A common approach in Photoacoustic Imaging (PAI) is to use a linear or curved piezoelectric transducer array, which provides flexibility and versatility during image acquisition. However, these PAI systems often have limited Field-of-View (FOV), resolution, and contrast, resulting in low quality images. In this study, a multi-transducer approach is proposed to improve FOV, resolution, and contrast, with the goal of facilitating human carotid plaque imaging. A prototype consisting of multiple Capacitive Micromachined Ultrasonic Transducers (CMUTs) on a flexible array with shared channels was developed and evaluated using simulated and ex-vivo human carotid plaque samples. In numerical simulations, the results are evaluated based on input ground truth parameters. For ex-vivo plaque samples, results for multi-transducer are evaluated and compared to the images acquired with single transducer. All the results demonstrate that the proposed approach improves contrast, FOV, and most notably, it allows resolving the structural information in the medium where more than 25% improvement in gCNR values is achieved in both simulations and experiments compared to the PA images obtained with single transducer.
Photoacoustic imaging (PAI) has a great potential to assess vulnerable plaques in the carotid artery. However, in vivo, PAI suffers from low angular coverage, limited field of view (FOV), and lateral resolution especially when imaging a few centimeters deep in the tissue. To improve these shortcomings, here, we propose to image with multiple capacitive micromachined ultrasound transducers on a flexible substrate with orientation sensors to improve the image quality independent of the patient anatomy. We tested the multi-perspective PAI on a phantom and the experimental results demonstrate improvement in FOV, angular coverage, and resolution, strongly increasing the diagnostic capability of the PAI system.
The assessment of tissue composition using photoacoustic imaging (PAI) is a promising approach. However, the signal-to-noise ratio in PAI systems are quite low in comparison to ultrasound imaging’s especially at few centimeters depth. Multi-perspective photoacoustic imaging (MP-PAI) using multiple capacitive micromachined ultrasound transducers (CMUTs) on a flexible substrate provide a cost-efficient way to improve field of view (FOV), resolution, and angular coverage. In this work, an encoding scheme based on Hadamard codes is proposed to improve the SNR in MP-PAI. The concept is validated in an experiment using a carotid plaque tissue sample demonstrating the increase in SNR imaging with three CMUTs.
Capacitive micromachined ultrasound transducers (CMUTs) are gaining more interest for photoacoustic imaging due to its low-cost, high bandwidth and flexibility in size and shape. However, the beampattern of CMUTs usually exhibits wide mainlobes and high sidelobes, degrading the imaging resolution and contrast. We propose to improve the beampattern with optimization of apodization by imposing conditions on the angular distribution of the signal energy received from a PA point source to minimize the sidelobes magnitude and maintain the mainlobe energy. Both simulations and experiments results demonstrate that the proposed apodization suppress the sidelobes up to 30dB when compared with Uniform weights.
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