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Results for “Reproducibility”

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At least 271 records · Page 15Linked to original sources

PubMed2001

Reproducibility of retinal mapping using optical coherence tomography.

OBJECTIVE: To assess the reproducibility of retinal thickness measurement using commercially available mapping software of optical coherence tomography (OCT). METHODS: Six radial scans, 6 mm long and centered on the fixation point, were performed on 10 eyes of 10 healthy volunteers and 10 eyes of 10 diabetic patients with clinically significant macular edema. Retinal thickness was measured automatically using the mapping software of OCT in the 9 macular Early Treatment Diabetic Retinopathy Study areas and in a central area 500 microm in diameter. Measurement reproducibility was tested by means of 3 series of scans performed by 2 different observers on 2 different days. Results were assessed by their repeatability and intraclass correlation coefficients (ICCs). RESULTS: In healthy subjects, intraobserver, interobserver, and intervisit reproducibility of retinal thickness measurements were excellent, with a repeatability coefficient of less than 7 microm and ICCs of greater than 0.89. In diabetic patients, the repeatability coefficient was less than 21 microm in all areas of the macula except one, with an ICC of greater than 0.98. Relative variations in measurements were small in both healthy and diabetic subjects, with reproducibilities of +/- 5% and +/- 6%, respectively. CONCLUSION: Retinal mapping software of OCT allows reproducible measurement of retinal thickness in both healthy subjects and diabetic patients with macular edema.

Adult↗

PubMed2005

Repeatability and reproducibility of fast macular thickness mapping with stratus optical coherence tomography.

OBJECTIVE: To determine the repeatability and reproducibility of retinal thickness measurements with the fast macular thickness mapping protocol of Stratus optical coherence tomography. METHODS: Ten eyes of 10 healthy subjects and 15 eyes of 15 diabetic patients with clinically significant macular edema (CSME) underwent 2 scanning sessions before and after pupil dilation during the same visit by 2 experienced examiners. Healthy subjects also received a third scanning session during a second visit. Repeatability and reproducibility for the foveolar center and for each of 9 Early Treatment of Diabetic Retinopathy Study (ETDRS)-like regions were calculated by their repeatability and reproducibility coefficients and intraclass correlation coefficients. RESULTS: The coefficients of repeatability were less than 8% in healthy subjects and less than 9% in patients with diabetes and CSME. The reproducibility coefficients were less than 10% and 11% in healthy subjects and diabetic patients with CSME, respectively. There was no significant difference between scans acquired by different observers or during different visits. The intraclass correlation coefficients were always greater than 0.80 and 0.98 in healthy subjects and diabetic patients with CSME, respectively. Average +/- SD thickness was found to be 223 +/- 14 and 404 +/- 108 mum for the central ETDRS-like region in healthy subjects and diabetic patients with CSME, respectively. CONCLUSION: With the fast macular thickness mapping protocol of Stratus ocular coherence tomography, our results indicate that retinal thickness measurements in dilated and undilated eyes of healthy subjects and diabetic patients with CSME are repeatable and reproducible.

Adolescent↗

PubMed2001

Interobserver reproducibility of cervical cytologic and histologic interpretations: realistic estimates from the ASCUS-LSIL Triage Study.

CONTEXT: Despite a critical presumption of reliability, standards of interpathologist agreement have not been well defined for interpretation of cervical pathology specimens. OBJECTIVE: To determine the reproducibility of cytologic, colposcopic histologic, and loop electrosurgical excision procedure (LEEP) histologic cervical specimen interpretations among multiple well-trained observers. DESIGN AND SETTING: The Atypical Squamous Cells of Undetermined Significance-Low-grade Squamous Intraepithelial Lesion (ASCUS-LSIL) Triage Study (ALTS), an ongoing US multicenter clinical trial. SUBJECTS: From women enrolled in ALTS during 1996-1998, 4948 monolayer cytologic slides, 2237 colposcopic biopsies, and 535 LEEP specimens were interpreted by 7 clinical center and 4 Pathology Quality Control Group (QC) pathologists. MAIN OUTCOME MEASURES: kappa Values calculated for comparison of the original clinical center interpretation and the first QC reviewer's masked interpretation of specimens. RESULTS: For all 3 specimen types, the clinical center pathologists rendered significantly more severe interpretations than did reviewing QC pathologists. The reproducibility of monolayer cytologic interpretations was moderate (kappa = 0.46; 95% confidence interval [CI], 0.44-0.48) and equivalent to the reproducibility of punch biopsy histopathologic interpretations (kappa = 0.46; 95% CI, 0.43-0.49) and LEEP histopathologic interpretations (kappa = 0.49; 95% CI, 0.44-0.55). The lack of reproducibility of histopathology was most evident for less severe interpretations. CONCLUSIONS: Interpretive variability is substantial for all types of cervical specimens. Histopathology of cervical biopsies is not more reproducible than monolayer cytology, and even the interpretation of LEEP results is variable. Given the degree of irreproducibility that exists among well-trained pathologists, realistic performance expectations should guide use of their interpretations.

Biopsy↗

PubMed2000

FMRI of visual encoding: reproducibility of activation.

fMRI, a noninvasive technique to measure brain activation, is gaining clinical interest, because its sensitivity enables individual assessments. However, more insight in the reproducibility of these measurements during higher cognitive tasks is necessary. We performed an fMRI study involving within- and between-subject reproducibility during encoding of complex visual pictures. Ten healthy subjects were studied on three occasions: twice in the same scanning session (study 1 and 2), and a third time, 3-24 days later (study 3). On all 30 occasions but one, activation was found in areas expected on the basis of previous studies, including the fusiform and lingual gyri, occipital and parietal areas, the (para)hippocampal area, and the frontal inferior sulcus. The reproducibility of the number of activated voxels in the whole brain was 72% and 63% (respectively, studies 1 and 2, and 1 and 3). The reproducibility of anatomical identical pixels that supplement these results was 49% and 36%. These reproducibility measures increase about 5-15% when only areas of expected activation are included. The quantitative measurements indicate that there is substantial variation in the volume of activation. The recognition of pictures as tested afterward explains part of this variation between subjects. Our findings indicate that whereas consistent patterns of activation exist, more insight is needed into what determines the volume of activation, especially to assess cognitive alterations in patients over time.

Adult↗

PubMed1994

Histologic grading of breast carcinoma. A reproducibility study.

BACKGROUND: A concern with the histologic grading of breast cancer is that tumor grading is a subjective evaluation that may have problems with reproducibility. METHODS: A single slide from 10 invasive breast cancers was submitted to 25 pathologists who practice in six separate groups. Pathologists graded the tumors using a modified Bloom-Richardson (B-R) scheme, and the results were compared. RESULTS: In 8 of the 10 cases, there was greater than 87% agreement by the pathologists as to the final combined B-R grade, with complete agreement in 2 cases. Only one case had any discrepant opinions that ranged from low to high grade, and this involved only 3 of the 25 pathologists. With respect to B-R score, the pathologists tended to score the tumors as either one of two adjacent scores. Due to this clustering, the B-R scheme appears reproducible into five groups: very low and very high grade tumors and B-R score "5,6," "6,7," and "7,8" tumors. This clustering was especially noticeable in two cases with split decisions, in which the discrepancy in final combined grade was largely due to the tumors being given B-R scores that straddled and were then condensed into two B-R grades. A consensus from each pathology group tended to merge with the majority opinion of all 25 pathologists and was correct for outliers. CONCLUSIONS: This study indicates that reproducibility of grading breast cancers can be achieved when a histologic grading scheme with specified guidelines is used. Pathologists must be aware of the limits of reproducibility, with appropriate guidelines being followed to help optimize agreement, and there should be an awareness of how pathologists group in their evaluations. Also, it may be advisable to better correlate or link reproducibility data with prognostic data in the design of grading schemes.

Breast Neoplasms↗

PubMed2002

Field test of the reproducibility of the semiflexed metatarsophalangeal view in repeated radiographic examinations of subjects with osteoarthritis of the knee.

OBJECTIVE: To estimate the reproducibility of the semiflexed metatarsophalangeal (MTP) view in repeat radiographic examinations of the knee of subjects with osteoarthritis (OA) with respect to radioanatomic alignment of the medial tibial plateau and the central x-ray beam and the precision of measurements of minimum medial tibiofemoral joint space width (JSW). METHODS: Thirty-eight subjects with definite knee OA underwent 2 semiflexed MTP examinations on the same day. Radioanatomic alignment of the medial tibial plateau and the x-ray beam (distance between anterior and posterior margins of the plateau) was measured manually (Lequesne method). Manual measurements of the JSW in repeat radiographs also were obtained. The reproducibility of JSW measurements was estimated by the method of Bland and Altman. RESULTS: Only 29% of the initial semiflexed MTP radiographs exhibited satisfactory radioanatomic alignment (intermargin distance < or =1 mm). However, intermargin distances in initial and repeat radiographs were highly correlated (r = 0.86, P < 0.01). In 89% of knees, the intermargin distance in the first examination was reproduced (+/- 1 mm) in the second examination. The standard error of measurement (mean of within-knee standard deviations of repeat JSW values) was 0.30 mm. The magnitude of discrepancy between repeat measurements of JSW was related positively to overall radiographic severity of knee OA (P < 0.05). CONCLUSION: The semiflexed MTP protocol affords highly reproducible radioanatomic positioning of the knee, although misalignment of the medial tibial plateau and the x-ray beam occurs in >70% of cases. Precision of measurement of JSW in the semiflexed MTP view approaches that associated with fluoroscopically assisted positioning protocols. However, the consequences of poor, albeit reproducible, alignment of the knee in serial semiflexed MTP radiographs in longitudinal studies of OA progression are currently unknown.

Aged↗

PubMed1994

Reproducibility of the spectral turbulence analysis of the signal-averaged electrocardiogram.

Spectral turbulence analysis (STA) of the signal-averaged electrocardiogram (SAECG) is a recently proposed technique to identify patients with ventricular tachycardia as well as patients at risk for arrhythmic events after acute myocardial infarction (MI). The short-term reproducibility of this technique has been previously reported; our study evaluates the reproducibility of STA by shifting the reference points. Twenty patients with acute MI were recruited. SAECG was recorded 13 days after onset of the acute MI. Unfiltered data were transferred and analyzed by personal computer software for spectral turbulence analysis according to the standard condition; reference points of the segment of interest were shifted from QRS offset -10 ms and QRS onset -10 ms to QRS offset +10 ms and QRS onset +10 ms, step 2 ms. Thus, 10 analyses were computed. Reproducibility of the results was calculated using the coefficient of variation (CV) and the relative error (RE). The reproducibility of the classification (RC) was defined as the percentage of the identical classification compared with the standard segment. CV of the intersegment correlation standard deviation was statistically higher than the other parameters regardless of the lead considered. RE was not different in each parameter and in each lead. RC was > 90% in all parameters, except in spectral entropy which showed an RC > 80%. Reproducibility of the STA introducing a temporal shift in the analyzed segments was high in all considered parameters.

Analysis of Variance↗

PubMed2003

Differences in the spatial and quantitative reproducibility between two second-dimensional gel electrophoresis systems.

Two-dimensional polyacrylamide gel electrophoresis (PAGE), together with 2-D gel electrophoresis (GE) analysis software, is a common technique to analyze a complex proteome. In order to accurately locate the differentially expressed proteins in human pituitary macroadenoma tissues in our long-term research program to clarify the molecular mechanisms of macroadenoma formation, a reproducible separation system is needed. An immobilized pH-gradient dry gel-strip (IPG strip) has been extensively used for first-dimensional isoelectric focusing (IEF), and has achieved a high degree of reproducibility in the IEF direction. For the second dimension (SDS-PAGE), different types of gel systems are available, including horizontal vs. vertical gel systems, and gradient vs. constant-percentage gels. A typical horizontal system is the Multiphor II system that analyzes one gel at a time, using a precast gradient gel (180 x 245 x 0.5 mm), and a typical vertical system is the Dodeca system, which analyzes up to 12 gels at a time, using usually a single-concentration gel (190 x 205 x 1 mm). The present study evaluated the spatial and quantitative reproducibility of the two systems for the separation of the complex human pituitary proteome. PDQuest software was used to analyze the digitized gel-image data, and SPSS statistical software was used to analyze the data. The results demonstrated a high percentage (>99%) of protein-spot matches within each electrophoretic system. The Dodeca gel system demonstrated better between-gel reproducibility for spot position, higher resolution in the Sodium dodecyl sulfate (SDS)-PAGE direction, lower gel background, better spot quality, and higher reproducibility of the spot volume.

Electrophoresis, Gel, Two-Dimensional↗

PubMedDate not supplied

Effect of artifacts due to flowing blood on the reproducibility of phase-contrast measurements of myocardial motion.

The reproducibility of myocardial motion trajectories calculated from cine phase-contrast (PC) velocity data is reduced by artifacts due to the inconsistent motion of intracardiac blood. Spatial presaturation reduces these artifacts but requires a longer sequence TR, with a potentially negative effect on trajectory accuracy and reproducibility. We investigated the effect of spatial presaturation on trajectory reproducibility. A mid-ventricular transaxial slice was imaged in five normal volunteers. The same slice was imaged three times each with sequences using spatial presaturation or not. Because the most serious artifacts originate in the heart chambers and propagate in the phase-encoded direction, myocardial regions that were in line with the heart chambers (in the phase-encode direction) had the highest artifact level in the scans without spatial presaturation. The reproducibility of trajectories for regions placed in these areas (the anterior wall, septum and posterior wall in the transaxial scans with phase encoding in the anterior-posterior direction) improved by a factor of two when presaturation was used (P < .001). In areas that were not in line with the heart chambers (eg, the anterior aspect of the lateral wall in the transaxial scans), the effect of presaturation was not significant. These results correlate well with the measured reduction in artifact level. The reproducibility of myocardial motion trajectories over large areas of the heart is improved to approximately 1 mm when presaturation is used. Therefore, use of presaturation is recommended for myocardial motion studies using cine PC velocity data.

Adult↗

PubMed2004

Evaluation of the reproducibility of intrarenal R2* and DeltaR2* measurements following administration of furosemide and during waterload.

PURPOSE: To estimate the reproducibility of BOLD MRI measurements in the evaluation of intrarenal oxygenation levels. MATERIALS AND METHODS: In this study, the reproducibility of semiquantitative BOLD MRI measurements performed on a 1.5 T scanner with a multiple gradient-echo sequence in the renal medulla and cortex, and their response to furosemide and waterload, were assessed in eight healthy young subjects (25.6 +/- 4.1 years). Each subject underwent an identical experimental procedure on two separate days. RESULTS: Renal R2* measurements were shown to be reproducible within approximately 12% from day to day based on a coefficient of variance (CV) analysis. The changes in R2* (DeltaR2*) following administration of furosemide were statistically significant, as shown by ANOVA and a paired Student's t-test, and were deemed reliable based on the reliable change index (RCI). However, DeltaR2* values following waterload were not statistically significant, and were not deemed reliable. CONCLUSION: R2* measurements were reproducible over 270 days within 12%. Furosemide produced a significant and reliable change (approximately 30%), and the magnitude of change (5.7 s(-1)) was reproducible and consistent with our previous data. The response to waterload, however, did not reach statistical significance, and the magnitude did not reach the level that we had previously reported.

Adult↗

PubMed2004

Intra- and interstudy reproducibility of coronary artery diameter measurements in magnetic resonance coronary angiography.

PURPOSE: To determine the intra- and interstudy reproducibility of right coronary artery diameter assessment using serial magnetic resonance (MR) coronary angiography. MATERIALS AND METHODS: Two-dimensional (2D) navigator-gated segmented fast low angle shot (FLASH) images of the proximal right coronary artery were acquired three times in 11 healthy volunteers, the first two times in the same study session and the third time after repositioning the subject in the scanner. Coronary artery diameters were determined using automated segmentation software and intra- and interstudy reproducibility calculated as the standard deviation (SD) of the signed differences between measurements within and between study sessions, respectively. The reproducibility of the segmentation software was determined by repeated analysis of each individual scan. RESULTS: One subject was excluded from the study due to poor-quality images. In the remaining 10 subjects, the mean (+/- SD) intrastudy difference in coronary artery diameters was -0.05 +/- 0.12 mm, a value that is very similar to between-frame (same-film) differences reported in quantitative coronary angiography (QCA). The mean (+/- SD) interstudy difference in coronary artery diameters was 0.16 +/- 0.43 mm, although this was greatly skewed by one subject with poor image plane repositioning. Excluding that subject resulted in a mean (+/- SD) interstudy difference of 0.04 +/- 0.20 mm. The reproducibility of the segmentation software was excellent, with the mean difference between repeat analyses of the images being 0.00 +/- 0.03 mm. CONCLUSION: The intrastudy variability of coronary artery diameter measurements is low, potentially allowing MR coronary angiography to be used as a tool for the noninvasive assessment of serial changes following pharmacological intervention. A major contributing factor to this is the high reproducibility of the segmentation software. Interstudy variability is approximately three times the intrastudy variability.

Adult↗

PubMed1991

Reproducibility of endoscopic sphincter of Oddi manometry.

Results from endoscopic sphincter of Oddi manometry are being used to support the diagnosis of sphincter dysfunction in patients with unexplained pain after cholecystectomy. However, there are few data on the reproducibility of manometric records or motility diagnosis during a second test. In this study, the reproducibility of manometric records was assessed in 12 patients with pain after cholecystectomy by performing a second study after three months. Manometric tracings were evaluated without access to patients details and scored for sphincter basal pressure, frequency and amplitude of phasic contractions, propagation of phasic contractions, and responses to intravenous injection of cholecystokinin octapeptide (20 ng/kg). At the initial manometric study, four patients were diagnosed as normal, four as stenotic, and four as dyskinetic. Those diagnosed as normal and stenotic at the first study had an identical diagnosis at the second study. However, the diagnosis of dyskinesia was reproduced only in two of the four patients. In the other two patients a diagnosis of "stenosis" and "normal" was made at the second study. Cholecystokinin octapeptide (20 ng/kg intravenous bolus) produced inhibition of phasic contractions in all studies, both initially and at three months. We conclude that endoscopic sphincter of Oddi manometry is reproducible when the initial diagnosis is either normal or stenosis. However, the diagnosis of dyskinesia is poorly reproducible, perhaps due to the episodic nature of this manometric disorder or to progression of sphincter of Oddi dysfunction.

Adult↗

PubMed1997

Validity and reproducibility of electrical impedance tomography for measurement of calf blood flow in healthy subjects.

The Sheffield electrical impedance tomography; (EIT) system produces images of changes in the distribution of resistivity within tissue. The paper reports on the application of electrical impedance tomography in monitoring volume changes in the limb during venous occlusion. The aim of the study is to assess the feasibility, reproducibility and validity of calf blood flow measurements by EIT. In 14 healthy volunteers calf blood flow is compared, as determined in a calf segment by strain-gauge plethysmography (SGP), with the impedance changes measured by EIT during rest and post-ischaemic hyperaemia. The measurements are repeated to assess reproducibility. The reproducibility for the EIT, assessed from the repeated measurements and expressed as a reproducibility coefficient, is 0.88 during rest and 0.89 during hyperaemia. The reproducibility coefficient for SGP data is 0.83 at rest and 0.67 during hyperaemia. Flow measurements, assessed by means of two methods, correlate well at rest (r = 0.89), but only moderately during hyperaemia (r = 0.51). The correlation coefficient for the pooled flow measurements is 0.98. It is concluded that EIT is a valid and reliable method for assessing blood flow in the limb. Possible applications of EIT in localising fluid changes are discussed.

Adult↗

PubMed2007

Longitudinal in vivo reproducibility of cartilage volume and surface in osteoarthritis of the knee.

OBJECTIVE: The aim of this study was to evaluate the longitudinal reproducibility of cartilage volume and surface area measurements in moderate osteoarthritis (OA) of the knee. MATERIALS AND METHODS: We analysed 5 MRI (GE 1.5T, sagittal 3D SPGR) data sets of patients with osteoarthritis (OA) of the knee (Kellgren Lawrence grade I-II). Two scans were performed: one baseline scan and one follow-up scan 3 months later (96 +/- 10 days). For segmentation, 3D Slicer 2.5 software was used. Two segmentations were performed by two readers independently who were blinded to the scan dates. Tibial and femoral cartilage volume and surface were determined. Longitudinal and cross-sectional precision errors were calculated using the standard deviation (SD) and coefficient of variation (CV%=100x[SD/mean]) from the repeated measurements in each patient. The in vivo reproducibility was then calculated as the root mean square of these individual reproducibility errors. RESULTS: The cross-sectional root mean squared coefficient of variation (RMSE-CV) was 1.2, 2.2 and 2.4% for surface area measurements (femur, medial and lateral tibia respectively) and 1.4, 1.8 and 1.3% for the corresponding cartilage volumes. Longitudinal RMSE-CV was 3.3, 3.1 and 3.7% for the surface area measurements (femur, medial and lateral tibia respectively) and 2.3, 3.3 and 2.4% for femur, medial and lateral tibia cartilage volumes. CONCLUSION: The longitudinal in vivo reproducibility of cartilage surface and volume measurements in the knee using this segmentation method is excellent. To the best of our knowledge we measured, for the first time, the longitudinal reproducibility of cartilage volume and surface area in participants with mild to moderate OA.

Adult↗

PubMed1997

Image interpretation in CT of laryngeal carcinoma: a study on intra- and interobserver reproducibility.

The object of our study was to evaluate the intra- and interobserver reproducibility of the interpretation of CT examinations of laryngeal carcinoma. The CT examinations of 100 laryngeal cancers were retrospectively reviewed twice by two independent reviewers. Involvement of different structures was assessed, using a standard scoring form. Statistical analysis was done using the Wilcoxon signed rank test and Cohen's kappa. A borderline significant difference between the observers (p < 0.04) was present. Fair to substantial intraobserver reproducibility (kappa = 0.29-0.86), and fair to substantial interobserver reproducibility (average kappa = 0. 26-0.74) were found for most laryngeal structures when a dichotomous categorical scale was used. On the average somewhat lower, but still fair to substantial, intraobserver (kappa = 0.36-0.72), and fair to moderate interobserver (average kappa = 0.29-0.47) reproducibility, were found when a nominal or ordinal categorical scale was used. In conclusion, the interpretation of CT images of laryngeal tumors is reproducible.

Carcinoma, Squamous Cell↗

PubMed2002

[Reproducibility of measuring retinal nerve fiber density. Comparison of optical coherence tomography with the nerve fiber analyzer and the Heidelberg retinal tomography device].

BACKGROUND: Glaucoma is associated with a progressive loss of retinal ganglion cell axons and the evaluation of the thickness of the retinal nerve fibre layer (RNFL) is important for early diagnosis and follow-up. Results of RNFL thickness measurements may vary according to the devices used. Therefore, the present study has analysed and compared the reproducibility of data obtained with three different instruments. METHODS: RNFL thickness was determined using a circular identification line around the optic nerve head by optical coherence tomography (OCT), a Heidelberg Retina Tomograph (HRT) and a Nerve Fiber Analyser (NFA). Each eye was tested six times. The values for RNFL thickness were calculated for the superior, inferior, nasal and temporal areas. A one-way analysis of variance with random effects was chosen to estimate the variance components. The intraclass correlation coefficient (ICC) as a measure of reliability and the coefficient of variation (CV%) as a measure of precision were determined to estimate the reproducibility of RNFL thickness measurements. RESULTS: With all three instruments, the reproducibility of measurements between the superior, inferior, temporal and nasal areas did not differ significantly suggesting that reproducibility does not depend on the thickness of the RNFL. Data obtained by NFA showed the highest ICC values (0.9) and lowest CV% values (7.0), followed by those obtained by HRT (reliability ICC 0.8; precision CV% 12). A markedly lower degree of reproducibility was found for the OCT compared to NFA and HRT (reliability ICC 0.5; precision CV% 15). CONCLUSION: The comparison of RNFL thickness measurements with OCT, NFA, and HRT showed that the NFA yielded the most reliable results followed by HRT.

Adolescent↗

PubMed1997

[Reproducibility of the pattern electroretinogram].

The pattern ERG (PERG) is used as an indicator of retinal ganglion cell function. Up to now, reports on the reproducibility of the PERG have been contradictory. We investigated the reproducibility under the conditions of the forthcoming ISCEV guidelines for the PERG. We simultaneously recorded the PERG and VEP in 42 eyes of 21 subjects to phase-reversing checkerboard stimuli with DTL electrodes. Both transient (2 rps) and steady-state (16 rps) stimulation was employed. The check sizes were 0.4 degree, 0.8 degree and 16 degrees, the mean luminance 45 cd/m2, the contrast 98%, and the field size 32 degrees x 27 degrees. Measurements were repeated at the same time of day after 1 week. In addition, we compared two different electrode positions in 16 eyes: (1) across the cornea along the lower lid; and deep in the conjunctival sac. With position (1) the amplitudes were found to be higher by 20% than (2). We calculated the coefficient of variation (CV) of amplitude as a measure of reproducibility. CV was 7 +/- 1% for the steady-state PERG, 9 +/- 1% for the transient PERG, 12 +/- 2% for the steady-state VEP and 14 +/- 3% for the transient VEP. For the latency of the PERG, the intersession CV was found to be 1.5%. Amplitude reproducibility was somewhat higher under steady-state as compared to transient stimulation; we attribute this to the high noise rejection of the Fourier analysis. Altogether, the amplitude reproducibility of the PERG is somewhat higher than that of the VEP.

Adult↗

PubMed2005

Reproducibility of activation in four motor paradigms. An fMRI study.

Most functional imaging data are collected in single session experiments; little is known about the reproducibility or test-retest reliability of the activation patterns found in these experiments. In our study, 15 healthy volunteers performed four simple motor-paradigms ("Hand", "Foot", "Mouth" and "Tongue") for functional magnetic resonance imaging (fMRI) in 3 sessions on different days. Reproducibility of activations in four anatomical regions (pre- and postcentral gyri, paracentral lobule and the supplementary motor area) was measured in terms of voxels active in all sessions (common voxels) relative to voxels active in single sessions, giving reliability coefficients from 0 to 1. Two significance levels were used to identify active voxels. Reproducibility of activations was highest for foot and hand movements in the primary motorsensory areas; reliability coefficients were in the range of 0.62 to 0.78. Activations for mouth movements showed a very poor reproducibility. Application of the more stringent statistical threshold always led to a reduction of reproducible voxels. Reliability of fMRI data is not only a theoretical issue, but is of special practical importance in clinical settings such as integration of fMRI into neuronavigation for neurosurgical planning. Much care has to be taken if only single session data are available for interpretation.

Adult↗