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Proceedings ArticleDOI

Improved Lateral Resolution Using sub Pitch Sampling of Ultrasound Data for Pulsed Laser Diode-Based Photoacoustic Imaging

TL;DR: In this paper, a linear translation-based approach was employed in which the array transducer is translated by sub-pitch amount to create an augmented RF frame data having denser lateral spatial sampling.
Abstract: The achievable resolution in PAT is dependent on the receive transducer parameters such as element size, inter-element spacing (pitch or sampling) and aperture length among a few other parameters. Ideally, dense spatial sampling of the generated photoacoustic signals using point detectors is required for obtaining the best possible image resolution in PAT. However, in most practical cases, data are acquired with only limited number of finite-sized detector elements. Manufacturing a high density, large-aperture linear array transducer with “sub©- $\lambda^{\prime \prime}$ pitch, especially at higher frequencies, is challenging and therefore is expensive. Hence, there is a need for alternate ways of increasing discrete array sampling for PAT application. In this work, we employ a linear translation-based approach in which the array transducer is translated by sub-pitch amount to create an augmented RF frame data having denser lateral spatial sampling. The results from simulation and experiments show 34% and 38% improvement in lateral resolution (LR) estimate, respectively, when using $\mathbf{a}\frac{\lambda}{4}$ -pitch configuration in comparison to using conventional $\lambda$ -pitch configuration.
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Journal ArticleDOI
TL;DR: It is demonstrated that by combining the recently described approach of subpitch translation on the receive-side ultrasound transducer alongside averaging of multiple frames, it is feasible to increase the depth sensitivity in a PLD-based PAT imaging system.
Abstract: Pulsed laser diodes (PLDs) promise to be an attractive alternative to solid-state laser sources in photoacoustic tomography (PAT) due to their portability, high-pulse repetition frequency (PRF), and cost effectiveness. However, due to their lower energy per pulse, which, in turn, results in lower fluence required per photoacoustic signal generation, PLD-based photoacoustic systems generally have maximum imaging depth that is lower in comparison to solid-state lasers. Averaging of multiple frames is usually employed as a common practice in high PRF PLD systems to improve the signal-to-noise ratio of the PAT images. In this work, we demonstrate that by combining the recently described approach of subpitch translation on the receive-side ultrasound transducer alongside averaging of multiple frames, it is feasible to increase the depth sensitivity in a PLD-based PAT imaging system. Here, experiments on phantom containing diluted India ink targets were performed at two different laser energy level settings, that is, 21 and $27~\mu \text{J}$ . Results obtained showed that the imaging depth improves by ~38.5% from 9.1 to 12.6 mm for 21- $\mu \text{J}$ energy level setting and by ~33.3% from 10.8 to 14.4 mm for 27- $\mu \text{J}$ energy level setting by using $\lambda $ /4-pitch translation and average of 128 frames in comparison to $\lambda $ -pitch data acquired with the average of 128 frames. However, the achievable frame rate is reduced by a factor of 2 and 4 for $\lambda $ /2 and $\lambda $ /4 subpitch translation, respectively.

2 citations


Additional excerpts

  • ...We recently demonstrated that an actuator-assisted translation of the regular λ-pitch linear array by sub-λ distances and creating an augmented denser matrix of raw ultrasound radiofrequency (RF) data resulted in improved resolution and contrast in the reconstructed PAT images from a low-cost PLDbased PAT imaging system [45], [46]....

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Proceedings ArticleDOI
01 Jul 2019
TL;DR: The preliminary results obtained from experiments suggest that the higher density data obtained by augmenting raw RF lines from λ/2 positions of a linear array transducer provides better signal strength from deeper located targets and thereby increasing the depth of penetration by about 15% that reaches up to a depth of 14.3 mm.
Abstract: In most cases, high energy solid state lasers such as Nd:YAG are used as source of illumination for Photoacoustic Tomography (PAT). However the bulkiness, high cost and low pulse repetition frequency (PRF) poses a challenge in translating this technology to an affordable clinical imaging option at bed-side. Pulsed Laser Diodes (PLD) on the other hand is portable, inexpensive and offers high PRF. However, the achievable depth of penetration using PLD is much lower than the solid state lasers. In this work, we demonstrate the feasibility of using sub-pitch translation approach on the receive-side ultrasound transducer to increase the depth sensitivity in PAT imaging system while using PLD as a source of illumination. The preliminary results obtained from experiments suggest that the higher density data obtained by augmenting raw RF lines from λ/2 positions of a linear array transducer provides better signal strength from deeper located targets and thereby increasing the depth of penetration by about 15% that reaches up to a depth of 14.3 mm.

1 citations


Cites background from "Improved Lateral Resolution Using s..."

  • ...Further, this approach was shown to perform better in terms of lateral resolution than mere averaging of the frames[21]....

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  • ...We recently demonstrated that an actuator assisted translation of the regular λ-pitch array by sub-λ distances and creating an augmented denser matrix containing additional raw RF lines from in-between element positions results in improved resolution and contrast in PAT images[21], [22]....

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