Capacitive micromachined ultrasound transducers for intravascular ultrasound imaging

Abstract

Intravascular ultrasound (IVUS) is a burgeoning imaging technology that provides vital information for the diagnosis of coronary arterial diseases. A significant constituent that enables the IVUS system to attain high-resolution images is the ultrasound transducer, which acts as both a transmitter that sends acoustic waves and a detector that receives the returning signals. Being the most mature form of ultrasound transducer available in the market, piezoelectric transducers have dominated the field of biomedical imaging. However, there are some drawbacks associated with using the traditional piezoelectric ultrasound transducers such as difficulties in the fabrication of high-density arrays, which would aid in the acceleration of the imaging speed and alleviate motion artifact. The advent of microelectromechanical system (MEMS) technology has brought about the development of micromachined ultrasound transducers that would help to address this issue. Apart from the advantage of being able to be fabricated into arrays with lesser complications, the image quality of IVUS can be further enhanced with the easy integration of micromachined ultrasound transducers with complementary metal-oxide-semiconductor (CMOS). This would aid in the mitigation of parasitic capacitance, thereby improving the signal-to-noise. Currently, there are two commonly investigated micromachined ultrasound transducers, piezoelectric micromachined ultrasound transducers (PMUTs) and capacitive micromachined ultrasound transducers (CMUTs). Currently, PMUTs face a significant challenge where the fabricated PMUTs do not function as per their design. Thus, CMUTs with different array configurations have been developed for IVUS. In this paper, the different ultrasound transducers, including conventional-piezoelectric transducers, PMUTs and CMUTs, are reviewed, and a summary of the recent progress of CMUTs for IVUS is presented.

Recent Advances in Transducers for Intravascular Ultrasound (IVUS) Imaging

“…The most powerful advantage of a solid-state catheter over a mechanical/rotational catheter is that electrical scanning allows for stable imaging, which makes it possible for accurate speckle analysis, and flow analysis and palpography in IVUS imaging. Four different categories of ultrasound transducers have been reported for IVUS imaging: conventional piezoelectric ultrasound transducer, piezo-composite micromachined ultrasound transducer (PC-MUT), piezoelectric micromachined ultrasound transducer (PMUT) and capacitive micromachined ultrasound transducer (CMUT) (Figure 4) [52][53][54]. The details about structures and fabrication processes of these four types of ultrasound transducers have been reported by many references.…”

“…Until now, due to the mature fabrication techniques, piezoelectric ultrasound transducers dominate the market of IVUS catheters [54]. Based on the different applications (mechanical/rotational catheter and solid-state catheter), they can be categorized into two types: single element and phased array.…”

“…The most commonly utilized piezoelectric material for the ultrasound transducer is lead zirconate titanate (PZT) ceramics, having a high electromechanical coupling coefficient. Other materials, such as lead magnesium niobatelead titanate (PMN-PT) single crystals and lead indium niobate-lead magnesium niobatelead titanate (PIN-PMN-PT) single crystals, that have even higher electromechanical Four different categories of ultrasound transducers have been reported for IVUS imaging: conventional piezoelectric ultrasound transducer, piezo-composite micromachined ultrasound transducer (PC-MUT), piezoelectric micromachined ultrasound transducer (PMUT) and capacitive micromachined ultrasound transducer (CMUT) (Figure 4) [52][53][54]. The details about structures and fabrication processes of these four types of ultrasound transducers have been reported by many references.…”

Mechanically Rotating Intravascular Ultrasound (IVUS) Transducer: A Review

“…The main difference between the two types of IVUS transducers is the method of image acquisition. Many advantages and disadvantages can be found when they are compared [ 102 , 103 , 104 , 105 ].…”

Active Temperature compensation for MEMS capacitive sensor

“…Capacitive sensors are realized by varying any of the three parameters of a capacitor: the distance between two plates, overlapped area of plates, and the dielectric constant of an insulator. Based on those physical changes, a wide variety of capacitive sensors have been developed, ranging from proximity sensing [1][2][3][4][5], position sensing [6,7], humidity sensing [8,9], tilt sensing [10,11], strain sensing [12,13,14], etc. As the capacitance is not dependent on the properties of the plate material, and thermal expansion is generally isotropic in three dimensions, capacitive sensors are generally considered to having low-temperature dependence compared with other sensor methods, such as resistive based [15] or resonant based [16].…”