Progression of atherosclerosis at one-year follow-up seen with volumetric intravascular ultrasound in femoropopliteal arteries

Automated tracing of the adventitial contour of aortoiliac and peripheral arterial walls in CT angiography (CTA) to allow calculation of non-calcified plaque burden

Aortoiliac and lower extremity arterial atherosclerotic plaque burden is a risk factor for the development of visceral and peripheral ischemic and aneurismal vascular disease. While prior research allows automated quantification of calcified plaque in these body regions using CT angiograms, no automated method exists to quantify soft plaque. We developed an automatic algorithm that defines the outer wall contour and wall thickness of vessels to quantify non-calcified plaque in CT angiograms of the chest, abdomen, pelvis, and lower extremities. The algorithm encodes the search space as a constrained graph and calculates the outer wall contour by deriving a minimum cost path through the graph, following the visible outer wall contour while minimizing path tortuosity. Our algorithm was statistically equivalent to a reference standard made by two reviewers. Absolute error was 1.9 ± 2.3% compared to the inter-observer variability of 3.9 ± 3.6%. Wall thickness in vessels with atherosclerosis was 3.4 ± 1.6 mm compared to 1.2 ± 0.4 mm in normal vessels. The algorithm shows promise as a tool for quantification of non-calcified plaque in CT angiography. When combined with previous research, our method has the potential to quantify both non-calcified and calcified plaque in all clinically significant systemic arteries, from the thoracic aorta to the arteries of the calf, over a wide range of diameters. This algorithm has the potential to enable risk stratification of patients and facilitate investigations into the relationships between asymptomatic atherosclerosis and a variety of behavioral, physiologic, pathologic, and genotypic conditions.

Vascular Remodeling in Atherosclerotic Femoral Arteries: Three-dimensional US Analysis

PURPOSE

To investigate the various modes of vascular remodeling of atherosclerotic femoral arteries and determine the associations between type of arterial remodeling and clinical data (age, sex, and medical history) and inflammatory parameters.

MATERIALS AND METHODS

Intravascular ultrasonography (US) of the femoral arteries was performed in 50 patients with clinical symptoms of peripheral vascular disease. To determine the arterial remodeling mode (expansive remodeling [ER], involving compensatory enlargement of the artery, or constrictive remodeling [CR], involving vessel constriction during progression of atherosclerosis), the cross-sectional areas (CSAs) of the external elastic membrane (EEM), lumen, and plaque-plus-media were measured every 0.1 mm by using three-dimensional reconstruction. Clinical, laboratory, and intravascular US data were compared in the different remodeling groups (dominant ER, dominant CR, or mixed remodeling) by using analysis of variance supplemented by Tukey-Kramer tests. Multivariate analysis was performed to test independent variables predicting dominant ER.

RESULTS

Intravascular US revealed the parallel existence of ER and CR in all patients: Increases and decreases in EEM in response to plaque growth could be observed within the same artery. ER dominated in 13 (26%) patients, and CR dominated in 11 (22%) patients: At least 80% of EEM CSAs were higher or lower than the mean of the EEM CSAs of the segments proximal and distal to the lesion. Patients with dominant ER had higher levels of serum C-reactive protein (CRP) compared with levels in patients with dominant CR and patients with mixed remodeling (1.62 mg/dL +/- 2.05 [standard deviation] vs 0.19 mg/dL +/- 0.33 and 0.21 mg/dL +/- 0.39, respectively, P < .005). Multivariate analysis revealed high CRP level to be a significant independent predictor for dominant ER (P < .01).

CONCLUSION

The parallel existence of ER and CR was found in all patients with peripheral atherosclerosis, with a dominance of vessel expansion in 26% of patients. Higher plasma CRP level was associated with dominant ER.