Optimal Enhancement Configuration of Silica Nanoparticles for Ultrasound Imaging and Automatic Detection at Conventional Diagnostic Frequencies
Optimal Enhancement Configuration of Silica Nanoparticles for Ultrasound Imaging and Automatic Detection at Conventional Diagnostic Frequencies
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DOI：
10.1097/rli.0b013e3181e6f42f
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发表时间：
2010-11-01
影响因子：
6.7
通讯作者：
Gigli, Giuseppe
中科院分区：
文献类型：
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作者：
Casciaro, Sergio;Conversano, Francesco;Gigli, Giuseppe
目的：实验研究二氧化硅纳米粒子在常规诊断超声场中的声学行为，并确定其作为靶向造影剂的合适配置（粒度和浓度）。我们还评估了自动检测靶向二氧化硅纳米颗粒的新方法对于未来组织分型应用的有效性。材料和方法：可变尺寸的二氧化硅纳米球（160，330，和660 nm直径）和浓度（10（10）-10（13）份/mL）分散在不同的定制设计的琼脂糖中。基于凝胶样本，并使用连接到射频信号采集研究平台的传统回声仪在7.5 MHz下成像。离线分析包括评估背散射超声振幅、图像亮度和通过射频信号处理的纳米颗粒自动检测。纳米颗粒背散射信号的幅度随颗粒数浓度线性增加，但图像亮度没有显示出相同的趋势，因为对数压缩导致达到“平台”，其中亮度对于颗粒浓度的进一步增加几乎保持恒定。另一方面，当颗粒直径增加时，背散射振幅和图像亮度都显示出显著的增加。考虑到肿瘤靶向的粒度限制（肿瘤内皮的孔径和网状内皮系统的捕获效应将有效使用的颗粒尺寸限制为小于380 nm），适当的折衷方案是使用浓度约为1 - 2 X 10（11）份/mL的330 nm二氧化硅纳米球。事实上，这些颗粒显示了数量浓度和直径值的最佳组合，以获得对常规回波描记图像的有效增强。此外，所开发的用于自动纳米颗粒检测的方法的灵敏度也具有最大值。（72.8%）与330-nm的颗粒，而与较大和较小的颗粒都较低（分别为64.1%和17.5%）。直径约330 nm的二氧化硅纳米颗粒是非常有前途的造影剂，用于超声成像和常规诊断中的特异性肿瘤靶向。频率，特别是在低剂量下已经可以以高灵敏度自动检测。未来的研究将进行，以评估具有不同几何形状/尺寸的纳米颗粒的声学行为，并提高自动检测算法的灵敏度。
Objectives: To experimentally investigate the acoustical behavior of silica nanoparticles within conventional diagnostic ultrasound fields and to determine a suitable configuration, in terms of particle size and concentration, for their employment as targetable contrast agents. We also assessed the effectiveness of a novel method for automatic detection of targeted silica nanoparticles for future tissue typing applications.Materials and Methods: Silica nanospheres of variable size (160, 330, and 660 nm in diameter) and concentration (10(10)-10(13) part/mL) were dispersed in different custom-designed agarose-based gel samples and imaged at 7.5 MHz with a conventional echograph linked to a research platform for radiofrequency signal acquisition. Off-line analysis included evaluation of backscattered ultrasound amplitude, image brightness, and nanoparticle automatic detection through radiofrequency signal processing.Results: Amplitude of nanoparticle-backscattered signals linearly increased with particle number concentration, but image brightness did not show the same trend, because the logarithmic compression caused the reaching of a "plateau" where brightness remained almost constant for further increments in particle concentration. On the other hand, both backscatter amplitude and image brightness showed significant increments when particle diameter was increased. Taking into account particle size constraints for tumor targeting (pore size of tumor endothelium and trapping effects because of reticuloendothelial system limit the dimension of effectively employable particles to less than 380 nm), a suitable compromise is represented by the employment of 330-nm silica nanospheres at a concentration of about 1 to 2 X 10(11) part/mL. These particles, in fact, showed the best combination of number concentration and diameter value to obtain an effective enhancement on conventional echographic images. Furthermore, also the sensitivity of the developed method for automatic nanoparticle detection had a maximum (72.8%) with 330-nm particles, whereas it was lower with both bigger and smaller particles (being equal to 64.1% and 17.5%, respectively).Conclusions: Silica nanoparticles at a diameter of about 330 nm are very promising contrast agents for ultrasound imaging and specific tumor targeting at conventional diagnostic frequencies, being in particular automatically detectable with high sensitivity already at low doses. Future studies will be carried out to assess the acoustic behavior of nanoparticles with different geometries/sizes and to improve sensitivity of the automatic detection algorithm.