Coherent-weighted three-dimensional image reconstruction in linear-array-based photoacoustic tomography

Abstract

While the majority of photoacoustic imaging systems used custom-made transducer arrays, commercially-available linear transducer arrays hold the benefits of affordable price, handheld convenience and wide clinical recognition. They are not widely used in photoacoustic imaging primarily because of the poor elevation resolution. Here, without modifying the imaging geometry and system, we propose addressing this limitation purely through image reconstruction. Our approach is based on the integration of two advanced image reconstruction techniques: focal-line-based three-dimensional image reconstruction and coherent weighting. We first numerically validated our approach through simulation and then experimentally tested it in phantom and in vivo. Both simulation and experimental results proved that the method can significantly improve the elevation resolution (up to 4 times in our experiment) and enhance object contrast.

Deep tissue photoacoustic computed tomography with a fast and compact laser system

“…With 50 Hz pulse repetition frequency, each 40-mm scan took 8 seconds, which was only one fifth of the imaging time mentioned in our previous study [39]. Photographs of the arm and palm are shown in Figs Figs.…”

“…Also, because most blood vessels were located within 15 mm of axial depths, we did not use any additional reconstruction methods to further improve the spatial resolution nor contrast ratio. For deep tissue imaging (> 30 mm), we could use our slitbase PACT [40] or coherent-weighted 3D reconstruction [39] to improve the image quality. It should also be noted that our current field of view is limited by the small lateral dimension of the transducer array (38 mm for L7-4).…”

Elevation resolution enhancement in 3D photoacoustic imaging using FDMAS beamforming

“…Then these beamformed data for all scanning lines stack together to form 3D photoacoustic imaging [7]. This 3D photoacoustic image suffers from poor elevation resolution out of the focal point.…”

“…This 3D photoacoustic image suffers from poor elevation resolution out of the focal point. To reduce the effect of the poor elevation resolution out of the focus point, the received RF data will be beamformed in the lateral then in the elevation directions to generate DAS (3D) beamforming technique [7]. In this beamforming technique, the FOV of each transducer element in the lateral and elevation direction will be taken on account.…”

“…For instance, Schwarz et.al [6] have applied bidirectional scan by using linear array transducer. Wang et.al [7] have combined coherent factor (CF) with focal line (FL) technique to improve elevation resolution when linear array transducer is used. In this study, the elevation resolution of the 3D photoacoustic image will be improved when linear array transducer is used by applying Filter delay multiply and sum (FDMAS) beamforming technique in 3D photoacoustic imaging.…”