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Dong Zhang

Publications and source records attributed to Dong Zhang.

At least 37 records · Page 2Linked to original sources
PubMed2006

Third order harmonic imaging for biological tissues using three phase-coded pulses.

Compared to the fundamental and the second harmonic imaging, the third harmonic imaging shows significant improvements in image quality due to the better resolution, but it is degraded by the lower sound pressure and signal-to-noise ratio (SNR). In this study, a phase-coded pulse technique is proposed to selectively enhance the sound pressure of the third harmonic by 9.5 dB whereas the fundamental and the second harmonic components are efficiently suppressed and SNR is also increased by 4.7 dB. Based on the solution of the KZK nonlinear equation, the axial and lateral beam profiles of harmonics radiated from a planar piston transducer were theoretically simulated and experimentally examined. Finally, the third harmonic images using this technique were performed for several biological tissues and compared with the images obtained by the fundamental and the second harmonic imaging. Results demonstrate that the phase-coded pulse technique yields a dramatically cleaner and sharper contrast image.

Algorithms↗
PubMed2006

Performance evaluation of eigendecomposition-based adaptive clutter filter for color flow imaging.

In this paper, a newly developed eigendecomposition-based adaptive filter is applied in flow velocity estimation and its performance is evaluated and compared with the static polynomial regression filter. Results demonstrate that the eigendecomposition-based filter is the fully-adaptive and can not only suppress the clutter signals with minimal loss of low-flow signal, but also give less influence on the flow velocity estimation especially under the circumstance of high clutter velocity.

Algorithms↗
PubMed2006

A novel approach for description of nonlinear field radiated from a concave source with wide aperture angle.

A new approach is proposed to study the nonlinear sound field radiated from a concave spherical source with a wide aperture angle. The nonlinear sound field is theoretically described by a set of equations deduced reversely from the second-order Westervelt nonlinear wave equation. To examine the validity of the theoretical model, numerical calculations are performed on a concave spherical radiator with the aperture angle wide up to 40 degrees. Numerical calculation is implemented by the finite difference time domain algorithm in the oblate spheroidal coordinate system. Numerical results are in agreement with those obtained by Kamakura's solutions.

Journal Article↗
PubMed2006

Ultrasonic characterization of porcine liver tissue at frequency between 25 to 55 MHz.

AIM: To study the relation between acoustic parameters and histological structure of biological tissue and to provide the basis for high-resolution image of biological tissues and quantitative ultrasonic diagnosis of liver disease. METHODS: Ultrasonic imaging and tissue characterization of four normal porcine liver and five cirrhotic liver tissue samples were performed using a high frequency imaging system. RESULTS: The acoustic parameters of cirrhotic liver tissue were larger than those of normal liver tissue. The sound velocity was 1577 m/s in normal liver tissue and 1631 m/s in cirrhotic liver tissue. At 35 MHz, the attenuation coefficient was 3.0 dB/mm in normal liver tissue and 4.1 dB/mm in cirrhotic liver tissue. The backscatter coefficient was 0.00431 dB/Srmm in cirrhotic liver tissue and 0.00303 dB/Srmm in normal liver tissue. The backscatter coefficient increased with the frequency. The high frequency images coincided with their histological features. CONCLUSION: The acoustic parameters, especially the sound backscatter coefficient, are sensitive to the changes of liver tissues and can be used to differentiate between the normal and pathological liver tissues. High frequency image system is a useful device for high-resolution image and tissue characterization.

Animals↗
PubMed2006

Granzyme A, which causes single-stranded DNA damage, targets the double-strand break repair protein Ku70.

Granzyme A (GzmA) induces caspase-independent cell death with morphological features of apoptosis. Here, we show that GzmA at nanomolar concentrations cleaves Ku70, a key double-strand break repair (DSBR) protein, in target cells. Ku70 is cut after Arg(301), disrupting Ku complex binding to DNA. Cleaving Ku70 facilitates GzmA-mediated cell death, as silencing Ku70 by RNA interference increases DNA damage and cell death by GzmB cluster-deficient cytotoxic T lymphocytes or by GzmA and perforin, whereas Ku70 overexpression has the opposite effect. Ku70 has two known antiapoptotic effects-facilitating DSBR and sequestering bax to prevent its translocation to mitochondria. However, GzmA triggers single-stranded, not double-stranded, DNA damage, and GzmA-induced cell death does not involve bax. Therefore, Ku70 has other antiapoptotic functions in GzmA-induced cell death, which are blocked when GzmA proteolyses Ku70.

Animals↗
PubMed2006

Syntheses, characterizations, and properties of electronically perturbed 1,1'-dimethyl-2,2'-bipyridinium tetrafluoroborates.

[reaction: see text] The syntheses of three new 2,2'-bipyridinium tetrafluoroborate sensitizers are reported. Their preliminary electrochemical and photophysical properties are compared to the properties of the more widely used pyrylium cation sensitizers. In addition, the first examples of triplet-triplet absorption spectra of 2,2'-bipyridinium ions are presented.

Journal Article↗
PubMed2006

Pancreatic cancer in the general population: Improvements in survival over the last decade.

BACKGROUND: It is unknown whether the improved survival seen at high-volume centers has been translated to all patients with pancreatic cancer. OBJECTIVE: To use the Surveillance, Epidemiology, and End Results (SEER) database to evaluate population-based trends in surgical resection and survival. METHODS: All patients diagnosed with pancreatic cancer from 1988-1999 were identified. The survival and proportion of patients undergoing surgical resection were compared for each of three equal time periods. RESULTS: There were 24,016 patients with pancreatic cancer. 19,533 had stage data available. 9% had localized, 29% had regional, and 62% had distant disease. Resection rates increased for patients with localized and regional disease over the three time periods. Survival increased for patients with regional and distant disease. For regional pancreatic cancer patients, 2-year survival increased from 9.5% to 13.5% (p < 0.0001) and from 21.5% to 28.9% following surgical resection (p = 0.002). For resected local/regional pancreatic cancer, the year of diagnosis was and independent predictor of improved survival (p = 0.0001). CONCLUSIONS: SEER patients with regional and distant pancreatic cancer have improved survival over the past decade in both unadjusted and adjusted models. The improvement is most striking for patients with regional disease and reflects increased resection rates and improved resection techniques over time.

Female↗
PubMed2006

A study on the relationship between HLA-DR, DQ antigen, and intracranial aneurysm in the Han nationality.

BACKGROUND: To investigate the relationship between HLA-DR, DQ antigen, and intracranial aneurysm in the Han nationality. METHODS: We compared the occurrence of HLA-DR and HLA-DQ antigens in patients with intracranial saccular aneurysm and in the control group by PCR and agarose gel electrophoresis. RESULTS: No statistically significant correlation between HLA-DR, HLA-DQ antigen frequency, and the pathogenesis and clinical characteristics of intracranial aneurysm has been found. CONCLUSIONS: We have not found any relationship between HLA-DR and HLA-DQ antigen frequency, haplotype frequency, and pathogenesis and clinical characteristics of intracranial aneurysm, but the patients who presented with HLA-DR53, DR52, DQ7(3), and DQ5(1) seem to be more likely to bear multiple intracranial aneurysms.

Adolescent↗
PubMed2006

External validation of medicare claims for breast cancer chemotherapy compared with medical chart reviews.

BACKGROUND: Although Medicare claims data have been increasingly used to examine the patterns and outcomes of cancer chemotherapy, their external validity has not been well studied. OBJECTIVES: We sought to validate Medicare claims for chemotherapy compared with medical chart reviews. PATIENTS AND METHODS: We completed medical chart reviews for 1228 women who were diagnosed with breast cancer at age 65 and older between 1993 and 1999 in New Mexico that were linked with Medicare claims data, achieving an estimated sensitivity of more than 90% and a 0.05 level of precision. RESULTS: Of the 150 subjects identified by Medicare claims as receiving chemotherapy within 6 months of diagnosis, 75% were confirmed by medical records as having received chemotherapy. Of the remaining 25% of cases without chart verification, (1) 33 cases had 7 or more claims for chemotherapy and also had specific chemotherapy drugs indicated in Medicare data, representing 22% (33/150) of all cases that received chemotherapy according to Medicare claims and (2) 4 cases had 1 to 6 claims for chemotherapy, representing 3% (4/150) of all cases with claims for chemotherapy. Of those 1078 subjects who did not receive chemotherapy according to Medicare claims, more than 99% were confirmed by chart reviews. Observed agreement on chemotherapy between Medicare claims and chart reviews was 94% and overall reliability (kappa) was 0.69 (95% confidence interval = 0.63-0.76). CONCLUSIONS: Of cases identified as receiving chemotherapy by Medicare claims, 97% had strong evidence and only 3% had weak evidence for receiving this therapy.

Aged↗
PubMed2006

Investigation of superharmonic sound propagation and imaging in biological tissues in vitro.

This article presents both theoretical and experimental studies on the superharmonic generation and its imaging in biological tissues. A superharmonic component is defined as a summation of the third-, fourth-, and fifth-order harmonics. A superharmonic signal is produced using an 8-mm-diam, 2.5-MHz planar piston source that is excited by eight-cycle, 2.5-MHz tone bursts. Axial and lateral field distributions of the superharmonic component and the second harmonic are first calculated based on the nonlinear KZK model and then compared with those experimentally determined at two different source pressures of 0.5 and 1 MPa. Results indicate that the amplitude of the superharmonic component can exceed that of the second harmonic, depending on the axial distance and the fundamental pressure amplitude. Also, the 3-dB beamwidth of the superharmonic component is about 23% narrower than that of the second harmonic. Additional experiments are performed in vitro using liver and fatty tissues in transmission mode and produced two-dimensional images using the fundamental, the second harmonic, and the superharmonic signals. Although the clinical applicability of this work still needs to be assessed, these results indicate that the superharmonic image quality is better than that of the other two images.

Acoustics↗
PubMed2006

Improved development by Taxol pretreatment after vitrification of in vitro matured porcine oocytes.

This study was designed to examine the effect of Taxol pretreatment on vitrification of porcine oocytes matured in vitro by an open pulled straw (OPS) method. In the first experiment, the effect of Taxol pretreatment and fluorescein diacetate (FDA) staining on parthenogenetic development of oocytes was evaluated. In the second experiment, viability, microtubule organization and embryo development of oocytes were assessed after oocytes were exposed to vitrification/warming solutions or after vitrification with or without Taxol pretreatment. The results showed that Taxol pretreatment and/or FDA staining did not negatively influence the oocyte's developmental competence after parthenogenetic activation. After being exposed to vitrification/warming solutions, the survival rate (83.3%) of the oocytes was significantly (P < 0.05) reduced as compared with that in the control (100%). Vitrification/warming procedures further reduced the survival rates of oocytes regardless of oocytes being treated with (62.1%) or without (53.8%) Taxol. The proportions of oocytes with normal spindle configuration were significantly reduced after the oocytes were exposed to vitrification/warming solutions (38.5%) or after vitrification with (10.3%) or without (4.1%) Taxol pretreatment as compared with that in control (76.8%). The rates of two-cell-stage (5.6-53.2%) embryos at 48 h and blastocysts (0-3.8%) at 144 h after activation were significantly reduced after exposure to vitrification/warming solutions or after vitrification as compared with control (90.9% and 26.6% respectively). However, the proportion of vitrified oocytes developed to two-cell stage was significantly higher when oocytes were pretreated with (24.3%) than without (5.6%) Taxol. These results indicate that pretreatment of oocytes with Taxol before vitrification helps to reduce the damage induced by vitrification and is a potential way to improve the development of vitrified porcine oocytes.

Animals↗
PubMed2006

Referral to medical oncology: a crucial step in the treatment of older patients with stage III colon cancer.

PURPOSE: Adjuvant chemotherapy for stage III colon cancer produces a substantial survival benefit, but many older patients do not receive chemotherapy. This study examines factors associated with medical oncology consultation and evaluates the impact of such consultation on chemotherapy use. PATIENTS AND METHODS: We used the Surveillance Epidemiology and End Results-Medicare linked database and identified 7,569 patients, aged 66-99, with stage III colon cancer diagnosed from 1992-1999. Modified Poisson regression was used to assess the relative risk for seeing a medical oncologist and for receiving chemotherapy as a function of individual characteristics. RESULTS: 78.08% of patients saw a medical oncologist within 6 months of diagnosis. Patients who were female, white, married, had low comorbidity scores, were diagnosed in more recent years, or had four or more positive lymph nodes were more likely to see a medical oncologist. Patients seeing a medical oncologist were 10 times more likely to receive chemotherapy (odds ratio, 9.98; 95% confidence interval, 8.21-12.14), after controlling for demographic and tumor characteristics. Chemotherapy use increased over time, but was substantially lower among older, black, and unmarried patients. CONCLUSIONS: Referral to medical oncology is one of the most important factors associated with receipt of chemotherapy among older patients with stage III colon cancer. Comorbidity decreases the likelihood of receiving chemotherapy, but its effect is the same for those who see a medical oncologist and all patients combined. Ensuring that high-risk patients are referred to medical oncology is a crucial step in quality care for patients with colon cancer.

Aged↗
PubMed2006

[Experimental study of mandibular periosteal distraction in rabbits].

OBJECTIVE: To investigate a novel technique for new bone formation--periosteal distraction osteogenesis. METHODS: A custom made periosteal distraction device was fixed to bilateral surface of the mandible in three rabbits. Periosteal distraction was performed on the left side of the mandible, the right side of the mandible served as the control. The animals were sacrificed at the end of distraction process. All the specimens were X-rayed and histologically examinated. RESULTS: All three animals survived with no obvious complications. Both in mass specimens and X-rays, there showed new bone formation on the distracted side of the mandible. In histological examinations, there was osteoblast-like cell infiltration and bone tissue formation in the distracted area. CONCLUSION: Periosteal distraction osteogenesis can provide a novel technique for the repair of bone defects.

Animals↗
PubMed2005

Information on chemotherapy and hormone therapy from tumor registry had moderate agreement with chart reviews.

BACKGROUND: Surveillance, Epidemiology, and End Results (SEER) cancer registries provide accurate information on cancer surgery and radiation, but the validity of registry data on chemotherapy and hormone therapy for breast cancer has not been well studied. We validated the registry data for chemotherapy and hormone therapy against an independent medical chart review. METHODS: We identified 1,228 women diagnosed with breast cancer at age > or = 65 in 1993-1999 in the New Mexico SEER Tumor Registry and completed medical chart reviews. RESULTS: Overall, there was moderate agreement between these two databases on chemotherapy that was received within 6 months of diagnosis. The observed agreement was 96.0%, with a kappa of 0.72 (95% confidence interval: 0.64-0.79). The sensitivity of the registry data for chemotherapy was 70.7% and the specificity was 98.2%. The positive predictive value of the registry data for chemotherapy was 77.8%. The sensitivity of the registry data for hormone therapy was 59.7%, and the specificity was 89.5%. The observed agreement for hormone therapy was 80.0%, with a kappa of 0.52 (0.46-0.57). CONCLUSION: Agreement on chemotherapy and hormone therapy between the New Mexico SEER Tumor Registry and chart reviews was moderate. The preferred approach would be to combine data from different sources to obtain more complete information.

Aged↗
PubMed2005

[Prevention and treatment of hepatitis B virus reinfection after liver transplantation].

OBJECTIVE: To study the efficacy of the protocol of combination of lamivudine with low dosage hepatitis B immuno-globulin (HBIG) to prevent HBV reinfection and of the treatment for HBV reinfection after liver transplantation. METHODS: From December 2000 to May 2003, 11 patients (follow-up is more than 1 year) had been transplanted due to HBV related end-stage liver disease or hepatocellular carcinoma. All patients received the protocol of combination of lamivudine with low dosage HBIG to prevent HBV reinfection after liver transplantation. Lamivudine was administered for more than 2 weeks. Preoperatively patients with HBV-DNA(-) and HBeAg(-) accepted HBIG 2000 IU intramuscular injection. Patients with HBV-DNA(+) or HBeAg(+) before operation accepted HBIG 4000 IU intramuscular injection, and patients with both HBV-DNA(+) and HBeAg(+) before operation accepted HBIG 6000 IU intramuscular injection. All patients took long-term lamivudine postoperatively. They accepted HBIG 800 IU/d for 1 week after transplantation. Two weeks after operation, dosage of HBIG was adjusted so that the titer of HBsAb was higher than 500 IU/L, but lower than 1000 IU/L, and this treatment lasted for 6 months. 6 months after operation, dosage of HBIG was adjusted so that tite of HBsAb higher than 300 IU/L but lower than 500 IU/L, and this treatment lasted for 6 months. One year after operation, dosage of HBIG was adjusted so that tite of HBsAb was higher than 100 IU/L but lower than 300 IU/L, and this treatment lasted for a long time. Examinations of liver function, HBV-DNA and hepatitis B were regularly taken. To observe the early turning to be negative rate, the later HBV reinfection rate, and the efficacy of the treatment for HBV reinfection. RESULTS: HBsAg, HBeAg and HBV-DNA in all patients turned to be negative in 1-4 days after operation. All patients responded to HBIG, and level of titer of HBsAb was elevated gradually. All patients was alive during the observation time. The regular examination of HBsAb showed that of HBsAb was in line with our expectation. Hepatitis B recurrence occurred in 1 patient 25 months after transplantation. Through using adefovir and adding the dosage of HBIG, the hepatitis B is in control. CONCLUSIONS: The protocol of combination of lamivudine with low dosage HBIG proved to be highly effective and safe in preventing the recurrence of HBV after liver transplantation. It also reduced the cost obviously.

Administration, Oral↗
PubMed2005

Multiwalled carbon nanotubes with chemically grafted polyetherimides.

Covalent attachment of a non-fluorinated polyetherimide onto the surface of carboxylic acid-functionalized multiwalled carbon nanotubes (MWNTs) has been achieved via grafting reactions. This confirms for the first time that the grafting reaction occurs at the nanotube surface when the carboxylic acid-functionalized MWNTs react with the polyetherimide with amine-terminated groups, through both amide and imide linkages formed at the interface between the carbon nanotubes and the polyetherimide. Additionally, an increase in the average molecular weight is detected in gel permeation chromatography when the polyetherimide is chemically attached onto the nanotubes. More interestingly, the chemical bonding at the interface provides much better interfacial adhesion and mechanical stress transfer, evidenced by a significant improvement in mechanical properties. As a result of the chemical attachment, the carbon nanotube-reinforced polyetherimide composite films have enhanced electrical conductivity, thermal deformation temperatures, and mechanical properties.

Journal Article↗
PubMed2005

Listeria-infected myeloid dendritic cells produce IFN-beta, priming T cell activation.

The intracellular bacterium Listeria monocytogenes infects dendritic cells (DC) and other APCs and induces potent cell-mediated protective immunity. However, heat-killed bacteria fail to do so. This study explored whether DC differentially respond to live and killed Listeria and how this affects T cell activation. To control for bacterial number, a replication-deficient strain, Lmdd, defective in D-alanine biosynthesis, was used. We found that DC internalize both live and heat-killed Lmdd and similarly up-regulate the expression of costimulatory molecules, a necessary step for T cell activation. However, only live Lmdd-infected DC stimulate T cells to express the early activation marker CD69 and enhance T cell activation upon TCR engagement. Infection with live, but not heat-killed, Lmdd induces myeloid DC to secrete copious amounts of IFN-beta, which requires bacterial cytosolic invasion. Exposure to high concentrations of IFN-beta sensitizes naive T cells for Ag-dependent activation.

Animals↗