Hara Hisao, Tsunoda Taro, Nemoto Naohiko, Yokouchi Itaru, Yamamoto Masaya, Ono Tsuyoshi, Moroi Masao, Suzuki Makoto, Sugi Kaoru, Nakamura Masato
Division of Cardiovascular Medicine, Toho University Ohashi Medical Center, Tokyo, Japan.
Cardiovasc Ultrasound. 2008 May 9;6:18. doi: 10.1186/1476-7120-6-18.
Accumulation of lipids within coronary plaques is an important process in disease progression. However, gray-scale intravascular ultrasound images cannot detect plaque lipids effectively. Radiofrequency signal analysis could provide more accurate information on preclinical coronary plaques.
We analyzed 29 zones of mild atheroma in human coronary arteries acquired at autopsy. Two histologic groups, i.e., plaques with a lipid core (group L) and plaques without a lipid core (group N), were analyzed by automatic calculation of integrated backscatter. One hundred regions of interest were set on the target zone. Radiofrequency signals from a 50 MHz transducer were digitized at 240 MHz with 12-bit resolution. The intensity of integrated backscatter and its distribution within each plaque were compared between the two groups.
Although the mean backscatter was similar between the groups, intraplaque variation of backscatter and backscatter in the axial direction were larger in group L than in group N (p = 0.02). Conventional intravascular ultrasound showed extremely low sensitivity for lipid detection, despite a high specificity. In contrast, a cut-off value>32 for the total variance of integrated backscatter identified lipid-containing plaque with a high sensitivity (85%) and specificity (75%).
Compared with conventional imaging, assessment of the intraplaque distribution of integrated backscatter is more effective for detecting lipid. As coronary atheroma progresses, its composition becomes heterogeneous and multi-layered. This radiofrequency technique can portray complex plaque histology and can detect the early stage of plaque progression.
冠状动脉斑块内脂质的积累是疾病进展的一个重要过程。然而，灰阶血管内超声图像无法有效检测斑块脂质。射频信号分析可为临床前冠状动脉斑块提供更准确的信息。
我们分析了29个在尸检时获取的人冠状动脉轻度动脉粥样硬化区域。通过自动计算背向散射积分，对两个组织学组，即有脂质核心的斑块（L组）和无脂质核心的斑块（N组）进行了分析。在目标区域设置了100个感兴趣区。来自50 MHz换能器的射频信号以240 MHz、12位分辨率进行数字化处理。比较了两组之间每个斑块内背向散射积分的强度及其分布。
尽管两组之间的平均背向散射相似，但L组斑块内背向散射的变化及轴向背向散射均大于N组（p = 0.02）。传统血管内超声对脂质检测的敏感性极低，尽管特异性很高。相比之下，背向散射积分总方差的截断值>32可识别含脂质斑块，其敏感性高（85%），特异性高（75%）。
与传统成像相比，评估背向散射积分在斑块内的分布对检测脂质更有效。随着冠状动脉粥样硬化的进展，其成分变得不均匀且呈多层结构。这种射频技术可以描绘复杂的斑块组织学特征，并能检测斑块进展的早期阶段。
