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Results for “Reproducibility”

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At least 289 records · Page 16Linked to original sources

PubMed2005

Repeatability and reproducibility of optic nerve head topography using the retinal thickness analyzer.

OBJECTIVE: The objective was to determine the reproducibility and repeatability of topographic disk parameters with the retinal thickness analyzer (RTA). METHODS: Thirty-nine eyes of 39 healthy subjects were included. Three observers performed three consecutive measurements of optic disk topography independently. Combined repeatability (intra-observer component of variability) and reproducibility (inter-observer component of variability, R and R) was assessed by variance component analysis. RESULTS: Six topographic parameters (disk area, cup area, cup volume, mean cup depth, maximum depth, and cup shape measure) revealed an acceptable repeatability and reproducibility expressed as the percentage of the total measurement variability (range 17.6-28.4%). The average reproducibility and repeatability of all optic disk parameters measured using the RTA was not acceptable (combined R and R = 33.4%). CONCLUSIONS: Repeatability and reproducibility of the optic disk topography analysis using the RTA reveals a high variation, and should, therefore, be interpreted carefully for glaucoma diagnosis and for monitoring the disease.

Adult↗

PubMed2005

Reproducibility of relationships between human ventilation, its components and oesophageal temperature during incremental exercise.

For human exercise at intensities greater than approximately 70 to 85% of maximal levels of exertion, ventilation (V E) increases proportionately to core temperature (T C) following distinct T C thresholds. This suggested T C in humans could be a modulator of exercise-induced ventilation. This study tested the reproducibility of relationships between oesophageal temperature (T oes) ventilation and its components during incremental exercise. On two nonconsecutive days, at an ambient temperature of 22.1+/-0.3 degrees C and RH of 45+/-5%, seven untrained adult males of normal physique pedaled on a seated cycle ergometer in an incremental exercise protocol from rest to the point of exhaustion. In each exercise session, ventilatory equivalents for oxygen consumption (VE.VO2 (1-)) and carbon dioxide production (VE.VCO2 (1-)) plus the components of V E, tidal volume (V T) and frequency of respiration (f), were expressed as a function of T oes. Results indicated the reproducibility criteria of Bland and Altman were met for the relationships between T oes and both (VE.VO2 (1-)) and (VE.VCO2 (1-)) as well as for relationships between T oes and each of V T and f. Intraclass correlation coefficients (R) for between-trial T oes thresholds for (R=0.91, P<0.05) and (R=0.88, P<0.05) were also high and significant. In both trials, after T oes increased by approximately 0.3 degrees C, V T demonstrated a distinct plateau point at a reproducible T oes (R=0.93, P<0.05) and f demonstrated a distinct and reproducible T oes threshold (R=0.84, P<0.05). In conclusion, the results illustrate that for humans, ventilation has a significant and reproducible relationship with core temperature during incremental exercise.

Adolescent↗

PubMed2003

Reproducibility of the 1998 World Health Organization/International Society of Urologic Pathology classification of papillary urothelial neoplasms of the urinary bladder.

OBJECTIVES: This study assessed the diagnostic agreement and intra- and inter-observer reproducibility of the World Health Organization/International Society of Urologic Pathology Consensus Classification of Urothelial Neoplasms (1998 WHO/ISUP classification) and the 1973 WHO classification. METHODS: A teaching set with 5 slides of each papillary neoplasm of low malignant potential, low-grade papillary carcinoma, high-grade papillary carcinoma, and a guideline, as well as a study set of 30 slides containing ten cases of each category, were sent to participants. Six pathologists expert in urological pathology reviewed the 30 slides of non-invasive papillary urothelial tumors in the study set. Diagnostic accuracy and reproducibility were evaluated using intra- and inter-rater techniques (kappa statistic). RESULTS: A moderate to substantial intra- and inter-observer reproducibility was achieved for both the 1998 WHO/ISUP and 1973 WHO classification. The results of the two classification systems were not different statistically ( P>0.05). Reproducibility was lower in low-grade tumors for both classifications. CONCLUSIONS: The new proposed classification system for non-invasive urothelial neoplasms does not increase the reproducibility. There is still a need for uniformity in grading in order to compare the different studies and therapies and to provide more accurate information for management.

Carcinoma, Papillary↗

PubMed2004

Reproducibility of diabetes mellitus diagnosis (WHO 1999 criteria) in women.

Reproducibility of diabetes mellitus (DM) diagnosis has been recognized as non-optimal and a few studies have analyzed its reproducibility using new diagnostic criteria. Our aim was to evaluate the reproducibility of WHO 1999 criteria for DM diagnosis in women. A total of 696 caucasian women with previous gestational diabetes mellitus (GDM) underwent an OGTT at a median of 6.2 years (interquartile range, 0.5-7.3) after delivery. When OGTT was diagnostic of DM, a second test was scheduled and performed after a median of 3 months (interquartile range, 1.6-10.6). At the second test, 35 women were diagnosed with DM (12 by fasting plasma glucose (FPG) alone, 10 by isolated post-challenge hyperglycemia (IPH), 10 by fasting and 2-h plasma glucose, 3 by symptoms of hyperglycemia plus measurement of plasma glucose). DM was confirmed in 56.3% of women diagnosed without symptoms. In this subgroup, reproducibility according to the abnormality at the first test was: 33.3% in those diagnosed by FPG alone, 40% in those diagnosed by IPH, and 100% in those diagnosed by both fasting and 2-h plasma glucose ( p<0.05 vs. the two previous groups). In women with former GDM, the reproducibility of DM diagnosis by FPG alone or IPH is similar and lower than the diagnosis made by abnormality in both values.

Adult↗

PubMed1991

A prospective evaluation of the immediate reproducibility of the signal-averaged ECG.

The purpose of this investigation was to prospectively evaluate the immediate reproducibility of the signal-averaged electrocardiogram (SAECG). A total of 114 patients undergoing evaluation for ventricular arrhythmias were enrolled in this protocol. Two consecutive SAECG's (40 Hz bidirectional high-pass filtering with a computer-automated system) were performed 10 minutes apart. Abnormal SAECG parameters were defined as (1) vector QRS duration more than 120 msec, (2) terminal root mean square (RMS) voltage less than 20 microV, and (3) low-amplitude signal (LAS) duration more than 40 msec. An SAECG was defined as abnormal if at least one vector parameter was abnormal. There was close correlation between vector parameters during the two SAECG observations: QRS duration had the highest reproducibility (r2 = 0.97, p less than 0.001) followed by terminal RMS voltage (r2 = 0.92, p less than 0.001), and LAS duration (r2 = 0.90, p less than 0.001). The mean (+/- SD) percentage of change between the two recordings was 2% +/- 2% of the QRS duration, 13% +/- 22% for terminal RMS voltage, and 7% +/- 11% for LAS duration. The reproducibility of an initially normal SAECG was 92% and of an initially abnormal SAECG, 96%. Seventeen patients (15%) had a change in one of the three vector parameters between the two recordings. There were no clinically significant differences between the 17 patients in whom the SAECG was nonreproducible and the 97 patients in whom the SAECG was reproducible. However, reproducibility was significantly higher in patients with an initially normal versus an initially abnormal SAECG (92% vs 76%, p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗

PubMed1989

Reproducibility of exercise-induced ventricular arrhythmia in patients undergoing evaluation for malignant ventricular arrhythmia.

In patients with malignant ventricular arrhythmia, the utility of exercise testing for exposing arrhythmias and guiding antiarrhythmic drug selection and dosage is not yet generally accepted. A major reservation relates to the issue of reproducibility of arrhythmia provocation. This prospective study comprised 28 patients referred for evaluation of ventricular arrhythmia. In half of these subjects the clinical arrhythmia was sustained ventricular tachycardia or ventricular fibrillation. Maximal exercise testing adhering to a Bruce protocol was performed on 2 separate days. No antiarrhythmic drugs were administered at the time of testing. Of the 28 patients, 27 had an increase in arrhythmia with exercise. The prevalence rates of arrhythmia were greater than 80% and did not significantly differ between test 1 and test 2. Excluding infrequent single ventricular premature complexes, the reproducibility of a test with positive outcome was 76%. Similarly, test-retest agreement, a bidirectional measure of reproducibility, was greater than 74%. Kappa coefficients ranged from 0.26 to 0.36 for all grades of arrhythmia, indicating that reproducibility was consistently greater than by chance alone. Linear regression analysis of arrhythmia frequency in the 2 tests yielded R values of 0.76 to 0.96 and slopes of 0.82 to 1.2. No patient had enough spontaneous variability in repetitive forms to suggest spurious efficacy or aggravation. For ventricular premature complexes there was an 8 to 14% incidence of spurious efficacy and a 4 to 7% incidence of spurious aggravation. These results suggest that exercise-induced ventricular arrhythmia is sufficiently reproducible to serve as an adjunct method in the evaluation and management of patients with potentially life-threatening ventricular arrhythmias.

Adult↗

PubMed1996

Short- and long-term reproducibility of time and frequency domain heart rate variability measurements in normal subjects.

OBJECTIVE: To obtain data relating to the reproducibility of the time and frequency domain measurements obtained from 10-min ECG recordings. METHODS: Eighteen normal volunteers underwent evaluations of time and frequency domain heart rate variability 2 weeks and 7 months after baseline analysis. The time domain parameters were mean NN, the standard deviation of NN intervals, the percentage of successive NN intervals > 50 ms and the root mean square successive difference of NN intervals. The frequency domain evaluations (total power, low frequency, and high frequency) were made by means of both the Fast Fourier Transform algorithm (FFT) and the autoregressive method (AR) from 10-min ECG recordings made under three different conditions: rest, controlled respiration, and after a passive head-up tilt test. Reproducibility was evaluated by means of the interclass correlation coefficient (ICC), comparing baseline values with the results obtained at the second week and the seventh month. Time domain evaluation were also made from 10-min ECG. RESULTS: All of the time domain measurements had an ICC > or = 0.75, except for the standard deviation of NN intervals, which had an ICC of 0.57. The frequency domain parameters obtained by means of either FFT or AR showed similar reproducibility. Low frequency was reproducible under all three conditions, total power only at rest, and high frequency only during controlled respiration. CONCLUSION: The reproducibility of frequency domain parameters depends on the analysed condition. These results are of primary importance when the effects of drugs or other interventions on heart rate variability are under investigation.

Adult↗

PubMedDate not supplied

Variation in late potentials and the reproducibility of their measurement.

The usefulness of a test depends on its reproducibility. This determines how closely the test result indicates the actual pathophysiologic state, how well it will predict that state in the future, and if interventions or further pathologic changes are reflected by the test. There is a variation in the parameters of the signal-averaged ECG, more so with spectral than with time domain measurements. These must be accounted for when estimating risk. If one presumes that risk is proportional to the extent of abnormality, then the variation in measurements simply means that only borderline cases can potentially be miscategorized. More important, the lack of reproducibility of measurements made from the signal-averaged ECG indicates that changes noted in an individual after an intervention, such as a surgical intervention, must be viewed with a jaundiced eye. Group changes are perhaps meaningful, and indicate a physiologic effect, but clinical decisions cannot be made unless the changes observed in an individual patient exceed the confidence limits of expected variation. There has been debate as to the usefulness of measurements made from the signal-averaged ECG in predicting antiarrhythmic drug effects (the effect of drugs is discussed elsewhere in this symposium). Here an analogy must be made to the suppression of asymptomatic ventricular ectopy. First, we cannot make a statement that there has been a drug effect unless the parameter measured changes beyond the confidence limits of normal variation or reproducibility. Second, we cannot translate a change in a measurement into a change in risk for arrhythmic events without subjecting that hypothesized relationship to a long-term placebo-controlled clinical trial, albeit acute electrophysiologic trials correlating changes in the signal-averaged ECG to ventricular tachycardia induction provide some insight. And perhaps the relationship must be tested independently for each drug assessed. In the same regard, there is much excitement about the benefits of thrombolytic therapy, but when diagnosing benefit to the individual patient we have to remember the lack of reproducibility of the measurements and also keep in mind that an improved signal-averaged ECG cannot be translated into an improved prognosis without long-term controlled studies. In summarizing the variation and reproducibility of measurements made from the signal-averaged ECG we avoided providing more than a sense of the extent of variation expected because precise confidence intervals depend on the particular techniques used to make the measurements.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

PubMed1990

Day to day reproducibility of electrically inducible ventricular arrhythmias in survivors of acute myocardial infarction.

Day to day reproducibility of the response to programmed ventricular stimulation has not been evaluated in survivors of acute myocardial infarction. Programmed ventricular stimulation was performed prospectively on 2 consecutive days in 56 patients on an average of 12 +/- 5 days (range 7 to 29) after an acute myocardial infarction. No patient had a history of documented or suspected sustained ventricular tachycardia or fibrillation occurring greater than 48 h after infarction. During initial programmed ventricular stimulation, 21 patients had induction of sustained ventricular tachycardia or fibrillation (Group I), and 35 patients had induction of either nonsustained ventricular tachycardia or no ventricular tachycardia (Group II). Repeat programmed ventricular stimulation in Group I patients induced sustained ventricular tachycardia or fibrillation in 16 of 21 patients (reproducibility 76%); the maximal induced response in the other 5 patients was nonsustained ventricular tachycardia in 2 patients and fewer than six repetitive ventricular responses in 3 patients. The day to day reproducibility was significantly higher for inducible sustained ventricular tachycardia of cycle length greater than or equal to 240 ms compared with rapid sustained ventricular tachycardia of cycle length less than 240 ms (100% versus 44%, p less than 0.009) or ventricular fibrillation (100% versus 43%, p less than 0.009). Repeat programmed ventricular stimulation in Group II patients did not induce sustained ventricular arrhythmias in 31 of 35 patients (reproducibility 89%). Thus, in survivors of acute myocardial infarction, inducible slow sustained ventricular tachycardia was a highly reproducible finding, whereas inducibility of rapid sustained ventricular tachycardia and ventricular fibrillation showed a significant day to day variability.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Immediate reproducibility of electrically induced sustained monomorphic ventricular tachycardia before and during antiarrhythmic therapy.

The immediate reproducibility of sustained ventricular tachycardia induction was evaluated prospectively during 106 studies performed in 53 patients with clinical sustained monomorphic ventricular tachycardia. Programmed electrical stimulation was performed twice, using the same protocol during 53 drug-free studies and 53 subsequent studies on antiarrhythmic therapy. Sustained monomorphic ventricular tachycardia was reproduced in 104 (98%) of the 106 studies. There was no significant difference in the incidence of reproducible tachycardia in the drug-free state compared with that observed during treatment with different classes of antiarrhythmic drugs. An increase in the number of extrastimuli was required to reinitiate the tachycardia in 9 (11%) of 83 studies in which single or double extrastimuli were initially required to induce the tachycardia. In 39 (37%) of 104 studies with reproducible tachycardia induction, the two tachycardias significantly differed in electrocardiographic (ECG) configuration and cycle length. These observations suggest that the overall reproducibility of ventricular tachycardia induction is sufficiently high to provide a reliable marker for evaluating the efficacy of therapeutic interventions. However, specific tachycardia characteristics such as cycle length and ECG configuration are more variable even within the same study and may be less useful in assessing the effects of subsequent interventions.

Anti-Arrhythmia Agents↗

PubMed1990

Characteristics of individuals and long term reproducibility of dietary reports: the Tecumseh Diet Methodology Study.

Food frequency reports in 1967-1969 were compared to frequency reports of the same foods asked retrospectively in 1982-1983 and 1967-1969 for 1184 respondents aged 45-64 years in the Tecumseh Community Health Study. The kappa statistic for concordance of the retrospective and baseline reports was used as a summary measure of the individual's ability to reproduce his or her earlier diet report. Reproducibility was estimated for total diet, represented by 83 foods, and for 9 subsets of foods of epidemiologic interest. In bivariate and multivariate analyses, reproducibility was strongly related to stability of diet; those whose diets changed least over the 15-year period had greatest diet reproducibility. Greater total diet reproducibility was also found among men with higher education, among women of less than 110% desirable weight reporting no special diet and among women reporting no medications. Consistent with current models of memory, the retrospective report of diet was strongly related to the current report of diet. Agreement between the retrospective and baseline diet reports was greater than agreement between the current and baseline diet reports. This indicates that, as a proxy for past diet, the retrospective report of diet is superior to the current report. Similar relationships were found for the 9 subset of foods.

Body Weight↗

PubMed2005

Reproducibility of Doppler echocardiographic assessment of left ventricular diastolic function in multicenter setting.

BACKGROUND: Whether Doppler echocardiography allows reliable assessment of left ventricular (LV) diastolic parameters in multicenter studies is disputed. METHODS: To assess interstudy reproducibility of Doppler echocardiographic parameters of LV filling and relaxation in multicenter setting, two laboratories assessed Doppler parameters of LV filling and relaxation twice within 24 hours in 56 participants. The study sample included hospitalized patients, clinically healthy outpatients, and healthy volunteers. All studies were performed according to a standardized protocol, and read by a single reader. RESULTS: In the whole study sample the reproducibility of the assessment of the ratio between the peak velocities of the early (E) and late (A) LV filling waves (E/A), of the E wave deceleration time and atrial filling fraction, measured at the mitral valve leaflet tips, was good (intraclass correlation coefficients, rho: 0.89-0.76); the reproducibility performance of the same parameters measured at the mitral anulus was less good. The reproducibility of the assessment of the isovolumic relaxation time was good (rho: 0.81), and that of the E-wave propagation rate (E-Vp), by color M-mode, was excellent (rho: 0.96). The reproducibility of the ratio E wave peak velocity/E-Vp was also fairly good (rho: 0.87). The classification of E-Vp < 45 cm/s and E-Vp > or = 55 cm/s showed the highest between-study reliability performance (agreement index kappa = 0.92 and 0.83, respectively, both P < .001), followed by E/A at mitral leaflet tips >1.5 or <0.8 (kappa = 0.78 and 0.74, respectively, both P < .01), whereas the worst reliability performance was shown by isovolumic relaxation time < 60 milliseconds (kappa = 0.05, P = not significant). CONCLUSIONS: Standardized procedures for imaging and readings allowed good reliability of serial Doppler echocardiographic evaluations of LV filling and relaxation parameters in multicenter setting.

Adult↗

PubMed2006

Reproducibility of white-coat and masked hypertension in ambulatory BP monitoring.

BACKGROUND: White-coat hypertension and masked hypertension have clinical and prognostic consequences. However, reproducibility of these phenomena is unknown. We examined the reproducibility of the white-coat and masking effects with real-life ambulatory blood pressure monitoring (ABPM). METHODS: In a retrospective analysis of a prospectively assembled ABPM database there were 196 subjects (age 58+/-16 years, 59% female, 73% treated for hypertension) who underwent repeat ABPM for standard clinical indications. White-coat hypertension (or isolated manual uncontrolled hypertension) was defined as normal (<135/85 mmHg) awake blood pressure (BP) and abnormal (>or=140/90 mmHg) manual BP. Masked hypertension (or isolated ambulatory uncontrolled hypertension) was defined as abnormal awake BP with normal manual BP. RESULTS: Treated and untreated subjects had similar distribution among hypertension subgroups; 16% white-coat hypertension (in treated subjects, isolated manual uncontrolled hypertension), 13% masked hypertension (in treated subjects, isolated ambulatory uncontrolled hypertension), 59% uncontrolled hypertension, 12% normal blood pressure (or controlled hypertension). In the second session the prevalence of white-coat and masked hypertension increased. Of 31 subjects with white-coat hypertension in the first session 19 (61%) remained ambulatory normotensive in the second session, while 18 of 25 (72%) masked hypertensive subjects remained ambulatory hypertensive. The reproducibility of the systolic manual-awake blood pressure difference was not inferior to that of other ambulatory variables. In untreated subjects the reproducibility of white-coat hypertension, masked hypertension and the white-coat effect was even better. CONCLUSION: In a real-life ABPM database, we found white-coat hypertension and the masking phenomenon to be reasonably reproducible, as compared to other BP variables.

Blood Pressure Determination↗

PubMed2006

Quadriceps and hamstring isokinetic strength and electromyographic activity measured at different ranges of motion: a reproducibility study.

Isokinetic strength measurements of the quadriceps and hamstring that are commonly conducted using a 90 degrees range of motion (RoM) may involve some risk to specific knee patient groups. Testing these muscles at a much shorter RoM may reduce the risk but in order to render this method clinically acceptable the reproducibility of the derived test findings has to be established. Therefore the main objective of this study was to assess the reproducibility of isokinetic peak torque and normalized EMG scores of these muscles based on 90 degrees (0-90 degrees flexion, LR) and three successive short RoMs: 0-30 degrees (SR1), 30-60 degrees (SR2) and 60-90 degrees (SR3). Eight healthy subjects were tested three times with a 2 week between-session interval. All tests were performed on the dominant limb and consisted of maximal concentric and eccentric exertions. The velocities applied were 90 degrees /s for LR and 30 degrees /s for each of the SRs. Findings indicated no between-session improvement in strength. Based on the coefficient of variation the measurement error for all isokinetic strength scores remained stable throughout the testing sessions ranging 0.6-13.9% with the absolute majority of instances less than 10%. The reproducibility of the EMG scores was poorer ranging 1.5-25% and 0.5-19% for the quadriceps and hamstring, respectively. It is concluded that testing of knee muscles at short (30 degrees ) RoMs does not compromise the reproducibility of the strength or EMG scores derived from the commonly used RoM of 90 degrees . However, whereas strength was reproducible to within the accepted clinical standards, the corresponding EMG scores were characterized by a wider error band.

Adult↗

PubMed2005

Relationships between tibial rim alignment and joint space width measurement reproducibility in non-fluoroscopic radiographs of osteoarthritic knees.

RATIONALE: Superimposition of the rims of the medial tibial plateau to within 1mm is an aim of fluoroscopic knee positioning protocols for osteoarthritic (OA) knee radiography and has also been proposed as a measure of quality for non-fluoroscopic methods. OBJECTIVE: To evaluate the effect of tibial rim alignment (TRA) on reproducibility of joint space width (JSW) measurement, both were measured from radiographs taken with each tibial plateau at a range of angles determined by different non-fluoroscopic views. METHODS: TRA and JSW measurements were taken from both knees of 100 OA patients each radiographed in fully extended, schuss/tunnel, and MTP views. Degree of TRA was compared with JSW reproducibility using correlation, and between groups defined both by the 1mm threshold and by TRA-defined quartiles. RESULTS: JSW reproducibility was dependent on the degree of TRA in the fully extended and schuss/tunnel flexed knee views, although the use of the specific TRA threshold of 1mm was not supported. In the MTP view, JSW measurement was found to be highly reproducible across the full range of TRA values. CONCLUSION: These results contradict claims that TRA to within 1mm is essential for useful measurement of JSW. It is an arbitrary threshold, of use in quality control (QC) for protocols which explicitly require such alignment, and the choice of QC criteria for other protocols should be evaluated on a view-by-view basis. The results confirm previous studies showing the MTP view to afford highly reproducible JSW measurement.

Aged↗

PubMed2006

Repeatability and reproducibility of posterior corneal curvature measurements by combined scanning-slit and placido-disc topography after LASIK.

OBJECTIVE: To assess the repeatability and reproducibility of posterior corneal curvature (PCC) measurements made by combined scanning-slit/Placido-disc topography (Orbscan II) after LASIK. DESIGN: Experimental instrument validation study. PARTICIPANTS: We recruited 22 consecutive postmyopic LASIK patients for the repeatability study and another 50 consecutive postmyopic LASIK patients for the reproducibility study. METHODS: To analyze intrasession repeatability, 1 examiner measured 22 postmyopic LASIK eyes 10 times successively in the shortest time possible. To study intersession reproducibility, the same operator obtained measurements from another 50 eyes with stable refraction in 2 consecutive visits at the same time of the day between 6 and 9 months after myopic LASIK. We explored any association between residual stromal bed thickness and measurement variability. MAIN OUTCOME MEASURES: Orbscan II scanning-slit PCC data, precision, within-subject coefficient of variation (CV(w)), limits of agreement (LoA), and intraclass correlation coefficient (ICC). RESULTS: For intrasession repeatability, precision was 0.067 mm (best-fit sphere [BFS]), 0.110 diopters (D; power within 5 mm), 0.158 D (power within 3 mm), and 0.46 (eccentricity). Repeatability was high for PCC BFS and power measurements within 3-mm and 5-mm zones (CV(w) ranged from 0.5%-1.2%) but poor for eccentricity data (CV(w), 31.6%). Correspondingly, ICCs ranged from 0.89 to 0.98 for PCC BFS and power, and the ICC was 0.20 for PCC eccentricity values. For intersession reproducibility, on average, no difference in PCC measurements could be found, indicating that when there is variability, it is due to random factors. The width of the 95% LoA between sessions was clinically acceptable for BFS (0.25 mm) and power (0.4 D [within 5 mm] and 0.6 D [within 3 mm]). Similarly, ICCs indicated good intersession reliability for BFS and power (0.98, 0.96, and 0.85 for BFS, power within 5 mm, and power within 3 mm, respectively) but poor reliability for eccentricity (0.59). Repeatability and reproducibility were unrelated to stromal bed thickness. CONCLUSIONS: Orbscan II provides reliable post-LASIK PCC data for symmetrical parameters (BFS and power), independent of the residual stromal bed thickness, but is unreliable for measurements that are radially asymmetrical (eccentricity). Orbscan II is useful for monitoring the PCC after LASIK once the early postoperative period is over.

Adult↗

PubMed2006

Prediction of lung tumour position based on spirometry and on abdominal displacement: accuracy and reproducibility.

BACKGROUND AND PURPOSE: A simulation investigating the accuracy and reproducibility of a tumour motion prediction model over clinical time frames is presented. The model is formed from surrogate and tumour motion measurements, and used to predict the future position of the tumour from surrogate measurements alone. PATIENTS AND METHODS: Data were acquired from five non-small cell lung cancer patients, on 3 days. Measurements of respiratory volume by spirometry and abdominal displacement by a real-time position tracking system were acquired simultaneously with X-ray fluoroscopy measurements of superior-inferior tumour displacement. A model of tumour motion was established and used to predict future tumour position, based on surrogate input data. The calculated position was compared against true tumour motion as seen on fluoroscopy. Three different imaging strategies, pre-treatment, pre-fraction and intrafractional imaging, were employed in establishing the fitting parameters of the prediction model. The impact of each imaging strategy upon accuracy and reproducibility was quantified. RESULTS: When establishing the predictive model using pre-treatment imaging, four of five patients exhibited poor interfractional reproducibility for either surrogate in subsequent sessions. Simulating the formulation of the predictive model prior to each fraction resulted in improved interfractional reproducibility. The accuracy of the prediction model was only improved in one of five patients when intrafractional imaging was used. CONCLUSIONS: Employing a prediction model established from measurements acquired at planning resulted in localization errors. Pre-fractional imaging improved the accuracy and reproducibility of the prediction model. Intrafractional imaging was of less value, suggesting that the accuracy limit of a surrogate-based prediction model is reached with once-daily imaging.

Abdomen↗

PubMed2002

Comparison of interstudy reproducibility of cardiovascular magnetic resonance with two-dimensional echocardiography in normal subjects and in patients with heart failure or left ventricular hypertrophy.

Fast breath-hold cardiovascular magnetic resonance (CMR) shows excellent results for interstudy reproducibility of left ventricular (LV) volumes, ejection fraction, and mass, which are thought to be superior to results of 2-dimensional echocardiography. However, there is no direct comparison of the interstudy reproducibility of both methods in the same subjects. A total of 60 subjects (normal volunteers [n = 20], or patients with heart failure [n = 20] or LV hypertrophy [n = 20]) underwent 2 CMRs and 2 echocardiographic studies for assessment of LV volumes, function, and mass. The interstudy reproducibility coefficient of variability was superior for CMR in all groups for all parameters. Statistical significance was reached for end-systolic volume (4.4% to 9.2% vs 13.7% to 20.3%, p <0.001), ejection fraction (2.4% to 7.3% vs 8.6% to 19.4%, p <0.001), and mass (2.8% to 4.8% vs 11.6% to 15.7% p <0.001), with a trend for end-diastolic volume (2.9% to 4.9% vs 5.5% to 10.5%, p = 0.17). The superior interstudy reproducibility resulted in considerably lower calculated sample sizes (reductions of 55% to 93%) required by CMR compared with echocardiography to show clinically relevant changes in LV dimensions and function. Thus, CMR has excellent interstudy reproducibility in normal, dilated, and hypertrophic hearts, and is superior to 2-dimensional echocardiography.

Adult↗