arXiv subjects

Souradip Paul

Publications and source records attributed to Souradip Paul.

4 recordsLinked to original sources

arXiv2022

A gel wax phantom for performance evaluation in diagnostic ultrasound: assessment of image uniformity, geometric accuracy, and diameter of a hyperechoic target

Purpose: To develop and validate a phantom for diagnostic ultrasound (US) scanners by embedding targets in gel wax to determine the image uniformity, lateral and axial resolution, and diameter of a stainless-steel disc. Materials and Methods: Acoustic property (AP), which includes the velocity of US (cus), acoustic impedance (Z), and attenuation coefficient in gel wax were determined. The cus, and attenuation coefficient were estimated using the pulse-echo technique. Z was obtained from the product of sample density (\r{ho}) and cus. Two rectangular frames using polytetrafluoroethylene (PTFE) sheets with holes separated by 5, 10, and 20 mm distances were constructed. Nylon filaments and SS-disc (diameter = 16.8 mm) were threaded through the frames and suitably placed in melted gel wax to obtain orthogonal targets. The targets were measured using computerized tomography (CT) and a 2-9 MHz US probe. Results: The AP of gel wax were cus=1418 m/s, \r{ho}= 0.87 g/cm3, Z=1.23 MRayls, attenuation coefficient= 0.88 dB/cm/MHz. The results of US imaging of the targets were compared with their physical sizes and served as baselines for the scanner and probe. The maximum error in distance measurement in the phantom US images was 7.1%, and the phantom volume decreased by 1.8% over 62 weeks. Conclusion: Gel wax can be useful in developing affordable, highly stable, and customizable diagnostic US phantoms that can be implemented widely.

physics.med-ph↗

arXiv2022

Photoacoustic Image Quality Improvement from a Single Cell Low Frequency PMUT

Photoacoustic image (PAI) quality improvement using a low frequency piezoelectric micromachined ultrasound transducer (PMUT) having the fundamental resonant frequency 1 MHz is being reported. Specifically, three different methods are implemented such as the frame averaging, mathematically improved algorithms, and a hardware position accurate arrangement in order to obtain unparallel PAI image quality. Validation study has been conducted in both agar phantom and ex-vivo tissue samples. Measurable image quantifiers in the form of full width at half maximum (FWHM), signal to noise ratio (SNR), and contrast ratio (CR) are used to evaluate the improvement in the image quality. It is found that the FWHM increases by 34%, SNR by 23% and CR by 25%, suggesting the efficacy of the methods to achieve better photoacoustic images employing PMUT-based detector. The study demonstrates that the suggested methods of improvement could play a key role in a promising cost-effective PMUT-PAI system in future.

physics.ins-det↗

arXiv2022

Higher-order correlation based real-time beamforming in photoacoustic imaging

Linear-array based photoacoustic images are reconstructed using the conventional delay-and-sum (DAS) beamforming method. Although the DAS beamformer is well suited for PA image formation, reconstructed images are often afflicted by noises, sidelobes, and other intense artifacts due to inaccurate assumptions of PA signal correlation. The work aims to develop an inversion method that reduces the occurrence of sidelobes and artifacts and improves image quality performance. We present a novel beamformer based on higher-order signal correlation, where more number of delayed PA signals are combined and summed up than the conventional delay-multiply-and-sum (DMAS). The proposed technique provides efficient improvements in resolution, contrast, and SNR compared to the traditional beamformers. Computational complexity in this method is shrunk to the same order of DAS $O(N)$. Therefore, this beamformer can be implemented in real-time PA image reconstruction. A GPU based study was performed on computation time. Proposed method almost executes in the same time frame of DAS and real-time DMAS. A validation study of the algorithm was accomplished both numerically and experimentally. Higher-order DMAS beamformers demonstrate superior reconstruction in all cases. The quantitative evaluation of the ex-vivo phantom shows that the proposed method leads to 51% and 6% improvement in FWHM, 81% and 39% improvement in SNR compared to DAS and DMAS, respectively. Conclusively, the proposed algorithm is very much potential and promising in real-time photoacoustic imaging and its applications.

physics.med-ph↗

arXiv2021

Noise adaptive beamforming for linear array photoacoustic imaging

Delay-and-sum (DAS) algorithms are widely used for beamforming in linear array photoacoustic imaging systems and are characterized by fast execution. However, these algorithms suffer from various drawbacks like low resolution, low contrast, high sidelobe artifacts and lack of visual coherence. More recently, adaptive weighting was introduced to improve the reconstruction image quality. Unfortunately, the existing state-of-the-art adaptive beamforming algorithms are computationally expensive and do not consider the specific noise characteristics of the acquired ultrasonic signal. In this article, we present a new adaptive weighting factor named the variational coherence factor (VCF), which takes into account the noise level variations of radio-frequency data. The proposed technique provides superior results in terms of image resolution, sidelobe reduction, signal-to-noise and contrast level improvement. The quantitative results of the numerical simulations and phantom imaging show that the proposed VCF assisted DAS method leads to 55% and 25% improvement in FWHM, 57% and 32% improvement in SNR, respectively, compared to the state-of-the-art DAS-based methods. The results demonstrate that the proposed method can effectively improve the reconstructed image quality and deliver satisfactory imaging performance even with a limited number of sensor elements. The proposed method can potentially reduce the instrumentation cost of the photoacoustic imaging system and contribute toward the clinical translation of the modality.

physics.med-ph↗