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At least 37 records · Page 2Linked to original sources
PubMed1993

Frequency versus time domain analysis of the signal-averaged electrocardiogram: reproducibility of the spectral turbulence analysis.

Reproducibility of the Spectral Turbulence Analysis. Spectral turbulence analysis (STA) of the signal-averaged electrocardiogram (ECG) is a new frequency domain method that analyzes the total high gain QRS complex and not only its terminal portion. This study examined the qualitative and quantitative short-term reproducibility of this technique (three recordings made within 25 min) in 68 subjects: 16 healthy volunteers; 22 patients with ventricular tachycardia and no evidence of heart disease; and 30 postinfarction patients with sustained ventricular tachycardia. The reproducibility of diagnosis of the STA was compared with that of the conventional time domain analysis of the signal-averaged ECG using standard criteria of abnormality. The reproducibility of numeric values of the spectral turbulence and of the time domain indices was performed by computing the ratios between standard deviation of measurements in individual subjects and standard deviations of all measurements. The reproducibility of diagnostic conclusions of the time domain analysis was slightly better than that of the STA but the differences were not significant (88%-91% of consistent time domain results vs 84% of consistent STA results). The numeric reproducibility of three STA parameters was slightly but not significantly inferior to that of the time domain indices whereas the reproducibility of the fourth STA variable, the intersegment correlation standard deviation (ISCSD), was significantly worse than that of the other indices. Of the two different ECG segments analyzed, the reproducibility of the STA variables calculated for the total QRS region was significantly better than that of the terminal low power QRS region. In conclusion, the qualitative and quantitative reproducibility of the STA is slightly but not significantly worse than that of the time domain analysis with the exception of the ISCSD, which is significantly less reproducible than all other parameters.

Adult↗
PubMed1997

Reproducibility of the signal averaged P wave: time and frequency domain analysis.

OBJECTIVE: To assess the reproducibility of time and frequency domain variables derived from the signal averaged P wave. DESIGN: Longitudinal within patient study. SETTING: Regional cardiothoracic centre. PATIENTS: 20 patients (10 with documented paroxysmal atrial fibrillation and 10 normal controls) were studied on three occasions to assess the reproducibility of repeated signal averaged P wave recordings. Digital P wave recordings were made on a further 10 patients on a single occasion and the recordings signal averaged twice in order to assess the reproducibility of the averaging system itself in the absence of biological variation. MAIN OUTCOME MEASURES: P wave duration, spatial velocity, and energies contained in frequency bands from 20, 30, and 60-150 Hz of the P wave spectrum were measured after P wave specific signal averaging. Coefficients of reproducibility were calculated for paired signal averaged P waves derived by signal averaging the same digital recordings on two separate occasions, for recordings performed in the same patients immediately after each other ("back to back") and those performed one week apart. RESULTS: System reproducibility when the same digital P wave recordings were signal averaged on two separate occasions was high (< 11% for all variables). For P wave duration the coefficient of reproducibility was 11.4% for back to back recordings and 13.1% for those one week apart. The reproducibility of spatial velocity and P wave energy was low. Variation in P wave morphology was noted when successive P waves from the same subject were examined. If recordings with the same P wave morphology were analysed the reproducibility of spatial velocity and P wave energy improved but remained significantly poorer than that for P wave duration. CONCLUSIONS: P wave duration is reproducible within subjects in the short and medium term. Frequency domain and spatial velocity analysis are poorly reproducible, due more to spontaneous variation in P wave morphology than to instability of the signal averaging process. This may limit the utility of signal averaged P wave variables other than duration for the prediction of atrial arrhythmia.

Adult↗
PubMedDate not supplied

Cerebrovascular reactivity evaluated by transcranial Doppler: reproducibility of different methods.

Transcranial Doppler is routinely used to assess the cerebrovascular reactivity, despite scarce information on its reproducibility. We evaluated the reproducibility of cerebrovascular reactivity measurements by this method utilizing different vasodilatory and vasoconstrictor stimuli. The cerebrovascular reactivity was measured in 45 healthy volunteers during hypercapnia induced by inhalation of a mixture of 5% CO2 and 95% O2, breath holding and rebreathing, and during hypocapnia induced by voluntary hyperventilation. Three sets of measurements were performed at times 0, 1, and 24 h to assess the within-observer short- and long-term reproducibility. The reproducibility was analyzed using the intraclass correlation coefficient. For the CO2 inhalation method, a good short-term (rI = 0.55; 95% CI = 0.39-0.68) and a good long-term (rI = 0.43; 95% CI = 0.25-0.59) reproducibility was found. For the breath-holding method a good short-term agreement was found (rI = 0.41; 95% CI = 0.22-0. 57), while the long-term reproducibility was poor (rI = 0.17; 95% CI = -0.03-0.36). Rebreathing showed a fair (rI = 0.31; 95% CI = 0.11-0. 48) short-term and a poor (rI = 0.17; 95% CI = -0.03-0.36) long-term reproducibility. For voluntary hyperventilation, the short-term reproducibility was good (rI = 0.53; 95% CI = 0.36-0.66), and the long- term reproducibility was fair (rI = 0.31; 95% CI = 0.11-0.48). In our study, CO2 inhalation and voluntary hyperventilation had the highest reproducibility and should be preferred when assessing cerebral vasoreactivity, especially in follow-up studies.

Adult↗
PubMed2003

Day-to-day reproducibility of Holter beat-by-beat analysis of repolarisation.

UNLABELLED: Reproducibility of Holter QT analysis is not well established and has been assessed only in one study. STUDY DESIGN: We evaluated the day-to-day reproducibility of different QT parameters--mean and max (four beats basis) 24h QT and QTc (Bazett formula), QT for heart rate 55-60 [QT60], 75-80 [QT80] and 95-100 [QT100] beats/min and QT/RR slope (calculated in moving window of 3000 beats in 50 beat steps). QT intervals were measured from 48h digital ECG (sampled at 256 Hz) recordings using Del Mar Medical's QT software in beat-to-beat fashion. The analysed group consisted of 6 women and 24 men--13 patients with hypertrophic cardiomyopathy, 5 healthy family members of the patients with hypertrophic cardiomyopathy, 7 patients with CAD and 5 with other diseases (hypertension, arrhythmia, aborted sudden death without organic heart disease). Reproducibility was analysed with the methods proposed by Bland and Altman. RESULTS: The overall reproducibility of repolarisation parameters was acceptable. Coefficient of reproducibility for mean 24h QT was 24ms, mean QTc 12ms, max QT 22ms, max QTc 24ms. The best reproducibility was observed for QT60, QT80 and QT100 - 12ms, respectively. The poorest day-to-day reproducibility was recorded for the QT/RR slope parameters, which was related to lower heart rate reproducibility. CONCLUSIONS: We can conclude that day-to-day reproducibility of Holter repolarisation analysis is acceptable. QT measurement in narrow heart rate windows has the best reproducibility. Accurate QT analysis requires good quality recording, T wave amplitude above 0.2mV and an interactive QT measurement tool which includes verification, editing abilities.

Cardiomyopathy, Hypertrophic↗
PubMed2003

Functional MR images and scientific inference: reproducibility maps.

Historically, reproducibility has been the sine qua non of experimental findings that are considered to be scientifically useful. Typically, findings from functional magnetic resonance imaging (fMRI) studies are assessed with statistical parametric maps (SPMs) using a p value threshold. However, a smaller p value does not imply that the observed result will be reproducible. In this study, we suggest interpreting SPMs in conjunction with reproducibility evidence. Reproducibility is defined as the extent to which the active status of a voxel remains the same across replicates conducted under the same conditions. We propose a methodology for assessing reproducibility in functional MR images without conducting separate experiments. Our procedures include the empirical Bayes method for estimating effects due to experimental stimuli, the threshold optimization procedure for assigning voxels to the active status, and the construction of reproducibility maps. In an empirical example, we implemented the proposed methodology to construct reproducibility maps based on data from the study by Ishai et al. (2000). The original experiments involved 12 human subjects and investigated brain regions most responsive to visual presentation of 3 categories of objects: faces, houses, and chairs. The brain regions identified included occipital, temporal, and fusiform gyri. Using our reproducibility analysis, we found that subjects in one of the experiments exercised at least 2 mechanisms in responding to visual objects when performing alternately matching and passive tasks. One gave activation maps closer to those reported in Ishai et al., and the other had related regions in the precuneus and posterior cingulate. The patterns of activated regions are reproducible for at least 4 out of 6 subjects involved in the experiment. Empirical application of the proposed methodology suggests that human brains exhibit different strategies to accomplish experimental tasks when responding to stimuli. It is important to correlate activations to subjects' behavior such as reaction time and response accuracy. Also, the latency between the stimulus presentation and the peak of the hemodynamic response function varies considerably among individual subjects according to types of stimuli and experimental tasks. These variations per se also deserve scientific inquiries. We conclude by discussing research directions relevant to reproducibility evidence in fMRI.

Brain↗
PubMed1981

Reproducibility of observations on restorative and exodontic needs.

The reproducibility of observations on restorative and exodontic needs was studied by re-examination of a sample of secondary school students during a survey of dental status and need for treatment. Reproducibility was analysed by both a quantitative approach using aggregate data and a qualitative approach using tooth by tooth comparison. Reproducibility of all examiners as a collective group for the aggregate data was found to decrease as the frequency of observation of the category of treatment decreased. A lower level of reproducibility was found using the qualitative approach, even for the more frequently observed categories of treatment. Inter-examiner reproducibility was lower than intra-examiner reproducibility. The performance of individual examiners varied greatly. Based on the WHO (1977) definitions of satisfactory reproducibility, most examiners showed satisfactory intra-examiner reproducibility of the aggregate data, but a less satisfactory performance was found for the intra-examiner reproducibility using the qualitative approach, and for inter-examiner reproducibility using both approaches. Individual performance and severity of assessment of need for treatment overall were associated with the number of years since graduation of the examiners. The results indicated a need for strengthened procedures for selection and improved calibration of examiners. Calibration needed to be emphasized in the areas of occlusal lesions and need for one-surface restorations, and for the less frequently observed categories of treatment.

Adolescent↗
PubMed1999

Reproducibility of BOLD-based functional MRI obtained at 4 T.

The reproducibility of activation patterns in the whole brain obtained by functional magnetic resonance imaging (fMRI) experiments at 4 Tesla was studied with a simple finger-opposition task. Six subjects performed three runs in one session, and each run was analyzed separately with the t-test as a univariate method and Fisher's linear discriminant analysis as a multivariate method. Detrending with a first- and third-order polynomial as well as logarithmic transformation as preprocessing steps for the t-test were tested for their impact on reproducibility. Reproducibility across the whole brain was studied by using scatter plots of statistical values and calculating the correlation coefficient between pairs of activation maps. In order to compare reproducibility of "activated" voxels across runs, subjects and models, 2% of all voxels in the brain with the highest statistical values were classified as activated. The analysis of reproducible activated voxels was performed for the whole brain and within regions of interest. We found considerable variability in reproducibility across subjects, regions of interest, and analysis methods. The t-test on the linear detrended data yielded better reproducibility than Fisher's linear discriminant analysis, and therefore seems to be a robust although conservative method. Preliminary data indicate that these modeling results may be reversed by preprocessing to reduce respiratory and cardiac physiological noise effects. The reproducibility of both the position and number of activated voxels in the sensorimotor cortex was highest, while that of the supplementary motor area was much lower, with reproducibility of the cerebellum falling in between the other two areas.

Adult↗
PubMed2006

Reproducibility of the measurement of active and passive cervical range of motion.

OBJECTIVE: The primary aim of this study was to assess the reproducibility of tests for the active and passive range of motion used in the physical examination for patients with neck pain. The secondary aim was to determine whether the history of the patients influences the reproducibility and the prevalence of positive findings. METHODS: Sixty-nine participants were recruited in 3 physical therapy practices. Two examiners independently performed a physical examination on all participants. The examiners were blinded for patient characteristics (neck pain/no neck pain) and each other's findings. History findings were available for only half the patients with neck pain. Cohen's kappa was used to express reproducibility. RESULTS: The reproducibility for active and passive range of motion was moderate (kappa = 0.52 and 0.54, respectively), but a wide range in kappa scores was found. Extension of the neck showed good reproducibility for both active and passive movements (kappa = 0.88 and 0.85), whereas lateral flexion showed poor reproducibility (kappa = 0.35 and 0.33). Knowledge of history had no influence on the reproducibility and prevalence of positive findings. CONCLUSION: The reproducibility for active and passive range of motion is moderate. Knowledge of the patient's history did not influence the reproducibility and prevalence of positive findings.

Adult↗
PubMed2000

Reproducibility of time-domain and three different frequency-domain techniques for the analysis of the signal-averaged electrocardiogram.

Because time-domain (TD) analysis of the signal-averaged ECG (SAECG) has some limitations that limit its use, several frequency-domain analysis techniques were developed in an attempt to improve the diagnostic ability of the SAECG. However, it is not known how reliable these techniques are at detecting late potentials. This prospective study compares the short-term reproducibility of 4 analysis techniques: TD analysis, spectral temporal mapping (STM), spectral turbulence analysis (STA), and acceleration spectrum analysis (ASA), in a large series of normal patients and post-myocardial infarction (MI) patients. Two consecutive SAECGs were recorded in 634 patients that were divided into 3 groups: 117 remote MI patients undergoing programmed electrical stimulation for the inducibility of ventricular tachycardia (Group 1), 407 consecutive acute MI survivors (Group 2), and in 110 healthy volunteers (Group 3). The diagnostic reproducibility of the 4 techniques was evaluated by comparing rates of inconsistent results (1 normal and the other abnormal). The numeric reproducibility for each technique was assessed by comparing the normalized differences of each single SAECG parameter between the 2 recordings. Inconsistent results of diagnostic reproducibility were observed in 4.1%, 6.9%, 9.8%, and 18.0%, with TD, STA, ASA, and STM, respectively. Comparisons of these rates were significantly different (P < .05) except between STA and ASA (P = .07). The numeric reproducibility was highest for TD parameters, lowest for STM factors of normality, and intermediate for STA and ASA indices. TD analysis remains the most reproducible SAECG analysis technique, whereas STM showed the worst reproducibility, which limits its clinical applicability. STA and ASA provide an acceptable intermediate reproducibility, the former being slightly, although not significantly, more reproducible than the latter.

Electrocardiography↗
PubMed2001

Reproducibility of two coronary calcium quantification algorithms in patients with different degrees of calcification.

PURPOSE: To evaluate the reproducibility of coronary calcium quantification algorithms by electron beam CT (EBT) in patients with different amounts of calcified plaque using the conventional (Agatston) score and an area score and to demonstrate a potential application of these results for evaluation of follow-up scans. METHODS: In 50 consecutive patients. the conventional calcium score (CCS = Agatston score) and the area score (AS) were summed for each artery and patient. Data were analyzed in four groups according to degrees of calcification: 0 (absent-minimal): CCS 0-9, I (mild): CCS 10-99, II (moderate): CCS 100-399, III (severe): CCS > or = 400. We determined and compared the reproducibility for each algorithm within and among groups. RESULTS: Median percent reproducibility improved with increasing amounts of calcified plaque for the CCS and the AS (p = 0.002 and p = 0.004, respectively). We demonstrate how these reproducibility values can be used to evaluate long-term follow-up studies. The reduction of median reproducibility per patient using the AS vs. the CCS was 32% (13 vs. 19%, respectively). On a vessel-by-vessel basis, the reduction of median reproducibility was 7% (24.3 vs. 22.6%, CCS vs. AS, p < 0.02), which was attributable to a 45% reduction in reproducibility in arteries with mild scores (46.1 vs. 25.5%, CCS vs. AS, p < 0.005). CONCLUSION: The AS has an improved reproducibility compared with the CCS, especially in patients with small amounts of coronary calcifications which may prove clinically useful. Different reproducibility values in different degrees of calcification can be used for an individual assessment of changes in amounts of coronary calcification.

Adult↗
PubMed2005

Reproducibility of postexercise ambulatory blood pressure in Stage I hypertension.

The accuracy and reproducibility of ambulatory blood pressure monitoring used in intervention and treatment studies is essential to assure the desired health outcomes. The reproducibility of ambulatory variables in pharmacological studies has been reported, however, the reproducibility of ambulatory blood pressure variables associated with exercise has not been reported. Thus, the purpose of this study was to investigate the reproducibility of the postexercise ambulatory blood pressure in Stage I hypertensive adults. It was hypothesized that the reproducibility of the ambulatory blood pressure variables would not be different following two corresponding exercise and control treatments. A total of 18 Stage I hypertensive adults (142.1+/-3.15/91.6+/-1.80 mmHg) performed four randomized, 24 h AmBP monitoring sessions: two following a 50 min treadmill walk (50% VO(2) peak) and two on control days. Variables measured were: (1) average systolic and diastolic pressures for 24 h, daytime (06:00-22:00 h) and night time (22:00-06:00 h) and (2) systolic and diastolic load for the same time periods. Both a nonsignificant paired t-test and an excellent intraclass correlation were used to define reproducibility of the variables between the 1st and 2nd exercise trials and between the 1st and 2nd control trials. Reproducibility was found for all the control variables except for nighttime diastolic load. Reproducibility was found for all the systolic and diastolic exercise variables. Ambulatory blood pressure measurements, including average systolic and diastolic blood pressures and systolic and diastolic loads for 24 h, daytime and night time periods are reproducible following exercise.

Adult↗
PubMed1997

Immediate and short-term reproducibility of the P wave signal-averaged electrocardiogram.

While abnormalities in the P wave SAECG have been associated with the occurrence of AF, its reproducibility has never been documented. The purpose of this study was to evaluate the immediate and short-term reproducibility of measurements from the P wave SAECG. P wave SAECGs were obtained using well-described techniques that utilize the QRS complex as the trigger and the P wave as template for averaging. In 28 subjects (8 controls, 11 with cardiac disease, 9 with prior AF), 3 P wave SAECGs were obtained: an initial study; on immediate reacquisition; and reacquisition after 4-5 days. Vector duration and RMS voltage of the terminal 20 ms of the P wave SAECG were measured and compared. The mean P wave duration was 152 +/- 14 ms on initial SAECG, 152 +/- 14 ms and 152 +/- 15 ms at immediate and short-term reacquisitions, respectively (both P = NS vs initial). The mean terminal RMS voltage was 6.4 +/- 6.0 mcV on initial SAECG, 6.4 +/- 5.9 mcV and 6.5 +/- 5.8 mcV at immediate and short-term reacquisitions, respectively (both P = NS vs initial). Linear regression analysis showed high reproducibility for both P wave duration (r = 0.94 for immediate and r = 0.96 for short-term reacquisition vs initial) but slightly less for terminal RMS voltage (r = 0.92 for immediate and r = 0.84 for short-term reacquisition vs initial). In subgroup analysis, P wave duration measurements were highly reproducible in controls, in subjects with cardiac disease, and in those with a history of AF. P wave duration was also reproducible for both males and females, as well as for subjects age > 65 years (r = 0.96 and 0.89 for immediate and short-term reacquisition, respectively). Terminal RMS voltage measurements were reproducible for controls, but less reproducible in other subgroups. In conclusion, P wave duration measurements on SAECG are reproducible when evaluated at immediate and short-term reacquisition regardless of age, sex, cardiac disease, or prior AF. Terminal RMS voltages were less reproducible, especially in patients with cardiac disease and/or prior AF. These findings may explain conflicting observations regarding the clinical utility of terminal P wave measurements.

Age Factors↗
PubMed1991

Acceptability and reproducibility criteria of the American Thoracic Society as observed in a sample of the general population.

An analysis of spirograms of 6,486 subjects from the general population, ages 8 to 90, was conducted to determine their ability to satisfy the American Thoracic Society's (ATS) acceptability and reproducibility criteria. The results indicate that both older and younger subjects had more difficulty satisfying the ATS acceptability and reproducibility criteria. The difficulty in satisfying the ATS reproducibility criterion, particularly in younger subjects, was in part associated with their smaller heights and lung volumes. A relatively uniform within-subject variability of FVC and FEV1 in terms of the mean differences between the largest and second largest FVC and FEV1, for all heights, was observed. In addition, unlike the ATS reproducibility criterion, when a constant 200-ml reproducibility criterion for FVC and FEV1 was used, there was no longer a significant difference between the number of reproducibility criterion failures for the 14 different height groups used. These results suggest that the ATS reproducibility criterion, based on a percentage of the FVC and FEV1, may inappropriately classify a higher percentage of subjects with smaller heights and lung volumes as having a nonreproducible test. In contrast, subjects with larger heights and lung volumes are much less likely to fail the ATS reproducibility requirement. These results emphasize the importance of following the ATS recommendation of using the reproducibility criterion only as a goal during data collection, not to classify a subject as having an invalid test.

Adolescent↗
PubMedDate not supplied

Interobserver reproducibility of immunohistochemical HER-2/neu evaluation in human breast cancer: the real-world experience.

In spite of the large number of studies on technical problems affecting the interlaboratory reproducibility of IHC HER-2/neu determination, only little is known about factors limiting the intra- and interobserver reproducibility in the actual practice of HER-2/neu expression analysis. The aim of the present INQAT study was to evaluate the intra- and inter-observer reproducibility of IHC HER-2 analysis among pathologists routinely working in Italian laboratories. Twenty immunostained slides were distributed to 12 pathologists who had to report, for each slide, the semiquantitative analysis of the percentage of immunopositive cells and the qualitative evaluation of the intensity of membrane staining. The intra- and interobserver reproducibility as well as the reproducibility between each laboratory and the reference values were quantified adopting an approach based on computation of the weighted kappa statistic (Kw). Additionally, in order to evaluate the contribution of each category to the overall agreement, the kappa category-specific statistics (Kcs) were estimated for both classification criteria by jointly considering all the participating laboratories. The intraobserver analyses showed a satisfactory level of reproducibility for both the percentage of positive cells (median Kw, 0.94; range: 0.80-0.96) and membrane staining (median Kw, 0.86; range: 0.78-0.96). Similarly, a fairly good level of reproducibility for the percentage of cells (median Kw, 0.89; range, 0.73-0.96) and the intensity of membrane staining (median Kw, 0.84; range, 0.72-0.92) were observed from comparisons with reference values. When all possible pairwise comparisons were performed, a satisfactory level of interobserver reproducibility was found for most laboratories. Kw values varied between 0.51 and 0.98 (median Kw, 0.80) and between 0.61 and 0.94 (median Kw, 0.81) for semiquantitative and qualitative measurements, respectively. Analysis of the contribution of the extreme categories to the overall agreement showed a substantial or almost perfect agreement for both classification criteria. Conversely, the contribution of intermediate categories appeared to be scarce or slight for the percentage of immunostained cells and slight or fair for the intensity of membrane staining. We conclude that, overall, the interobserver reproducibility in IHC analysis of HER-2/neu expression is satisfactory, although classification of the intermediate categories is problematic, both with regard to the percentage of immunostained cells and the intensity of membrane staining.

Breast Neoplasms↗
PubMed1998

Reproducibility of spirometrically controlled CT lung densitometry in a clinical setting.

The aim of this study was to assess the reproducibility of quantitative, spirometrically gated computed tomographic (CT) lung densitometry at defined levels of inspiration in hospitalized patients. On two consecutive days, spirometrically gated CT sections were obtained from 20 hospitalized patients at 5 cm above and 5 cm below the carina, and at 90 and 10% of the vital capacity (VC). The mean, modal and median lung densities were calculated, the cut-off points of the frequency distribution of Hounsfield units (HU) defining the lowest and the highest 10th percentile, as well as the histogram full width at half maximum. The lung density parameters of corresponding CT sections of both studies were compared. Reproducibility was expressed as the standard deviation of the signed difference between the results of Day 1 and Day 2 divided by the square root of 2. Reproducibility data were correlated with results of airflow limitation. At 90% VC, reproducibility was of the order of 3-14 HU in both lung zones. At 10% VC, reproducibility was worse by approximately a factor of three. No relationship was found between reproducibility and results of airflow limitation. In conclusion, objective measurement of lung density at spirometrically controlled levels of inspiration is a reproducible method in assessing pulmonary density. Reproducibility of lung density measurements is not influenced by severe respiratory insufficiency. The most reproducible computed tomographic lung density measurements can be obtained at 90% vital capacity.

Absorptiometry, Photon↗
PubMed2003

Reproducibility of functional MR imaging results using two different MR systems.

BACKGROUND AND PURPOSE: In the application of functional MR imaging for presurgical planning, high reproducibility is required. We investigated whether the reproducibility of functional MR imaging results in healthy volunteers depended on the MR system used. METHODS: Visual functional MR imaging reproducibility experiments were performed with 12 subjects, by using two comparable 1.5-T MR systems from different manufacturers. Each session consisted of two runs, and each subject underwent three sessions, two on one system and one on the other. Reproducibility measures D (distance in millimeters) and R(size) and R(overlap) (ratios) were calculated under three conditions: same session, which compared runs from one session; intersession, which compared runs from different sessions but from the same system; and intermachine, which compared runs from the two different systems. The data were averaged per condition and per system, and were compared. RESULTS: The average same-session values of the reproducibility measures did not differ significantly between the two systems. The average intersession values did not differ significantly as to the volume of activation (R(size)), but did differ significantly as to the location of this volume (D and R(overlap)). The average intermachine reproducibility did not differ significantly from the average intersession reproducibility of the MR system with the worst reproducibility. CONCLUSION: The location of activated voxels from visual functional MR imaging experiments varied more between sessions on one MR system than on other MR system. The amount of the activated voxels is independent of the MR system used. We suggest that sites performing functional MR imaging for presurgical planning measure the intersession reproducibility to determine an accurate surgical safety margin.

Adult↗
PubMed2004

Reproducibility of biofilm processes and the meaning of steady state in biofilm reactors.

The need for reproducing biofilm processes is undisputable - the quality of biofilm research depends on this reproducibility. However, as many biofilm researchers know, long-term biofilm processes are notoriously difficult to reproduce. To avoid problems related to biofilm reproducibility two strategies are used: (1) to study very young biofilms that have accumulated for a few hours to a few days only, and (2) to run biofilm experiments only once. The first approach trades reproducibility for relevance because natural biofilms are usually older, often much older than a few days. This approach can be applied to answer questions relevant to initial events of biofilm formation but not questions relevant to long-term biofilm accumulation. The second approach conceals the problem of biofilm reproducibility. To assure reproducibility of biofilm processes, we methodically followed a procedure for growing biofilms in terms of microbial makeup, media composition, temperature, surface preparation, etc. Despite all this effort the reproducibility of our results for long term growth is unimpressive. Consequently, the question had to be asked: Are biofilm processes reproducible? The experiments described in this paper address this question. Biofilms grown in two identical and identically operated biofilm reactors had comparable structure only until the first sloughing event. After that, biofilms had different patterns of accumulation.

Biofilms↗
PubMed1995

The reproducibility of reported height and body weight in repeated questionnaire surveys.

Reproducibility of reported height and weight were studied via repeated questionnaire surveys distributed to subjects within a year. Effects of the factors which might influence the reproducibility of these values were investigated. Although only about half of the subjects reported the same height and 30% the same weight on the second questionnaire, no change was found in average height and weight after a one year interval for both male and female subjects. The reproducibility decreased with age for both height and weight. Smokers tended to have lower reproducibility for height than non-smokers. The shorter subjects had lower height reproducibility than their taller counterparts, while heavier subjects had lower weight reproducibility than light subjects. It was observed that the lower the weight reproducibility, the lower the height reproducibility and vice versa. Reported height or weight figures ending in zero or five were more frequent than the expected 10% with low reproducibility.

Adult↗