Acoustic characterization of contrast-to-tissue ratio and axial resolution for dual-frequency contrast-specific acoustic angiography imaging.
Acoustic characterization of contrast-to-tissue ratio and axial resolution for dual-frequency contrast-specific acoustic angiography imaging.
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DOI：
10.1109/tuffc.2014.006466
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发表时间：
2014-10
期刊：
影响因子：
--
通讯作者：
Dayton PA
中科院分区：
文献类型：
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作者：
Lindsey BD;Rojas JD;Martin KH;Shelton SE;Dayton PA
最近，双频换能器通过以低频发射并接收由微泡造影剂散射的宽带超谐波回波，实现了脉管系统的高空间分辨率和高对比度成像，具有最小的组织伪影。在这项工作中，我们研究的成像参数优化对比度，组织比双频成像和空间分辨率的关系。在水浴装置中使用共焦活塞换能器，以测量信噪比（SNR）、对比度-组织比（CTR）和轴向分辨率，用于在较低频率（1.5 - 8 MHz）下发射并在较高频率（7.5 - 25 MHz）下接收时微泡造影剂非线性散射的超声成像。改变的参数包括发射波的频率和峰值负压、接收换能器的中心频率、微泡浓度和微泡尺寸。CTR在最低传输频率下最大化，但对于1.5-3.5 MHz范围内的成像是可接受的。在这些频率下，当使用中心频率为10的接收换能器时，CTR被优化，当以1.5MHz以1600 kPa的峰值负压发射并且以10 MHz的中心频率接收时，出现25.5dB的最大CTR。轴向分辨率受接收中心频率的影响更大，随着发射频率的增加，测得的脉冲长度略有下降。主要含有4 μ m直径气泡的微泡群体产生最大CTR，其次是1 μ m和2 μm气泡。不同浓度对测试参数的影响很小。CTR依赖于发射频率和峰值压力，通过在两个啮齿动物体内成像证实。这些发现可能会改善浅表或管腔癌（如乳腺癌、前列腺癌和结肠癌）血管重塑的成像。
Recently, dual frequency transducers have enabled high-spatial resolution and high-contrast imaging of vasculature with minimal tissue artifacts by transmitting at a low frequency and receiving broadband superharmonic echoes scattered by microbubble contrast agents. In this work, we examine the imaging parameters for optimizing contrast-to-tissue ratio for dual-frequency imaging and the relationship with spatial resolution. Confocal piston transducers are used in a water bath setup to measure the signal-to-noise ratio (SNR), contrast-to-tissue ratio (CTR), and axial resolution for ultrasound imaging of non-linear scattering of microbubble contrast agents when transmitting at a lower frequency (1.5 – 8 MHz) and receiving at a higher frequency (7.5 – 25 MHz). Parameters varied include the frequency and peak negative pressure of transmitted waves, center frequency of the receiving transducer, microbubble concentration, and microbubble size. CTR is maximized at the lowest transmission frequencies but would be acceptable for imaging in the 1.5–3.5 MHz range. At these frequencies, CTR is optimized when a receiving transducer with a center frequency of 10 is used, with the maximum CTR of 25.5 dB occurring when transmitting at 1.5 MHz with a peak negative pressure of 1600 kPa and receiving with a center frequency of 10 MHz. Axial resolution is influenced more heavily by receiving center frequency, with a weak decrease in measured pulse lengths associated with increasing transmit frequency. A microbubble population containing predominately 4 μm-diameter bubbles yielded the greatest CTR, followed by 1 and then 2 μm bubbles. Varying concentration showed little effect over the tested parameters. CTR dependence on transmit frequency and peak pressure were confirmed through in vivo imaging in two rodents. These findings may lead to improved imaging of vascular remodeling in superficial or luminal cancers such as those of the breast, prostate, and colon.