Beamforming in 3D IVUS imaging
Date Issued
2007
Date
2007
Author(s)
Shen, I-Ming
DOI
zh-TW
Abstract
Ultrasound is a non-radiative, real-time, cost-effective and portable medical imaging modality, which is widely used in clinical applications. Intravascular ultrasound (IVUS) uses a transducer mounted on catheter tips to get an inside view of blood vessels. It can provide the estimation of stenosis in blood vessels and has the ability of real-time imaging, interventional therapy guiding and flow measurement. There are two kinds of IVUS imaging: side-looking and forward-looking. For side-looking IVUS, a limited number of connections results in poor beam-forming. For forward-looking IVUS, on the other hand, the spatial and temporal resolution are both limited. The objective of this research is to investigate the imaging performance and the system requirement of 3D IVUS imaging system.
For side-looking IVUS, we propose a single-wire multi-element synthetic aperture system. In this way, we can decrease the number of connections by using multiplexer and synthetic aperture focusing technique (SAFT), and do beam-forming using optimal filtering. Simulation results show that after applying the optimal filtering, the lateral beam widths are identical with theoretical results. Besides, the system is practical for medical applications because of its high singal-to-noise ratio (SNR) and low electrical impedance.
For forward-looking IVUS, we look into two approaches. First, we use a sparse vernier array to simplify the fabrication of high frequency 2D array transducers, and to reduce the number of elements with only little degradation of spatial resolution. Second, we find appropriate transmit and receive pairs from ring-annular array so that the system has enough frame rate avoiding motion artifact and still keeps good spatial resolution. Furthermore, we use coded excitation to improve SNR of the system. By applying all methods above in simulations, we can realize a 3D imaging system with a SNR of 40 dB, a frame rate of 360 frames/sec, and a side-lobe level of -30 dB under the constraints of the given transducer size, hollow aperture and axial resolution. Thus we can provide full 3D image information with both side-looking and forward-looking IVUS systems.
Capacitive micro-machined ultrasonic transducer (CMUT) is a new transducer technology with advantages of easy fabrication, improved bandwidth, and easy integration with front-end circuits. It is a potential tool for IVUS imaging. In this research, we use CMUTs for some preliminary characterization measurements and imaging experiments. We demonstrate the imaging feasibility of CMUTs. In the future, we can combine all the beam-forming techniques with CMUTs to carry out the 3D IVUS imaging system.
Subjects
血管內超音波
側向視野
前向視野
波束成像
微型電容式超音波探頭
Intravascular ultrasound (IVUS)
side-looking
forward-looking
beam-forming
capacitive micro-machined ultrasonic transducer (CMUT)
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-R94921053-1.pdf
Size
23.31 KB
Format
Adobe PDF
Checksum
(MD5):1de5f3dc158cbceeb7004c3fad440f11