RESUMO
To clarify the potential of a novel system using the acoustic impedance difference imaging (AIDI) method for diagnosis of skin disorders, we used it on a coin and swine skin. An ultrasound wave with a central frequency of 20 MHz, emitted from a fused quartz rod with a diameter of 1.25 mm, was focused on the surface of the coin and skin samples. The difference in acoustic impedance was determined by the reflection-type interference-based acoustic impedance measurement method. The processed data were produced as greyscale images on which the maximum measured amplitudes were mapped. We applied the method to a coin. Swine skin, burned and covered with an acrylic sheet with a thickness of 0.2 mm (a few times the half-wavelength) to eliminate the undulations of the skin surface, was employed to obtain processed images from which undulation data were excluded. All the processed images obtained corresponded almost exactly with the magnified optical ones. In the processed images of swine skin, a marked difference was found after the burning procedure. The processed images obtained using the AIDI method reflected not only the undulations but also other information such as elasticity. In conclusion, our system using AIDI has the potential to become a useful modality for the diagnosis of skin disorders.
RESUMO
PURPOSE: This paper describes an investigation into direct observation of microscopic images of tissue using a thin acoustic wave guide. METHODS: First, the characteristics of the ultrasonic wave propagated in a fused quartz fiber were measured using the reflection method in order to study the insertion loss and the frequency shift of the ultrasonic wave transmitted from the transducer. Next, a receiving transducer was placed close to the end of the fiber, and the characteristics of the ultrasonic waves propagated through the acoustic coupling medium were measured using the penetration method in order to study the insertion loss and the frequency-dependent attenuation of the penetrated waves. Finally, a C-mode image was obtained by optimizing the measuring conditions using the results of the above measurements and scanning the ultrasonic beams on a target (coin) in water. RESULTS: A reflected wave with a peak frequency of approximately 220 MHz was obtained from the end of the fiber. The transmitted ultrasonic waves propagated through the acoustic coupling medium were detected with a frequency range of approximately 125-170 MHz, and the maximum detectable distance of the waves was approximately 1.2 mm within the 100-MHz frequency range. Finally, a high-frequency C-mode image of a coin in water was obtained using a tapered fused quartz fiber. CONCLUSION: The results suggest that it is necessary to improve the signal-to-noise ratio and reduce the insertion loss in the experimental system in order to make it possible to obtain microscopic images of tissue.
