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31.
In computed tomography (CT), the beam hardening effect has been known to be one of the major sources of deterministic error that leads to inaccuracy and artifact in the reconstructed images. Because of the polychromatic nature of the x-ray source used in CT and the energy-dependent attenuation of most materials, Beer's law no longer holds. As a result, errors are present in the acquired line integrals or measurements of the attenuation coefficients of the scanned object. In the past, many studies have been conducted to combat image artifacts induced by beam hardening. In this paper, we present an iterative beam hardening correction approach for cone beam CT. An algorithm that utilizes a tilted parallel beam geometry is developed and subsequently employed to estimate the projection error and obtain an error estimation image, which is then subtracted from the initial reconstruction. A theoretical analysis is performed to investigate the accuracy of our methods. Phantom and animal experiments are conducted to demonstrate the effectiveness of our approach. 相似文献
32.
An in vivo model has been developed for chronic observation of the effects of ischemia on cortical bone remodeling and perfused vascularity. Diaphragm occluders were implanted around the right common iliac artery of four rabbits and inflated to produce 10 h of ischemia to the limb. Microcirculation was monitored with intravital microscopy of injected fluorescent microspheres and FITC-Dextran 70 through a bone window, the tibial bone chamber implant (BCI). Bone resorption and apposition in the BCI were indicated with mineralization dyes. Between 2 and 12 h following release of the occluder, secondary ischemia/no-reflow and other evidence of reperfusion injury were observed. Vessel damage was suggested by abnormally high leakage of FITC-D70 from the few vessels perfused during secondary ischemia. In the weeks following occluder release perfused vasculature increased beyond pre-occlusion levels. Net bone resorption reached a maximum when vascularity passed normal levels. In order to further validate the arterial occlusion model for osteonecrosis, techniques for (1) confirming bone death and (2) detecting increased leukocyte adherence to endothelial cells were added. The dead cell stain Ethidium homodimer-1 was used to tag dead osteocytes immediately after occlusion and produced a measure designated osteonecrosis index. To detect leukocytes adhering to vessel walls, carboxyfluorescein diacetate, succinimidyl ester was injected at occluder release. An increase in the number of adherent leukocytes was detected. © 1999 Biomedical Engineering Society.
PAC99: 8764Rr, 8717-d, 8719Tt 相似文献
33.
34.
Changes of lymphoproliferative responses of T cell subsets to allergen and mitogen after hyposensitization in asthmatic children 总被引:3,自引:0,他引:3
K H Hsieh 《The Journal of allergy and clinical immunology》1984,74(1):34-40
The cellular basis for the mechanism of hyposensitization was studied by examining the changes in the numbers and proliferative responses to house dust and phytohemagglutinin (PHA) of T cell subsets of 25 house dust-sensitive asthmatic children before and 1 yr after hyposensitization. The results demonstrated (1) No difference was observed in the mean percentages of OKT3+ cells and OKT8+ cells between normal subjects and patients both before and after hyposensitization, but the absolute numbers of both types of cells in untreated patients were much higher than in the normal subjects or treated patients because of relative lymphocytosis in the untreated patients, (2) While the mean percentage of OKT4+ cells of the untreated patients was lower than that of the normal subjects (40.8 +/- 4.7% vs 44.8 +/- 4.5%, p less than 0.007), the absolute number was higher in the former than that in the latter because of the same reason. After hyposensitization, the mean percentage of the OKT4+ cells was slightly increased, and (3) Hyposensitization was able to restore the proliferative capability to PHA and depress the sensitivity to specific allergen of OKT4+ cells on the one hand and augment the proliferative responses to both PHA and allergen of OKT8+ cells on the other. Taken together, these immunologic changes may explain partly the suppressed IgE-antibody production and decreased lymphoproliferative response to specific allergen after hyposensitization. 相似文献
35.
Hwang JL Huang LW Hsieh BC Tsai YL Huang SC Chen CY Hsieh ML Chen PH Lin YH 《Human reproduction (Oxford, England)》2003,18(1):45-49
BACKGROUND: The introduction of GnRH antagonists such as cetrorelix acetate has made possible the simplification of ovarian stimulation. However, the most effective protocol for their administration has not yet been clearly defined. METHODS: Forty women with male-factor infertility undergoing 40 ICSI cycles were included in the study. Clomiphene citrate at 100 mg a day was given from cycle day 3 through day 7. hMG at 150 IU was given on cycle days 4, 6 and 8, and was adjusted from day 9 according to the follicular and hormone responses. Cetrorelix acetate at 2.5 mg was administered when the leading follicle reached 14 mm. The remaining 0.5 mg was divided into two 0.25 mg injections for possible later use. Serum FSH, LH, estradiol and progesterone levels were measured daily from the day of cetrorelix acetate injection until hCG was given. RESULTS: Serum LH level was suppressed effectively for 4 days. Four patients (10%) needed one or two additional injections of 0.25 mg cetrorelix acetate. No premature LH surge was detected in any of the women treated. Sixteen women became pregnant (40%), of which 14 pregnancies (35%) were ongoing at the time of writing. CONCLUSIONS: This study demonstrates that this new protocol is feasible for couples with male-factor infertility undergoing ICSI. 相似文献
36.
Yu-Li Liu Cathy Shen-Jang Fann Chih-Min Liu Jer-Yuarn Wu Shuen-Iu Hung Hung-Yu Chan Jiahn-Jyh Chen Chin-Yu Lin Shih-Kai Liu Ming H Hsieh Tzung-Jeng Hwang Wen-Chen Ouyang Chun-Ying Chen Jin-Jia Lin Frank Huang-Chih Chou Ching-Mo Chueh Wei-Ming Liu Ming-Min Tsuang Stephen V Faraone Ming T Tsuang Wei J Chen Hai-Gwo Hwu 《American journal of medical genetics. Part B, Neuropsychiatric genetics》2006,(4):418-420
Several studies have suggested that the regulator of G-protein signaling 4 (RGS4) may be a positional and functional candidate gene for schizophrenia. Three single nucleotide polymorphisms (SNP) located at the promoter region (SNP4 and SNP7) and the intron 1 (SNP18) of RGS4 have been verified in different ethnic groups. Positive results have been reported in these SNPs with different numbers of SNP combinatory haplotypes. In this study, these three SNP markers were genotyped in 218 schizophrenia pedigrees of Taiwan (864 individuals) for association analysis. Among these three SNPs, neither SNP4, SNP7, SNP18 has shown significant association with schizophrenia in single locus association analysis, nor any compositions of the three SNP haplotypes has shown significantly associations with the DSM-IV diagnosed schizophrenia. Our results fail to support the RGS4 as a candidate gene for schizophrenia when evaluated from these three SNP markers. 相似文献
37.
Heng-Shuen Chen Fei-Ran Guo Chien-Tsai Liu Yue-Joe Lee Jye-Horng Chen Chia-Chin Lin Sheng-Mou Hou Bor-Shen Hsieh 《International journal of medical informatics》1998,50(1-3):59-68
National Taiwan University College of Medicine (NTUCM) introduced small groups of teaching and basic-clinical integrated courses for medical students in 1992. By using computer network and multimedia techniques, this study tried to overcome barriers to learning in small group teaching. The Department of Medical Informatics of NTUCM established campus networking and computer classrooms and provided Internet and intranet network services including mail, netnews, bulletin board systems (BBS), world wide web (WWW), gopher, ftp and local file servers. To implement an interactive learning environment, the authors first tried mail lists, newsgroups and BBS. Next an integrated learning system prototype on the WWW was developed to provide functions including online syllabus, discussion boards simulated to BBS, online talk, interactive case studies, virtual classroom with video on demand (VOD) and Internet medical resources. The results showed that after the medical students completed the required course of medical informatics and had good network access using a network to communicate with each other became a daily practice. In the future, the system will extend to the tutoring of clinical practice and continuing medical education. The authors expect a national medical education network and more international cooperation and exchange. 相似文献
38.
OBJECTIVE: A pilot study to determine health belief factors associated with osteoporosis prevention behaviors in peri-and postmenopausal women. DESIGN: We administered a survey to a convenience sample of 60 women aged 40-95 years old in an urban family practice center and an associated retirement community. The self-reported questionnaire addressed demographics, osteoporosis risk factors, current preventive behaviors for osteoporosis, and health beliefs. RESULTS: The majority of women (89%) believed that osteoporosis is a serious condition, but only 29% perceived a personal susceptibility. Women were less concerned about osteoporosis when compared with cancer, cardiovascular disease, and neurologic disorders. Only 40% of women were taking active measures to prevent osteoporosis. There was no significant relationship between active osteoporosis prevention behaviors and five health belief factors (motivation, barrier, active participant in health care, frustration, and benefit) (p >or= 0.43). However, active behaviors to prevent osteoporosis were found to correlate with the single item "I am worried about developing osteoporosis" (p = 0.03). Most women surveyed would be willing to exercise and take calcium and a multivitamin to prevent osteoporosis. CONCLUSION: Few women are taking active measures to prevent osteoporosis despite their belief that it is a serious condition. Our data suggest that most women do not perceive a personal susceptibility to the disease. Only women who reported actively worrying about developing osteoporosis were more likely to be engaged in significant osteoporosis preventive behaviors. 相似文献
39.
Burrell JH Boyn AM Kumarasamy V Hsieh A Head SI Lumbers ER 《The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology》2003,274(2):952-961
Right (RVFW) and left (LVFW) ventricular free wall cardiac myocytes were collected from 25 fetal sheep aged 77-146 days gestation (term = 150 days gestation), six saline-infused catheterized fetal sheep (129 GD), and five lambs to measure gestational changes in uni- and binucleated cardiac myocyte numbers and cell volumes by confocal microscopy. At 77 days gestation, 2% of the myocytes were binucleated, which increased to 50% at 135 days gestation and 90% at 4-6 weeks after birth. RVFW uni- and binucleated myocytes were larger than those in the LVFW, and cell volumes of RVFW uni- and binucleated and LVFW binucleated myocytes (but not LVFW uninucleated myocytes) increased with gestation. Before birth, the approximate number of myocytes was greater in the LVFW than in the RVFW (P < 0.001). Before 110 GD, cardiac growth appeared to be due to myocyte hyperplasia, as approximate myocyte numbers and VFW weight increased at the same rate. After 110 days gestation, the approximate myocyte number/g VFW weight decreased, which suggests that myocyte hypertrophy, as well as hyperplasia, was occurring in association with the appearance of a greater proportion of binucleated cells after that time. By 4-6 weeks of age, there was marked hypertrophy of myocytes and an apparent reduction in myocyte number. 相似文献
40.