The present study illustrates the design, fabrication, and evaluation of a novel multifocal point (MFP) transducer based on polyvinylidene fluoride (PVDF) film for high-frequency ultrasound application. The fabricated MFP surface was press-focused using a computer numerical control (CNC) machining tool-customized multi-spherical pattern object. The multi-spherical pattern has five spherical surfaces with equal area and connected continuously to have the same energy level at focal points. Center points of these spheres are distributed in a linear pattern with 1 mm distance between each two points. The radius of these spheres increases steadily from 10 mm to 13.86 mm. The designed MFP transducer had a center frequency of 50 MHz and a −6 dB bandwidth of 68%. The wire phantom test was conducted to study and demonstrate the advantages of this novel design. The obtained results for MFP transducer revealed a significant increase (4.3 mm) of total focal zone in the near-field and far-field area compared with 0.48 mm obtained using the conventional single focal point transducer. Hence, the proposed method is promising to fabricate MFP transducers for deeper imaging depth applications.
In this study, a new approach was investigated to extract reference phases from the scanning acoustic microscope to calculate the speed of sound when dealing with the slope of the stage and fluctuation of the scanning lines. To capture the slope and the fluctuation pattern, data of the first lines along the horizontal and vertical axes on the stage were used. A corrective function was then utilized to improve the accuracy of reference phase extraction. The method was then corroborated by demonstrating tumor discrimination in mice skin by means of scanning acoustic microscopy (SAM). B16-F10 melanoma cells were used to grow the tumor. Hematoxylin and eosin (H&E) staining was applied for histology characterization of the sample. A comparison of both acoustics and histology was conducted. Phase analysis was performed to examine the effects of both slope and fluctuation. The results showed that our approach significantly improved the tumor detection and accuracy of scanning acoustic microscopy.
We propose line-field white light interferometry using a tunable-path-difference source, improving imaging performance. By simultaneously acquiring signals along the line, the system has higher imaging speed and stability for a wide field of view imaging.
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