Emmer Marcia, Vos Hendrik J, van Wamel Annemieke, Goertz Dave E, Versluis Michel, de Jong Nico
Biomedical Engineering, Thoraxcentre, Erasmus MC, Rotterdam, The Netherlands.
Ultrasonics. 2007 Dec;47(1-4):74-7. doi: 10.1016/j.ultras.2007.07.004. Epub 2007 Aug 6.
Recent optical and acoustical studies have shown a threshold behaviour in the response of phospholipid-coated contrast agents, for a certain range of sizes. Below the acoustic pressure threshold, the microbubbles' scattering efficacy is significantly reduced compared to that above the threshold. Here we investigate the clinical relevance of the observed threshold behaviour. A cardiac ultrasound scanner system was used to analyse the pressure-dependence of the scatter intensity. The scattering of a native suspension of a phospholipid-coated contrast agent was compared to that of a suspension in which microbubbles with a size larger than 3.0 microm in diameter were extracted. A power modulation scheme at the fundamental frequency was applied. After linearly scaling and subtracting the B-mode images recorded at 70 and 200 kPa, the contrast-to-tissue ratio (CTR) of the native suspension was 3.2dB, whereas the CTR of the filtered suspension was 20 dB. The 17 dB difference is attributed to the threshold behaviour. Well-established ultrasound imaging techniques such as fundamental power modulation imaging could benefit from the pressure-dependent scattering properties of this type of contrast microbubbles.
最近的光学和声学研究表明，对于一定尺寸范围的磷脂包被的造影剂，其响应存在阈值行为。在声压阈值以下，与阈值以上相比，微泡的散射效率显著降低。在此，我们研究观察到的阈值行为的临床相关性。使用心脏超声扫描仪系统分析散射强度的压力依赖性。将磷脂包被的造影剂的天然悬浮液的散射与其中提取了直径大于3.0微米的微泡的悬浮液的散射进行比较。应用了基频功率调制方案。在对70和200 kPa下记录的B模式图像进行线性缩放和相减后，天然悬浮液的对比组织比（CTR）为3.2dB，而过滤后悬浮液的CTR为20 dB。17 dB的差异归因于阈值行为。诸如基频功率调制成像等成熟的超声成像技术可以受益于这类对比微泡的压力依赖性散射特性。
