Intraobserver Variability Of Measurements Research Articles

3-D Ultrasound Segmentation of the Placenta Using the Random Walker Algorithm: Reliability and Agreement

Volumetric segmentation of the placenta using 3-D ultrasound is currently performed clinically to investigate correlation between organ volume and fetal outcome or pathology. Previously, interpolative or semi-automatic contour-based methodologies were used to provide volumetric results. We describe the validation of an original random walker (RW)-based algorithm against manual segmentation and an existing semi-automated method, virtual organ computer-aided analysis (VOCAL), using initialization time, inter- and intra-observer variability of volumetric measurements and quantification accuracy (with respect to manual segmentation) as metrics of success. Both semi-automatic methods require initialization. Therefore, the first experiment compared initialization times. Initialization was timed by one observer using 20 subjects. This revealed significant differences (p < 0.001) in time taken to initialize the VOCAL method compared with the RW method. In the second experiment, 10 subjects were used to analyze intra-/inter-observer variability between two observers. Bland–Altman plots were used to analyze variability combined with intra- and inter-observer variability measured by intra-class correlation coefficients, which were reported for all three methods. Intra-class correlation coefficient values for intra-observer variability were higher for the RW method than for VOCAL, and both were similar to manual segmentation. Inter-observer variability was 0.94 (0.88, 0.97), 0.91 (0.81, 0.95) and 0.80 (0.61, 0.90) for manual, RW and VOCAL, respectively. Finally, a third observer with no prior ultrasound experience was introduced and volumetric differences from manual segmentation were reported. Dice similarity coefficients for observers 1, 2 and 3 were respectively 0.84 ± 0.12, 0.94 ± 0.08 and 0.84 ± 0.11, and the mean was 0.87 ± 0.13. The RW algorithm was found to provide results concordant with those for manual segmentation and to outperform VOCAL in aspects of observer reliability. The training of an additional untrained observer was investigated, and results revealed that with the appropriate initialization protocol, results for observers with varying levels of experience were concordant. We found that with appropriate training, the RW method can be used for fast, repeatable 3-D measurement of placental volume.

Reliability of Mid-Upper Arm Circumference Measurements taken by Community Health Nurses

Mid upper arm circumference-based diagnosis of severe acute malnutrition is seen as very attractive because it is assumed to be simple to use in measuring the arm and also requires a single cut-off without having to compute an index or compare to a reference population. The circumference of the left upper arm measured at the mid-point between the tip of the shoulder and the tip of the elbow is referred to as mid upper arm circumference (MUAC). MUAC was originally used in emergency settings where huge populations had to be screened within a short time. However, in the past few years the development of community therapeutic care of acute malnutrition implied a need for a diagnostic tool. The general objective of the study was to assess the inter- and intra-observer variability in MUAC measurements of under-five children by community health nurses in selected communities of the Northern Region in Ghana. A community-based cohort study was conducted on a convenience sample of 120 community health nurses and nursing students from selected communities in the Northern region of Ghana. Each CHN measured MUAC for four unique children on three consecutive days to assess intra-observer variability. To assess inter-observer variability, 50 independent nursing students took MUAC measures of four children on the same day. Bland Altman plots showed a high degree of agreement of MUAC measures taken repeatedly for three days by the same observers and ICC= 0.993. MUAC measures among observers (inter-observer) and ICC =0.042 showed a considerable level of variability among different observers. This study showed that MUAC is reliable when repeated measures are taken on children by the same observers, but using different observers for the same children showed a high level of variability.

The Fetal Modified Myocardial Performance Index: Is Automation the Future?

The fetal modified myocardial performance index (Mod-MPI) is a noninvasive, pulsed-wave Doppler-derived measure of global myocardial function. This review assesses the progress in technical refinements of its measurement and the potential for automation to be the crucial next step. The Mod-MPI is a ratio of isovolumetric to ejection time cardiac time intervals, and the potential for the left ventricular Mod-MPI as a tool to clinically assess fetal cardiac function is well-established. However, there are wide variations in published reference ranges, as (1) a standardised method of selecting cardiac time intervals used in Mod-MPI calculation has not been established; (2) cardiac time interval measurement currently requires manual, inherently subjective placement of callipers on Doppler ultrasound waveforms; and (3) ultrasound machine settings and ultrasound system type have been found to affect Mod-MPI measurement. Collectively these factors create potential for significant inter- and intraobserver measurement variability. Automated measurement of the Mod-MPI may be the next key development which propels the Mod-MPI into routine clinical use. A novel automated system of Mod-MPI measurement is briefly presented and its implications for the future of the Mod-MPI in fetal cardiology are discussed.

Developing an accurate method for estimating thyroid volume in calves using ultrasonography.

Diseases of the thyroid gland with struma formation can occur in calves suffering from iodine deficiency. The aim of the study was to develop a guideline for standardized ultrasonographic examination of the thyroid gland in order to determine its volume. Sonographic measurements of the thyroid lobes were carried out on three standardized axes in calves up to 3 months of age (n = 83). Total volume (V SON ) was calculated using the formula for an ellipsoid body. Forty three of the enrolled animals were euthanized. The lobes of their thyroid glands were dissected and measured with a slide gauge, and V SLG was calculated accordingly. In addition, thyroid volume was measured using the method of water displacement (V AQU ) and this was used as a gold standard in correlation and regression analyses with sonographic and slide gauge values. Intraobserver variability of sonographic measurements was dependent on side and axis, and ranged between 3.04% and 7.35%. In the euthanized calves with a body mass of 52.4 ± 17.1 kg, V SLG was 4.5 ± 1.4 ml, V SON was 6.5 ± 1.7 ml, and V AQU was 7.9 ± 2.4 ml (mean ± standard deviation). Instead of the formula for ellipsoid bodies which underestimates thyroid volume, we developed a new formula derived from regression analysis. Body mass and thyroid volume correlated significantly. With the formula presented, thyroid volume of calves can be estimated by ultrasonographic measurement of three axes and compared to predicted values based on body mass.

Supine to standing Cobb angle change in idiopathic scoliosis: the effect of endplate pre-selection.

BackgroundSupine imaging modalities provide valuable 3D information on scoliotic anatomy, but the altered spine geometry between the supine and standing positions affects the Cobb angle measurement. Previous studies report a mean 7°-10° Cobb angle increase from supine to standing, but none have reported the effect of endplate pre-selection or whether other parameters affect this Cobb angle difference.MethodsCobb angles from existing coronal radiographs were compared to those on existing low-dose CT scans taken within three months of the reference radiograph for a group of females with adolescent idiopathic scoliosis. Reformatted coronal CT images were used to measure supine Cobb angles with and without endplate pre-selection (end-plates selected from the radiographs) by two observers on three separate occasions. Inter and intra-observer measurement variability were assessed. Multi-linear regression was used to investigate whether there was a relationship between supine to standing Cobb angle change and eight variables: patient age, mass, standing Cobb angle, Risser sign, ligament laxity, Lenke type, fulcrum flexibility and time delay between radiograph and CT scan.ResultsFifty-two patients with right thoracic Lenke Type 1 curves and mean age 14.6 years (SD 1.8) were included. The mean Cobb angle on standing radiographs was 51.9° (SD 6.7). The mean Cobb angle on supine CT images without pre-selection of endplates was 41.1° (SD 6.4). The mean Cobb angle on supine CT images with endplate pre-selection was 40.5° (SD 6.6). Pre-selecting vertebral endplates increased the mean Cobb change by 0.6° (SD 2.3, range -9° to 6°). When free to do so, observers chose different levels for the end vertebrae in 39% of cases. Multi-linear regression revealed a statistically significant relationship between supine to standing Cobb change and fulcrum flexibility (p = 0.001), age (p = 0.027) and standing Cobb angle (p < 0.001). The 95% confidence intervals for intra-observer and inter-observer measurement variability were 3.1° and 3.6°, respectively.ConclusionsPre-selecting vertebral endplates causes minor changes to the mean supine to standing Cobb change. There is a statistically significant relationship between supine to standing Cobb change and fulcrum flexibility such that this difference can be considered a potential alternative measure of spinal flexibility.

Gastrointestinal ultrasonography of normal Standardbred neonates and frequency of asymptomatic intussusceptions.

BackgroundUltrasonographic appearance of the gastrointestinal (GI) tract of equine neonates has not been completely described.ObjectivesTo describe (1) sonographic characteristics of the GI segments in normal nonsedated equine neonates, (2) intra‐ and interobserver variation in wall thickness, and (3) the sonographic appearance of asymptomatic intussusceptions, and (4) to compare age and sonographic findings of foals with and without asymptomatic intussusceptions.AnimalsEighteen healthy Standardbred foals ≤5 days of age.MethodsProspective, cross‐sectional blinded study. Gastrointestinal sonograms were performed stall‐side. Intraobserver variability in wall thickness measurements was determined by calculating the coefficient of variation (CV). The Bland–Altman method was used to assess interobserver bias. Student's t‐test and Fisher's exact test were used to test the association among presence of intussusceptions, age, and selected sonographic findings.ResultsThe reference ranges (95% predictive interval) for wall thickness were 1.6–3.6 mm for the stomach, 1.9–3.2 mm for the duodenum, 1.9–3.1 mm for the jejunum, 1.3–2.2 mm for the colon, and 0.8–2.7 mm for the cecum. Intraobserver wall thickness CV ranged from 8 to 21% for the 2 observers for 5 gastrointestinal segments. The interobserver bias for wall thickness measurements was not significant except for the stomach (0.14 mm, P < .05) and duodenum (0.29 mm, P < .05). Diagnostic images of mural blood flow could not be obtained. Asymptomatic intussusceptions were found in 10/18 neonates. Associations between sonographic variables or age and the presence of intussusceptions were not found.Conclusions and Clinical ImportanceSonographic characteristics of the GI tract of normal Standardbred neonates can be useful in evaluating ill foals. Asymptomatic small intestinal intussusceptions occur in normal Standardbred neonates.

Intraobserver variability in fibroid size measurements: estimated effects on assessing fibroid growth.

To evaluate intraobserver variability of fibroid sonographic measurements and apply this factor to fibroid growth assessment. Study participants were African American women aged 23 to 34 years who had never had a diagnosis of uterine fibroids. All participants underwent transvaginal sonography to screen for the presence of previously undiagnosed fibroids (≥0.5 cm in diameter). The diameters of up to 6 fibroids were measured in 3 perpendicular planes at 3 separate times during the examinations by experienced sonographers. Intraobserver variability as measured by the coefficient of variation (CV) for fibroid diameter and volume was calculated for each fibroid, and factors associated with the CV were assessed by regression models. The impact of variability on growth assessment was determined. Ninety-six of 300 women screened were found to have at least 1 fibroid, yielding a total of 174 fibroids for this analysis. The mean CV for the 3 measurements of fibroid maximum diameter was 5.9%. The mean CV for fibroid volume was 12.7%. Fibroid size contributed significantly to intraobserver variability (P = .04), with greater variability for smaller fibroids. Fibroid type (submucosal, intramural, or subserosal) was not important. Fibroids from the same woman tended to have similar measurement variability when assessed for volume but not for maximum diameter. Calculations showed that when following up fibroids, as much as a 20% increase in diameter could be due to measurement error, not "true growth." A small fibroid must have a greater change in size than a large fibroid to conclude that it is growing, but even for small fibroids an increase in diameter of greater than 20% is likely to indicate true growth, not measurement variability.

Inter- and intra-observer variability in cervical measurement by ultrasound in the first and second trimesters of pregnancy: does it matter?

The aim of this study was to evaluate the inter- and intra-observer variabilities in the cervical length (CL) measurement by transvaginal ultrasound (TVU) in the first and second trimesters of pregnancy. A total of 55 singleton pregnant women were evaluated in the first or second ultrasound. Each patient was blindly evaluated by three of the four observers who performed three measurements each. In the first and second trimesters, patients were evaluated at 12.3 weeks (mean) and 21.3 weeks (mean), respectively. The intra-class correlation coefficients (ICC) between observers in the first and second trimesters were 0.76 and 0.72, respectively, and the ICCs within observers were 0.889 and 0.899, respectively. In both trimesters, the main source of variance was the patient and the second source of variance was the interaction, Patient×Observer (12.0% and 13.5%, respectively). The observer and measurement explained a small proportion of variance in both trimesters (1.4% and 0.4%, respectively in the 1st trimester, and 3.3% and 0%, respectively in the 2nd trimester). The residual variances were 10.6% and 11.2%, and the standard errors of measurement were 1.78 mm and 1.82 mm for the first and second trimesters, respectively. TVU is a reliable and reproducible method by which to predict preterm birth in both the first and second trimesters.

CT-based quantitative evaluation of radiation-induced lung fibrosis: a study of interobserver and intraobserver variations.

PurposeThe degree of radiation-induced lung fibrosis (RILF) can be measured quantitatively by fibrosis volume (VF) on chest computed tomography (CT) scan. The purpose of this study was to investigate the interobserver and intraobserver variability in CT-based measurement of VF.Materials and MethodsWe selected 10 non-small cell lung cancer patients developed with RILF after postoperative radiation therapy (PORT) and delineated VF on the follow-up chest CT scanned at more than 6 months after radiotherapy. Three radiation oncologists independently delineated VF to investigate the interobserver variability. Three times of delineation of VF was performed by two radiation oncologists for the analysis of intraobserver variability. We analysed the concordance index (CI) and inter/intraclass correlation coefficient (ICC).ResultsThe median CI was 0.61 (range, 0.44 to 0.68) for interobserver variability and the median CIs for intraobserver variability were 0.69 (range, 0.65 to 0.79) and 0.61(range, 0.55 to 0.65) by two observers. The ICC for interobserver variability was 0.974 (p < 0.001) and ICCs for intraobserver variability were 0.996 (p < 0.001) and 0.991 (p < 0.001), respectively.ConclusionCT-based measurement of VF with patients who received PORT was a highly consistent and reproducible quantitative method between and within observers.

Intraobserver and interobserver variability in computed tomography size and attenuation measurements in patients with renal cell carcinoma receiving antiangiogenic therapy: Implications for alternative response criteria

Alternative response criteria have been proposed in patients with metastatic renal cell carcinoma (mRCC) who are receiving vascular endothelial growth factor (VEGF)-targeted therapy, including 10% tumor shrinkage as an indicator of response/outcome. However, to the authors' knowledge, intraobserver and interobserver measurement variability have not been defined in this setting. The objective of the current study was to determine intraobserver and interobserver agreement of computed tomography (CT) size and attenuation measurements to establish reproducible response indicators. Seventy-one patients with mRCC with 179 target lesions were enrolled in phase 2 and phase 3 trials of VEGF-targeted therapies and retrospectively studied with Institutional Review Board approval. Two radiologists independently measured the long axis diameter and mean attenuation of target lesions at baseline and on follow-up CT. Concordance correlation coefficients and Bland-Altman plots were used to assess intraobserver and interobserver agreement. High concordance correlation coefficients (range, 0.8602-0.9984) were observed in all types of measurements. The 95% limits of agreement for the percentage change of the sum longest diameter was -7.30% to 7.86% for intraobserver variability, indicating that 10% tumor shrinkage represents a true change in tumor size when measured by a single observer. The 95% limits of interobserver variability were -16.3% to 15.4%. On multivariate analysis, the location of the lesion was found to significantly contribute to interobserver variability (P = .048). The 95% limits of intraobserver agreement for the percentage change in CT attenuation were -18.34% to 16.7%. In patients with mRCC who are treated with VEGF inhibitors, 10% tumor shrinkage is a reproducible radiologic response indicator when baseline and follow-up studies are measured by a single radiologist. Lesion location contributes significantly to measurement variability and should be considered when selecting target lesions.

Intra-observer, inter-experiment and inter-observer variability of left ventricular volumes and mass measurements in mice using an 11.7 Tesla MRI

Background In cardiovascular research, there is an increasing interest in high-field MRI to characterize cardiac anatomy and function in small rodents. However, data on reproducibility of the method are scarce. Our aim was to evaluate the intra-observer, inter-experiment and inter-observer variability of left ventricular (LV) mass and volumes measurements in mice using an 11.7T MRI scanner. Methods Seven 10 weeks-old C57Bl6J male mice were studied, including 4 animals with a surgical transverse aortic constriction in order to produce cardiac hypertrophy. 3 were sham (control) mice. During the entire procedure, animals were anaesthetized with Isoflurane 1-3%, in a temperature-controlled setting. Scan were retrospectively gated for electrocardiogram (ECG) and respiration. Imaging was performed on a 11.7 Tesla Bruker MR scanner. Cardiac scout images were obtained in the conventional planes with a tripilot sequence. A 2D cine FLASH sequence was applied to acquire a set of 7 contiguous short axis images covering the entire ventricles, perpendicular to the LV long axis. One day after the procedure, mice were scanned again under the same conditions. The LV systolic function was assessed from each stack of images by tracing epicardial and endocardial borders, including papillary muscles, on the Segment software (Medviso, Sweden). End-diastolic (EDV), end-systolic (ESV) and stroke volume (SV) were determined (µl). LV ejection fraction (EF, in %) and LV mass (mg) were subsequently deduced. One stack of images was analyzed twice by the same person, and once by an independent observer. Results Accurate quantitative data were obtained in all animals. The Table 1 lists the mean ± SD values and the Bland-Altman and Pearson analysis results. The best reproducibility was obtained for the measurements of LV mass and EDV, with a coefficient of variability (Cov) between 1.70 and 12%. More variation was found in ESV measurement (CoV 1-70-22.40%). Results for SV and EF were the less reproducible, with a CoV between 14.52 and 31.45%. The Pearson correlation coefficient indicates good correlation between all methods for all parameters (r square between 0.81 and 0.99), except for the SV, particularly in terms of inter-experiment reproducibility (r square =0.03). Conclusions In our hands, reproducibility was excellent for LV mass and EDV, good for ESV and EF to al esser extent, and more limited for the stroke volume, with a bad inter-observer correlation. This highlights the need to interpret our results by taking into account these limitations, focusing on more reproducible parameters when interpreting data.

Fetal left brachiocephalic vein in normal and abnormal conditions

To establish values of fetal left brachiocephalic vein (LBCV) dimensions during normal pregnancy and determine whether routine assessment of the LBCV may help in identifying fetuses with congenital abnormalities of this vessel. Fetal LBCV was assessed prospectively during ultrasound examinations in 431 normal singleton pregnancies. The visualization rate of the transverse view of the upper fetal chest at the level of drainage of the LBCV into the superior vena cava (SVC) by two-dimensional (2D) and 2D plus color Doppler ultrasound was evaluated. Reference ranges of LBCV diameter during non-complicated pregnancies were established. Interobserver and intraobserver measurement variability was analyzed. In addition, a retrospective review of the hospital medical records of 91 pregnancies with fetuses diagnosed with LBCV abnormalities was performed. Sonographic assessment of the fetal LBCV was consistently achieved in the second and third trimesters and in some fetuses in the first trimester of pregnancy. In normal fetuses LBCV diameter increased significantly throughout pregnancy, with a mean value of 0.7 mm at 11 weeks and 4.9 mm at term. Dilation of the fetal LBCV was noted in five cases of intracranial arteriovenous malformation and six cases of supracardiac type total anomalous pulmonary venous connection. Abnormal course of the LBCV was noted in 12 fetuses. In 63 fetuses with a persistent left SVC and a right SVC the LBCV was absent. This is the first study describing an effective sonographic approach for the assessment of fetal LBCV dimensions during pregnancy. The normative data may provide an additional means of detecting rare anomalies of systemic and pulmonary veins during pregnancy.

1113 3D Digital Capture of Head Circumference and Volume in Neonates - A Method Evaluation

BackgroundManual measurement of head circumference (HC) is used to quantify head growth in preterm infants. Laser shape digitizers offer semi-automatic HC measuring and additional information on head volume (HV). Reliability...

Real-Time 3D Echocardiographic Quantification of Left Atrial Volume: Multicenter Study for Validation With CMR

We studied in a multicenter setting the accuracy and reproducibility of 3-dimensional echocardiography (3DE)-derived measurements of left atrial volume (LAV) using new, dedicated volumetric software, side by side with 2-dimensional echocardiography (2DE), using cardiac magnetic resonance (CMR) imaging as a reference. Increased LAV is associated with adverse cardiovascular outcomes. Although LAV measurements are routinely performed using 2DE, this methodology is limited because it is view dependent and relies on geometric assumptions regarding left atrial shape. Real-time 3DE is free of these limitations and accordingly is an attractive alternative for the evaluation of LAV. However, few studies have validated 3DE-derived LAV measurements against an accepted independent reference standard, such as CMR imaging. We studied 92 patients with a wide range of LAV who underwent CMR (1.5-T) and echocardiographic imaging on the same day. Images were analyzed to obtain maximal and minimal LAV: CMR images using standard commercial tools, 2DE images using a biplane area-length technique, and 3DE images using Tomtec LA Function software. Intertechnique comparisons included linear regression and Bland-Altman analyses. Reproducibility of all 3 techniques was assessed by calculating the percentage of absolute differences in blinded repeated measurements. Kappa statistics were used to compare 2DE and 3DE classification of normal/enlarged against the CMR reference. 3DE-derived LAV values showed higher correlation with CMR than 2DE measurements (r = 0.93 vs. r = 0.74 for maximal LAV; r = 0.88 vs. r = 0.82 for minimal LAV). Although 2DE underestimated maximal LAV by 31 ± 25 ml and minimal LAV by 16 ± 32 ml, 3DE resulted in a minimal bias of -1 ± 14 ml for maximal LAV and 0 ± 21 ml for minimal LAV. Interobserver and intraobserver variability of 2DE and 3DE measurements of maximal LAV were similar (7% to 12%) and approximately 2 times higher than CMR (4% to 5%). 3DE classified enlarged atria more accurately than 2DE (kappa: 0.88 vs. 0.71). Compared with CMR reference, 3DE-derived LAV measurements are more accurate than 2DE-based analysis, resulting in fewer patients with undetected atrial enlargement.

Evaluation of transvesical intra‐abdominal pressure measurement in hospitalized dogs

To (1) evaluate intra-abdominal pressure (IAP) measurements in dogs with possible risk factors for the development of intra-abdominal hypertension (IAH); (2) determine intra-observer variability of IAP measurements; and (3) determine interobserver variability of IAP measurements. Prospective, observational, pilot study. Veterinary teaching hospital. Fourteen client-owned dogs, requiring urinary catheterization, admitted to the ICU. Using the risk factors for IAH established for human patients as defined by the World Society of Abdominal Compartment Syndrome, dogs were assigned to either an IAH risk or no risk group. A commercially available IAP monitoring system was used to obtain 3 direct, transvesical IAP measurements. The primary investigator obtained the first 2 IAP measurements. A secondary investigator obtained the third IAP measurement. Dogs in the IAH risk group (n = 9/14) had significantly higher mean IAPs (9.4 ± 3.4 mm Hg) than dogs in the no risk group (n = 5/14; 4.1 ± 0.9 mm Hg) (P < 0.05). Measurements recorded by the primary investigator were compared to determine intra-observer variability. Pearson's correlation coefficient was 0.98 (P < 0.0001). Bland-Altman analysis determined a mean difference in IAP measurements of -0.3 mm Hg (95% confidence interval from 0.13 to -0.71 mm Hg) indicating an intra-observer variability of less than 0.8 mm Hg. Measurements recorded by the primary and secondary investigator were compared to determine interobserver variability. Pearson's correlation coefficient was 0.95 (P < 0.0001). Bland-Altman analysis determined a mean difference in IAP measurements of 0 mm Hg (95% confidence interval from 1.1 to -1.1 mm Hg) indicating an interobserver variability of less than 2.0 mm Hg. Dogs with predefined human risk factors for IAH had higher IAP than dogs without risk factors. IAP monitoring appears to have low variability within and across observers.

Assessment of intra-observer variability in measurement of high-grade brain tumors

A 25% increase in bidimensional products (BPs) of tumor diameter has been used as a criterion for brain tumor progression. We studied intra-observer variability in measurements of BPs. Ten patients with contrast-enhancing glioblastoma multiforme underwent baseline and follow-up MR imaging. Seven observers measured BPs in various planes. Differences in BPs between scans were expressed as a percentage of baseline. This calculation was performed for both readings of the baseline and follow-up scans. Differences between change from baseline to follow-up on each reading (termed D values) were calculated for each reader (total of 196 D values). Median D value in each plane was calculated for each reader. Range of D values was 12.36-33.64% in axial plane (average 10.63%), 12.18-38.62% in coronal plane (average 26.84%) and 15.12-35.48% in sagittal plane (average 26.11%). Across all planes, 88 (45%) D values were >25%. When all imaging planes for any single observation were combined, in 76% of cases, at least one D value of >25% was seen. Based on the high degree of intra-observer variability, tumor measurements producing an increase in BP of >25% can routinely be obtained solely by chance.

Reproducibility of Lumen and Vessel Wall Measurements in Carotid Magnetic Resonance Imaging

Atherosclerotic carotid artery disease is estimated to represent the etiology for one quarter of all strokes. Carotid magnetic resonance imaging and magnetic resonance angiography are promising tools in the evaluation of carotid atherosclerotic vascular disease. In this study, we evaluate the reliability of high resolution carotid wall magnetic resonance (MR) imaging by investigating the inter-observer, intra-observer, and inter-scan variability in measurements of carotid vessel total lumen area and mean wall thickness. This HIPAA compliant study received IRB approval and all subjects gave written informed consent. Nineteen subjects were imaged on a 3T MRI scanner with custom-built 4-element receive-only phased-array coils optimized for carotid anatomy. Three observers manually drew regions of interest around the lumen and outer wall for both left and right carotid arteries. Intraclass correlation coefficients (ICC) showed excellent agreement between Observer 1 and the others (>0.92). A two- way analysis of variance (ANOVA) found no significant difference between observers (p>0.05). Intra-observer variability for Observer 1 was measured by coefficient of variation (CV) with 0.03 for total lumen area and 0.03 for mean wall thickness. Similarly, the inter-scan variability of Observer 1 was found by CV to be 0.05±0.02 for total lumen area and 0.04±0.03 for mean wall thickness. Our results demonstrate that the MR measurements of total lumen area and mean wall thickness are highly reproducible and provide a reliable foundation for the evaluation of carotid atherosclerotic vascular disease.

Analysis of pulse wave velocity in the thoracic aorta by flow‐sensitive four‐dimensional MRI: Reproducibility and correlation with characteristics in patients with aortic atherosclerosis

To measure aortic pulse wave velocity (PWV) using flow-sensitive four-dimensional (4D) MRI and to evaluate test-retest reliability, inter- and intra-observer variability in volunteers and correlation with characteristics in patients with aortic atherosclerosis. Flow-sensitive 4D MRI was performed in 12 volunteers (24 ± 3 years) and 86 acute stroke patients (68 ± 9 years) with aortic atherosclerosis. Retrospectively positioned 28 ± 4 analysis planes along the entire aorta (inter-slice-distance = 10 mm) and frame wise lumen segmentation yielded flow-time-curves for each plane. Global aortic PWV was calculated from time-shifts and distances between the upslope portions of all available flow-time curves. Inter- and intra-observer variability of PWV measurements in volunteers (7% and 8%) was low while test-retest reliability (22%) was moderate. PWV in patients was significantly higher compared with volunteers (5.8 ± 2.9 versus 3.8 ± 0.8 m/s; P = 0.02). Among 17 patient characteristics considered, statistical analysis revealed significant (P < 0.05) but low correlation of PWV with age (r = 0.25), aortic valve insufficiency (r = 0.29), and pulse pressure (r = 0.28). Multivariate modeling indicated that aortic valve insufficiency and elevated pulse pressure were significantly associated with higher PWV (adjusted R(2) = 0.13). Flow-sensitive 4D MRI allows for estimating aortic PWV with low observer dependence and moderate test-retest reliability. PWV in patients correlated with age, aortic valve insufficiency, and pulse pressure.

Evaluation of Global Left Ventricular Systolic Function Using Three-Dimensional Echocardiography Speckle-Tracking Strain Parameters

The aim of this study was to evaluate the capacity and reproducibility of three-dimensional echocardiographic (3DE) strain parameters in the assessment of global left ventricular (LV) systolic function. A total of 128 subjects with differing LV ejection fractions were investigated using two-dimensional echocardiographic (2DE) and 3DE strains. Three-dimensional echocardiographic strain allows obtaining longitudinal, circumferential, radial, and area strains. First, values of global longitudinal strain (GLS) by 2DE and 3DE speckle-tracking analyses were compared. Thereafter, 3DE strain parameters were correlated with LV ejection fraction and indexed output. Last, the variability of 3DE versus 2DE strain measurements as well as recorded time of analysis were assessed. After excluding 21 patients for insufficient image quality, four for arrhythmia, two for severe valvular disease, and one for severe dyspnea, the final population consisted of 100 patients. Comparison between 2DE and 3DE GLS revealed high correspondence (r = 0.91, y = 1.04x - 0.71) and mean error measurement of -1.3% (95% confidence interval, -5.7 to 3.2). Among strain parameters, global area strain exhibited the highest correlation with LV ejection fraction (y = -1.65 + 10.4, r = -0.92, P < .001). Intraobserver measurement variability proved acceptable: 8% for GLS (vs 6% on 2DE analysis), 7% for circumferential strain (vs 15% on 2DE analysis), 7% for radial strain (vs 33% on 2DE analysis), and 5% for global area strain. The mean error between two measurements was lower with 3DE than 2DE analysis for circumferential and radial strains but similar for GLS. The mean time of analysis was of 117 ± 16 sec for 3DE analysis, which was 25% less than for 2DE analysis (P < .001). Of all strain parameters, new 3DE area strain correlated best with common LV systolic function parameters and is thus the most promising approach, while all 3DE strain markers exhibited good reproducibility.

Semiautomated Image Processing Method for Identification and Quantification of Geographic Atrophy in Age-Related Macular Degeneration

To determine intraobserver and interobserver longitudinal measurement variability of novel semiautomated software for quantification of age-related macular degeneration-associated geographic atrophy (GA) based on confocal scanning laser ophthalmoscopy fundus autofluorescence (FAF) imaging. Three-field FAF (excitation 488 nm, emission 500-700 nm), near-infrared reflectance (820 nm), and blue reflectance (488 nm) images of 30 GA subjects were recorded according to a standardized protocol at baseline after 6 and 12 months. At all visits, the GA area was analyzed on central FAF images by seven independent readers using semiautomated software. The software allows direct export of FAF images from the database and semiautomated detection of atrophic areas by shadow correction, vessel detection, and selection of seed points. The mean size of atrophy at baseline and the mean progression rate were 5.96 mm² (range, 1.80-15.87) and 1.25 mm²/year (0.42-2.93), respectively. Mean difference of interobserver agreement (Bland-Altman statistics) ranged from -0.25 to 0.30 mm² for the baseline visit and from -0.14 to 0.11 mm²/year for the atrophy progression rate. Corresponding reflectance images were helpful for lesion boundary discrimination, particularly for evaluation of foveal GA involvement and when image quality was poor. The new image processing software offers an accurate, reproducible, and time-efficient identification and quantification of outer retinal atrophy and its progression over time. It facilitates measurements both in natural history studies and in interventional trials to evaluate new pharmacologic agents designed to limit GA enlargement.