Department of Vascular Surgery, University of Maryland School of Medicine, Baltimore, Md; Vascular Service, Veterans Affairs Medical Center, Baltimore, Md.
Department of Bioengineering, George Mason University, Fairfax, Va.
J Vasc Surg. 2019 Sep;70(3):858-868. doi: 10.1016/j.jvs.2018.11.050. Epub 2019 Mar 6.
Quantification of carotid plaque morphology (geometry and tissue composition) may help stratify risk for future stroke and assess plaque progression or regression in response to medical risk factor modification. We assessed the feasibility and reliability of morphologic measurements of carotid plaques using computed tomography angiography (CTA) and determined the minimum detectable change in plaque features by this approach.
CTA images of both carotid arteries in 50 patients were analyzed by two observers using a semiautomatic image analysis program, yielding 93 observations per user (seven arteries were excluded because of prior stenting). One observer repeated the analyses 4 weeks later. Measurements included total plaque volume; percentage stenosis (by diameter and area); and tissue composition for calcium, lipid-rich necrotic core (LRNC), and intraplaque hemorrhage (IPH). Reliability of measurements was assessed by intraclass and interclass correlation and Bland-Altman plots. Dice similarity coefficient (DSC) and modified Hausdorff distance (MHD) assessed reliability of geometric shape measurements. We additionally computed the minimum amount of change in these features detectable by our approach.
The cohort was 51% male (mean age, 70.1 years), and 56% had a prior stroke. The mean (± standard deviation) plaque volume was 837.3 ± 431.3 mm, stenosis diameter was 44.5% ± 25.6%, and stenosis area was 58.1% ± 29.0%. These measurements showed high reliability. Intraclass correlation coefficients for plaque volume, percentage stenosis by diameter, and percentage stenosis by area were 0.96, 0.87, and 0.83, respectively; interclass correlation coefficients were 0.88, 0.84, and 0.78. Intraclass correlations for tissue composition were 0.99, 0.96, and 0.86 (calcium, LRNC, and IPH, respectively), and interclass correlations were 0.99, 0.92, and 0.92. Shape measurements showed high intraobserver (DSC, 0.95 ± 0.04; MHD, 0.16 ± 0.10 mm) and interobserver (DSC, 0.94 ± 0.05; MHD, 0.19 ± 0.12 mm) luminal agreement. This approach can detect a change of at least 3.9% in total plaque volume, 1.2 mm in calcium, 4.3 mm in LRNC, and 8.6 mm in IPH with the same observer repeating measurements and 9.9% in plaque volume, 1.9 mm in calcium, 7.9 mm in LRNC, and 6.8 mm in IPH for two different observers.
Carotid plaque geometry (total volume, diameter stenosis, and area stenosis) and tissue composition (calcium, LRNC, and IPH) are measured reliably from clinical CTA images using a semiautomatic image analysis program. The minimum change in plaque volume detectable is ∼4% if the same observer makes both measurements and ∼10% for different observers. Small changes in plaque composition can also be detected reliably. This approach can facilitate longitudinal studies for identifying high-risk plaque features and for quantifying plaque progression or regression after treatment.
通过计算断层血管造影术（CTA）对颈动脉斑块形态（几何形状和组织成分）进行定量分析，有助于对未来中风风险进行分层，并评估对医疗风险因素改变的斑块进展或消退情况。我们评估了使用 CTA 对颈动脉斑块进行形态测量的可行性和可靠性，并确定了这种方法可检测到的斑块特征的最小可检测变化。
对 50 例患者的双侧颈动脉 CTA 图像由两位观察者使用半自动图像分析程序进行分析，每位观察者获得 93 次观察结果（由于先前的支架置入术，有 7 个动脉被排除）。一位观察者在 4 周后重复进行分析。测量包括总斑块体积、直径和面积的狭窄百分比以及钙、富含脂质的坏死核心（LRNC）和斑块内出血（IPH）的组织成分。通过组内相关系数和组间相关系数以及 Bland-Altman 图评估测量的可靠性。Dice 相似系数（DSC）和修正的 Hausdorff 距离（MHD）评估了几何形状测量的可靠性。我们还计算了我们的方法可以检测到的这些特征的最小变化量。
该队列中 51%为男性（平均年龄 70.1 岁），56%有既往中风史。平均（±标准差）斑块体积为 837.3±431.3mm，直径狭窄程度为 44.5%±25.6%，面积狭窄程度为 58.1%±29.0%。这些测量值具有很高的可靠性。斑块体积、直径狭窄百分比和面积狭窄百分比的组内相关系数分别为 0.96、0.87 和 0.83；组间相关系数分别为 0.88、0.84 和 0.78。组织成分的组内相关系数分别为 0.99、0.96 和 0.86（钙、LRNC 和 IPH），组间相关系数分别为 0.99、0.92 和 0.92。形态测量结果显示出较高的观察者内（DSC，0.95±0.04；MHD，0.16±0.10mm）和观察者间（DSC，0.94±0.05；MHD，0.19±0.12mm）管腔一致性。这种方法可以检测到总斑块体积至少变化 3.9%、钙变化 1.2mm、LRNC 变化 4.3mm、IPH 变化 8.6mm，如果由同一位观察者重复测量，如果由两位不同的观察者进行测量，则斑块体积变化可检测到 9.9%、钙变化 1.9mm、LRNC 变化 7.9mm、IPH 变化 6.8mm。
使用半自动图像分析程序，从临床 CTA 图像中可以可靠地测量颈动脉斑块的几何形状（总体积、直径狭窄和面积狭窄）和组织成分（钙、LRNC 和 IPH）。如果由同一位观察者进行两次测量，则可检测到的斑块体积最小变化约为 4%；如果由两位不同的观察者进行测量，则可检测到的斑块体积最小变化约为 10%。也可以可靠地检测到斑块成分的微小变化。这种方法可以促进识别高危斑块特征的纵向研究，并评估治疗后斑块的进展或消退情况。
