Toward Real-Time Giga-Voxel Optoacoustic/Photoacoustic Microscopy: GPU-Accelerated Fourier Reconstruction with Quasi-3D Implementation

We propose a GPU-accelerated implementation of frequency-domain synthetic aperture focusing technique (SAFT) employing truncated regularized inverse k-space interpolation. Our implementation achieves sub-1s reconstruction time for data sizes of up to 100 M voxels, providing more than a tenfold decrease in reconstruction time as compared to CPU-based SAFT. We provide an empirical model that can be used to predict the execution time of quasi-3D reconstruction for any data size given the specifications of the computing system.

3D Internal Visualization of Concrete Structure Using Multifaceted Data for Ultrasonic Array Pulse-Echo Tomography

This research proposes a 3D internal visualization using ultrasonic pulse-echo tomography technique to evaluate accurately the state of concrete structures for their efficient maintenance within a limited budget. Synthetic aperture focusing technique (SAFT) is used as a post-processing algorithm to manipulate the data measured by the ultrasonic pulse-echo technique. Multifaceted measurements improve the weakness of the existing ultrasonic pulse-echo tomography technique that cannot identify the area beyond a reflector as well as the area located far away from measuring surfaces. The application of apodization factor, pulse peak delay calibration and elimination of trivial response not only complements the weaknesses of the SAFT algorithm but also improves the accuracy of the SAFT algorithm. The results show that the proposed method reduces the unnecessary surface noise and improves the expressiveness of the reflector’s boundaries on the resulting images. It is expected that the proposed 3D internal visualization technique will provide a useful non-destructive evaluation tool in combination with another structure evaluation method.

Shear Horizontal Guided Wave Corrosion Detection and Quantification in Pipes via Linear Scanning Magnetostrictive Transducers (MST)

Shear horizontal (SH) guided waves are being widely considered as a promising tool for locating wall thinning corrosion in pipelike structures. One established approach to excite such waves in pipes is through the magnetostrictive transducers (MsT), which is an electromagnetic-based guided wave transducer that offers unique advantages over other transducer types. A common practice for fast screening of defects is using an automated probe positioning system. In this paper, we report the usage of a newly designed linear scanning MsT, where an iron cobalt (FeCo) strip of a predefined length wound with radio frequency (RF) coils is attached to the testing structure using shear wave couplants and a moving permanent magnet driven by a stepper motor is used to excite SH guided waves at predefined positions. In this fashion, manual manipulation of probe is minimized which significantly increases testing speed. The performance of the linear scanning MsT at corrosion inspection is evaluated experimentally by introducing “V” shaped gradual wall thinning patches of different depths and locations on a 406 mm outer diameter (OD) steel pipe with 10 mm wall thickness. The reflection and transmission amplitudes of SH modes, as well as indications from B-scan and synthetic aperture focusing technique (SAFT) images, are extracted for corrosion detection and quantification. Numerical modeling is also conducted to facilitate the understanding of SH waves interaction with defects.

An analytical approach to optimize radial synthetic aperture focusing for volumetric transrectal ultrasound imaging

In this paper, we present a novel analytical approach to optimize radial synthetic aperture focusing framework for high-definite and high-sensitive volumetric transrectal ultrasound imaging (TRUS-rSAF). A closed-form analytical description of beam profile defines spatial resolution and grating lobe positions in the TRUS-rSAF imaging of radial plane and validated by a heuristic testing of the critical parameters. Given the theoretical foundation, we optimize the TRUS-rSAF system configuration to balance the spatial and temporal resolution, grating lobe artifacts, and signal-to-noise ratio (SNR) in radial plane with a design criterion to outperform a clinical volumetric TRUS (TRUS-REF) imaging. The results showed that the proposed analytical optimization provides significant improvements of imaging quality in radial plane even over an in-plane microconvex TRUS imaging. Therefore, our analytical approach provides a optimal framework for effective TRUS-rSAF imaging in clinics.

An analytical approach to optimize radial synthetic aperture focusing for volumetric transrectal ultrasound imaging

In this paper, we present a novel analytical approach to optimize radial synthetic aperture focusing framework for high-definite and high-sensitive volumetric transrectal ultrasound imaging (TRUS-rSAF). A closed-form analytical description of beam profile defines spatial resolution and grating lobe positions in the TRUS-rSAF imaging of radial plane and validated by a heuristic testing of the critical parameters. Given the theoretical foundation, we optimize the TRUS-rSAF system configuration to balance the spatial and temporal resolution, grating lobe artifacts, and signal-to-noise ratio (SNR) in radial plane with a design criterion to outperform a clinical volumetric TRUS (TRUS-REF) imaging. The results showed that the proposed analytical optimization provides significant improvements of imaging quality in radial plane even over an in-plane microconvex TRUS imaging. Therefore, our analytical approach provides a optimal framework for effective TRUS-rSAF imaging in clinics.

Frequency-Domain Synthetic Aperture Focusing Techniques for Imaging with Single-Element Focused Transducers

Synthetic aperture focusing techniques (SAFT) make the lateral spatial resolution of the conventional ultrasound imaging from a single-element focused transducer more uniform. In this work, two new frequency-domain SAFT (FD-SAFT) algorithms are proposed, which are based on 2D matched filtering techniques. The first algorithm is the FD-SAFT virtual disk source (FD-VDS) that treats the focus of a focused transducer as a finite sized virtual source and the diffraction effect in the far-field is accounted for in the image reconstruction. The second algorithm is the FD-SAFT deconvolution (FD-DC) that uses the simulated point spread function of the imaging system as a matched filter kernel in the image reconstruction. These algorithms were implemented for pulsed and linear frequency modulated chirp excitations. The performance of these algorithms was studied using a series of simulations and experiments, and it was compared with the conventional B-mode and time-domain virtual point source SAFT (TD-VPS) imaging techniques. The image quality was analyzed in terms of spatial resolution, sidelobe level, signal-to-noise ratio (SNR), contrast resolution, contrast-to- speckle ratio, and ex vivo tissue image quality. The results showed that the FD-VDS had the highest spatial resolution and FD-DC had the second highest spatial resolution. In addition, FD-DC had generally the highest SNR. The computation run time of the proposed methods was significantly lower than the TD-VPS. Furthermore, chirp excitation improves the SNR of all methods by about 8 dB without significantly affecting the spatial resolution and sidelobe level. Thus, the FD-VDS and FD-DC methods offer efficient solutions to make the spatial resolution of conventional B-mode imaging more uniform.

Frequency-Domain Synthetic Aperture Focusing Techniques for Imaging with Single-Element Focused Transducers

Synthetic aperture focusing techniques (SAFT) make the lateral spatial resolution of the conventional ultrasound imaging from a single-element focused transducer more uniform. In this work, two new frequency-domain SAFT (FD-SAFT) algorithms are proposed, which are based on 2D matched filtering techniques. The first algorithm is the FD-SAFT virtual disk source (FD-VDS) that treats the focus of a focused transducer as a finite sized virtual source and the diffraction effect in the far-field is accounted for in the image reconstruction. The second algorithm is the FD-SAFT deconvolution (FD-DC) that uses the simulated point spread function of the imaging system as a matched filter kernel in the image reconstruction. These algorithms were implemented for pulsed and linear frequency modulated chirp excitations. The performance of these algorithms was studied using a series of simulations and experiments, and it was compared with the conventional B-mode and time-domain virtual point source SAFT (TD-VPS) imaging techniques. The image quality was analyzed in terms of spatial resolution, sidelobe level, signal-to-noise ratio (SNR), contrast resolution, contrast-to- speckle ratio, and ex vivo tissue image quality. The results showed that the FD-VDS had the highest spatial resolution and FD-DC had the second highest spatial resolution. In addition, FD-DC had generally the highest SNR. The computation run time of the proposed methods was significantly lower than the TD-VPS. Furthermore, chirp excitation improves the SNR of all methods by about 8 dB without significantly affecting the spatial resolution and sidelobe level. Thus, the FD-VDS and FD-DC methods offer efficient solutions to make the spatial resolution of conventional B-mode imaging more uniform.