Abstract
.SignificanceDuring the development and early testing phases of new photoacoustic (PA) breast imaging systems, several choices need to be made in aspects of system design and measurement sequences. Decision-making can be complex for state-of-the-art systems such as 3D hybrid photoacoustic-ultrasound (PA-US) breast imagers intended for multispectral quantitative imaging. These systems have a large set of design choices and system settings that affect imaging performance in different ways and often require trade-offs. Decisions have to be made carefully as they can strongly influence the imaging performance.AimA systematic approach to assess the influence of various choices on the imaging performance in carefully controlled laboratory situations is crucial before starting with human studies. Test objects and phantoms are used for first imaging studies, but most reported structures have a 2D geometry and are not suitable to assess all the image quality characteristics (IQCs) of 3D hybrid PA-US systems.ApproachOur work introduces a suite of five test objects designed for hybrid PA-US systems with a 3D detection aperture. We present the test object designs and production protocols and explain how they can be used to study various performance measures. To demonstrate the utility of the developed objects, measurements are made with an existing tomographic PA system.ResultsTwo test objects were developed for measurements of the US detectors’ impulse responses and light distribution on the breast surface. Three others were developed to assess image quality and quantitative accuracy of the PA and US modes. Three of the five objects were imaged to demonstrate their use.ConclusionsThe developed test objects allow one to study influences of various choices in design and system settings. With this, IQCs can be assessed as a function of measurement sequence settings for the PA and US modes in a controlled way. Systematic studies and measurements using these objects will help to optimize various system settings and measurement protocols in laboratory situations before embarking on human studies.
Highlights
Photoacoustic (PA) tomography is an emerging non-invasive imaging technique that is making its entry into the clinics for applications in breast imaging.[1,2] The technique enables the Journal of Biomedical OpticsDownloaded From: https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics on 12 Jan 2022 Terms of Use: https://www.spiedigitallibrary.org/terms-of-useJuly 2022 Vol 27(7)Dantuma et al.: Suite of 3D test objects for performance assessment of hybrid photoacoustic-ultrasound. . .visualization of blood vessels deep in the breast with high resolutions using the intrinsic and wavelength-specific optical absorption contrast of hemoglobin in the blood.[3,4] Depending on the configuration of the ultrasound (US) detection array, images with two or three dimensions can be generated
IQCs can be assessed as a function of measurement sequence settings for the PA and US modes in a controlled way
For assessment of the PA image quality, as part of phase (ii), we focus on the spatial resolution and imaging depth, as these are performance characteristics that report on the detail and extent to which the breast volume can be imaged
Summary
Photoacoustic (PA) tomography is an emerging non-invasive imaging technique that is making its entry into the clinics for applications in breast imaging.[1,2] The technique enables the Journal of Biomedical OpticsDownloaded From: https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics on 12 Jan 2022 Terms of Use: https://www.spiedigitallibrary.org/terms-of-useJuly 2022 Vol 27(7)Dantuma et al.: Suite of 3D test objects for performance assessment of hybrid photoacoustic-ultrasound. . .visualization of blood vessels deep in the breast with high resolutions using the intrinsic and wavelength-specific optical absorption contrast of hemoglobin in the blood.[3,4] Depending on the configuration of the ultrasound (US) detection array, images with two or three dimensions can be generated. The pixel intensities in the resulting image depend, among others, on the concentration and the optical absorption coefficient (μa) of hemoglobin in the blood.[5] Quantitative photoacoustic (QPA) imaging[6] seeks to map estimates of chromophore concentrations in tissue, which could be intrinsic, such as hemoglobin or lipids, or exogenous, such as contrast agents. This is achieved using multiple excitation wavelengths for PA imaging since chromophores often have wavelength-dependent optical absorption. An estimation of the blood oxygen saturation (SO2) is often the goal of QPA as it can provide insights into the breast and tumor physiology
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