Forsberg F, Shi W T, Goldberg B B
Department of Radiology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Ultrasonics. 2000 Mar;38(1-8):93-8. doi: 10.1016/s0041-624x(99)00148-1.
Ultrasound contrast agents promise to improve the sensitivity and specificity of diagnostic ultrasound imaging. It is of great importance to adapt ultrasound equipment for optimal use with contrast agents e.g., by exploiting the nonlinear properties of the contrast microbubbles. Harmonic imaging is one technique that has been extensively studied and is commercially available. However, harmonic imaging is associated with problems, due to second harmonic generation and accumulation within the tissue itself. Given the lack of subharmonic generation in tissue, one alternative is the creation of subharmonic images by transmitting at the fundamental frequency (fo) and receiving at the subharmonic (fo/2). Subharmonic imaging should have a much better lateral resolution and may be suitable for scanning deep-lying structures owing to the higher transmit frequency and the much smaller attenuation of scattered subharmonic signals. In this paper, we will review different aspects of subharmonic imaging including implementation, in-vitro gray-scale imaging and subharmonic aided pressure estimation.
超声造影剂有望提高诊断超声成像的灵敏度和特异性。使超声设备适应与造影剂的最佳使用非常重要，例如通过利用造影微泡的非线性特性。谐波成像就是一种已被广泛研究且已商业化的技术。然而，由于组织自身内二次谐波的产生和积累，谐波成像存在一些问题。鉴于组织中缺乏次谐波产生，一种替代方法是通过以基频（f₀）发射并在次谐波（f₀/2）接收来创建次谐波图像。次谐波成像应具有更好的横向分辨率，并且由于更高的发射频率和散射次谐波信号的更小衰减，可能适用于扫描深部结构。在本文中，我们将综述次谐波成像的不同方面，包括实现、体外灰阶成像和次谐波辅助压力估计。
