Improving Spatial Resolution Using Incoherent Subtraction of Receive Beams Having Different Apodizations.
Improving Spatial Resolution Using Incoherent Subtraction of Receive Beams Having Different Apodizations.
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DOI：
10.1109/tuffc.2018.2876285
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发表时间：
2019-01
期刊：
影响因子：
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通讯作者：
Oelze ML
中科院分区：
文献类型：
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作者：
Agarwal A;Reeg J;Podkowa AS;Oelze ML
在超声成像中，减少侧面瓣可以使图像失真更小，伪影更少。一般来说，去甲化用于降低副瓣，以增加主瓣的宽度，从而降低横向分辨率。零相减成像（NSI）是一种非线性图像处理技术，它在相同射频数据的副本上使用不同的接收方式来保持低副瓣电平，同时提高横向分辨率。用三种不同的apoapoed函数创建的图像组合在一起，形成一个低副瓣水平的图像，与传统的矩形apoapoed相比，横向分辨率明显提高。为了评估该技术在不同成像任务中的性能，我们在ATS539模型上进行了实验，其中包含线目标来评估横向分辨率，以及圆柱形消声和高回声目标来评估对比度。将NSI图像与矩形apozed图像和最小方差波束形成图像进行了比较。在实验中，观察到的表观横向分辨率提高了35倍以上的因素，与矩形apodiczation。通过估计横向分辨率（- 6 db接收波束宽度）、主瓣与副瓣比（MSR）和噪比（CNR）来评估图像质量。使用焦距为2 （f/2）的NSI成像，从ATS模体中的小导线目标测量到的- 6 db波束宽度为0.03λ，而矩形apodization为2.79λ。与矩形根尖化相比，NSI的旁瓣减少了32.9 dB。然而，当使用NSI方案时，观察消声和高回声目标对比的能力降低，即，消声目标的CNR从- 3.05降至- 1.01，高回声目标的CNR从1.65降至0.45。
In ultrasonic imaging, reduction of lateral sidelobes can result in an improved image with less distortion and fewer artifacts. In general, apodization is used to lower sidelobes in exchange for increasing the width of the mainlobe and thus decreasing lateral resolution. Null subtraction imaging (NSI) is a nonlinear image processing technique that uses different receive apodizations on copies of the same RF data to maintain low sidelobe levels while simultaneously improving lateral resolution. The images created with three different apodization functions are combined to form an image with low sidelobe levels and apparent improvements in lateral resolution compared to conventional rectangular apodization. To evaluate the performance of this technique for different imaging tasks, experiments were performed on an ATS539 phantom containing wire targets to assess lateral resolution and cylindrical anechoic and hyperechoic targets to assess contrast. NSI images were compared against rectangular apodized images and minimum variance (MV) beamformed images. In experiments, the apparent lateral resolution was observed to improve by a factor of more than 35 times when compared to rectangular apodization. Image quality was assessed by estimation of lateral resolution (−6-dB receive beamwidth), mainlobe to sidelobe ratio (MSR) and contrast-to-noise ratio (CNR). Imaging with NSI using a focal number of 2 (f/2), the −6-dB beamwidth on receive as measured from a small wire target in the ATS phantom was 0.03λ compared to 2.79λ for rectangular apodization. Sidelobes were observed to decrease by 32.9 dB with NSI compared to rectangular apodization. However, the ability to observe the contrast of anechoic and hyperechoic targets reduced when utilizing the NSI scheme, i.e., the CNR decreased from −3.05 to −1.01 for anechoic targets and 1.65 to 0.45 for the hyperechoic targets.