Key result
Automated edge-detected carotid IMT measurements showed slightly weaker associations with cardiovascular risk factors compared to manual tracing (model r2 18.5% vs 19.5%, P<0.0001).
Why the study?
Does automated edge-detected IMT measurement provide equivalent associations with cardiovascular risk factors compared to manual-traced IMT in a multi-ethnic cohort?
Observational (n=5,640)
Does automated edge-detected IMT measurement provide equivalent associations with cardiovascular risk factors compared to manual-traced IMT in a multi-ethnic cohort?
Absolute Event Rate: 18.5% vs 19.5%
p-value: p=<0.0001
Automated edge-detection for carotid IMT yields values with comparable associations to cardiovascular risk factors as manual tracing, while reducing inter-reader bias.
Automated IMT may not supplant manual tracing for risk assessment; leaves open its utility in reducing variability for large cohort studies.
BACKGROUND AND PURPOSE: Carotid intima-media thickness (IMT) is a marker of cardiovascular disease derived from ultrasound images of the carotid artery. In most outcome studies, human readers identify and trace the key IMT interfaces. We evaluate an alternate approach using automated edge detection. METHODS: We studied a subset of 5640 participants with an average age 61.7 years (48% men) of the Multi-Ethnic Study of Atherosclerosis composed of whites, Chinese, Hispanic, and blacks that are part of the Multi-Ethnic Study of Atherosclerosis IMT progression study. Manual tracing IMT (mt-IMT) and edge-detected IMT (ed-IMT) measurements of the far wall of the common carotid artery served as outcome variables for multivariable linear regression models using Framingham cardiovascular risk factors and ethnicity as independent predictors. RESULTS: Measurements of mt-IMT were obtainable in 99.9% (5633/5640) and measurements of ed-IMT were obtainable in 98.9% (5579/5640) of individuals. Average ed-IMT was 0.19 mm larger than mt-IMT. Inter-reader systematic differences (bias) in IMT measurements were apparent for mt-IMT but not ed-IMT. Based on complete data for 5538 individuals, associations of IMT with risk factors were stronger (P<0.0001) for mt-IMT (model r2, 19.5%) than for ed-IMT (model r2, 18.5%). CONCLUSIONS: We conclude that this edge-detection process generates IMT values equivalent to manually traced ones because it preserves key associations with cardiovascular risk factors. It also decreases inter-reader bias, potentially making it applicable for use in cardiovascular risk assessment.
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Polak et al. (2011) conducted an observational in Cardiovascular risk (n=5,640). Automated edge-detected carotid intima-media thickness (ed-IMT) measurement vs. Manual tracing IMT (mt-IMT) was evaluated on Association with Framingham cardiovascular risk factors (model r2) (p=<0.0001). Automated edge-detected carotid IMT measurements showed slightly weaker associations with cardiovascular risk factors compared to manual tracing (model r2 18.5% vs 19.5%, P<0.0001).