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PubMed2006

Measuring orthopedic implant wear on standard radiographs with a precision in the 10 microm-range.

The aim of this study has been to explore and verify whether the use of a previously designed Analysis-by-Synthesis algorithm is capable to precisely measuring implant wear. The abrasion of polyethylene particles is seen as the main reason for the loosening of prosthetic components in the hip. It lies in the sub-millimeter range, and precision is a crucial point in wear measurement. In the Analysis-by-Synthesis algorithm, the synthetic X-ray image of the implant is matched to its original X-ray projection. This intensity based approach and the use of X-ray images with their inherent high resolution allow principally precise measurements. Wear has been defined based on the estimated implant parameters and under minimization of the impact of the main sources of error. The latter was theoretically studied in a sensitivity analysis. The use of the algorithm was tested in vitro as well as in vivo. In experimental data, the accuracy and the impact of the pelvic position and orientation were studied. The precision was assessed using dual radiographs of 20 patients with total hip replacement. A standard deviation of 49 microm was found.

Equipment Failure Analysis↗
PubMed2005

Effects of clozapine on memory function in the rat neonatal hippocampal lesion model of schizophrenia.

Clozapine is an effective atypical antipsychotic drug used to treat schizophrenia. It has the advantage of producing fewer extrapyramidal motor side effects than typical antipsychotic drugs such as haloperidol. Schizophrenia involves more than the hallmark symptom of psychosis. Substantial cognitive impairment is also seen. Effective drug treatments against the cognitive impairment of schizophrenia need to be developed. The current study was conducted to determine the effects of clozapine on working memory in the rat neonatal hippocampal lesion model of schizophrenia, which includes symptoms of cognitive impairment. Infant Sprague-Dawley rats were given ibotenic acid lesions of the hippocampus on day 7 of age (using the day of birth as day 0). Controls were given vehicle infusions. In adulthood, the rats were trained on the 8-arm radial maze using the win-shift procedure. After 6 sessions of training, the lesioned rats and their controls were administered repeated injections of saline or clozapine (2.5 mg/kg) for the next 12 sessions of training. The females had significant radial-arm maze choice accuracy impairments caused by either clozapine or the hippocampal lesion, but the combination of the two treatments had no additive effect. The males showed a different pattern of effects. Intact males did not show a significant clozapine-induced impairment, whereas males with hippocampal lesions did show significant clozapine-induced impairment although hippocampal lesions by themselves did not significantly impair male choice accuracy. These data show that clozapine can cause memory impairment and it potentiates rather than reverses hippocampal lesion-induced deficits. There are critical sex-related differences in these effects.

Analysis of Variance↗
PubMed2005

Ethical considerations in the early composite tissue allograft experience: a review of the Louisville Ethics Program.

This paper reviews the formulation and evolution of the ethical component in one of the earliest clinical composite tissue allograft (CTA) programs, the hand transplantation program in Louisville, Kentucky, USA. The purpose was to derive lessons and define principles to give guidance for future programs and introduction of new CTA. We reviewed the initial ethical considerations, including input from respected ethical scholars, guidelines for innovative procedures transparency in public and professional scrutiny, and compliance with human studies regulations (IRB approval). We found the initial focus on ethics, scholarly input, guidelines for innovative procedures, and human studies protection regulations to be valid. Moreover, we noted the effect of autonomy in subjective, quality-of-life benefits on equipoise and effective risk-benefit analysis in effective informed consent. We found that psychiatric screening and support to be exceptionally valuable in protecting autonomy, suitability for participation, assessing personality organization, and determining compliance ability. We conclude that the program ethical principles were validated. For future CTA programs and procedures, we recommend an ethical emphasis with adherence to high standards and transpire to independence to scrutiny and oversight. We recommend protection of autonomy judgments in equipoise judgment and informed consent. We recommend skilled psychiatric screening and support. We endorse scholarship, scientific accuracy, and data sharing.

Humans↗
PubMed2006

Pandemic influenza preparedness: the critical role of the syringe.

In the face of an almost unprecedented threat of a global pandemic of influenza it is imperative that stockpiling of appropriate drugs and devices begin now. One vital device is an appropriate syringe for delivering vaccine. With the potential for millions to be infected and the vaccine supply severely stretched it is imperative that the syringe used to vaccinate waste as little vaccine as possible and thus allow for a maximum number of persons to be vaccinated. Our study tested seven leading candidate vaccine syringes for dosing accuracy, dose-capacity per vial, medication wastage and a battery of ergonomic features. One device, the Flu+trade mark syringe, proved superior to the others in all important categories, possibly due to its low dead-space volume and its dosing accuracy. The data suggest that switching to this device from any of the others tested would provide between 2 and 19% additional vaccine doses per vial if the current 10-dose vials are used. Extrapolations from this data suggest that many thousands to millions of additional persons could be vaccinated in mass campaigns. Use of a syringe of this type, and the vaccine savings that would accrue, would likely be important in reducing morbidity and mortality in the event of a pandemic of influenza.

Disease Outbreaks↗
PubMed1975

Analysis of fluorescence decay curves by means of the Laplace transformation.

A computational procedure is described for the analysis of fluorescence decay data convolved with a lamp flash of finite width. The computer program calculates the ratio of the Laplace transforms of the decay and the lamp flash for different values of s to give the transforms of the impulse response for each value of s. These are set equal to the analytical Laplace transforms of the decay law involved. Solution of the nonlinear simultaneous equations yields the desired decay parameters. The method can be modified to analyze data that contains a component due to scattered light and can also provide essential information regarding transit time changes of the photomultiplier with changes in emission wavelength. The method was tested by the analysis of real and simulated data. The accuracy of the analysis depends on the degree of correlation among the parameters.

Fluorescence↗
PubMed2001

Tibial intramedullary nail distal interlocking screw placement: comparison of the free-hand versus distally-based targeting device techniques.

Intramedullary nailing is the standard treatment for closed and some open unstable diaphyseal tibia fractures. Fluoroscopy, while essential for proper nail placement can subject the surgical team and patient to substantial radiation. A new targeting system for tibia nail distal interlocking was developed by Orthofix to limit fluoroscopy. This prospective clinical study compares the Orthofix targeting system versus a free-hand technique for the tibial nail distal interlocking. Fifty eight consecutive patients with sixty tibial fractures amenable for nail fixation were randomly assigned into two equal groups: Group 1: Orthofix distally based distal targeting device and Group 2: a free-hand technique. In all the cases stabilization was achieved with a reamed statically locked tibial nail. Recorded data included accuracy of screw placement, duration of surgery prior to and during distal interlocking, and the fluoroscopy time prior to and during distal interlocking. Both groups revealed comparable fracture patterns. In all fractures the technical aspects of the surgical treatment were performed without complications. There was no statistically significant difference between the groups in the mean time of surgery prior to (62.02 vs. 61.01 min, P=0.92) and during distal interlocking (17.06 vs. 19.08 min, P=0.55), or in the total surgical time (81 vs. 85 min), respectively. Neither was there a statistically significant difference in the mean fluoroscopy time prior to distal interlocking (69 vs. 81 s, p=0.22) nor in the total fluoroscopy time (84 vs. 117 s). There was however, a statistically significant difference between the Orthofix and free-hand groups with regards to the mean fluoroscopy time during distal interlocking (15 vs. 36 s, P=0.01, respectively). This study demonstrates that the distally based distal targeting device by Orthofix for tibial nailing can significantly decrease the mean fluoroscopy time necessary to complete distal interlocking versus free-hand technique.

Adolescent↗
PubMed2001

Correcting out-of-plane errors in two-dimensional imaging using nonimage-related information.

Two-dimensional imaging with a single camera assumes that the motion occurs in a calibrated plane perpendicular to the camera axis. It is well known that kinematic errors result if the object fails to remain in this plane and that if both the distance to the calibration plane from the camera and the distance out-of-plane are known, an analytical correction for the out-of-plane error can be made. Less well appreciated is that out-of-plane distance can frequently be acquired from other, nonimage-related information. In the two examples given, the mediolateral center of pressure coordinate of the foot measured from a force plate and the measured landing point of a shot put throw were used. In both cases, the resulting out-of-plane correction improved the accuracy of the 2-D kinematic data dramatically. These examples also demonstrate that the use of nonimage-related data can increase the accuracy of kinematic data without an increase in the complexity of the experiment.

Diagnostic Errors↗
PubMed1999

Diagnosis of mediastinal masses in pediatric patients using mediastinoscopy and the Chamberlain procedure.

BACKGROUND/PURPOSE: Mediastinal masses commonly are referred to the pediatric surgeon and can be difficult diagnostic problems. Various techniques have been used to perform biopsy in the mediastinum, but there are few reports of mediastinoscopy or Chamberlain procedure in children in the literature. The authors reviewed their experience with these techniques in a pediatric oncology population. METHODS: The medical records of all patients on the pediatric surgical service between 1987 and 1997, inclusive, who underwent mediastinoscopy or Chamberlain procedure were reviewed. Demographic data, diagnostic accuracy, complications, operating time, and blood loss were recorded. RESULTS: Sixteen consecutive patients underwent 13 Chamberlain procedures and six mediastinoscopies over the above period. Diagnostic accuracy was found to be 95% overall (100% for Chamberlain procedure, 83% for mediastinoscopy). Five complications occurred in the Chamberlain group and none in the mediastinoscopy group. No complication required thoracotomy or sternotomy. Among patients whose sole reason for admission was diagnosis of a mediastinal mass, the mean hospital stay was 1.7+/-0.8 days (n = 7) for those who underwent Chamberlain procedure and 1.4+/-0.9 days (n = 4) for those who underwent mediastinoscopy. One mediastinoscopy was performed as an ambulatory procedure. CONCLUSION: Mediastinoscopy and the Chamberlain procedure are effective and safe techniques for biopsy of mediastinal masses in this age group.

Adolescent↗
PubMed2002

PCDD/Fs emissions inventory in the Lombardy Region: results and uncertainties.

The results of an assessment study of both industrial and non-industrial dioxin and furan (PCDD/Fs) emissions in the Lombardy Region (Italy) are outlined below. The main data source refer to 1997, and are compiled from the Lombardy Emissions Inventory (developed under the framework of the Regional Air Quality Plan) together with documented emissions factors available. Due to the uncertain nature of the emissions assessment, results are provided as a most probable value within a given range. Total PCDD/Fs emissions in Lombardy average 33 g I-TEQ y(-1), ranging from minimum 13 g I-TEQ y(-1) to maximum 88 g I-TEQ y(-1). The main PCDD/Fs sources are waste incineration, electric arc furnace for steel production, vehicle diesel combustion and residential wood combustion. Incineration emission factors are expected to decrease over the period 2005-2010, in compliance with legal requirements. This will prioritize control over the remaining main PCDD/Fs contributors. Due to limited information available concerning this data, the accuracy of which is uncertain, further research is needed to evaluate the future role of these sources.

Benzofurans↗
PubMed1999

Cerebrovascular biomodelling: a technical note.

BACKGROUND: Recently computed tomographic angiography (CTA) and MR angiography (MRA) have been used to image cerebrovascular structures. Although CTA and MRA are accurate and sensitive imaging modalities, limitations have been identified in relation to image interpretation. Stereolithographic (SL) biomodelling is a new technology that allows three-dimensional (3D) CT and MR data to be used to accurately manufacture solid plastic replicas of anatomical structures. A prospective trial of SL biomodelling in cerebrovascular surgery has been performed to investigate the feasibility and clinical utility of this new display medium. METHODS: Fifteen patients with cerebral aneurysms and 1 patient with a cerebral arteriovenous malformation (AVM) were selected. 3D CT and/or MR angiograms were acquired and 19 solid anatomical biomodels manufactured using the rapid prototyping technology of stereolithography. The biomodels were used for patient education, diagnosis, operative planning and surgical navigation. RESULTS: The biomodels replicated the CTA and MRA source data. The accuracy of one biomodel was verified by comparison with a post mortem specimen, which corresponded exactly in the x and y planes but differed by 2 mm in the z plane. The ability to closely study an overview of complex cerebrovascular anatomy from any perspective on a solid biomodel was reported to enhance the surgeon's understanding, particularly when conventional images were equivocal. Cerebrovascular biomodels were found to be useful when positioning the patient's head for surgery, for selecting the best aneurysm clip and for the simulation of clipping. Patient informed consent was anecdotally improved. Disadvantages of the technology were the cost and manufacturing time. CONCLUSIONS: Cerebrovascular biomodelling may have utility in complex cases or when the standard imaging is felt to be equivocal.

Adult↗
PubMed2001

Variability in the assessment of adverse events in a multicenter clinical trial.

BACKGROUND: Consistent documentation, characterization, and evaluation of adverse events (AEs) are needed during multicenter clinical trials to ensure accuracy of data reported to the US Food and Drug Administration and in the medical literature. OBJECTIVE: The purpose of this study was to identify and characterize variations in the assessment of AEs by clinical trial personnel. METHODS: During the annual meeting of personnel from a multicenter, controlled clinical trial of an investigational new drug treatment for opioid dependence, an oral presentation of procedures for AE data collection was given to 25 principal investigators and ancillary study personnel who assessed AEs for the study. A post-test using 3 hypothetical AE cases in which AEs were categorized by type of reaction, relatedness to study drug, severity, action taken, and outcome was completed by study participants. Cases and expected responses were reviewed for content and validity by clinical research pharmacists who were not involved with the study. The level of agreement with expected responses was assessed using McNemar symmetry chi-square tests. RESULTS: Assessments of type of AE, relatedness to study drug, and severity were less frequently aligned with expected responses than were action taken and outcome (P < 0.013). Less consistency with expected responses was found in I case than in the other 2, suggesting that certain types of AEs may be more difficult to assess. CONCLUSIONS: There was considerable variability in categorization of AEs in an exercise following training for AE data collection. Type of report, relatedness, and severity were found to have more variability in reporting than did action taken or outcome. The results suggest that unless data are gathered to verify reliability of reporting, subcategorization of AE data should be undertaken cautiously. Further research is needed regarding methods for improving consistency in reporting of AEs.

Clinical Trials as Topic↗
PubMedDate not supplied

Age and experience-dependent representational reorganization during spatial learning.

Previously, we found that aged rats showed a significant enhancement of hippocampal CA1 place cell spatial specificity, as well as a reduction of hilar place cell spatial specificity, during asymptote performance of a spatial memory task. Because such an age effect was not observed when animals performed a nonspatial task, the present study tested the hypothesis that the different patterns of spatial selectivity observed in memory and nonmemory tests reflected a redistribution of spatial representations that occurred in response to changing task demands. In the present experiment, after animals became familiar with the test environment and motor demands of performance on a radial maze, CA1 and hilar place cells were recorded as they learned a spatial memory task. CA1 place cells recorded from unimpaired old, but not impaired old or young, animals became more spatially selective as animals learned the task. Hilar spatial selectivity for both age groups was not significantly related to choice accuracy. These data support the hypothesis that at least a subpopulation of aged rats may benefit from reorganization of spatial representations in such a way that the normal age-related spatial learning deficit is attenuated.

Aging↗
PubMed1999

Comparison of two measurement techniques for clinical wear.

OBJECTIVES: Clinical wear of restorations is generally evaluated by marginal integrity over time. In this study, both a subjective and an objective method for wear assessment are compared, and the relative advantages and disadvantages of each are considered. METHODS: A surface evaluation technique for quantitative measurement of wear, as developed at the University of Minnesota (UMN) has been compared to the commonly employed method of wear assessment used by Leinfelder (LF). Measurements were made by comparing suitable casts of restored teeth before and after clinical function. Semi-quantitative wear assessment was studied in comparison with detailed quantitative information about the topology of the pre- and post-wear occlusal surfaces obtained from stylus profilometry and processed by imaging techniques. Fourteen model sets of baseline, 2, 3 and 5 year old Class II composite restorations from a Danish clinical trial were evaluated using both techniques. RESULTS: In general, after 5 years of function, the digitizing method (UMN) generated wear values that were twice as high, indicating that general wear of restorative materials is underestimated by the LF-method. CONCLUSIONS: The comparison clearly revealed the advantages and limitations of each technique. Evaluation of wear by means of the LF technique provides global semi-quantitative data on restoration margins relative to enamel, underestimating general wear of the restorative material. Advanced 3-D measuring techniques such as the UMN method provide extensive quantitative data regarding wear patterns of the entire occlusal surface, i.e. restoration and enamel. Such a highly accurate technique is capable of differentiation between wear behavior of restorative materials early on in clinical studies. In addition, through its digital alignment procedure, the UMN method provides data on accuracy of the replication process used in clinical studies.

Analysis of Variance↗
PubMed2000

Analysis of head motion prior to and during proton beam therapy.

PURPOSE: We report on the use of a noninvasive patient motion monitoring system to evaluate the amount of head motion prior to and during proton radiation therapy sessions. METHODS AND MATERIALS: Two optical displacement sensors, placed close to the patient's head, were used for online monitoring of the head position, with submillimeter accuracy. Motion data, including the difference between start and end position (Dx) and the maximum displacement during the recorded session (Dx-max), were acquired for pretreatment sessions to analyze alignment radiographs, and for treatment sessions. We have recorded 102 pretreatment and 99 treatment sessions in 16 patients immobilized with a thermoplastic mask, and 44 pretreatment and 56 treatment sessions in 13 patients immobilized with vacuum-assisted dental fixation. To avoid incorrect data analysis due to replicate observations, only 1 pretreatment and 1 treatment session per patient were selected at random for statistical comparison of mean or median motion parameters in different subgroups. RESULTS: Both techniques showed similar immobilization efficiencies. The median Dx and Dx-max values were 0. 18 mm and 0.46 mm, respectively, for 16 treatment sessions with mask immobilization, and 0.22 mm and 0.50 mm, respectively, for 13 treatment sessions with dental immobilization. Motion parameters for pretreatment and treatment sessions were not statistically different. CONCLUSION: Online verification of patient's head motion is feasible and provides valuable data for confirmation of proper treatment delivery in individual patients, as well as for the evaluation of different immobilization methods.

Adolescent↗
PubMed1986

Quantitative high-performance affinity chromatography: evaluation of use for analyzing peptide and protein interactions.

To examine analytical high-performance affinity chromatography as a microscale method for characterizing macromolecular interactions, the chromatographic behavior was evaluated of Arg8-vasopressin on bovine neurophysin II covalently immobilized in its monomer form on several new high-flow and pressure-resisting affinity supports. Zonal elution of both tritiated and unlabeled peptide hormone and an extension of theoretical treatment of analytical affinity chromatography allowed determination of equilibrium dissociation constants of hormone binding to immobilized bovine neurophysin II. Microamounts of hormone, ranging from 0.05 to 15 micrograms, were eluted within 20-30 min, with a quantitative recovery of the amount injected. For zones containing more than 5 micrograms, continuous elution monitoring was possible by ultraviolet absorbance, providing greater speed and accuracy in data analysis. The values obtained for the equilibrium dissociation constants were in good agreement with those previously measured in solution. The above hormone-protein evaluation system has led to identification of several pressure-resistant affinity supports, including silica-, agarose- and glass-based matrices, which are appropriate for use with high-performance liquid chromatographic instrumentation for affinity chromatographic analysis of macromolecular interactions.

Animals↗
PubMed1997

Capillary electrophoresis with laser-induced fluorescence detection, an adequate alternative to high-performance liquid chromatography, for the determination of ciprofloxacin and its metabolite desethyleneciprofloxacin in human plasma.

A method to determine plasma concentrations of ciprofloxacin and its metabolite desethyleneciprofloxacin (M1) by CE with HeCd laser-induced fluorescence detection is described. Following precipitation of proteins and centrifugation supernatant is injected hydrodynamically (10 s, 0.5 p.s.i.) into the capillary. Overall analysis time for the quantification of both analytes was 7 min. The total amount of plasma needed for multiple injections (n>5) was 10-20 microl. Data on accuracy and precision are presented. The assay performance is compared to the specifications of a validated HPLC method, which is routinely used for the quantification of ciprofloxacin and M1 in body fluids. Both methods showed comparable accuracy and precision for both analytes throughout the whole working range (inter-day precision <9%; inter-day accuracy 96-110%). The limit of quantification (LOQ) of 20 microg/l (M1 10 microg/l) for the CE procedure was slightly higher than for the HPLC method, where 10 microg/l (M1 2.5 microg/l) was determined. However, application of the methods to human plasma samples derived from a clinical study proved that comparable results are obtained and that the sensitivity of the HPCE method was sufficient to fully describe typical plasma concentration time profiles of ciprofloxacin and its metabolite M1. Both the adequate sensitivity and the required smaller sample volume compared to HPLC indicate that the method is feasible for clinical studies where sample amounts are limited, e.g., studies to investigate pharmacokinetics in pediatric patients. Preclinical studies form another possible application of this technique.

Anti-Infective Agents↗
PubMed1998

Capillary electrophoresis with laser-induced fluorescence: a routine method to determine moxifloxacin in human body fluids in very small sample volumes.

The feasibility of capillary electrophoresis with HeCd laser-induced fluorescence detection as a validated routine method for bioanalytical analysis is reported. Method evaluation, validation and results of the determination of moxifloxacin (BAY 12-8039), a new antimicrobially active 8-methoxy-quinolone, in plasma and microdialysate are described. After a one step sample preparation the samples can be injected directly into the capillary. The volume of microdialysate and plasma, respectively, needed for more than 50 injections is only 10 microl and 20 microl. Total run time is less than 7 min using a 27 cm capillary on commercial instrumentation. An analysis time of less than 1 min was shown to be possible, however it could not be used routinely since appropriate instrumentation was not available. Evaluation is based on the relative corrected peak area (analyte/I.S.). The method's dynamic range comprises three orders of magnitude (plasma: 2.5-5000 microg/l; microdialysate: 5-5000 microg/l). Validation according to international guidelines yielded data on accuracy and precision of the method throughout the entire working range of inter-day precision: plasma <6%, microdialysate <5% and inter-day accuracy: plasma <2%, microdialysate <4%. The crossvalidation with an existing HPLC method utilizing clinical study samples shows linear correlation. In view of its adequate sensitivity and high selectivity capillary electrophoresis with laser-induced fluorescence is a very versatile tool in pharmacokinetic studies of quinolones, especially in situations with limited sample volumes: e. g. pediatrics, patients at risk, animal-, microdialysis- and tissue-kinetic studies. Validation parameters and other features, like high sample throughput and robustness, are comparable to or even better than HPLC. Further necessary improvements of the capillary electrophoresis with laser-induced fluorescence instrumentation (autosampler, vials, parallel capillaries) and its use in bioanalytical routine analysis are discussed.

Anti-Infective Agents↗
PubMed2001

An HPLC assay and a microbiological assay to determine levofloxacin in soft tissue, bone, bile and serum.

A simple, specific and sensitive HPLC assay for levofloxacin in serum, bile, soft tissue and bone was evaluated and validated. The samples were prepared by protein precipitation with acids and methanol, which yielded high recoveries (for serum and bile>98% and for bone and soft tissue>90%). The compounds were separated on a reversed phase column with an acidic mobile phase containing triethylamine. The eluate was monitored by fluorescence detection. The HPLC assay is linear over the usable concentration range (0.1-40 microg/ml) and it provides good validation data for accuracy and precision. Although comparison of HPLC results to the results of a microbiological assay showed congruent results (regression coefficients>0.967). HPLC should be the method of choice for determination of levofloxacin in biological matrices.

Anti-Infective Agents↗