Abstract ▼ AI-Helper

Medical ultrasound is considered the safest non-invasive imaging modality and being widely used in a number of clinical applications. Conventional 2D ultrasonic imaging provides cross-sectional images for internal organs. However, with the fast advancement of ultrasound technologies, the demand for ...

Medical ultrasound is considered the safest non-invasive imaging modality and being widely used in a number of clinical applications. Conventional 2D ultrasonic imaging provides cross-sectional images for internal organs. However, with the fast advancement of ultrasound technologies, the demand for 3D ultrasonic imaging has been growing rapidly as it provides more information on patent’s overall physical conditions than conventional 2D imaging does. Transducers used for 3D imaging are divided into two types; a mechanical wobbling transducer and a 2D array transducer. A mechanical wobbling transducer obtains several 2D images by mechanically moving a conventional 1D array transducer and forms a 3D image by combining those 2D images. Thus a wobbling transducer is subject to mechanical abrasion during use that could result in distortion of the 3D image. This makes the 2D array transducer an ideal solution for 3D imaging, but the 2D array transducer is technically the most challenging approach to have true real-time 3D images. Typical piezoelectric 2D array transducers have a large number of channels which makes fabrication a difficult process. The problem can be resolved by machining the whole 2D array on a piezoelectric plate as a single unit and using a new conductive backer that has been developed in this study. Conductive pillars were molded in a polymeric matrix following the process similar to those for fabricating 1-3 piezocomposites. Many different combinations of pillar and matrix materials have been experimented in order to find the backer material that achieves the best acoustic performance (high impedance and attenuation) and manufacturability. As a result, graphite has been found the best material for the pillars and an epoxy mixture with tungsten powders for the matrix. The conductive backer has been fabricated to have the size of 25.4×25.4×3.0 ㎣. This conductive backer has been attached to the rear surface of a piezoelectric layer to work as both an electric wire plate and an acoustic backer. Once the stack composed of the piezoelectric layer and the conductive backer is ready, the rest of the fabrication processes is similar to those for a conventional linear array, which are much simpler than those for a module type transducer. The 64×64 matrix array transducer developed in this study has a center frequency of 3.5 ㎒ and a fractional bandwidth of 65.7% and is expected to contribute to the advancement of 3D ultrasound imaging technology.

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