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在平面超声场中,由于菲涅尔和夫朗和费衍射,不管在近场区还是在远场区都形成强度的非均匀分布。在垂直于超声束的轴的截面上,强度分布也是不均匀的。由于超声的生物效应的研究及医学应用都需要精确知道超声场的强度,所以从本世纪廿年代起直到最近,都不断有人进行这方面的研究工作。不少学者都曾强调过了解和测定强度分布的重要性,如Baum早就指出过,探头中心的输出强度要严格测定,决不允许超过组织的安全剂量。他研究出了超声生物效应的等响应曲线(可逆损伤,不
In planar ultrasound fields, due to Fresnel and Fraunhofer diffraction, a non-uniform distribution of intensities occurs in both near-field and far-field regions. The intensity distribution is also non-uniform over the cross-section perpendicular to the axis of the ultrasound beam. Since the biological effects of ultrasound and medical applications require accurate knowledge of the intensity of the ultrasound field, research efforts in this field have been conducted continuously since the 1920s until recently. Many scholars have emphasized the importance of understanding and measuring intensity distributions, as Baum pointed out long ago that the output intensity of the probe center should be rigorously determined and must never exceed the tissue safe dose. He developed equal response curves for ultrasound biological effects (reversible lesions, no