This PDF file contains the front matter associated with SPIE Proceedings Volume 8089, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We report on the optoacoustic (OA) imaging of the whole mouse body using a biocompatible contrast agent - highly purified, pegylated gold nanorods (GNR) - which has strong optical absorption in the near-infrared region and low level of toxicity. In vitro toxicity studies showed no significant change in survival rates of the cultured normal epithelium IEC-6 cells when incubated for 24 hours with up to 1 nM of GNR. In vivo toxicity studies in nude mice showed no pathological changes in liver 1 month after the IV injection of GNR with intra-body concentration around 0.25-0.50 nM. In order to study the enhancement of the OA contrast and accumulation of GNR in different tissues, we performed 3D OA imaging of live nude mice with IV-injected GNR. The enhancement of the OA contrast in comparison with the images of the untreated mice was visible starting 1 hour after the GNR injection. The OA contrast of kidneys, liver, and spleen peaked at about 2-3 days after the administration of the GNR, and then was gradually reducing.

Existing imaging modalities like microwave- or radiofrequency (RF) induced thermoacoustic tomography systems show the potential for resolving structures deep inside tissue due to the high penetration properties of RF. However, one of the major drawbacks of existing thermoacoustic tomography systems with pulse modulated carrier frequency excitation is the compromise between efficient signal generation and attainable spatial resolution. In order to overcome limitations of conventional thermoacoustic imaging methods, we herein present and experimentally validate our novel approach towards high resolution thermoacoustic tomography. Instead of carrier-frequency amplification, we utilize ultrahigh-energy electromagnetic impulses at nanosecond duration with near-field energy coupling, thus maintaining thermoacoustic signal strength without compromising spatial resolution. Preliminary experiments on highly absorbing objects, consisting of copper wires with characteristic sizes of ~100 μm, reveal the resolution performance which yields 160 μm. Furthermore, benefits like its cost effectiveness, simplicity and compactness with the potential application in small animal imaging as well as human body imaging show that thermoacoustic tomography with impulse excitation is a promising imaging modality which has a broad range of applications.

Distinguishing the tumor from the background neo-plastic tissue is challenging for cancer surgery such as surgical resection of glioma. Attempts have been made to use visible or fluorescent markers to delineate the tumors during surgery. However, the systemic injection of the dyes requires high dose, resulting in negative side effects. A novel method to delineate rat brain tumors intra-operatively, as well as post-operatively, using a highly sensitive photoacoustic imaging technique enhanced by tumor targeting blue nanoparticle as contrast agent is demonstrated. The nanoparticles are made of polyacrylamide (PAA) matrix with covalently linked Coomassie-Blue dye. They contain 7.0% dye and the average size is 80nm. Their surface was conjugated with F3 peptide for active tumor targeting. These nanoparticles are nontoxic, chemically inert and have long plasma circulation lifetime, making them suitable as nanodevices for imaging using photoacoustics. Experiments on phantoms and rat brains tumors ex-vivo demonstrate the high sensitivity of photoacoustic imaging in delineating the tumor, containing contrast agent at concentrations too low to be visualized by eye. The control tumors without nanoparticles did not show any enhanced signal. This study shows that photoacoustic imaging facilitated with the nanoparticle contrast agent could contribute to future surgical procedures for glioma.

Various gold nanostructures have being investigated for medical and biological uses, such as surface enhanced-Raman spectroscopy (SERS) and photoacoustic imaging (PAI), each having its advantages and limitations depending on the specific application. For many imaging and spectroscopic applications, it would be beneficial to use near infrared (NIR) excitation as well as small gold nanospheres which can easily reach the cytoplasm and cell nucleus. For that purpose, we propose a novel nanostructure, the "shell aggregate," which consists of small nanospheres aggregated (mono/bi-layer) around a core such as an intracellular organelle. The extinction efficiency of such monolayer and bilayer shell aggregates is thoroughly investigated with appropriate simulations using the Discrete Dipole Approximation (DDA) method. The effect of parameters such as the overall radius of the nanostructure, the small nanosphere radius, and the distance between the nanospheres, on the extinction efficiency factor of the nanostructures was examined. The results indicate that the extinction spectra appear to depend heavily on the distance between the small nanospheres. Two distinct absorption peak wavelengths are observed for a specific nanostructure. The monolayer shell aggregate provides a reasonably tunable plasmon resonance wavelength while the small size of its components can be exploited for intracellular distribution.

Optoacoustic imaging can noninvasively provide visualization of vasculature structures with optical contrast well below the skin surface. For meaningful biological investigations, high-resolution at mesoscopic penetration depths and therefore thorough adaption of the systematic arrangement to the object of interest is required. A suitable modular optoacoustic tomography system is presented here and its performance is demonstrated in three exemplary studies on imaging agar phantoms, mouse head vasculature and mouse tumor vasculature ex-vivo.

Dynamic contrast enhanced magnetic resonance is used to image high-risk patients for breast cancer because of its higher sensitivity to tumors than mammography. We focus on Near Infrared Spectroscopy (NIRS) imaging and Fluorescence Molecular Tomography (FMT), emerging imaging techniques that non-invasively quantify optical properties of total hemoglobin, oxygen saturation, water content, scattering, lipid concentration and endogenous Protoporphyrin IX (PpIX) emission. We present methods on combining the synergistic attributes of DCE-MR, NIRS, and FMT for in-vivo imaging of breast cancer in three dimensions using a custom optical MR breast coil and diffusion based light modeling software, NIRFAST. We present example results from a breast cancer patient. Preliminary results show elevated hemoglobin values and water fraction. Fluorescence values in the tumor region, however, were not always elevated above the surrounding tissue as we had expected. The additional information gained from NIRS and FMT may improve the ability to distinguish between malignant and benign lesions during MR imaging. These dual modality instruments will provide complex anatomical and molecular prognostic information, and may decrease the number of biopsies, thereby improving patient care.

Numerical analysis is implemented to investigate biological sample starting from Digital Holographic (DH) recording. The aim is to improve visualization and detection of cow spermatozoa. Digital holograms are recorded in the off-axis geometry where optical setup is a Mach-Zehnder interferometer. Then holograms are numerically manipulated to retrieve, besides the usual Quantitative Phase Map (QPM), Differential Interference Contrast (DIC) visualization. Furthermore, a new approach, named digital self-referencing holography, is described it's able to accomplish quantitative phase analysis especially useful for specimen flowing in microfluidic channels.

A novel setup for fluorescence imaging of 3-dimensional cell cultures is described. The method is based on structured illumination by various light sources and detection of images in individual cellular planes.

Identifying cardiac safety is becoming increasingly important for new drugs under development, since it is compulsory for the approval of almost all pharmaceutical drugs. In contrast to conventional electrophysiological in vitro assays that are based on a single entity, the hERG channel, primary cardiomyocytes based readouts seem to be more comprehensive. Such an action potential readout for those cells can be performed with contact-free optical methods. Here we reveal the details of both, the optical arrangement and the procedure to screen cardiac myocytes based on naïve action potentials. Furthermore we evaluate the differences between neonatal and adult cardiac myocytes from rats based on a selection of test substances (quinidine, 4-aminopyridine and E-4031) and relate it to the human situation. Finally the results are discussed in the context of emerging genetically encoded potential sensors and latest development in optical detection technologies.

Tissue-engineered constructs require noninvasive monitoring of cellular viability prior to implantation. In a preclinical study on human Ex Vivo Produced Oral Mucosa Equivalent (EVPOME) constructs, nonlinear optical molecular imaging was employed to extract morphological and functional information from intact constructs. Multiphoton excitation fluorescence images were acquired using endogenous fluorescence from cellular nicotinamide adenine dinucleotide phosphate [NAD(P)H] and flavin adenine dinucleotide (FAD). The images were analyzed to report quantitatively on tissue structure and metabolism (redox ratio). Both thickness variations over time and cell distribution variations with depth were identified, while changes in redox were quantified. Our results show that nonlinear optical molecular imaging has the potential to visualize and quantitatively monitor the growth and viability of a tissue-engineered construct over time.

Coronary artery disease (CAD) is a major cause of death in the United States and results from the accumulation of atherosclerotic plaques in the arteries of the heart. Plaques accumulate as the result of the retention of low-density lipoprotein (LDL) particles in the sub-endothelium of the arterial wall. In mouse aorta, these lesions form primarily at the branching sites or bifurcations. However, in the coronary system, data has shown that late-stage plaque formation occurs throughout the proximal segments of the arteries. In order to better understand plaque formation in the coronary arteries, we have developed an osmium tetroxide (OsO₄) stained coronary wall imaging protocol performed using microcomputed tomography (microCT). OsO₄ is a heavy metal contrast agent that readily binds to lipids. Our data in 3- to 25-week old C57BL6 wild-type mice shows that the coronary vessel walls are highlighted by the use of the contrast agent. We expect that this combination of OsO₄ and microCT will allow us to investigate the coronary artery wall in atherogenesis models of mice to characterize plaque formation.

A skin depth map was built reconstructing photoacoustic signals at several wavelengths of visible and infrared light. The mapping technique was used to follow the diffusion through the skin of near-infrared absorbing dyes. Such dyes can be useful for photodynamic therapy (PDT) of skin lesions and are investigated as contrast agents for photoacoustic tomography (PAT), because they strongly absorb light at wavelengths where the skin is more transparent.

Multispectral optoacoustic (photoacoustic) tomography (MSOT) exploits high resolutions given by ultrasound detection technology combined with deeply penetrating laser illumination in the near infrared. Traces of molecules with different spectral absorption profiles, such as blood (oxy- and de-oxygenated) and biomarkers can be recovered using multiple wavelengths excitation and a set of methods described in this work. Three unmixing methods are examined for their performance in decomposing images into components in order to locate fluorescent contrast agents in deep tissue in mice. Following earlier works we find Independent Component Analysis (ICA), which relies on the strong criterion of statistical independence of components, as the most promising approach, being able to clearly identify concentrations that other approaches fail to see. The results are verified by cryosectioning and fluorescence imaging.