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Evaluation of Adjoint Methods in Photoacoustic Tomography with Under-Sampled Sensors

Lin, H; Azuma, T; Unlu, MB; Takagi, S; (2018) Evaluation of Adjoint Methods in Photoacoustic Tomography with Under-Sampled Sensors. In: Frangi, A and Schnabel, J and Davatzikos, C and Alberola-López, C and Fichtinger, G, (eds.) Proceedings of the International Conference on Medical Image Computing and Computer Assisted Intervention – MICCAI 2018. Springer: Cham. Green open access

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Abstract

Photo-Acoustic Tomography (PAT) can reconstruct a distribution of optical absorbers acting as instantaneous sound sources in subcutaneous microvasculature of a human breast. Adjoint methods for PAT, typically Time-Reversal (TR) and Back-Projection (BP), are ways to refocus time-reversed acoustic signals on sources by wave propagation from the position of sensors. TR and BP have different treatments for received signals, but they are equivalent under continuously sampling on a closed circular sensor array in two dimensions. Here, we analyze image quality with discrete under-sampled sensors in the sense of the Shannon sampling theorem. We investigate resolution and contrast of TR and BP, respectively in one source-sensor pair configuration and the frequency domain. With Hankel's asymptotic expansion to the integrands of imaging functions, our main contribution is to demonstrate that TR and BP have better performance on contrast and resolution, respectively. We also show that the integrand of TR includes additional side lobes which degrade axial resolution whereas that of BP conversely has relatively small amplitudes. Moreover, omnidirectional resolution is improved if more sensors are employed to collect the received signals. Nevertheless, for the under-sampled sensors, we propose the Truncated Back-Projection (TBP) method to enhance the contrast of BP using removing higher frequency components in the received signals. We conduct numerical experiments on the two-dimensional projected phantom model extracted from OA-Breast Database. The experiments verify our theories and show that the proposed TBP possesses better omnidirectional resolution as well as contrast compared with TR and BP with under-sampled sensors.

Type: Proceedings paper
Title: Evaluation of Adjoint Methods in Photoacoustic Tomography with Under-Sampled Sensors
Event: International Conference on Medical Image Computing and Computer Assisted Intervention – MICCAI 2018
ISBN: 978-3-030-00928-1
ISBN-13: 978-3-030-00927-4
Open access status: An open access version is available from UCL Discovery
DOI: 10.1007/978-3-030-00928-1_9
Publisher version: https://doi.org/10.1007/978-3-030-00928-1_9
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Photoacoustic tomography, Adjoint method, Time-reversal, Back-projection, Hankel asymptotic expansion, Resolution, Contrast
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Computer Science
URI: https://discovery.ucl.ac.uk/id/eprint/10088418
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