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首页> 外文会议>Photons Plus Ultrasound: Imaging and Sensing 2007; Progress in Biomedical Optics and Imaging; vol.8 no.14; Proceedings of SPIE-The International Society for Optical Engineering; vol.6437 >Photoacoustic contrast enhancement using selective subband imaging: experimental results
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Photoacoustic contrast enhancement using selective subband imaging: experimental results

机译：使用选择性子带成像增强光声对比度：实验结果

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摘要

In photoacoustic imaging, the difference of optical absorption determines the contrast between two media. In this study, a contrast enhancement method based on choosing various frequency subbands for photoacoustic imaging is proposed. Typically, a laser beam irradiates a medium of interest, and the optical energy decays with different rates as the optical absorption changes. The decay profiles result in acoustic pressure waveforms to propagate with various frequency components, which cause the acoustic frequency variation. The frequency band for a medium with high absorption is found significantly up-shifted from that for a medium with one order lower absorption. Accordingly, besides the amplitude difference due to the absorption, the contrast between two media with varied absorption can be further enhanced by choosing a high frequency band of the receiving signals for imaging. This method was demonstrated by simulations and experiments. The simulation, which is based on the Beer-Lambert law, verified the appearance of frequency variation due to the disparity of absorption coefficients. The experiments were performed by using agar phantom with various concentrations of graphite to create optical absorptions with more than tens times difference. For absorbers with absorption coefficients from 2.5 cm~(-1) to 100 cm~(-1), the peak frequencies and the -6 dB bandwidths of the PA signals increase from 1.17 to 3.83 MHz and from 2.17 to 7.58 MHz, respectively. The subband image at band 7-14 MHz shows 13-25 dB intensity difference between two agars with respective absorption of 41.75 cm~(-1) and 5.01 cm~(-1), while the difference is 9-15 dB at band 0-7 MHz, thus demonstrating that the contrast can be enhanced between two media using the selective subband imaging. The potential of improving the contrast between biological tissues and contrast agent with a significant higher absorption is revealed.
机译：在光声成像中，光吸收的差异决定了两种介质之间的对比度。在这项研究中，提出了一种基于选择各种频率子带进行光声成像的对比度增强方法。通常，激光束照射感兴趣的介质，并且随着光吸收率的变化，光能以不同的速率衰减。衰减曲线导致声压波形以各种频率分量传播，从而导致声频变化。发现具有高吸收率的介质的频带与具有低一级吸收率的介质的频带明显上移。因此，除了由于吸收而引起的振幅差之外，通过选择用于成像的接收信号的高频带，可以进一步增强具有变化的吸收的两种介质之间的对比度。通过仿真和实验证明了该方法。基于比尔-朗伯定律的仿真验证了由于吸收系数差异而引起的频率变化。通过使用带有各种浓度石墨的琼脂模型来进行实验，以产生相差十倍以上的光吸收。对于吸收系数从2.5 cm〜（-1）到100 cm〜（-1）的吸收器，PA信号的峰值频率和-6 dB带宽分别从1.17 MHz增加到3.83 MHz和从2.17 MHz增加到7.58 MHz。 7-14 MHz频段的子带图像显示两个琼脂之间的强度差异为13-25 dB，分别具有41.75 cm〜（-1）和5.01 cm〜（-1）的吸收，而0频段的差异为9-15 dB -7 MHz，因此证明可以使用选择性子带成像在两种媒体之间增强对比度。揭示了以显着更高的吸收率改善生物组织和造影剂之间的对比度的潜力。

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