Introduction to optoacoustic imaging Xosé Luís Deán Ben IBMI – Institute of Biological and Medical Imaging 16.01.2012
Imaging: Seeing is believing IBMI Institute of Biological und Medical Imaging
Imaging modalities Weissleder R. and Pittet M. J. Imaging in the era of molecular oncology. Nature 452:580-9 (2008) IBMI Institute of Biological und Medical Imaging
Why optical imaging? (+) High resolution (+) High sensitivity (+) Safe, non-ionizing (+) Low cost (+) Intrinsic molecular and functional contrast (+) Versatility of contrast agents The interaction of photons with tissue components provides a suitable basis for functional and molecular imaging techniques IBMI Institute of Biological und Medical Imaging
Propagation of light within tissues (optical scattering) Scattering No scattering IBMI Institute of Biological und Medical Imaging
Propagation of light within tissues (optical scattering) Ntziachristos V. Going deeper than microscopy: the optical imaging frontier of biology. Nat. Methods 7:603-614 (2010) Scattering No scattering IBMI Institute of Biological und Medical Imaging
Why diffuse optical imaging? (+) High resolution (+) High sensitivity (+) Safe, non-ionizing (+) Low cost (+) Intrinsic molecular and functional contrast (+) Versatility of contrast agents The interaction of photons with tissue components provides a suitable basis for functional and molecular imaging techniques IBMI Institute of Biological und Medical Imaging
Optical imaging scales Microscopic Mesoscopic Macroscopic 10 -2 DOT Imaging resolution [m] 10 -3 FMT ? 10 -4 Optoacoustics MFT 10 -5 OPT SPIM 2P/MP 10 -6 Confocal Microscopy 10 -5 10 -3 10 -2 Penetration depth [m]
The optoacoustic (photoacoustic) effect Alexander Graham Bell (1847-1922) Alexander Graham Bell discovered that you can generate sound by flashing a focused beam of light with rotating slotted disk onto selenium in 1880
Optoacoustic imaging Absorption of short- pulsed laser light Hardware Acoustic wave measurement at several locations Software Image reconstruction Acoustic scattering is much lower than optical scattering in biological tissues Optoacoustic imaging combines high contrast of pure optical methods with high spatial resolution of pure ultrasonic imaging IBMI Institute of Biological und Medical Imaging
Intrinsic contrast (blood) Laufer J. et al. Three-dimensional noninvasive imaging of the vasculature in the mouse brain using a high resolution photoacoustic scanner. Applied Optics 48:D299-306 (2009)
Optoacoustic tomography (reconstruction) Forward problem Γ ∂ H ( r ' ) ∫ = p ( r , t ) dS ' ( t ) π ∂ − 4 c t | r r ' | Acoustic pressure Optical absorption S ' ( t ) p r ( , t ) H ( r ' ) Inverse problem ?
Anatomical imaging Brecht H. P. et al. Whole-body three-dimensional optoacoustic tomography system for small animals. Journal of Biomedical Optics 14:064007 (2009)
Anatomical imaging Ma R. et al. Non-invasive whole-body imaging of adult zebrafish with optoacoustic tomography (under review)
Optoacoustic microscopy Wang L. V. Multiscale photoacoustic microscopy and computed tomography. Nat. Photonics 3:503-9 (2009)
Functional imaging (single-wavelength) Optoacoustic signals are sensitive to functional cerebral hemodynamic changes in response to whisker stimulation Wang X. et al. Noninvasive laser-induced photoacoustic tomography for structural and functional in vivo imaging of the brain. Nat. Biotechnology 21:803-6 (2003)
Functional imaging (multiple wavelengths) Zhang H. F. Functional photoacoustic microscopy for high-resolution and noninvasive in vivo imaging. Nat. Biotechnology 24:848-51 (2006)
Molecular imaging (multispectral optoacoustic tomography) Hb The spectral dependence of the absortion is different for different substances HbO 2 GoldNR The distribution of a given substance AF750 (component) is estimated by unmixing images at several wavelengths Razansky D. et al. Multispectral photoacoustic imaging of fluorochromes in small animals. Optics Letters 32:2891-3 (2007)
Molecular imaging (multispectral optoacoustic tomography) Razansky D. et al. Multispectral opto-acoustic tomography of deep-seated fluorescent proteins in vivo. Nat. Photonics 3:412-7 (2009)
Real-time imaging Buehler A. et al. Video rate optoacoustic tomography of mouse kidney perfusion. Optics Letters 35:2475-7 (2010)
Endoscopy Yang J. M. et al. Photoacoustic endoscopy. Optics Letters 34:1591-3 (2009)
Prospective applications • Cancer research (angiogenesis is highly correlated with the severity of tumors) • Cardiovascular imaging (hemoglobin provides an excellent contrast) • Neuroscience (probably with the help of cranial windows, where s O 2 is related to neural activities) • Cancer radiotherapy and chemotherapy (hypoxia is often responsible for resistance to therapy) • Trauma evaluation (optical absorption is associated with both hemorrhage and edema) • Endoscopic imaging (with miniaturized optical and ultrasonic components integrated into a single probe) • Molecular Imaging (using endogenous and exogenous contrast)
Acknowledgments INSTITUTE OF BIOLOGICAL AND MEDICAL IMAGING Prof. Dr. Vasilis Ntziachristos Dr. Daniel Razansky All scientists and staff
Thank you
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