Biomedical subjects

W B Bilker

Publications and source records attributed to W B Bilker.

8 recordsLinked to original sources

PubMed1997

Reproducibility and reliability of volumetric measurements of olfactory eloquent structures.

RATIONALE AND OBJECTIVES: The authors assessed the reliability and reproducibility of volumetric measurements of olfactory bulbs and tracts (OBTs) and temporal lobes (TLs) with magnetic resonance (MR) imaging. METHODS: Repetitive MR imaging of two phantoms and OBTs and TLs of patients was performed. Regions of interest were manually drawn around the relevant structures, and their volumes were measured at workstations. Intra- and interobserver variability for the two readers were measured. Intraclass and Pearson correlation coefficients and mean percentage differences were calculated. RESULTS: The measured phantom volumes were within 1.9%-12% of the true volumes with a variability of < or = 5%. Intraclass and Pearson correlation coefficients were > or = 0.919 for measurements by a single reader and > or = 0.924 for measurements by different readers. The inter- and intraobserver variabilities were < or = 4.2% for TL and 11.3%-14.6% for OBTs. CONCLUSION: Volumetric measurements of the olfactory apparatus can be reliably and accurately reproduced from MR images.

Humans↗

PubMed1996

Effect of dialyzer reuse on survival of patients treated with hemodialysis.

OBJECTIVE: To evaluate the impact of dialyzer reuse on the survival of US hemodialysis patients. STUDY DESIGN AND PARTICIPANTS: Nonconcurrent cohort study of 27938 patients beginning hemodialysis in the United States in 1986 and 1987. MAIN OUTCOME MEASURE: Patient survival. RESULTS: Dialysis in freestanding facilities reprocessing dialyzers with the combination of peracetic and acetic acids was associated with greater mortality than treatment in facilities not reprocessing dialyzers (rate ratio [RR],1.10, 95% confidence interval [CI], 1.02-1.18; P=.02) In contrast, there was no significant difference between survival in freestanding facilities reprocessing dialyzers with either formaldehyde (RR,1.03, 95% CI, 0.96-1.10; P=.45) or glutaraldehyde (RR, 1.13, 95% CI, 0.95-1.35, P=.18) and survival in freestanding facilities not reprocessing dialyzers. Among freestanding facilities reprocessing dialyzers, use of peracetic/acetic acid was associated with a higher rate of death than use of formaldehyde (RR = 1.08, 95% CI, 1.01-1.14; P=.02). There was no statistical difference between survival in hospital-based facilities reprocessing dialyzers with either peracetic/acetic acid (RR=0.95, 95% CI, 0.85-1.06; P=.40), formaldehyde (RR=1.06, 95% CI, 0.98-1.15; P=.12), or glutaraldehyde (RR=1.09, 95% CI, 0.71-1.67; P=.70) and survival in hospital-based facilities not reprocessing dialyzers. In addition, choice of sterilant was not associated with a statistically significant difference in survival among hospital-based facilities reprocessing dialyzers. CONCLUSIONS: Dialysis in freestanding facilities reprocessing dialyzers with peracetic/acetic acid may be associated with worse survival than dialysis in free-standing facilities not reprocessing dialyzers or in those reprocessing with formaldehyde. We were unable to determine whether these relationships arose from greater comorbidity among patients treated in facilities using peracetic/acetic acid, poor quality of dialysis procedures in these facilities, or direct toxicity of peracetic/acetic acid. These findings raise important concerns about potentially avoidable mortality among US hemodialysis patients treated in dialysis facilities reprocessing hemodialyzers.

Adult↗

PubMed1996

Effectiveness of live-attenuated Japanese encephalitis vaccine (SA14-14-2): a case-control study.

BACKGROUND: Japanese encephalitis is a major cause of death and disability throughout Asia, including the Indian subcontinent. Although an effective vaccine for Japanese encephalitis is available, hundreds of millions of susceptible individuals remain unimmunised because of the vaccine's cost. In 1988, an inexpensive live-attenuated vaccine (SA14-14-2) was licensed in China. We have measured the effectiveness of this vaccine. METHODS: In a case-control study in rural Sichuan Province, China, the 56 cases consisted of children admitted to hospital with acute Japanese encephalitis, and were confirmed serologically. 1299 village-matched and age-matched controls were identified, and vaccination histories obtained from pre-existing written records. FINDINGS: The effectiveness of one dose was 80% (95% Cl 44 to 93%); that of two doses was 97.5% (86 to 99.6%). Controlling for multiple potential confounders did not alter these results. INTERPRETATION: We conclude that a regimen of two doses of live-attenuated Japanese encephalitis vaccine, administered 1 year apart, is effective in the prevention of clinically important disease. Subsequent study is needed to assure the safety of this vaccine.

Animals↗

PubMed1996

A semiparametric extension of the Mann-Whitney test for randomly truncated data.

In many applications, statistical data are frequently observed subject to a retrospective sampling criterion resulting in pure right-truncated data. In classical testing problems, the Mann-Whitney test is used for testing the equality of two distributions. A semiparametric extension of this test is developed for the case when truncation is present. We consider a model in which the truncation distribution is parameterized, while the lifetime distribution is left as a nonparametric component. The method is seen to be applicable to many patterns of truncation including left truncation, right truncation, and doubly truncated data for which no other nonparametric or semiparametric test is currently available. Applications of the semiparametric method are given. Simulation results indicate that for pure right-truncated data the semiparametric test is more powerful than a recent nonparametric test.

Acquired Immunodeficiency Syndrome↗

PubMed1994

Predictability of rehospitalization for schizophrenia.

This analysis examines the predictability of the course of schizophrenia using long-term follow-up data on hospital episodes in a cohort of patients from a psychiatric case register in Denmark. We focus on whether clinical and sociodemographic data collected during the first episode are related to the number of hospitalizations during follow-up and the association of patients' course of hospitalizations with the risk of being rehospitalized. A Poisson regression model and a proportional hazards model were used to address these questions. Age of onset and time to the first rehospitalization were strong early predictors of chronicity of course, as measured by the number of psychiatric hospitalizations for each schizophrenic patient. The results also show that the risk of rehospitalization depends on the previous tenures in the community.

Adolescent↗

PubMed1993

Clinical trial of cefamandole, cefazolin, and cefuroxime for antibiotic prophylaxis in cardiac operations.

A relatively large number of comparative trials of antibiotic prophylaxis in cardiac surgery have been published, many of which have serious design flaws. Despite the large number of studies, no single antibiotic regimen has emerged as clearly superior in preventing postoperative site infections. To determine if a superior regimen could be identified with a study designed to avoid flaws found in previous studies, we undertook a randomized, double-blind clinical trial of three cephalosporins. From March 1987 to February 1990, 2759 adults underwent median sternotomies: 1641 completed study participation, 203 were enrolled but were dropped from the study for protocol violations, and 815 were excluded. The characteristics of all 2759 patients were recorded with respect to case mix and infection risk factors, and the patients were followed-up by the same nurse throughout hospitalization and for 6 weeks after discharge for the assessment of infection outcome status. Of the 1641 participants, 141 (8.6%) had one or more operative site infections: 46 of 549 (8.4%) cefamandole recipients, 46 of 547 (8.4%) cefazolin recipients, and 49 of 545 (9.0%) cefuroxime recipients (p = 0.92). The sites of infection and the depth of tissue involvement were not significantly different across groups. Because no differences in effectiveness in preventing postoperative site infections were demonstrated in a rigorously designed trial, the costs of the drugs, including the costs of their preparation and delivery, may be the only variables by which to choose among these three antibiotic prophylaxis regimens.

Adult↗

PubMedDate not supplied

Posttraumatic olfactory dysfunction: MR and clinical evaluation.

PURPOSE: To evaluate the sites of injury in patients with posttraumatic olfactory deficits and to compare damage with findings on clinical olfactory tests. METHODS: Twenty-five patients with posttraumatic olfactory dysfunction were examined by means of olfactory testing, endoscopy, and MR imaging. MR surface-coil scans through the olfactory bulbs and tracts and head-coil scans of the temporal lobes were evaluated. Quantitative and qualitative gradings of damage to the olfactory bulbs, tracts, subfrontal region, hippocampus, and temporal lobes were compared with results on tests of odor identification, detection, memory, and discrimination. RESULTS: Twelve patients were anosmic, eight had severe impairment, and five were mildly impaired. Injuries to the olfactory bulbs and tracts (88% of patients), subfrontal region (60%), and temporal lobes (32%) were found, but these did not correlate well with individual olfactory test scores. Volumetric analysis showed that patients without smell function had greater volume loss in olfactory bulbs and tracts than did those posttraumatic patients who retained some sense of smell. Qualitative and quantitative assessments of damage showed few significant correlations with olfactory tests, probably because of multifocal injuries, primary olfactory nerve damage, and the constraints of a small sample size on the detection of clinically significant differences. CONCLUSION: MR imaging shows abnormalities in patients with posttraumatic olfactory dysfunction at a very high rate (88%), predominantly in the olfactory bulbs and tracts and the inferior frontal lobes.

Adolescent↗

PubMedDate not supplied

Use of preoperative MR to predict dural, perineural, and venous sinus invasion of skull base tumors.

PURPOSE: To assess the accuracy of MR imaging in predicting dural, venous sinus, and perineural invasion by skull base tumors. METHODS: The preoperative MR images of 22 patients who had resection of skull base neoplasms were evaluated for the following characteristics: dural enhancement, pial enhancement, local perineural invasion by adjacent tumor, and venous sinus invasion by tumor. The greatest width of dural enhancement was measured, and the character of dural enhancement was noted. The pathologic and surgical reports were reviewed retrospectively with specific attention to dural, venous, and local perineural invasion. RESULTS: Of the 22 patients studied, dural invasion by tumor was confirmed in eight patients, vascular invasion in six patients, and perineural invasion in four patients. The sensitivity of dural enhancement in predicting invasion was 88%, the specificity 50%, and the accuracy 64%. When enhancement and focal nodularity were present, the sensitivity remained at 88%; however, specificity was 100% and accuracy 95%. If the dural enhancement was more than 5 mm thick, sensitivity, specificity, and accuracy were 75%, 100%, and 91%, respectively. Predicting tumor invasion of the dura by the presence of pial enhancement was 50% sensitive and 100% specific. Venous sinus/jugular vein invasion was predicted with 100% sensitivity, 94% specificity, and 95% accuracy. Local perineural invasion was predicted with 100% sensitivity, 50% specificity, and 59% accuracy. CONCLUSIONS: The presence of pial enhancement, focal dural nodules, or dural thickening of more than 5 mm is highly accurate in predicting the presence of neoplastic dural invasion. Linear enhancement of dura does not imply dural infiltration by tumor. Venous invasion by tumor can be predicted accurately with preoperative MR imaging.

Adult↗