Shi Hairong, Varghese Tomy, Mitchell Carol C, McCormick Matthew, Dempsey Robert J, Kliewer Mark A
Department of Medical Physics, The University of Wisconsin-Madison, Madison, WI 53706, USA.
Ultrasonics. 2009 Dec;49(8):779-85. doi: 10.1016/j.ultras.2009.06.004. Epub 2009 Jul 3.
We have previously reported on the equivalent scatterer size, attenuation coefficient, and axial strain properties of atherosclerotic plaque ex vivo. Since plaque structure and composition may be damaged during a carotid endarterectomy procedure, characterization of in vivo properties of atherosclerotic plaque is essential. The relatively shallow depth of the carotid artery and plaque enables non-invasive evaluation of carotid plaque utilizing high frequency linear-array transducers. We investigate the ability of the attenuation coefficient and equivalent scatterer size parameters to differentiate between calcified, and lipidic plaque tissue. Softer plaques especially lipid rich and those with a thin fibrous cap are more prone to rupture and can be classified as unstable or vulnerable plaque. Preliminary results were obtained from 10 human patients whose carotid artery was scanned in vivo to evaluate atherosclerotic plaque prior to a carotid endarterectomy procedure. Our results indicate that the equivalent scatterer size obtained using Faran's scattering theory for calcified regions are in the 120-180 microm range while softer regions have larger equivalent scatterer size distribution in the 280-470 microm range. The attenuation coefficient for calcified regions as expected is significantly higher than that for softer regions. In the frequency bandwidth ranging from 2.5 to 7.5 MHz, the attenuation coefficient for calcified regions lies between 1.4 and 2.5 dB/cm/MHz, while that for softer regions lies between 0.3 and 1.3 dB/cm/MHz.
我们之前曾报道过动脉粥样硬化斑块在体外的等效散射体大小、衰减系数和轴向应变特性。由于在颈动脉内膜切除术过程中斑块结构和成分可能会受到破坏，因此对动脉粥样硬化斑块的体内特性进行表征至关重要。颈动脉和斑块相对较浅的深度使得利用高频线性阵列换能器对颈动脉斑块进行无创评估成为可能。我们研究了衰减系数和等效散射体大小参数区分钙化斑块组织和脂质斑块组织的能力。较软的斑块，尤其是富含脂质和纤维帽较薄的斑块更容易破裂，可归类为不稳定或易损斑块。初步结果来自10名人类患者，在颈动脉内膜切除术之前对他们的颈动脉进行了体内扫描以评估动脉粥样硬化斑块。我们的结果表明，使用法朗散射理论获得的钙化区域的等效散射体大小在120 - 180微米范围内，而较软区域的等效散射体大小分布更大，在280 - 470微米范围内。正如预期的那样，钙化区域的衰减系数明显高于较软区域。在2.5至7.5兆赫兹的频率带宽内，钙化区域的衰减系数在1.4至2.5分贝/厘米/兆赫兹之间，而较软区域的衰减系数在0.3至1.3分贝/厘米/兆赫兹之间。
