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Biomedical subjects

B Zhen

Publications and source records attributed to B Zhen.

28 records · Page 2Linked to original sources
PubMed1997

[Effects of a high-pass filter on the Doppler blood flow signal].

A high-pass filter is used to remove the large signals scattered or reflected from stationary and slow moving objects in many clinical CW Doppler units. theoretical results are presented that such a filter will lead to overestimate of the mean velocity of Doppler blood flow. As for different frequency signals, high-pass filter have different amplitudes and phase responses, consequently, nonlinear phase shift is produced. It is proved by computer experiment that nonlinear phase shift caused by high-pass filter hardly has any effects on Doppler flow power spectrum if the high-pass filter does not affect the amplitudes of signals.

Blood Flow Velocity↗
PubMed1996

Machining risk of beryllium disease and sensitization with median exposures below 2 micrograms/m3.

We examined the prevalence of beryllium sensitization in relation to work process and beryllium exposure measurements in a beryllia ceramics plant that had operated since 1980. We interviewed 136 employees (97.8% of the workforce), ascertained beryllium sensitization with the beryllium lymphocyte proliferation blood test, and reviewed historical industrial hygiene measurements. Of eight beryllium-sensitized employees (5.9%), six (4.4% of participating employees) had granulomatous disease on transbronchial lung biopsy. Machinists had a sensitization rate of 14.3% compared to a rate of 1.2% among other employees. Machining had significantly higher general area and breathing zone measurements than did other processes in the time period in which most beryllium-sensitized cases had started machining work. Daily weighted average (DWA) estimates of exposure for matching processes also exceeded estimates for other work processes in that time period, with a median DWA of 0.9 microgram/m3. Machining process DWAs accounted for the majority of DWAs exceeding the 2.0 micrograms/m3 OSHA standard, with 8.1% of machining DWAs above the standard. We conclude that lowering machining process-related exposures may be important to lowering risk of beryllium disease.

Air Pollutants, Occupational↗
PubMed1996

Risk of silicosis in a Colorado mining community.

We investigated exposure-response relations for silicosis among 134 men over age 40 who had been identified in a previous community-based random sample study in a mining town. Thirty-two percent of the 100 dust-exposed subjects had radiologic profusions of small opacities of I/O or greater at a mean time since first silica exposure of 36.1 years. Of miners with cumulative silica exposures of 2 mg/m3-years or less, 20% had silicosis; of miners accumulating > 2 mg/m3 years, 63% had silicosis. Average silica exposure was also strongly associated with silicosis prevalence rates, with 13% silicotics among those with average exposure of 0.025-0.05 mg/m3, 34% among those with exposures of > 0.05-0.1 mg/m3, and 75% among those with average exposures > 0.1 mg/m3. Logistic regression models demonstrated that time since last silica exposure and either cumulative silica exposure or a combination of average silica exposure and duration of exposure predicted silicosis risk. Exposure-response relations were substantially higher using measured silica exposures than using estimated silica exposures based on measured dust exposures assuming a constant silica proportion of dust, consistent with less exposure misclassification. The risk of silicosis found in this study is higher than has been found in workforce studies having no follow-up of those leaving the mining industry and in studies without job title-specific silica measurements, but comparable to several recent studies of dust exposure-response relationships which suggest that a permissible exposure limit of 0.1 mg/m3 for silica does not protect against radiologic silicosis.

Adult↗
PubMed1995

Endemic work-related febrile respiratory illness among construction workers.

Construction workers building Denver International Airport (DIA) reported work-related respiratory and flulike symptoms of several months duration. We performed a cross-sectional interview study of 495 randomly selected DIA workers from six contractors in comparison with preplacement workers. We defined cases as workers with two work-attributed lower respiratory symptoms and one work-attributed systemic symptom. Case rates were significantly higher among DIA workers (34%) compared with those who had never worked at DIA (2%). Risk factors for illness included exposure to fireproofing (OR, 4.21; 95% CI, 1.95-9.08), work in tunnels and adjoining areas (OR, 3.07; 95% CI, 1.84-5.12), length of DIA employment (OR, 0.65; 95% CI, 0.46-0.92), and preexisting bronchitis (OR, 2.43; 95% CI, 1.17-5.05). Our industrial hygiene investigation revealed alkaline dust (pH 11) present at a worksite associated with elevated risk of illness, and we identified airborne Penicillium mold widely distributed indoors at DIA. Clinical evaluation of 26 self-identified symptomatic DIA employees, including bronchoalveolar lavage and biopsy in 10, revealed work-related asthma in three workers and histologic evidence of chronic bronchitis in four who had never smoked. We concluded that future investigations of endemic work-related febrile respiratory illness among construction workers should evaluate its association with indoor exposure to dusts from alkaline fireproofing, Penicillium mold, mycotoxins, and bacterial bioaerosols.

Adult↗
PubMed1995

Are axillary recurrence and overall survival affected by axillary extranodal tumor extension in breast cancer? Implications for radiation therapy.

PURPOSE: To determine the overall survival and local recurrence significance of axillary lymph node extranodal tumor extension (ETE) and whether axillary/chest-wall irradiation influenced any of these outcomes. MATERIALS AND METHODS: The records of 81 breast cancer patients treated with radical or modified radical mastectomy at a single surgical practice were eligible for study. Thirty-four patients had ETE: 17 with focal ETE (< 10 x high-power field) and 17 with extensive ETE (> 10 x high-power field). RESULTS: With a median follow-up duration of 92 months, only two patients had an axillary recurrence (2%): one had focal ETE and one had no ETE. Neither of these patients received axillary radiation therapy. Overall survival and recurrence-free survival were significantly decreased with ETE in patients whether axillary radiation therapy had been administered or not. Analysis showed that the age of the patient correlated significantly with extensive ETE (P = .04) and that the number of positive lymph nodes (< or = three v > three) correlated significantly with ETE (whether focal or extensive) (P = .0001). A multivariate analysis of extranodal tumor extension and number of positive lymph nodes showed that ETE was associated with decreased survival (P = .05), although to a lesser degree than number of positive lymph nodes (P = .003). CONCLUSION: These results show that ETE is associated with decreased survival and increased recurrence rates regardless of the extent of the radiation therapy field. Also, ETE does not necessarily indicate a significantly increased incidence of axillary recurrence. Therefore, axillary irradiation based on this pathologic finding may not be indicated.

Age Factors↗
PubMed1995

Does administration of chemotherapy before radiotherapy in breast cancer patients treated with conservative surgery negatively impact local control?

PURPOSE: To determine if a delay of irradiation to the intact breast for administration of adjuvant chemotherapy results in increased local recurrence in breast cancer. PATIENTS AND METHODS: The records of 262 women with 264 cases of breast cancer were reviewed. Group I contained 105 patients treated with conservative surgery, chemotherapy, and radiotherapy. Group II contained 157 patients (used as a concurrent control) treated with conservative surgery and radiotherapy only. Eighty-nine percent of subjects in group I received all chemotherapy before radiotherapy. Fifty-eight percent of patients received hormone therapy. Seventy-one percent of patients had negative surgical margins, and 74% had negative lymph nodes. For group I, conservative surgery-radiotherapy intervals in months were less than 1 (five, 5%), > or = 1 to less than 3 (10, 9%), > or = 1 to less 6 (48, 46%), and > or = 6 (42, 40%), mean of 5. For group II, the intervals were less than 1 (20, 13%), > or = 1 to less than 3 (123, 79%), > or = 3 to less than 6 (11, 7%), and > or = 6 (two, 1%), mean of 1.5. RESULTS: Thirty patients (11.5%) have disease recurrence (19 distant [6%] and 12 local [5%]). There were no significant differences in local recurrence (group I, four [4%]; group II, eight [5%]; difference not significant). There were no significant differences in local recurrence in any surgery-radiotherapy interval within each group. Although we found marginal increases in the percentage of local recurrences in group I patients (with prolonged surgery-radiotherapy intervals) who had positive margins, positive lymph nodes, and tumor size more than 2 cm versus group II (without prolonged surgery-radiotherapy intervals), these results were not significant. CONCLUSION: We could not identify any surgery-radiotherapy interval that resulted in increased local recurrence if radiotherapy was delayed for administration of adjuvant chemotherapy in breast cancer patients. Because of the heterogenous population of breast cancer patients, our results also support the need for further study to determine the optimum integration of radiotherapy and chemotherapy in the management of the conservatively treated breast.

Adult↗
PubMed1994

Sample size determination for an exponential survival model with an unrestricted covariate.

We derive formulae for estimating sample size and power for detecting the effect of an unrestricted covariate on survival time. These are useful in designing survival studies with different patterns of recruitment and follow-up when survival time is exponentially distributed. We use the asymptotic covariance matrix, conditional expectation and Taylor's expansion techniques to develop these formulae. Computer simulations indicate that the asymptotic approximations used in developing the formulae are good over a range of parameter values and different patterns of recruitment and follow-up that are relevant to survival studies.

Computer Simulation↗
PubMed1994

Compartmentalized immune response reflects clinical severity of beryllium disease.

Although beryllium disease has been associated with a bronchoalveolar lavage (BAL) lymphocytosis and T cell-mediated immune response, we do not know if either the BAL cellular profile or the compartmentalized pulmonary response to the antigen reflect the severity of the disease. We studied 110 subjects divided into three groups of subjects: beryllium disease patients (n = 55), beryllium-sensitized patients without disease (n = 8), and control subjects (n = 47). Evaluation included completion of a respiratory symptom questionnaire, clinical examination, chest radiograph, spirometry, body plethysmographic lung volumes, and diffusing capacity (DLCO). In the patient groups, we performed maximal exercise testing with an indwelling arterial line. In addition, we examined BAL and performed blood and BAL beryllium lymphocyte transformation tests (BeLT) as measures of the beryllium-specific T cell-mediated response in these two compartments. In beryllium disease patients we correlated the BAL cellular constituents with clinical parameters indicative of disease severity. Beryllium disease patients exhibited elevated numbers of white cells and lymphocytes in BAL compared with both other groups; however, this lymphocytic alveolitis was significantly obscured in smokers. The BAL cellular constituents correlated with BAL BeLT but not with the blood BeLT. BAL cellular constituents also correlated with the radiographic profusion of small opacities, FEV1/FVC, DLCO, maximal achievable work load, VO2max, and measures of gas exchange at rest and at maximum exercise. We conclude that the lymphocyte-predominant pulmonary inflammatory response in beryllium disease is related to the magnitude of the localized response to antigen and that BAL cellularity, differential cell count, and BeLT reflect beryllium disease clinical severity.(ABSTRACT TRUNCATED AT 250 WORDS)

Berylliosis↗
PubMed1993

Epidemiology of beryllium sensitization and disease in nuclear workers.

We examined the epidemiology of chronic beryllium disease among a stratified, random sample (n = 895) of nuclear weapons workers using the blood beryllium lymphocyte transformation (BeLT) test and chest radiograph for case identification. Of 18 new cases of beryllium sensitization, 12 had beryllium disease, and three more developed pulmonary granulomas on lung biopsy over the succeeding 2 yr. Beryllium-sensitized cases did not differ from noncases in age, gender, race, ethnicity, smoking, most respiratory symptoms, spirometric or radiographic abnormalities, or job tenure. The six sensitized cases without initial disease differed from beryllium disease cases in having greater pack-years of smoking. Sensitization occurred among workers with inadvertent or bystander exposure, such as a secretary and security guard. However, beryllium sensitization risk was higher for machinists (4.7%) and for persons reporting measured overexposure (7.4%, odds ratio 5.1); exposure beginning before 1970 (3.6%, odds ratio 2.7); consistent beryllium exposure (3.4%); and sawing (4.7%) or band sawing (6.0%) of beryllium metal. We conclude that both individual susceptibility to sensitization and exposure circumstances are important in developing disease.

Adult↗