Department of Circulation and Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Feb;58(2):338-48. doi: 10.1109/TUFFC.2011.1811.
A post-processing adjustment technique to enhance dual-frequency second-order ultrasound field (SURF) reverberation-noise suppression imaging in medical ultrasound is analyzed. Two variant methods are investigated through numerical simulations. They both solely involve post-processing of the propagated high-frequency (HF) imaging wave fields, which in real-time imaging corresponds to post-processing of the beamformed receive radio-frequency signals. Hence, the transmit pulse complexes are the same as for the previously published SURF reverberation-suppression imaging method. The adjustment technique is tested on simulated data from propagation of SURF pulse complexes consisting of a 3.5-MHz HF imaging pulse added to a 0.5-MHz low-frequency soundspeed manipulation pulse. Imaging transmit beams are constructed with and without adjustment. The post-processing involves filtering, e.g., by a time-shift, to equalize the two SURF HF pulses at a chosen depth. This depth is typically chosen to coincide with the depth where the first scattering or reflection occurs for the reverberation noise one intends to suppress. The beams realized with post-processing show energy decrease at the chosen depth, especially for shallow depths where, in a medical imaging situation, a body-wall is often located. This indicates that the post-processing may further enhance the reverberation- suppression abilities of SURF imaging. Moreover, it is shown that the methods might be utilized to reduce the accumulated near-field energy of the SURF transmit-beam relative to its imaging region energy. The adjustments presented may therefore potentially be utilized to attain a slightly better general suppression of multiple scattering and multiple reflection noise compared with non-adjusted SURF reverberation-suppression imaging.
一种用于增强医学超声双频二次超回波（SURF）混响噪声抑制成像的后处理调整技术进行了分析。通过数值模拟研究了两种变体方法。它们都只涉及传播高频（HF）成像波场的后处理，这在实时成像中对应于波束形成接收射频信号的后处理。因此，发射脉冲序列与之前发表的 SURF 混响抑制成像方法相同。该调整技术在由 SURF 脉冲序列传播产生的模拟数据上进行了测试，这些脉冲序列由添加到 0.5MHz 低频声速操纵脉冲的 3.5MHz HF 成像脉冲组成。构建了带有和不带有调整的成像发射波束。后处理涉及滤波，例如通过时间移位，以使在所选深度处两个 SURF HF 脉冲相等。该深度通常选择为与要抑制的混响噪声的第一次散射或反射发生的深度一致。在所选深度处，具有后处理的波束显示出能量下降，特别是在医学成像情况下，身体壁通常位于较浅的深度。这表明后处理可能进一步增强 SURF 成像的混响抑制能力。此外，还表明该方法可用于减少 SURF 发射波束的近场能量相对于其成像区域能量的累积。因此，与未经调整的 SURF 混响抑制成像相比，所提出的调整可能潜在地用于实现稍好的抑制多重散射和多重反射噪声的效果。
