- Email: [email protected]
Austrian National Research Network on Photoacoustic Imaging
ARTICLE IN PRESS
Medical Laser Application 24 (2009) 113–115 www.elsevier.de/mla
NEWS FROM THE LASER INSTITUTES
Austrian National Research Network on Photoacoustic Imaging
Background and organization Photoacoustic Imaging (PAI) is becoming a major tool for preclinical studies owing to its unique property of combining aspects of optical and ultrasound imaging. Its potential for in-vitro and in-vivo imaging has been demonstrated both in tomographic set-ups and in photoacoustic microscopy. Enabled by funding from the Austrian Science Fund (FWF), the National Research Network (NFN) ‘‘Photoacoustic Imaging in Biology and Medicine’’ was established in April 2008. It is represented by an interdisciplinary consortium of experts in photoacoustic imaging in Austria. The consortium consists of researchers from: Speaker:
Prof. Dr. Otmar Scherzer
Contact:
Staff:
Department of Mathematics University of Innsbruck ICT Building Technikerstr. 21a/2 A-6020 Innsbruck, Austria Phone: +43 512 507 6109 Fax: +43 512 507 2758 E-mail: [email protected] Internet: http://pai.uibk.ac.at
Principal investigators: 4 Scientists: 10 Ph.D. students: 6 Administrator: 1 Total: 21
1615-1615/$ - see front matter doi:10.1016/j.mla.2009.02.047
Department of Mathematics, University of Innsbruck (Prof. Otmar Scherzer, speaker of the NFN) Department of Radiology, Medical University of Innsbruck (Prof. Werner Jaschke) Upper Austrian Research, Linz (Dr. Peter Burgholzer) Department of Physics, University of Graz (Prof. Gu¨nther Paltauf)
This consortium emerged from an earlier collaboration in a project on photoacoustic imaging (2005–2008) that was also funded by the FWF and involved the mathematics group from Innsbruck and the physics groups from Linz and Graz.
Overall concept Within the NFN, research in physics and mathematics is heavily driven by input from medicine. The main goal is to steer the technique towards practical applicability
ARTICLE IN PRESS 114
Medical Laser Application 24 (2009) 113–115
and routine for biomedical applications. Thus the NFN aims at developing and characterizing novel physical devices for preclinical inspections based on modern mathematical tools and inversion techniques. Challenging questions about medical applications related to early cancer diagnosis and cancer treatment, are of particular interest. This network combines research areas currently considered to play a significant role in photoacoustics, namely mathematics, medicine, and physics.
Subprojects Detection methods and devices for PAI (Department of Physics, University Graz) The contribution of the physics group in Graz to the PAI research network is the development of ultrasound detectors and their implementation in PAI devices (Fig. 1). Detector design involves the investigation of novel optical methods for high bandwidth ultrasound measurements based on photonic techniques, such as optical waveguide interferometry. Moreover, methods are developed using the imaging of pressure distributions with a CCD camera. This will allow for combining
the accuracy of optical methods with the speed of parallel detection. Also piezoelectric technology is employed to design specially shaped sensors. The implementation of the developed sensor technology in PAI devices, including the design of scanning and signal acquisition procedures, is a further core activity within this subproject.
PAI taking acoustic inhomogeneities and attenuation into account (Upper Austrian Research, Linz) Recently, in this group a PAI set-up was developed using an optical fiber-based Fabry–Perot interferometer (Fig. 2). The subproject is based on this PAI set-up. The development of fiber-based interferometers with polymer fibers instead of glass fibers (now in use) will increase the sensitivity of the imaging device. Various short-comings for high-resolution imaging are addressed in this project, such as: varying sound velocities and (at least partial) compensation of frequency-dependent attenuation. Further developments on the PAI set-up for improving image quality, resolution and reduction of measurement time are carried out in collaboration with the partner from the University of Graz.
Development and implementation of reconstruction algorithms for PAI (Department of Mathematics, University of Innsbruck) While the physical key ingredients for PAI imaging are optimal sensors and set-ups, the mathematical key
Fig. 1. Slices from a three-dimensional photoacoustic tomography image of a mouse heart.
Fig. 2. High-resolution, three-dimensional photoacoustic tomography of a horse hair with a knot, acquired with the fiber-based Fabry–Perot interferometer.
ARTICLE IN PRESS Medical Laser Application 24 (2009) 113–115
115
tools in PAI research involve inversion techniques, reconstruction formulas and filtering techniques, which can be implemented efficiently in software. The applied mathematics group contributes to this research network on PAI with mathematical modeling and simulation, novel reconstruction formulas, filtering techniques and efficient computational algorithms. The developed methods are implemented as computer software, which is used by the physicists designing new experimental setups and by the medical doctors and biologists performing experiments. Moreover, mathematical modeling of the next generation PAI scanner technology, which takes into account attenuation and acoustic inhomogeneities, is planned.
In-vivo and in-vitro imaging with PAI (Department of Radiology, Medical University of Innsbruck) Photoacoustic imaging has the potential to improve visualization of breast cancer. In addition, PAI allows for non-invasive measurement of tissue oxygenation in vivo, which can be used for the detection of malignant tissue as well as for guiding or monitoring novel therapies. The aim of the present subproject is to evaluate the potentials of PAI for breast cancer imaging in vitro and in vivo. Prior to clinical applications, phantom studies have to be conducted to define imaging characteristics of PAI. For in-vitro studies, biopsy and surgical specimens will be used. For in-vivo studies, an established mouse model will serve as a biological model for the development of breast cancer in human beings. Acoustic detection systems like the interferometer devices developed by the partners in Linz and Graz are employed (Fig. 3).
Future perspectives We believe that such a NFN network, consisting of Austrian research groups with a long-standing research background in the relevant topics, can be competitive. By mutually benefiting from each other, we hope to
Fig. 3. Experimental set-up for three-dimensional photoacoustic tomography using optical detection of ultrasound.
reach a new conceptual and technological level in the research area of medical applications in PAI.
Recent publications [1] Zangerl G, Scherzer O, Haltmeier M. Circular integrating detectors in photo and thermoacoustic tomography. Inverse Probl Sci Eng 2009;17(1):133–42. [2] Grasmair M, Haltmeier M, Scherzer O. Sparse regularization with lq penalty term. Inverse Problems 2008;25(5): 055020. [3] Gebauer B, Scherzer O. Impedance-acoustic tomography. SIAM J Appl Math 2008;69(2):565–76. [4] Burgholzer P, Bauer-Marschallinger J, Gru¨n H, Haltmeier M, Paltauf G. Temporal back-projection algorithms for photoacoustic tomography with integrating line detectors. Inverse Problems 2007;23(6):S65–80. [5] Paltauf G, Nuster R, Haltmeier M, Burgholzer P. Experimental evaluation of reconstruction algorithms for limited view photoacoustic tomography with line detectors. Inverse Problems 2007;23(6):S81–94.
Medical Laser Application 24 (2009) 113–115 www.elsevier.de/mla
NEWS FROM THE LASER INSTITUTES
Austrian National Research Network on Photoacoustic Imaging
Background and organization Photoacoustic Imaging (PAI) is becoming a major tool for preclinical studies owing to its unique property of combining aspects of optical and ultrasound imaging. Its potential for in-vitro and in-vivo imaging has been demonstrated both in tomographic set-ups and in photoacoustic microscopy. Enabled by funding from the Austrian Science Fund (FWF), the National Research Network (NFN) ‘‘Photoacoustic Imaging in Biology and Medicine’’ was established in April 2008. It is represented by an interdisciplinary consortium of experts in photoacoustic imaging in Austria. The consortium consists of researchers from: Speaker:
Prof. Dr. Otmar Scherzer
Contact:
Staff:
Department of Mathematics University of Innsbruck ICT Building Technikerstr. 21a/2 A-6020 Innsbruck, Austria Phone: +43 512 507 6109 Fax: +43 512 507 2758 E-mail: [email protected] Internet: http://pai.uibk.ac.at
Principal investigators: 4 Scientists: 10 Ph.D. students: 6 Administrator: 1 Total: 21
1615-1615/$ - see front matter doi:10.1016/j.mla.2009.02.047
Department of Mathematics, University of Innsbruck (Prof. Otmar Scherzer, speaker of the NFN) Department of Radiology, Medical University of Innsbruck (Prof. Werner Jaschke) Upper Austrian Research, Linz (Dr. Peter Burgholzer) Department of Physics, University of Graz (Prof. Gu¨nther Paltauf)
This consortium emerged from an earlier collaboration in a project on photoacoustic imaging (2005–2008) that was also funded by the FWF and involved the mathematics group from Innsbruck and the physics groups from Linz and Graz.
Overall concept Within the NFN, research in physics and mathematics is heavily driven by input from medicine. The main goal is to steer the technique towards practical applicability
ARTICLE IN PRESS 114
Medical Laser Application 24 (2009) 113–115
and routine for biomedical applications. Thus the NFN aims at developing and characterizing novel physical devices for preclinical inspections based on modern mathematical tools and inversion techniques. Challenging questions about medical applications related to early cancer diagnosis and cancer treatment, are of particular interest. This network combines research areas currently considered to play a significant role in photoacoustics, namely mathematics, medicine, and physics.
Subprojects Detection methods and devices for PAI (Department of Physics, University Graz) The contribution of the physics group in Graz to the PAI research network is the development of ultrasound detectors and their implementation in PAI devices (Fig. 1). Detector design involves the investigation of novel optical methods for high bandwidth ultrasound measurements based on photonic techniques, such as optical waveguide interferometry. Moreover, methods are developed using the imaging of pressure distributions with a CCD camera. This will allow for combining
the accuracy of optical methods with the speed of parallel detection. Also piezoelectric technology is employed to design specially shaped sensors. The implementation of the developed sensor technology in PAI devices, including the design of scanning and signal acquisition procedures, is a further core activity within this subproject.
PAI taking acoustic inhomogeneities and attenuation into account (Upper Austrian Research, Linz) Recently, in this group a PAI set-up was developed using an optical fiber-based Fabry–Perot interferometer (Fig. 2). The subproject is based on this PAI set-up. The development of fiber-based interferometers with polymer fibers instead of glass fibers (now in use) will increase the sensitivity of the imaging device. Various short-comings for high-resolution imaging are addressed in this project, such as: varying sound velocities and (at least partial) compensation of frequency-dependent attenuation. Further developments on the PAI set-up for improving image quality, resolution and reduction of measurement time are carried out in collaboration with the partner from the University of Graz.
Development and implementation of reconstruction algorithms for PAI (Department of Mathematics, University of Innsbruck) While the physical key ingredients for PAI imaging are optimal sensors and set-ups, the mathematical key
Fig. 1. Slices from a three-dimensional photoacoustic tomography image of a mouse heart.
Fig. 2. High-resolution, three-dimensional photoacoustic tomography of a horse hair with a knot, acquired with the fiber-based Fabry–Perot interferometer.
ARTICLE IN PRESS Medical Laser Application 24 (2009) 113–115
115
tools in PAI research involve inversion techniques, reconstruction formulas and filtering techniques, which can be implemented efficiently in software. The applied mathematics group contributes to this research network on PAI with mathematical modeling and simulation, novel reconstruction formulas, filtering techniques and efficient computational algorithms. The developed methods are implemented as computer software, which is used by the physicists designing new experimental setups and by the medical doctors and biologists performing experiments. Moreover, mathematical modeling of the next generation PAI scanner technology, which takes into account attenuation and acoustic inhomogeneities, is planned.
In-vivo and in-vitro imaging with PAI (Department of Radiology, Medical University of Innsbruck) Photoacoustic imaging has the potential to improve visualization of breast cancer. In addition, PAI allows for non-invasive measurement of tissue oxygenation in vivo, which can be used for the detection of malignant tissue as well as for guiding or monitoring novel therapies. The aim of the present subproject is to evaluate the potentials of PAI for breast cancer imaging in vitro and in vivo. Prior to clinical applications, phantom studies have to be conducted to define imaging characteristics of PAI. For in-vitro studies, biopsy and surgical specimens will be used. For in-vivo studies, an established mouse model will serve as a biological model for the development of breast cancer in human beings. Acoustic detection systems like the interferometer devices developed by the partners in Linz and Graz are employed (Fig. 3).
Future perspectives We believe that such a NFN network, consisting of Austrian research groups with a long-standing research background in the relevant topics, can be competitive. By mutually benefiting from each other, we hope to
Fig. 3. Experimental set-up for three-dimensional photoacoustic tomography using optical detection of ultrasound.
reach a new conceptual and technological level in the research area of medical applications in PAI.
Recent publications [1] Zangerl G, Scherzer O, Haltmeier M. Circular integrating detectors in photo and thermoacoustic tomography. Inverse Probl Sci Eng 2009;17(1):133–42. [2] Grasmair M, Haltmeier M, Scherzer O. Sparse regularization with lq penalty term. Inverse Problems 2008;25(5): 055020. [3] Gebauer B, Scherzer O. Impedance-acoustic tomography. SIAM J Appl Math 2008;69(2):565–76. [4] Burgholzer P, Bauer-Marschallinger J, Gru¨n H, Haltmeier M, Paltauf G. Temporal back-projection algorithms for photoacoustic tomography with integrating line detectors. Inverse Problems 2007;23(6):S65–80. [5] Paltauf G, Nuster R, Haltmeier M, Burgholzer P. Experimental evaluation of reconstruction algorithms for limited view photoacoustic tomography with line detectors. Inverse Problems 2007;23(6):S81–94.