added into Ca(OH)2 slurry to increase the solubility of Ca(OH)2 by neutralization. The improvement of SO2 removal by 5-10% occurred under the condition of both 50% relative solubility and constant pH of slurry. But SO2 removal efficiency decreased steeply when the relative solubility approached 100% and the pH of the slurry decreased rapidly. For the practical application of the solubility effect, NH4Cl and NH4OH were selected as additives. Ammonium chloride (NH4Cl) which could improved Ca(OH)2 solubility removed more SO2 by 5-10% than NH4OH which showed no change in solubility. The optimal result was obtained when the slurry was fed at the ratio of 0.25mol NH4Cl/mol Ca(OH)2. The Ca(OH),/NH4Cl sorbent could remove more SO2 and improve Ca(OH)2 utilization than Ca(OH)2 sorbent in the Ca/S stoichiometric range of 1.0-1.4. It was concluded that the increase of sorbent solubility made the improvement in SO2 removal efficiency and Ca(OH)2 utilization.

Absorption↗
PubMed2001

Focal pulmonary uptake during Tc-99m myocardial perfusion SPECT imaging.

PURPOSE: To evaluate the incidence and origin of abnormal focal pulmonary uptake during myocardial perfusion SPECT imaging (MSPECT). METHODS: For evaluation of chest pain, 790 men and 581 women (mean age, 56 +/- 13 years) underwent MSPECT. All of them received adenosine for pharmacologic stress and Tc-99m tetrofosmin (TF, n = 817) or Tc-99m sestamibi (MIBI, n = 554) for myocardial perfusion imaging. RESULTS: Review of chest radiography with or without computed tomography revealed 111 (8.1%) focal pulmonary diseases. Among them, 38 (34.2%) showed focal pulmonary uptake (TF, 22; MIBI, 16); 27 (30.7%) of 88 showed previous pulmonary tuberculosis; 2 of 10 (20%) benign pulmonary nodules; 4 of 5 (80%) metastatic lung cancers; 2 of 4 (50%) primary lung cancers; and 3 of 4 (75%) pneumonias. No difference in uptake was noted for the two imaging agents. Intensity of uptake did not vary with origin of the uptake. Focal abnormal pulmonary uptake was found in 2.8% of patients undergoing MSPECT and in 34.2% of patients in whom radiological examinations showed regional pulmonary disease. In patients with abnormal pulmonary uptake on MSPECT, 16% had a malignant lesion, whereas 75% of patients with a pulmonary nodule shown on radiography and focal pulmonary uptake on MSPECT had a malignant lesion. CONCLUSIONS: Although the incidence of abnormal pulmonary uptake during MSPECT was very low, the incidence of malignant lesions in the patients with nodular pulmonary uptake was relatively high.

Adenosine↗
PubMed2001

Adaptive time-reversal mirror.

The time-reversal mirror uses the received signal from a probe source to refocus the signal at the probe source location by backpropagating the time-reversed version of the received signal. In this study, an adaptive method is described to steer a null to an arbitrary position in a waveguide while maintaining a distortionless response at the probe source location. As an application, selective focusing in free space is demonstrated.

Journal Article↗
PubMed2001

A case of isolated posterior capsule rupture and traumatic cataract caused by blunt ocular trauma.

An isolated rupture of the posterior capsule that is caused by a blunt ocular trauma has been rarely reported and is usually detected incidentally during surgery for a complicated cataract. We found an isolated posterior capsule rupture on the third day after trauma in a 25-year-old man who was admitted for the treatment of traumatic hyphema and we performed a phacoemusification and anterior vitrectomy with PC-IOL, implantation because of the traumatic cataract which had progressed after the injury. The PC-IOL was implanted safely into the capsular bag without severe enlargement of the posterior capsular rupture. The break seems to function as a capsulotomy which provides a clear visual axis. We report this case with a review of the literatures.

Adult↗
PubMed2000

Intestinal protein loss in patients with haemorrhagic fever with renal syndrome.

BACKGROUND: In haemorrhagic fever with renal syndrome (HFRS) vascular dysfunction has been observed in various organs, but the involvement of the intestine has not yet been reported. This study was performed to evaluate the association of intestinal protein loss in this disease with other clinical parameters reflecting vascular permeability or disease severity. METHODS: Twenty patients with HFRS were included in this study. Intestinal protein loss was measured by (99m)Tc-human serum albumin ((99m)Tc-HSA) scintigraphy in the acute stage, and quantitative analysis of protein loss was measured by the faecal clearance of alpha 1-antitrypsin (C(AT)) in the acute and the recovery stages. C(AT) was then compared with clinical parameters reflecting disease activity and vascular permeability. RESULTS: (99m)Tc-HSA scintigraphy was positive in 13 (65%) patients, and C(AT) in the acute stage was significantly increased as compared with C(AT) in the recovery stage (40.5+/-24.1 vs 9.2+/-4.2 ml/day, P<0.001). C(AT) was associated with serum albumin levels, frequency of hypotensive episodes, severity of acute renal failure, and degree of thrombocytopenia. CONCLUSIONS: Our data suggest that the increased vascular permeability of HFRS is associated with the increased intestinal loss of plasma proteins, which might represent one of the parameters of disease severity in HFRS.

Adult↗
PubMed1999

Dipyridamole modulated Tc-99m sestamibi lung SPECT in small cell lung cancer.

PURPOSE: In this study, the authors wanted to determine whether dipyridamole-modulated MIBI (dipyridamole-MIBI) could enhance the prediction of the response to chemotherapy in patients with small cell lung cancer. METHODS: Twenty-seven patients with biopsy-proved small cell lung cancer (25 men, 2 women; mean age, 61 +/- 7 years) underwent dipyridamole-MIBI SPECT 3 to 7 days before starting chemotherapy (80 mg/m2 etoposide and 80 mg/m2 cisplatin every 3 or 4 weeks for at least two cycles). Tomographic images before and after dipyridamole (0.84 mg/kg) were acquired 1 hour after injection of 370 (10 mCi) and 1,110 (30 mCi) MBq MIBI, respectively. The response to chemotherapy was grouped as specified as complete response (CR), partial (PR), no change (NC), or progressive disease (PD), according to the change in tumor size on chest roentgenography and CT. Patients showing CR and PR were classified as responders, and those who showed NC and PD were considered nonresponders. RESULTS: Among the 27 patients, 22 were responders (3 CR, 19 PR) and 5 were nonresponders (3 NC, 2 PD). The tumor-to-normal lung ratio (T:NL) of responders was significantly higher than that of nonresponders. The diagnostic accuracy of the T:NL ratio to differentiate responders and nonresponders was 33.3%, with a cutoff value of 2.5, which was significantly improved to 77.8% when an increased T:NL ratio after dipyridamole was assigned to a nonresponder. Furthermore, all patients with CR showed diminished T:NL ratios after dipyridamole, and all patients with NR showed an increased T:NL ratio after dipyridamole. CONCLUSION: Dipyridamole-MIBI SPECT could enhance the prediction of response to chemotherapy in patients with small cell lung cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Double-phase Tc-99m sestamibi scintimammography to assess angiogenesis and P-glycoprotein expression in patients with untreated breast cancer.

This study evaluated the relation of Tc-99m sestamibi (MIBI) uptake and washout in untreated breast cancer with immunohistochemically determined angiogenesis and P-glycoprotein expression. Thirty-one patients with untreated breast cancer were studied prospectively. Tc-99m MIBI scintigraphy and immunohistochemical analyses of angiogenesis and P-glycoprotein expression were used to evaluate surgically removed tumor tissues. Anterior and both lateral planar images were acquired 10 and 180 minutes after intravenous injection of 740 MBq (20 mCi) Tc-99m MIBI. The tumor-to-normal breast ratio (T:N) and washout index (early T:N - late T:N divided by early T:N) were calculated. A significant correlation was found between angiogenesis and T:N at early and late images. Pearson's correlation coefficients and probability values were r = 0.54, P = 0.002 at early images and r = 0.47, P = 0.008 at late images. The T:N of both early and late images were not different among different groups of P-glycoprotein expression (P = 0.367 and P = 0.113, respectively), although the washout index was significantly different among the groups (P = 0.001). A strong correlation was found between the washout index and P-glycoprotein expression (r = 0.67, P < 0.01). Double-phase scintimammography to assess the early tumoral uptake and washout of Tc-99m MIBI can be used as a simple functional test for in vivo imaging of tumoral angiogenesis and P-glycoprotein expression in patients with untreated breast cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Evaluation of functional changes in the medial temporal region during intracarotid amobarbital procedure by use of SPECT.

PURPOSE: Because the main blood supply to the medial temporal region is through the posterior cerebral artery, the validity of the intracarotid amobarbital procedure (IAP) is still debated. To verify clinical validity of the IAP, we investigated changes in neuronal function in the medial temporal region during IAP. METHODS: Brain single photon emission computed tomography (SPECT) was performed during IAP (IAP-SPECT) in 22 patients with temporal lobe epilepsy (TLE), and regional cerebral blood flow (rCBF) in the medial and lateral temporal regions of interest (ROIs) was measured quantitatively. To determine the distribution of sodium amobarbital, in another 20 patients with TLE, SPECT images were obtained after intracarotid injection of 99mTc-HMPAO mixed with sodium amobarbital. RESULTS: Mean rCBF was 89.2% in the medial temporal region and 81.6% in the lateral temporal region: in the former region, it was significantly lower than that shown by the results of interictal SPECT (99.1%; p < 0.001). In a few patients, however, rCBF did not decrease in the medial temporal region. In only 25% of patients, the medial temporal region was visualized in SPECT images obtained after intracarotid injection of 99mTc-HMPAO. CONCLUSIONS: The results in this study demonstrate that IAP is valid because the medial temporal region is inactivated in spite of infrequent delivery of sodium amobarbital. We assume that intratemporal diaschisis is operating for the inactivation of neuronal function. IAP-SPECT with intratemporal ROIs may be useful for monitoring changes in neuronal function in the medial temporal region during IAP.

Adolescent↗