Multispectral Opto-acoustic Tomography (MSOT) of the Brain and Glioblastoma Characterization Neal C. Burton a, b , Manishkumar Patel c , Stefan Morscher a, b, d , Wouter H.P. Driessen a, b , Jing Claussen a, b , Nicolas Beziere a , Thomas Jetzfellner a , Adrian Taruttis a , Daniel Razansky a, d , Bohumil Bednar c , Vasilis Ntziachristos a, d, ⁎ a Institute for Biological and Medical Imaging, Helmholtz Center Munich, Neuherberg, Germany b iThera Medical, GmbH, Munich, Germany c Merck Department of Imaging, West Point, Pennsylvania, USA d Chair for Biological Imaging, Technical University of Munich, Munich, Germany abstract article info Article history: Accepted 19 September 2012 Available online 28 September 2012 Keywords: Multispectral opto-acoustic tomography In vivo imaging Nanoparticles Glioblastoma Brain Brain research depends strongly on imaging for assessing function and disease in vivo. We examine herein multispectral opto-acoustic tomography (MSOT), a novel technology for high-resolution molecular imaging deep inside tissues. MSOT illuminates tissue with light pulses at multiple wavelengths and detects the acous- tic waves generated by the thermoelastic expansion of the environment surrounding absorbing molecules. Using spectral unmixing analysis of the data collected, MSOT can then differentiate the spectral signatures of oxygenated and deoxygenated hemoglobin and of photo-absorbing agents and quantify their concentra- tion. By being able to detect absorbing molecules up to centimeters deep in the tissue it represents an ideal modality for small animal brain imaging, simultaneously providing anatomical, hemodynamic, func- tional, and molecular information. In this work we examine the capacity of MSOT in cross-sectional brain im- aging of mice. We find unprecedented optical imaging performance in cross-sectional visualization of anatomical and physiological parameters of the mouse brain. For example, the potential of MSOT to charac- terize ischemic brain areas was demonstrated through the use of a carbon dioxide challenge. In addition, indocyanine green (ICG) was injected intravenously, and the kinetics of uptake and clearance in the vascula- ture of the brain was visualized in real-time. We further found that multiparameter, multispectral imaging of the growth of U87 tumor cells injected into the brain could be visualized through the intact mouse head, for example through visualization of deoxygenated hemoglobin in the growing tumor. We also demonstrate how MSOT offers several compelling features for brain research and allows time-dependent detection and quantification of brain parameters that are not available using other imaging methods without invasive procedures. © 2012 Published by Elsevier Inc. Introduction Neuroimaging has transformed brain research and clinical neurolo- gy by enabling early diagnosis of disease and critical feedback on the ef- ficacy of treatments (Hargreaves, 2008; Wong et al., 2009). In addition, non-invasive imaging has enabled correlations between brain function and behavior (Logothetis, 2008). However, there is always a need to improve upon current technologies. Innovation, driven by assessing and offering alternatives to the limitations of current technologies, has and will continue to drive new discoveries in neuroimaging. There are currently many modalities available for neuroimaging, each with their own benefits and limitations. X-ray-based computed tomography (CT) and magnetic resonance imaging (MRI) provide anatomical infor- mation at high spatial resolution but with limited molecular specificity (Histed et al., 2012). On the other hand, positron emission tomography (PET) and fluorescence molecular tomography (FMT) are molecular im- aging modalities (Ntziachristos and Razansky, 2010), but have low res- olution. Intravital microscopy has molecular specificity at high resolution, but is limited by shallow tissue penetration and requires in- vasive procedures (Lichtman and Fraser, 2001). We studied the performance of multispectral opto-acoustic tomog- raphy (MSOT) for neuroimaging in mice. MSOT combines the high res- olution of anatomical techniques such as MRI, the molecular specificity of PET or FMT and the contrast of optical imaging to offer a highly potent NeuroImage 65 (2013) 522–528 Abbreviations: MSOT, multispectral opto-acoustic tomography; FMT, fluorescence molecular tomography; NIR, near infrared; ICG, indocyanine green; X-ray CT, X-ray computerized tomography; MRI, magnetic resonance imaging; PET, positron emission tomography; FDA, food and drug administration; HEPES, 4-(2-hydroxyethyl)-1- piperazineethanesulfonic acid; i.v., intravascular. ⁎ Corresponding author at: 1 Ingolstaedter Landstrasse, Building 56, Room 29, Neuherberg, 85764, Germany. Fax: +49 89 3187 3017. E-mail address: v.ntziachristos@tum.de (V. Ntziachristos). 1053-8119/$ – see front matter © 2012 Published by Elsevier Inc. http://dx.doi.org/10.1016/j.neuroimage.2012.09.053 Contents lists available at SciVerse ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/ynimg