A 35 MHz/105 MHz Dual-Element Focused Transducer for Intravascular Ultrasound Tissue Imaging Using the Third Harmonic

Abstract

The superharmonic imaging of tissue has the potential for high spatial and contrast resolutions, compared to the fundamental and second harmonic imaging. For this technique, the spectral bandwidth of an ultrasound transducer is divided for transmission of ultrasound and reception of its superharmonics (i.e., higher than the second harmonic). Due to the spectral division for the transmission and reception, transmitted ultrasound energy is not sufficient to induce superharmonics in media without using contrast agents, and it is difficult that a transducer has a -6-dB fractional bandwidth of higher than 100%. For the superharmonic imaging of tissue, thus, multi-frequency array transducers are the best choice if available; transmit and receive elements are separate and have different center frequencies. However, the construction of a multi-frequency transducer for intravascular ultrasound (IVUS) imaging is particularly demanding because of its small size of less than 1 mm. Here, we report a recently developed dual-element focused IVUS transducer for the third harmonic imaging of tissue, which consists of a 35-MHz element for ultrasound transmission and a 105-MHz element for third harmonic reception. For high quality third harmonic imaging, both elements were fabricated to have the same focus at 2.5 mm. The results of tissue mimicking phantom tests demonstrated that the third harmonic images produced by the developed transducer had higher spatial resolution and deeper imaging depth than the fundamental images.

Mechanically Rotating Intravascular Ultrasound (IVUS) Transducer: A Review

“…Yoon et al [ 172 ] proposed a dual-element IVUS transducer with separately press-focused elements for superimposed multifrequency IVUS images, and Shih et al [ 173 ] presented a dual-element IVUS transducer for IVUS elastography. Thereafter, Lee et al [ 100 , 145 , 174 ] developed an IVUS transducer composed of two or three elements sharing the same focal point for tissue harmonic imaging, frequency compounding imaging, and superimposed multifrequency imaging. Owing to the confocal structure, the proposed transducer could achieve harmonic signals more effectively than a multielement IVUS transducer with elements carrying their own image axis.…”

Optimized integrated design of a high-frequency medical ultrasound transducer with genetic algorithm

“…Creating a cross-sectional image of tissues using ultrasonic waves has become very common in modern medicine, due to being less expensive and risky as opposed to common imaging methods [1]. The imaging resolution of ultrasonic imaging increases with increasing working frequency of the US probe, so HF US imaging has become a new and valuable tool in applications such as skin imaging [2][3][4], eye imaging [1,5], intravascular imaging [6][7][8][9], Carotid artery imaging and elastography [10,11] and small animal imaging [12,13].…”