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| 題 名 | A Substitution Method for Focused Beams |
|---|---|
| 作 者 | 郭益源; | 書刊名 | 中華民國音響學刊 |
| 卷 期 | 3:1 1995.05[民84.05] |
| 頁 次 | 頁14-21 |
| 分類號 | 440.12 |
| 關鍵詞 | 背散射係數; 代換法; 平面波; |
| 語 文 | 英文(English) |
| 中文摘要 | 由Sigelmann及Reid共同提出之代換法,被視為用以量測生物體組織超音波背散 射係數標準方法。此方法須使用平面波來檢測被測物,這是起因於在導出表示式時應用了 〞影像源〞理論來描述超音波從一平面完全反射面反射情形。在一平面活塞式換能器的遠 場,聲波是可以被認為是平面波,然而對於其它樣式的換能器,例如球面聚焦換能所輻射 的聲波,在聚焦點以外的區域,是不能被假設成平面波,因此〞影像源〞理論就不能使用 於此情況。球面聚焦換能器的優點是能夠增強檢測聲波的強度,高強度聲波是使用高頻率 聲波來檢測時所必須的。本文之目的在提出一個修改的代換法以適合球面聚焦聲波,而重 點為重新導出在一球面聚焦換能器聚焦點附近的聲波被一平面完全反射面反射時之表示式 。 |
| 英文摘要 | A substitution method, proposed by Sigelmann and Reid, has been using as the standard method to measure the ultrasonic backscattering coefficient of a biological tissue. This method requires a plane wave to interrogate the tested samples because the "image source" theory was practiced to derive an expression for the ultrasonic wave reflected from a plane perfect reflector. In the far field zone of flat piston transducers the sound wave can be assumed a plane wave. Nevertheless, for the configuration other than a flat piston, for example, a spherical focused transducer whose sound wave deparing from the focal point cannot be assumed a plane wave. The "Image source" theory may not be appropriate to this situation. The advantage of a spherical focused transducer is to increase the interrogating sound intensity that is necessitated to the measurements at high frequencies. A modified substitution method is proposed for this purpose based upon the remodeling of the expression for an ultrasonic wave at the neighbor of the focal point of a spherically focused transducer reflected from a plane perfect reflector. |
本系統中英文摘要資訊取自各篇刊載內容。