Flexible array curvature and sound speed estimations with a maximum spatial lag-one coherence metric

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Flexible transducer arrays have the potential to conform to various organ shapes and sizes during photoacoustic image-guided interventions. However, incorrect sound speeds and array shapes can interfere with photoacoustic target localization and degrade image quality. We propose a metric to estimate the sound speed surrounding a target and the radii of curvature of flexible arrays with approximately concave shapes. The metric is defined as the maximum lag-one spatial coherence of the time-delayed, zero-mean channel data received from a region of interest surrounding a photoacoustic target (which we abbreviate as mLOC). Performance is demonstrated with simulated and experimental phantom data. Three photoacoustic targets were simulated in k-Wave with 1540 m/s medium sound speed, and photoacoustic signals were received by a transducer with a flat shape and an 81.3 mm radius of curvature. To acquire experimental photoacoustic data with the flexible array placed on flat and curved surfaces, an optical fiber paired with a hollow metal needle was inserted into an 83-mm-radius hemispherical plastisol phantom at three locations. When implementing beamforming time delays to calculate mLOC, the associated sound speed and radii of curvature ranged 1080-2000 m/s and 60-120 mm, respectively. The sound speed and array curvature estimated by the maximized mLOC were 1540 m/s and 81 mm, respectively, in simulation, resulting in accuracies of 100% and 99.63%, respectively. The sound speed in the phantom was empirically estimated by the maximum of mLOC as 1543 m/s, which led to the array curvature estimation of 85 mm and the corresponding accuracy of 97.59%. Results demonstrate the potential of mLOC to approximate sound speeds and array radii when these variables are unknown in future flexible array imaging scenarios.

Original languageEnglish (US)
Title of host publicationPhotons Plus Ultrasound
Subtitle of host publicationImaging and Sensing 2024
EditorsAlexander A. Oraevsky, Lihong V. Wang
ISBN (Electronic)9781510669437
StatePublished - 2024
EventPhotons Plus Ultrasound: Imaging and Sensing 2024 - San Francisco, United States
Duration: Jan 28 2024Jan 31 2024

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


ConferencePhotons Plus Ultrasound: Imaging and Sensing 2024
Country/TerritoryUnited States
CitySan Francisco

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Biomaterials
  • Radiology Nuclear Medicine and imaging


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