Dept of Biomed Eng, Thoraxcenter, Rotterdam, Netherlands.
IEEE Trans Ultrason Ferroelectr Freq Control. 2009 Nov;56(11):2370-9. doi: 10.1109/TUFFC.2009.1325.
Radial modulation imaging is a new promising technique to improve contrast-enhanced ultrasound images. The method is based on dual-frequency insonation of contrast agent microbubbles. A low-frequency (LF) pulse is used to modulate the responses of the microbubbles to a high-frequency (HF) imaging pulse. Inverting the LF pulse induces amplitude and phase differences in the HF response of contrast agent microbubbles, which can be detected using Doppler techniques. Although the technique has been successfully implemented, no consensus persists on parameter choice and resulting effects. In a separate study, "compression-only" behavior of coated microbubbles was observed. Compression-only behavior could be beneficial for radial modulation imaging. This was investigated using high-speed camera recordings and simulations. We recorded the vibrations of 78 single microbubbles in a dual-frequency ultrasound field. The results showed that the LF pulse induced significant compression-only behavior, which for microbubble sizes below and at HF resonance resulted in high radial amplitude modulation. It, however, also appeared that, for radial modulation imaging, microbubble size is more important than resonance and compression-only effects.
径向调制成像是一种提高对比增强超声图像对比度的新技术。该方法基于双频超声对造影微泡的激发。低频（LF）脉冲用于调制造影微泡对高频（HF）成像脉冲的响应。反转 LF 脉冲会在造影微泡的 HF 响应中产生幅度和相位差，这些可以使用多普勒技术检测到。尽管该技术已经成功实施，但在参数选择和产生的效果方面仍存在分歧。在另一项研究中，观察到了涂层微泡的“仅压缩”行为。仅压缩行为可能对径向调制成像有益。这使用高速摄像记录和模拟进行了研究。我们在双频超声场中记录了 78 个单个微泡的振动。结果表明，LF 脉冲会引起明显的仅压缩行为，对于低于 HF 共振频率和处于 HF 共振频率的微泡大小，会导致高的径向幅度调制。然而，对于径向调制成像，微泡大小比共振和仅压缩效应更重要。
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