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Zhe Chen

Publications and source records attributed to Zhe Chen.

At least 37 records · Page 2Linked to original sources
PubMed2005

Performance evaluation of functional medical imaging compression via optimal sampling schedule designs and cluster analysis.

In previous work we have described a technique for the compression of positron emission tomography (PET) image data in the spatial and temporal domains based on optimal sampling schedule designs (OSS) and cluster analysis. It can potentially achieve a high data compression ratio greater than 80:1. However, the number of distinguishable cluster groups in dynamic PET image data is a critical issue for this algorithm that has not been experimentally analyzed on clinical data. In this paper, the problem of experimentally determining the ideal cluster number for the algorithm for PET brain data is addressed.

Algorithms↗
PubMed2005

The cocktail party problem.

This review presents an overview of a challenging problem in auditory perception, the cocktail party phenomenon, the delineation of which goes back to a classic paper by Cherry in 1953. In this review, we address the following issues: (1) human auditory scene analysis, which is a general process carried out by the auditory system of a human listener; (2) insight into auditory perception, which is derived from Marr's vision theory; (3) computational auditory scene analysis, which focuses on specific approaches aimed at solving the machine cocktail party problem; (4) active audition, the proposal for which is motivated by analogy with active vision, and (5) discussion of brain theory and independent component analysis, on the one hand, and correlative neural firing, on the other.

Attention↗
PubMed2005

A novel model-based hearing compensation design using a gradient-free optimization method.

We propose a novel model-based hearing compensation strategy and gradient-free optimization procedure for a learning-based hearing aid design. Motivated by physiological data and normal and impaired auditory nerve models, a hearing compensation strategy is cast as a neural coding problem, and a Neurocompensator is designed to compensate for the hearing loss and enhance the speech. With the goal of learning the Neurocompensator parameters, we use a gradient-free optimization procedure, an improved version of the ALOPEX that we have developed, to learn the unknown parameters of the Neurocompensator. We present our methodology, learning procedure, and experimental results in detail; discussion is also given regarding the unsupervised learning and optimization methods.

Algorithms↗
PubMed2005

Serum protein fingerprinting coupled with artificial neural network distinguishes glioma from healthy population or brain benign tumor.

To screen and evaluate protein biomarkers for the detection of gliomas (Astrocytoma grade I-IV) from healthy individuals and gliomas from brain benign tumors by using surface enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF-MS) coupled with an artificial neural network (ANN) algorithm. SELDI-TOF-MS protein fingerprinting of serum from 105 brain tumor patients and healthy individuals, included 28 patients with glioma (Astrocytoma I-IV), 37 patients with brain benign tumor, and 40 age-matched healthy individuals. Two thirds of the total samples of every compared pair as training set were used to set up discriminating patterns, and one third of total samples of every compared pair as test set were used to cross-validate; simultaneously, discriminate-cluster analysis derived SPSS 10.0 software was used to compare Astrocytoma grade I-II with grade III-IV ones. An accuracy of 95.7%, sensitivity of 88.9%, specificity of 100%, positive predictive value of 90% and negative predictive value of 100% were obtained in a blinded test set comparing gliomas patients with healthy individuals; an accuracy of 86.4%, sensitivity of 88.9%, specificity of 84.6%, positive predictive value of 90% and negative predictive value of 85.7% were obtained when patient's gliomas was compared with benign brain tumor. Total accuracy of 85.7%, accuracy of grade I-II Astrocytoma was 86.7%, accuracy of III-IV Astrocytoma was 84.6% were obtained when grade I-II Astrocytoma was compared with grade III-IV ones (discriminant analysis). SELDI-TOF-MS combined with bioinformatics tools, could greatly facilitate the discovery of better biomarkers. The high sensitivity and specificity achieved by the use of selected biomarkers showed great potential application for the discrimination of gliomas patients from healthy individuals and gliomas from brain benign tumors.

Adult↗
PubMed2005

Combination of small interfering RNAs mediates greater inhibition of human hepatitis B virus replication and antigen expression.

OBJECTIVES: To evaluate the inhibitory effect mediated by combination of small interfering RNAs (siRNAs) targeting different sites of hepatitis B virus (HBV) transcripts on the viral replication and antigen expression in vitro. METHODS: (1) Seven siRNAs targeting surface (S), polymerase (P) or precore (PreC) region of HBV genome were designed and chemically synthesized. (2) HBV-producing HepG2.2.15 cells were treated with or without siRNAs for 72 h. (3) HBsAg and HBeAg in the cell culture medium were detected by enzyme-linked immunoadsorbent assay. (4) Intracellular viral DNA was quantified by real-time PCR (Polymerase Chain Reaction). (5) HBV viral mRNA was reverse transcribed and quantified by real-time PCR. (6) The change of cell cycle and apoptosis was determined by flow cytometry. RESULTS: Our data demonstrated that synthetic small interfering RNAs (siRNAs) targeting S and PreC gene could efficiently and specifically inhibit HBV replication and antigen expression. The expression of HBsAg and HBeAg and the replication of HBV could be specifically inhibited in a dose-dependent manner by siRNAs. Furthermore, our results showed that the combination of siRNAs targeting various regions could inhibit HBV replication and antigen expression in a more efficient way than the use of single siRNA at the same final concentration. No apoptotic change was observed in the cell after siRNA treatment. CONCLUSION: Our results demonstrated that siRNAs exerted robust and specific inhibition on HBV replication and antigen expression in a cell culture system and combination of siRNAs targeting different regions exhibited more potency.

Apoptosis↗
PubMed2005

Relative biological effectiveness of 103Pd and 125I photons for continuous low-dose-rate irradiation of Chinese hamster cells.

Monolayers of Chinese hamster lung cells (CCL-16) in a polystyrene phantom were irradiated in vitro by 103Pd and 125I sources at dose rates of 6 to 72 cGy/h. Cell survival curves for acute high-dose-rate irradiation (over 30 Gy/h) were also measured using nearly monoenergetic X-ray beams which were designed to simulate the mean energies of photons emitted by 125I and 103Pd and also using a clinical 250 kVp X-ray beam. A profound dose-rate effect is observed over the dose-rate range of 6 to 20 cGy/h. An inverse dose-rate effect was observed for both radionuclides, with its onset occurring at a dose rate of about 20-30 cGy/h. The average RBE of 103Pd relative to 125I was determined to be 1.45 +/- 0.07, 1.41 +/- 0.07, 0.70 +/- 0.07 and 1.49 +/- 0.07 at dose rates of 6.9, 12.6, 19.0 and 26.7 cGy/h, respectively. Because 103Pd implants are generally prescribed at a higher initial dose rate (21 cGy/h) than the corresponding 125I implants (7 cGy/h), the effects of both dose rate and photon energy on biological response must be considered together. For the CCL-16 cells, the RBE of 103Pd at 19.0 cGy/h relative to that of 125I at 6.9 cGy/h was estimated to be 2.3 +/- 0.5.

Animals↗
PubMed2005

[Study of a qualitative diagnostic criterion for basic syndromes of traditional Chinese medicine in patients with primary liver cancer].

OBJECTIVE: To work out a qualitative diagnostic criterion for basic syndromes of traditional Chinese medicine in patients with primary liver cancer. METHODS: Based on the collection and analysis of related medical literature, clinical investigation, and experts' discussion, a preliminary qualitative diagnostic criterion for basic syndromes of traditional Chinese medicine in patients with primary liver cancer was formulated. Then it was used in clinic to be verified and revised repeatedly till it was improved to be a satisfied formal criterion. RESULTS: The basic syndromes listed in the qualitative diagnostic criterion for basic syndromes in patients with primary liver cancer consisted of two parts: excessive syndromes, including the syndromes of stagnation of qi, blood stasis, excess-heat and dampness, and deficient syndromes, including the syndromes of deficiency of qi, deficiency of blood, deficiency of yin and deficiency of yang. Each of the above syndromes could be diagnosed according to specific combination of its corresponding symptoms or signs. The clinical verification results showed that the total matching ratio was 73.92% between the diagnoses made according to the criterion and the diagnoses acquired from the experts' experience. CONCLUSIONS: The qualitative diagnostic criterion for basic syndromes of traditional Chinese medicine in patients with primary liver cancer is coincident with the experts' clinical practice. However, it needs to be further studied.

Adult↗
PubMed2005

[Ginsenosides combined with dexamethasone in preventing and treating postembolization syndrome following transcatheter arterial chemoembolization: a randomized, controlled and double-blinded prospective trial].

OBJECTIVE: To observe the effect of ginsenosides (GS) and low dose glucocorticoid in preventing and treating the postembolization syndrome following transcatheter arterial chemoembolization (TACE). METHODS: Eighty patients with primary liver carcinoma were randomly divided into 4 double-blinded groups, with 20 patients in each group. Patients in groups A, B, C, D were treated with placebo, dexamethasone (Dex), GS, Dex and GS, respectively. The changes of clinical symptoms and laboratory tests after TACE were observed. RESULTS: Dex combined with GS markedly decreased the occurrence ratio and lasting time of the symptoms such as nausea, vomiting, fever and pain, and protected the function of liver as compared with the placebo (P<0.05). Single use of Dex or GS improved some symptoms as compared with the placebo, but it was not as good as the combination of Dex and GS. CONCLUSION: Dex combined with GS can effectively prevent and treat the postembolization syndrome following TACE.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

Relationship between endothelial dysfunction and serum homocysteine in patients with coronary lesions.

OBJECTIVE: To investigate the relationship between vascular endothelial dysfunction and serum homocysteine (HCY) level in patients with coronary lesions. METHODS: Serum HCY, serum nitric oxide (NO), plasma endothelin-1 (ET-1), and circulation endothelial cell (CEC) were measured in 76 patients who received coronary angiography. Fifty-four patients with a stenosis of 50% or more at least in one coronary atery were as coronary artery disease (CAD) group. Other 22 cases with no recognizable plaque and/or stenosis were as control group. HCY level was detected using an enzyme immunoassay kit. NO concentration was measured using a nitrate reductase kit. Radio-immunoassay was applied to analyse the ET-1 level, and CEC was measured by flow cytometry. RESULTS: The levels of HCY, ET-1, and CEC in patients with coronary lesions were significantly increased in comparison with control group (P < 0.01), while NO level in CAD group was significantly lower compared with that in control (P < 0.01). Using a multivariate stepwise regression analysis, HCY level had a positive correlation with ET-1 level (r = 0.420, P < 0.05) and CECs number (r = 0.423, P < 0.05); and had a negative correlation with NO/ET-1 (r = -0.403, P < 0.05). But there was no significant correlation between HCY and NO levels. CONCLUSIONS: HCY might lead to endothelial cell injury, which would provide a plausible mechanism for the relationship between hyperhomocysteinemia and development of coronary artery disease. HCY can be considered as a predictor for preliminary or active coronary lesion.

Aged↗
PubMed2005

[Inhibition of hepatitis B virus by combined siRNAs in vitro].

Small interfering RNA (siRNA) technology is a powerful tool to knockdown gene expression in mammalian cells including genes of viral origin. To study the inhibition of hepatitis B virus (HBV) by combined siRNAs in vitro, HepG2 2.2.15, a human hepatoblastoma cell that constitutively produces HBV particles, was transfected with 12 siRNAs that were designed to target different regions on HBV genome. Enzyme-linked immunosorbent assay was used to measure the HBsAg and HBeAg levels in culture media, and HBV replication was determined by real-time quantitative PCR. The results showed that HBV replication could be inhibited by treatment with these siRNAs in a dose-dependent manner. The expression of HBsAg was inhibited by 80% and 90% with 80 nmol/L single siRNA treatment and 20 nmol/L combined siRNAs treatment, respectively. HBeAg was inhibited by about 60% with single siRNA treatment, and the inhibition didn't increase much in the case of combined siRNAs treatment. HBV replication was inhibited by 90% with 80 nmol/L single siRNA treatment or 20 nmol/L combined siRNAs treatment. These data provide solid evidence for developing new approaches in HBV treatment with combined siRNAs.

Enzyme-Linked Immunosorbent Assay↗
PubMed2004

Honokiol induces apoptosis through p53-independent pathway in human colorectal cell line RKO.

AIM: To investigate the signal pathway of honokiol-induced apoptosis on human colorectal carcinoma RKO cells and to evaluate whether p53 and p53-related genes were involved in honokiol-treated RKO cells. METHODS: Cell cycle distribution and subdiploid peak were analyzed with a flow cytometer and DNA fragment with electrophoresis on agarose gels. Transcriptional level of Bax, Bcl-2, Bid and Bcl-xl was accessed by RT-PCR. Western blotting was used to measure p53 protein expression and other factors related to apoptosis. Proliferation inhibition of two cell lines (RKO, SW480) with high expression of p53 and one cell line with p53 negative expression (LS180) was monitored by MTT assay. RESULTS: Honokiol induced RKO cell apoptosis in a dose-dependent manner. The mRNA expression level and protein level of Bid were up-regulated while that of Bcl-xl was down-regulated, but no changes in Bax and Bcl-2 were observed. Western blotting showed p53 expression had no remarkable changes in honokiol-induced RKO cell apoptosis. LS180 cells treated with honokiol exhibited apparent growth inhibition like RKO cells and Sw480 cells. CONCLUSION: Honokiol can induce RKO cells apoptosis through activating caspase cascade by p53-indepenent pathway.

Antineoplastic Agents, Phytogenic↗
PubMed2004

Matching the dosimetry characteristics of a dual-field Stanford technique to a customized single-field Stanford technique for total skin electron therapy.

PURPOSE: To compare the dosimetry characteristics of a customized single-field and a matching dual-field electron beam for total skin electron therapy (TSET) within the framework of the Stanford technique. To examine and quantify its impact on patient dosimetry. METHODS AND MATERIALS: Two characteristically different electron beams were used for TSET employing the Stanford technique: a single-field beam created from a pencil beam of electrons passing through 7 meters of air and a dual-field beam created from two heavily scattered electron beams directed at oblique angles to patients. The dosimetry characteristics of the two beams were measured by using ionization chambers, radiographic films, and thermal luminescent detectors. The impact of beam characteristic on patient dosimetry was quantified on both anthromorphic phantoms and on patients. Treatment protocols aimed at matching the patient dose between the two systems were established on the basis of these and other measurements. RESULTS: The dual-field beam was matched to the single-field beam, resulting in approximately the same mean energy (approximately 4.0 MeV) and most probable energy (approximately 4.5 MeV) at their respective treatment source-to-patient-surface distance (SSD). The depth dose curves on the beam axis were nearly identical for both beams. X-ray contamination on the beam axis was 0.43% for the dual-field beam, slightly higher than that (0.4%) of the single-field beam. The beam uniformity, however, was quite different: the dual-field beam was more uniform in the vertical direction but was worse in the lateral direction compared to the single-field beam. For a TSET treatment using the Stanford technique, the composite depth dose curves were nearly identically at the level of beam axis: with an effective depth of maximum buildup (d(max)) at approximately 1 mm below the skin surface and the depth to 80% depth dose at around 6 mm. The overall X-ray contamination was approximately 1.0% and 1.2% for the single-field and dual-field system, respectively. Away from the beam axis level, treatment using either beam was able to deliver over 90% of prescription dose to the main body surfaces. For body surfaces tangential to the beam axis (e.g., top of head and shoulders), the dose was low especially when using the dual-field beam. By adding boost radiation to the tangential surfaces and by adjusting the planned shielding for critical structures, the total dose to the patient over a complete course of TSET treatment could be matched closely for the two systems. CONCLUSIONS: Although the depth doses can be matched at the level of the beam axis, there exist some characteristic differences in the angular distribution of the electrons between the large SSD single-field beam and the short SSD dual-field beam. These differences resulted in lower dose delivered to "tangential" body surfaces and to body structures that extended farther laterally when using the dual-field beam. However, by adjusting the treatment protocol regarding the boost irradiation and planned shielding, the total dose to patients from a complete course of TSET treatment using the dual-field beam can be matched to that given by the single-field beam. Special attention should be paid to the dosimetry at the "tangential" body surfaces when commissioning a dual-field TSET system.

Electrons↗
PubMed2004

Development of a rat solid tumor model for continuous low-dose-rate irradiation studies using 125I and 103Pd sources.

PURPOSE: To develop an experimental technique for studying the radiobiology of continuous low-dose-rate irradiation (CLDRI) using clinical brachytherapy sources emitting low energy photons for a rat solid tumor model. METHODS AND MATERIALS: BA1112 tumors were grown between the ears of 14-week-old male WAG/Rij rats by interdermal inoculation. A radioactive source afterloading system, which consists of a lightweight helmet sutured to the rat and a nine-source polystyrene applicator, was fabricated for in vivo tumor irradiation by (125)I and (103)Pd brachytherapy sources. This system has a 12 x 12 mm opening in the center to accommodate the tumor and its growth during irradiation (the diameter of a typical BA1112 tumor was about 6 mm when radiation was applied). The spatial locations of the nine sources were optimized to produce an as uniform as possible three-dimensional dose distribution to the central portion of the applicator for both the (125)I and (103)Pd sources. Absolute dose delivered by the applicator was verified by point dose measurements using calibrated TLD in a polystyrene phantom that mimics the scattering environment of the tumor on the rat. RESULTS: The feasibility of tumor cure experiments using the experimental technique presented in this work was demonstrated. The technique was used to study the influence of initial dose rate on the in vivo tumor cure probability of BA1112 tumors irradiated by (125)I and (103)Pd sources at dose rates varying from 8-20 cGy/h. The technique was also used for studying the in vitro tumor cell survival following in vivo CLDRI irradiation of the tumor. CONCLUSION: An experimental technique using an in vivo tumor model has been developed for studying the radiobiological effects of continuous low-dose-rate irradiations using (125)I sources alone, (103)Pd sources alone, or a mixture of (125)I and (103)Pd sources.

Animals↗
PubMed2004

A technique to re-establish dose distributions for previously treated brain cancer patients in external beam radiotherapy.

Tumor recurrences or new tumors may develop after irradiation of local lesion(s) in the brain, and additional radiotherapy treatments are often needed for previously treated patients. It is critical to re-establish the dose distributions delivered during the previous treatment in the current patient geometry, so that the previous dose distributions can be accurately taken into consideration in the design of the current treatment plan. The difficulty in re-establishing the previous treatment dose distributions in the current patient geometry arises from the fact that the patient position at the time of reirradiation is different from that at the previous treatment session. Simple re-entry of the previous isocenter coordinates, gantry, and couch and collimator angles into the new treatment plan would result in incorrect beam orientations relative to the new patient anatomy, and therefore incorrect display of the previous dose distributions on the current patient anatomy. To address this issue, a method has been developed so that the previous dose distributions can be accurately re-established in the framework of the current brain treatment. The method involves 3 matrix transformations: (1) transformation of beams from machine coordinate system to patient coordinate system in the previous treatment; (2) transformation of beams from patient coordinate system in the previous treatment to patient coordinate system in the current treatment; and (3) transformation of beams from patient coordinate system in the current treatment to machine coordinate system. The transformation matrices used in the second transformation are determined by registration using a mutual information-based algorithm with which the old and new computed tomography (CT) scan sets are registered automatically without human interpretation. A series of transformation matrices are derived to calculate the isocenter coordinates, the gantry, couch, and collimator angles of the beams for the previous treatment in the current patient geometry, and the previous dose distributions are re-established on the current CT images. The method has been proven to be successful and robust.

Algorithms↗
PubMed2004

Having the memory of an elephant: long-term retrieval and the use of analogues in problem solving.

The authors report 4 experiments exploring long-term analogical transfer from problem solutions in folk tales participants heard during childhood, many years before encountering the target problems. Substantial culture-specific analogical transfer was found when American and Chinese participants' performance was compared on isomorphs of problems solved in European versus Chinese folk tales. There was evidence of transfer even among participants who did not report being reminded of the source tale while solving the target problem. Comparisons of different versions of a target problem indicated that similarity of solution tool affected accessing, mapping, and executing components of problem solving, whereas similarity of goal object had only a moderate effect on accessing. High school students also evidenced greater transfer than did middle school students.

Adolescent↗
PubMed2004

Schema induction in problem solving: a multidimensional analysis.

The present research examined the processes of schema formation in problem solving. In 4 experiments, participants experienced a series of tasks analogous to A. S. Luchins' (1942) water jar problems before attempting to solve isomorphic target problems. Juxtaposing illustrative source instances varying in procedural features along multiple dimensions promoted the construction of a general schema that facilitated solving an isomorphic problem requiring a novel procedure. Exposure to less variant problems led to faster initial learning, but narrower and fixed schemas (mental set), whereas exposure to variant procedures led to slower initial learning, but broader and more flexible schemas. The findings support the dimensional specificity hypothesis: Generalization along 1 dimension facilitates transfer to a target problem differing from the source problems in that dimension.

Humans↗