Identification of Atherosclerotic Plaque Components With Intravascular Ultrasound Elastography In Vivo

Abstract

Background-Intravascular ultrasound elastography assesses the local strain of the atherosclerotic vessel wall. In the present study, the potential to identify different plaque components in vivo was investigated. Methods and Results-Atherosclerotic external iliac and femoral arteries (nϭ24) of 6 Yucatan pigs were investigated.Before termination, elastographic data were acquired with a 20-MHz Visions catheter. Two frames acquired at end-diastole with a pressure differential of Ϸ4 mm Hg were acquired to obtain the elastograms. Before dissection, x-ray was used to identify the arterial segments that had been investigated by ultrasound. Specimens were stained for collagen, fat, and macrophages. Plaques were classified as absent, early fibrous lesion, early fatty lesion, or advanced fibrous plaque. The average strains in the plaque-free arterial wall (0.21%) and the early (0.24%) and advanced fibrous plaques (0.22%) were similar. Higher average strain values were observed in fatty lesions (0.46%) compared with fibrous plaques (Pϭ0.007). After correction for confounding by lipid content, no additional differences in average strain were found between plaques with and without macrophages (Pϭ0.966). Receiver operating characteristic analysis revealed a sensitivity and a specificity of 100% and 80%, respectively, to identify fatty plaques. The presence of a high-strain spot (strain Ͼ1%) has 92% sensitivity and 92% specificity to identify macrophages. Conclusions-To the best of our knowledge, this is the first time that intravascular ultrasound elastography has been validated in vivo. Intravascular ultrasound (IVUS) has proven to be a powerful technique to assess the geometry of the vessel wall and plaque. However, the sensitivity and specificity to detect lipid cores remains low. 3,4 IVUS elastography assesses the local radial strain in the tissue caused by an intraluminal pressure differential. In vitro experiments revealed different strain values in fibrous and fatty plaques in human coronary and femoral arteries. 5 Feasibility experiments in patients showed that reproducible elastograms could be obtained. 6 The aim of this study was to validate IVUS elastography in vivo with an atherosclerotic Yucatan minipig model. Additionally, we studied whether atheroma and macrophages were related with strain values. Methods AnimalsSix atherosclerotic Yucatan pigs, average weight 40 kg, were studied. To induce atherosclerosis, pigs were put on an atherogenic diet. Two weeks thereafter, the external iliac and femoral arteries were denuded with a 4-F endothelial Fogarty catheter. The atherogenic diet was continued for 9 to 10 months after which femoral and internal iliac arteries were stented for the purpose of another study. Subsequently, the atherogenic diet was replaced by a regular diet. No intervention was performed in the denuded external iliac arteries that were visualized for the present study. The following 42 days, 3 pigs were treated with a drug and 3 pigs served as controls for the purpose of another study. ANOVA reveale...

Elastographic imaging of strain distribution in the anterior cruciate ligament and at the ligament–bone insertions

“…Ultrasound elastography as an elasticity imaging modality has been extensively validated theoretically and experimentally. [38][39][40][41][42][43][44][45]53 Several of the elastographic studies and related theoretical models focused on articular cartilage. 42,44,45 For example, poroelastography, 44 or elastographic imaging of poroelastic tissues, has Figure 3.…”

“…Elastography or elasticity imaging has been used to map mechanical responses and calculate material properties by comparing ultrasound or MR images acquired before and after mechanical loading. This technique, developed in the early 1990s as an alternative tool for early tumor detection and diagnosis based on the principle of palpation, 37,38 has been extensively validated and utilized in intravascular and cardiovascular applications in vivo, 39,40 as well as in the guidance of thermal therapy procedures. 41 Elastography has been used to determine both elastic and mechanical properties of tissues.…”

Characterizing Vulnerable Plaque Features With Intravascular Elastography

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Incidence of High-Strain Patterns in Human Coronary Arteries

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