CC BY
20B-I-23
Triple modality transmission-reflection optoacoustic ultrasound (TROPUS) computed tomography of small animals
E. Mercep1, X.L. Dean-Ben2'3, D. Razansky2,3 1iThera Medical GmbH, Munich, Germany
2Faculty of Medicine and Institute of Pharmacology and Toxicology, University of Zurich, Switzerland
3Institute for Biomedical Engineering and Department of Information Technology and Electrical Engineering, ETH Zurich, Switzerland
Rapid progress in the development of multispectral optoacoustic tomography techniques has enabled unprecedented insights into biological dynamics and molecular processes in vivo and noninvasively at penetration and spatiotemporal scales not covered by modern optical microscopy methods [2]. Ultrasound imaging provides highly complementary information on elastic and functional tissue properties and further aids in enhancing optoacoustic image quality [2]. We devised the first hybrid transmission-reflection optoacoustic ultrasound (TROPUS) small animal imaging platform that combines optoacoustic tomography with both reflection- and transmissionmode ultrasound computed tomography. The system features full-view cross-sectional tomographic imaging geometry for concomitant noninvasive mapping of the absorbed optical energy, acoustic reflectivity, speed of sound and acoustic attenuation in whole live mice with submillimeter resolution and unrivaled image quality [3]. Graphics processing unit (GPU)-based algorithms employing spatial compounding and bent-ray tracing iterative reconstruction were further developed to attain real-time rendering of ultrasound tomography images in the full ring acquisition geometry. In vivo mouse imaging experiments revealed fine details on the organ parenchyma, vascularization, tissue reflectivity, density and stiffness (Fig. 1).
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Fig. 1. Hybrid transmission-reflection optoacoustic ultrasound (TROPUS) whole-body mouse imaging. (a) Representative cross-sections acquired in the optoacoustic mode. (b) The corresponding reflection-mode ultrasound images. (c), (d) The corresponding transmission-mode ultrasound images showing the distribution of the speed of sound and acoustic attenuation, respectively. Annotations: 1: spinal cord; 2: liver; 3: vena porta; 4: vena cava; 5: aorta; 6: stomach; 7: ribs; 8: skin/fat layer; 9: spleen; 10: right kidney; 11: cecum; 12: pancreas; 13: intestines; 14:
muscle.
We further used the speed of sound maps retrieved by the transmission ultrasound tomography to improve optoacoustic reconstructions via two-compartment modeling. The newly developed synergistic multimodal combination offers unmatched capabilities for imaging multiple tissue properties and biomarkers with high resolution, penetration and contrast.
Acknowledgements: Financial support is acknowledged from the European Research Council under grant ERC-2015-CoG-682379 and German Research Foundation Grant RA1848/5-1.
References
[1] X. L. Dean-Ben, S. Gottschalk, B. McLarney, S. Shoham, D. Razansky. Advanced optoacoustic methods for multi-scale imaging of in vivo dynamics. Chem Soc Rev 46, 2158-2198 (2017).
[2] Mercep E, Burton NC, Claussen J, Razansky D. Whole-body live mouse imaging by hybrid reflection-mode ultrasound and optoacoustic tomography. Opt Lett 40, 4643-4646 (2015).
[3] E. Mercep, J. L. Herraiz, X. L. Dean-Ben, and D. Razansky. Transmission-reflection optoacoustic ultrasound (TROPUS) computed tomography of small animals. Light Sci Appl 8, 18 (2019).
