Variability Of Ultrasound Measurements Research Articles

Ovarian Cystadenomas: Growth Rate and Reliability of Imaging Measurements.

To evaluate the growth rate of benign ovarian cystadenomas and the degree of variability in ultrasound measurements. Two independent retrospective cohorts of women found to have benign cystadenomas at surgery were identified. To assess growth rate, ultrasounds on women in a community-based health system were reviewed and the growth rate was determined based on the maximum reported size dimension using a mixed effect model. To assess measurement variability, two radiologists independently measured presurgical adnexal imaging findings for women in a tertiary care referral setting. Interobserver, intra-observer, and intermodality (cine clip versus still images) variability in measurements was determined using correlation coefficients (CC) and Bland-Altman analysis, with the proportion of measurements varying by more than 1 cm calculated. For growth rate assessment, 405 women with 1412 ultrasound examinations were identified. The median growth rate was 0.65 cm/year with mucinous cystadenomas growing faster at 0.83 cm/year compared to 0.51 cm/year for serous cystadenomas (median test P < .0001). To evaluate measurement variability, 75 women were identified with 176 ultrasound studies. The within-subject standard deviations for ultrasound measurements were 0.74 cm for cine clip images and 0.41 cm for static images, with 11% of measurements overall differing by more than 1cm. Cystadenomas grow on average 0.65 cm/year, which is similar in magnitude to the inherent error observed in measurement on ultrasound, suggesting that repeat ultrasound at intervals of longer than a year will often be needed to accurately assess growth if a cyst represents a benign cystadenoma.

Intraobserver and Interobserver Variability in Ultrasound Measurements of Thyroid Nodules.

The purpose of this study was to assess the intraobserver and interobserver variability in ultrasound (US) measurements of thyroid nodules. We performed a prospective study of the US examinations of 73 patients with 122 thyroid nodules greater than 5 mm in size. Ultrasound measurements in 4 dimensions (anteroposterior, transverse, longitudinal, and maximum diameters) and measurement of the estimated volume (using the ellipsoid formula) of each thyroid nodule were performed twice by 2 independent radiologists (A and B, with 10 years and 6 months of experience, respectively). The intraobserver and interobserver variability in measurements of thyroid nodules was assessed by a Bland-Altman analysis of agreement. The absolute values for intraobserver and interobserver variability were compared by a paired t test. The 95% intraobserver and interobserver limits of agreement for the anteroposterior, transverse, longitudinal, and maximum diameters and estimated volume of thyroid nodules were ±18.2%, ± 14.3%, and ±21.0%; ± 17.2%%, ± 17.3%, and 18.2%; ± 14.6%, ± 15.5%, and ±22.3%; ± 13.8%, ± 15.5%, and ±19.6%; and ±30.2%, ± 27.7%, and ±44.1%, respectively. The absolute values for intraobserver variability were lower than those for interobserver variability for all measurements. There was considerable intraobserver and interobserver variability in US measurement of thyroid nodules, which must be taken into account during follow-up US examinations of patients with thyroid nodules.

Variability in Ultrasound Measurement of Hyoid Bone Displacement and Submental Muscle Size Using 2 Methods of Data Acquisition

Objective: This study compares variability in measures of hyoid bone displacement and submental muscle size using 2 methods of ultrasound transducer placement: fixed and hand-held. Patients and Methods: Twenty-four healthy participants (11 males, 13 females) aged between 51 and 84 years were scanned using both methods. Repeated measures were collected within and across 3 sessions. Results: A nonlinear mixed effects model was used to estimate the effects of the method, trial, and session. The fixed transducer produced greater within- and across-session variability on several measures compared to the hand-held method. Fixed-transducer measurements of hyoid bone displacement were 9.4% smaller compared to hand-held measurements (F[1, 24.34] = 3.58, p = 0.07). Conclusion: Results suggest that using a fixed transducer does not necessarily improve measurement accuracy of swallowing outcomes in a healthy system. The wide variability in individual measures indicates that further research is required before ultrasound is used for outcome measurement in rehabilitation.

The potential impact on clinical outcomes and service provision of variability in ultrasound measurement of peak systolic velocity in a multi-centre vascular network

The potential impact on clinical outcomes and service provision of variability in ultrasound measurement of peak systolic velocity in a multi-centre vascular network

Perioperative compliance with VSGBI quality improvement framework for major limb amputations in a single vascular centre

Perioperative compliance with VSGBI quality improvement framework for major limb amputations in a single vascular centre

Use of Carotid Intima-Media Thickness Regression to Guide Therapy and Management of Cardiac Risks

Although carotid intima-media thickness (IMT) has been broadly used as a tool to evaluate cardiovascular risk, its role as a surrogate endpoint is still debated. The main issue is the fact that no study has ever been powered to show a relationship between changes in carotid IMT during follow-up and cardiovascular events. A meta-analysis of existing clinical studies was performed to investigate this relationship but it failed to demonstrate a predictive role of regression in carotid IMT for cardiovascular events. The reasons for the lack of a clear evidence for a predictive role of IMT progression are unknown but are likely multifactorial. Firstly, it may depend on the fact that this index is not a pure atherosclerosis index. Second, carotid atherosclerosis does not always reflect coronary atherosclerosis. Furthermore, methodologic problems related to intra- and interobserver variability make this index not adequately reproducible when tracking the progression of carotid atherosclerosis. A further meta-analysis based on individual patient data, instead of published data, has been planned to better address the predictive role of IMT. Lastly, in the future, the variability of ultrasound measurements of carotid IMT are likely to be reduced by further development of automatic calculation of this index by magnetic resonance imaging.

ASUM Press Release.

ASUM would like to draw your attention to recent research conducted by the University of London and the Katholieke Universiteit Leuven, Belgium, published in the November 2011 issue of Ultrasound in Obstetrics and Gynaecology. The studies suggest that given inter-observer variability in ultrasound measurements and the significant variation in early embryonic growth, a more conservative approach to the diagnosis of early pregnancy loss is warranted. The recommendation which has been temporarily endorsed by the RCOG suggests a mean sac diameter (MSD) cut off > 25 mm and a crown rump length (CRL) cut off> 7 mm be introduced to minimise the risk of a false positive diagnosis of miscarriage. While this research awaits confirmation from other centres ASUM suggests interim caution and highlights the importance of transvaginal confirmation of early pregnancy failure. It should also be noted that many other factors are used when assessing early pregnancy failure, including the presence of a yolk sac, shape of the gestation sac, position within the uterine cavity or cervix, progress from a previous scan and correlation with known gestational age especially in IVF pregnancies.

OC20.02: Assessment of sonographers' variability in ultrasound measurements of BPD, HC, AC and FL

OC20.02: Assessment of sonographers' variability in ultrasound measurements of BPD, HC, AC and FL

Reproducibility of ultrasound measurement of the abdominal aorta

Abdominal aortic aneurysm (AAA) screening and surveillance programmes use ultrasound imaging to measure the anteroposterior (AP) diameter of the infrarenal aorta. The aim of this study was to examine potential observer bias and variability in ultrasound measurements. Studies were identified for review via a MEDLINE database search (1966-2009). References supplied in accessed papers were also checked for potential relevance. Consistent search terminology, and inclusion and exclusion criteria were used to ensure quality of data. Nine papers were available to review. Variation in intraobserver repeatability and interobserver reproducibility was identified. Six studies reported intraobserver repeatability coefficients for AP aortic diameter measurements of 1·6-4·4 mm. These were below the 5-mm level regarded as acceptable by the UK and USA AAA screening programmes. Five studies had interobserver reproducibility below the level of 5 mm. Four studies, however, reported poor reproducibility (range from -2 to +5·2 to -10·5 to +10·4); these differences may have had a significant clinical impact on screening and surveillance. The studies used different methodologies with no standardized measurement techniques. Measurements were taken by observers from different medical disciplines of varying grade and levels of training. Standard training and formal quality assurance of ultrasound measurements are important components of an effective AAA screening programme.

OP20.01: Variability of ultrasound measurements with different machine/probe combinations assessed using a phantom: implications for dating

To assess how the variability in a lateral measurements using different probe/machine combinations can affect 1st and 2nd trimester biometry. A 40 mm lateral spaced target was considered most appropriate for 1st trimester crown–rump length (CRL) and 2nd trimester femur length (FL) growth assessment and was measured within an ultrasound phantom (CIRS Model 040), using commonly available ultrasound equipment < 5 years old. The target was imaged using sixteen different modern machine/probe combinations: 2DTA(7); 3DTA(3); 2DTV(4) and 3DTV(2). Intra-operator variability was calculated from 5 separate measurements of each frozen image, one operator performed all measurements. See Table 1. Whilst the different machine/probe combinations made a relatively modest difference for CRL dating (max 2 days; 39–42 mm), the same errors resulted in large differences for FL growth (max 9 days; 39–42 mm). The differences observed reflect machine/probe and intra-observer variability. Incremental CRL growth with time is rapid, but FL growth is much more horizontal leaving this measurement more prone to both observer and machine/probe errors. These issues should be borne in mind when recommending how fetal biometry measurements are best used in dating pregnancies.

OP17.04: Variability of ultrasound measurements with different machine/probe combinations assessed using a phantom: implications for NT screening

OP17.04: Variability of ultrasound measurements with different machine/probe combinations assessed using a phantom: implications for NT screening

OP20.02: Variability of ultrasound measurements with different machine/probe combinations assessed using a phantom

using commonly available ultrasound equipment <5 years old. The target was imaged using sixteen different modern machine/probe combinations: 2DTA(7); 3DTA(3); 2DTV(4) and 3DTV(2). Intraoperator variability was calculated from 5 separate measurements of each frozen image, one operator performed all measurements. Results: See Table 1. Whilst the different machine/probe combinations made a relatively modest difference for CRL dating (max 2 days; 39–42 mm), the same errors resulted in large differences for FL growth (max 9 days; 39–42 mm). The differences observed reflect machine/probe and intra-observer variability. Conclusions: Incremental CRL growth with time is rapid, but FL growth is much more horizontal leaving this measurement more prone to both observer and machine/probe errors. These issues should be borne in mind when recommending how fetal biometry measurements are best used in dating pregnancies.

OC149: Interobserver and intraobserver variability in ultrasound measurement of lower uterine segment after a previous cesarean section

OC149: Interobserver and intraobserver variability in ultrasound measurement of lower uterine segment after a previous cesarean section

How can the variability in ultrasound measurement of intima-media thickness be reduced? Studies of interobserver variability in carotid and femoral arteries.

A critical component in scientific studies of most biological variables is the variation or error in measurements which leads to non-identical results of repeated measurements from the same subject. The aim of this study was to investigate whether the interobserver error (s) in measurement of intima-media thickness (IMT) in carotid and femoral arteries could be decreased if the mean value obtained using two ultrasound images from each of the right and left arteries was used in the analyses instead of the mean value obtained using images from only the right artery. In addition, we wished to evaluate two different reading procedures, one based on manual tracing of echo interfaces and the other on automated edge detection. In a methodological study, 50 subjects were examined with ultrasound twice in the same day by two independent laboratory technologists. The ultrasound images were analysed in two ways: using a computerized manual tracing analysing system and an automated analysing system. When both right and left carotid arteries were examined (manual reading), the interobserver error was smaller than that determined for the examination of only the right artery, for IMTmean in both the common carotid artery (P = 0.06) and the carotid artery bulb (P < 0.05). The interobserver error was also significantly smaller for double-sided vs. one-sided examination with automated reading of IMTmean in the common carotid artery (P < 0.01) and in the carotid artery bulb (P < 0.01). The coefficient of variation (CV) for measurement in the common carotid artery decreased from 8.6% (one-sided, manual reading) to 5.3% (double-sided, automated reading). The interobserver error in measurement of IMT in the common femoral artery did not improve by examination of both right and left arteries. The results from this study show that the interobserver errors in measurement of IMT can be decreased by using ultrasound images from both the right and the left carotid arteries, and that the use of an automated analysing system greatly simplifies the reading of ultrasound images with sustained low variability.

Intra- and interobserver variability in ultrasound measurements of abdominal aortic diameter. The Tromsø study

To assess the variability of ultrasonographic measurements at different levels of the abdominal aorta. Reproducibility study as part of a population health screening for abdominal aortic aneurysm. In 1994/1995 a total of 6892 subjects underwent ultrasound examination of the abdominal aorta. Variability of measurements was assessed in the beginning and end of the survey period by inviting 112 randomly selected participants to a second ultrasound scan within 3 weeks of the first scan. The subjects were examined by an experienced radiologist and three sonographers who had been given a short course in ultrasonography. All examiners were blinded to each other's results. Variability was similar in the beginning and end of the survey period. Both the intra- and interobserver variability were less than 4 mm for all sonographers in measurements of maximal infrarenal aortic diameter, and variability was similar for measurements in the anterior-posterior and transverse plane. Variability was greater for measurements at the renal level than aortic bifurcation level. The radiologist had lower variability than the other sonographers. Ultrasound measurements of the maximal diameter can be obtained with a high degree of accuracy. Inexperienced sonographers may achieve acceptable performance given appropriate training and surveillance.

Differences in observer variability of ultrasound measurements of the proximal and distal abdominal aorta.

To assess the observer variability of ultrasound measurements of the abdominal aorta and to study whether observer variability is influenced by the site of measurement or cardiovascular risk factors. Population based screening programme for abdominal aortic aneurysms. For 135 subjects taking part in a screening programme for abdominal aortic aneurysms, two of the three ultrasonographers measured the distal and proximal ultrasound diameter of the abdominal aorta, using B-mode ultrasound, according to the Rotterdam study scanning protocol. The mean difference between two different observers was 0.06 mm (95% CI-0.15 to 0.27) for measurements of the distal aorta and 0.32 mm (95% CI 0.09 to 0.55) for the proximal aorta. Maximal differences between observers for measurements of both the distal and proximal aortic diameter were 4.0 mm. Interobserver variability in the proximal and distal measurements of the abdominal aorta was not related to the level of the major cardiovascular risk indicators. However, interobserver variability in ultrasound measurements of the proximal aorta increased with increasing waist circumference and increasing diameter of the proximal aorta. Ultrasonographic readings of the distal and proximal aortic measurements can be interpreted within a range of plus or minus 3 mm. Ultrasound measurements are more accurate for the distal than for the proximal measurement. Definition of the aortic diameter based on a combination of both distal and proximal measurement may be more accurate.

3.P.346 How can the variability in ultrasound measurement of intima-media thickness be reduced?

3.P.346 How can the variability in ultrasound measurement of intima-media thickness be reduced?

Quality of the measurement of the infrarenal aortic diameter by ultrasound.

To assess quality and variability in measurements of the infrarenal aortic diameter by ultrasound, and to recommend quality control measures to improve consistency in measurements of the infrarenal aortic diameter (IAD) in a long running screening programme. An aneurysm screening programme in Huntingdon. Quality of the ultrasound image was subjectively assessed by each ultrasonographer. Quality of the measurements was assessed by analysing the frequency of measurements that were outside the normal variability of the estimated true diameter. The interobserver variability was measured by analysing repeated measurements of the IAD in the same patient by two ultrasonographers, using the same scanner. The variability between different scanners was measured by analysing repeat measurements of the IAD in the same patient by the same ultrasonographer, using two scanners. The intraobserver variability was estimated by analysing all patients with three consecutive measurements of the IAD, carried out by the same ultrasonographer. Although the subjective assessment of the quality of the ultrasound image of the aorta varied, there were no statistically significant differences in the likelihood of obtaining measurements outside the limits of agreement between the ultrasonographers. The interobserver, intraobserver, and between scanner variability of ultrasound measurements of the IAD were all around 6 mm. The variability in ultrasound measurements of aortic diameters is acceptable for clinical decision making, and the interobserver variability is very similar to the long term intraobserver variability. Quality control measures are suggested to maintain long term consistency of ultrasound measurements of the IAD.