Medical Acoustic Imaging Research Articles

Aberration Correction with Low-Frequency Transmission for Medical Acoustic Imaging

Phase aberration is one of the major causes of deterioration in the quality of medical acoustic imaging. To suppress the effect of aberration, we employ a focused transmit beam with a low center frequency for the calculation of an aberration correction value set. The aberration correction value set is applied to an imaging process utilizing high-frequency transmission. To evaluate the focus quality under severe aberration conditions, we introduce an evaluation criterion for beam patterns using the second moment of the acoustic field. The result implies that in severe aberration conditions without aberration correction, a low-frequency transmission acquires a better beam pattern, and the aberration correction value set for a high-frequency transmission should be calculated using a low-frequency transmission.

Experimental Study of High-Range-Resolution Medical Acoustic Imaging for Multiple Target Detection by Frequency Domain Interferometry

We employed frequency domain interferometry (FDI) for use as a medical acoustic imager to detect multiple targets with high range resolution. The phase of each frequency component of an echo varies with the frequency, and target intervals can be estimated from the phase variance. This processing technique is generally used in radar imaging. When the interference within a range gate is coherent, the cross correlation between the desired signal and the coherent interference signal is nonzero. The Capon method works under the guiding principle that output power minimization cancels the desired signal with a coherent interference signal. Therefore, we utilize frequency averaging to suppress the correlation of the coherent interference. The results of computational simulations using a pseudoecho signal show that the Capon method with adaptive frequency averaging (AFA) provides a higher range resolution than a conventional method. These techniques were experimentally investigated and we confirmed the effectiveness of the proposed method of processing by FDI.

3P5-8 Experimental Study of Small Calculus Detection for Medical Acoustic Imaging Using Correlation between Echo Signals(Poster Session)

3P5-8 Experimental Study of Small Calculus Detection for Medical Acoustic Imaging Using Correlation between Echo Signals(Poster Session)

2P7a-15 Small Calculi Detection for Medical Acoustic Imaging with Correlation between Ultrasonic Echo Signals(Poster Session)

2P7a-15 Small Calculi Detection for Medical Acoustic Imaging with Correlation between Ultrasonic Echo Signals(Poster Session)

P1-53 A study on the radiation pattern using focusing method for the 3-D medical acoustic imaging system with a reflector and a 2-D array(Poster session 1)

P1-53 A study on the radiation pattern using focusing method for the 3-D medical acoustic imaging system with a reflector and a 2-D array(Poster session 1)

P1-44 Optimization of Mirror Curvature and Sidelobe Suppression of a Real-time 3-D Medical Acoustic Imaging System with a Reflector and a Small Array

P1-44 Optimization of Mirror Curvature and Sidelobe Suppression of a Real-time 3-D Medical Acoustic Imaging System with a Reflector and a Small Array

Piezoelectric polymer composite arrays for ultrasonic medical imaging applications

The predominant sensor materials used in medical acoustic imaging have traditionally been piezoelectric ceramics (PZT, LaNbO 3, etc.) More recently piezoelectric polymers (PVDF) have been used in this area. Polymers present several advantages over ceramics (very flexible, easy to process, good acoustic matching to tissue, good reception constant), but also have some major drawbacks (poor emission constant, low coupling coefficient). Composite piezoelectric materials aim to incorporate the most advantageous properties of ceramics and polymers. This paper investigates the electrical and mechanical properties of two different piezoelectric polymer composite materials (Piezoflex1 and Piezel) to assess their performance for medical imaging applications. Practical transducer constructions with corona-poled, PCB-backed and diced-array architectures have been manufactured with the composites, and their performance evaluated in pulse-echo mode. The results obtained, using a simple object as target, confirm the potential use of the composite materials in medical imaging applications.