PHOTOACOUSTIC IMAGING FOR MEDICAL DIAGNOSTICS.
PHOTOACOUSTIC IMAGING FOR MEDICAL DIAGNOSTICS.
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DOI：
10.1121/1.4788648
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发表时间：
2012-10-01
期刊：
影响因子：
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通讯作者：
Emelianov SY
中科院分区：
文献类型：
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作者：
Bayer CL;Luke GP;Emelianov SY
光声成像有潜力为多种流行疾病提供实时、非侵入性诊断，因为该技术具有独特的能力，能够以与超声波相当的空间分辨率可视化活体组织深处的分子变化。光声成像是一种混合成像技术，它将光学成像的对比度能力和光谱灵敏度与超声波的分辨率和组织穿透能力结合起来。在光声成像过程中，材料吸收光能，并通过非辐射弛豫将光转化为热能。当材料受热时，由于其热弹性，它们的尺寸会膨胀，从而产生压力波。这些压力波可以传播通过周围环境并在表面被检测到。这种效应对于经历过夏季雷暴的每个人来说都很熟悉——闪电迅速加热空气，导致空气膨胀并产生可听见的雷声。一般来说，引起材料膨胀的加热（例如热声效应）可能是由多种形式的能量转移引起的，但“光声”一词具体指将光转换为热，从而产生特征声波。光声效应最早由亚历山大·格雷厄姆·贝尔于 1880 年发现。1他的实验推断，间歇性强光可以加热光学吸收材料，从而导致材料膨胀，从而产生可听的振动波。贝尔证明，深色纤维比较浅色纤维产生的声音更大，这一原理与当今使用的一般光声关系一致——所产生的光声信号的幅度与吸收的光量成正比。贝尔还表明，通过用棱镜分离白光，光和纤维的某些颜色组合可以产生更大的声音。如今，多波长光声成像使用相同的原理，改变光的波长并将光声响应的幅度与被成像材料的吸收光谱相关联。
Photoacoustic imaging has the potential to provide real-time, non-invasive diagnosis of numerous prevalent diseases, due to the technology’s unique ability to visualize molecular changes deep within living tissue with spatial resolution comparable to ultrasound. Photoacoustic imaging is a hybrid imaging technique that combines the contrast capabilities and spectral sensitivities of optical imaging with the resolution and tissue penetration capabilities of ultrasound. During the photoacoustic imaging process, materials absorb light energy, and convert the light to heat via non-radiative relaxation. When materials heat, they expand in size due to their thermoelastic properties, which generates a pressure wave. These pressure waves can propagate through the surrounding environment to be detected at the surface. This effect is familiar to everyone who has experienced a summer thunderstorm—lightning rapidly heats the air, resulting in the air expanding and generating audible thunder. In general, the heating which induces the expansion of the material (eg, the thermoacoustic effect) could be caused by many forms of energy transfer, but the term “photoacoustic” specifies the conversion of light into heat, resulting in the generation of characteristic sound waves.The photoacoustic effect was first discovered by Alexander Graham Bell in 1880. 1 His experiments deduced that an intermittent bright light could heat optically absorbing materials, causing expansion of the material in a way that generated audible vibrational waves. Bell demonstrated that darker fibers produced louder sounds than lighter fibers, a principle which is consistent with the general photoacoustic relationship in use today—the amplitude of the generated photoacoustic signal is proportional to the amount of absorbed light. Bell also showed, by separating white light with a prism, certain color combinations of light and fibers could generate a louder sound. Today, multiwavelength photoacoustic imaging uses this same principle, changing the wavelength of the light and correlating the amplitude of the photoacoustic response to the absorption spectra of the materials being imaged.