Goertz David E, Frijlink Martijn E, de Jong Nico, van der Steen A F W
Biomedical Engineering Department, Erasmus Medical Centre, Rotterdam, The Netherlands.
Ultrasound Med Biol. 2006 Apr;32(4):569-77. doi: 10.1016/j.ultrasmedbio.2006.01.002.
An experimental lipid encapsulated contrast agent comprised substantially of micrometer to submicrometer diameter bubbles was evaluated for its capacity to produce nonlinear scattering in response to high transmit frequencies. Agent characterization experiments were conducted at transmit frequencies of 20 and 30 MHz with bandwidths of 5, 15 and 25% using a broadband focused PVDF transducer. The presence of subharmonic energy was observed for all bandwidths at a wide range of pressures (0.49 to 5.7 MPa and 0.45 to 4.5 MPa for the 20 and 30 MHz cases, respectively). Distinct ultraharmonics were observed only in the 5% bandwidth cases. Second harmonic energy was also present, but this was at least partly due to nonlinear propagation, as indicated by linear scatterer signals. Evidence of destruction was found only at higher peak negative pressures (e.g., >2 MPa for 30 MHz 5% bandwidth pulse). The results suggest that small lipid bubble formulations may be useful for the purposes of high frequency nonlinear contrast imaging.
评估了一种主要由直径为微米至亚微米的气泡组成的实验性脂质包裹造影剂，以确定其在高发射频率下产生非线性散射的能力。使用宽带聚焦聚偏二氟乙烯（PVDF）换能器，在20和30 MHz的发射频率下，以5%、15%和25%的带宽进行了造影剂表征实验。在很宽的压力范围内（20 MHz情况下为0.49至5.7 MPa，30 MHz情况下为0.45至4.5 MPa），所有带宽均观察到了次谐波能量。仅在5%带宽的情况下观察到了明显的超谐波。二次谐波能量也存在，但如线性散射体信号所示，这至少部分是由于非线性传播所致。仅在较高的负峰值压力下（例如，30 MHz 5%带宽脉冲时>2 MPa）发现了破坏迹象。结果表明，小脂质泡制剂可能对高频非线性造影成像有用。
