Dr. Robert A. Kruger Profile

Dr. Robert A. Kruger

President at OptoSonics Inc

SPIE Involvement:

Conference Program Committee | Author

Publications (39)

PROCEEDINGS ARTICLE | February 24, 2010

Polarization effects in thermoacoustic CT of biologic tissue at 434 MHz

Proc. SPIE. 7564, Photons Plus Ultrasound: Imaging and Sensing 2010

KEYWORDS: Waveguides, Polarization, Tissues, Ultrasonics, Tomography, Transducers, Computed tomography, Microwave radiation, Dielectric polarization, Absorption

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PROCEEDINGS ARTICLE | February 24, 2010

Co-registered photoacoustic, thermoacoustic, and ultrasound mouse imaging

Proc. SPIE. 7564, Photons Plus Ultrasound: Imaging and Sensing 2010

KEYWORDS: Waveguides, Tissues, Imaging systems, Sensors, Ultrasonography, Computed tomography, Photoacoustic spectroscopy, Tissue optics, Microwave radiation, 3D image processing

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PROCEEDINGS ARTICLE | February 24, 2010

Evaluation of Her2 status using photoacoustic spectroscopic CT techniques

Proc. SPIE. 7564, Photons Plus Ultrasound: Imaging and Sensing 2010

KEYWORDS: Near infrared, Tumors, Scanners, Spectroscopy, Luminescence, Oxygen, Data acquisition, Near infrared spectroscopy, Photoacoustic spectroscopy, In vivo imaging

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PROCEEDINGS ARTICLE | February 24, 2010

Ex vivo hemoglobin status study using photoacoustic computed tomography small animal scanner

Proc. SPIE. 7564, Photons Plus Ultrasound: Imaging and Sensing 2010

KEYWORDS: Imaging systems, Blood, Scanners, Error analysis, Molecules, Oxygen, Monte Carlo methods, Acoustics, Photon transport, Absorption

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PROCEEDINGS ARTICLE | February 24, 2010

Monitor hemoglobin concentration and oxygen saturation in living mouse tail using photoacoustic CT scanner

Proc. SPIE. 7564, Photons Plus Ultrasound: Imaging and Sensing 2010

KEYWORDS: Veins, Blood, Scanners, Spectroscopy, Imaging spectroscopy, Arteries, Oxygen, Bone, Photoacoustic spectroscopy, Acoustics

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PROCEEDINGS ARTICLE | February 23, 2010

Dynamic optical angiography of mouse anatomy using radial projections

Proc. SPIE. 7564, Photons Plus Ultrasound: Imaging and Sensing 2010

KEYWORDS: Sensors, Image processing, Scanners, Data acquisition, Temporal resolution, Angiography, Photoacoustic tomography, Photoacoustic spectroscopy, Spatial resolution, Signal detection

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PROCEEDINGS ARTICLE | February 25, 2009

HYPR-spectral photoacoustic CT for preclinical imaging

Proc. SPIE. 7177, Photons Plus Ultrasound: Imaging and Sensing 2009

KEYWORDS: Signal to noise ratio, 3D acquisition, Sensors, Scanners, Composites, Computed tomography, Photoacoustic spectroscopy, Spatial resolution, 3D image processing, Preclinical imaging

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PROCEEDINGS ARTICLE | March 18, 2008

HYPR: constrained reconstruction for enhanced SNR in dynamic medical imaging

Proc. SPIE. 6913, Medical Imaging 2008: Physics of Medical Imaging

KEYWORDS: Signal to noise ratio, Magnetic resonance imaging, Image processing, X-rays, Composites, Medical imaging, Angiography, Convolution, Positron emission tomography, Lawrencium

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PROCEEDINGS ARTICLE | February 28, 2008

Improving limited-view reconstruction in photoacoustic tomography by incorporating a priori boundary information

Proc. SPIE. 6856, Photons Plus Ultrasound: Imaging and Sensing 2008: The Ninth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

KEYWORDS: Biomedical optics, Ultrasonography, Tomography, Transducers, Photoacoustic tomography, Acquisition tracking and pointing, Reconstruction algorithms, Photoacoustic spectroscopy, Tissue optics, Absorption

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PROCEEDINGS ARTICLE | February 13, 2007

Photoacoustic molecular imaging

Proc. SPIE. 6437, Photons Plus Ultrasound: Imaging and Sensing 2007: The Eighth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

KEYWORDS: Breast, Infrared imaging, Breast cancer, Tissues, Receptors, Molecular imaging, Photoacoustic spectroscopy, In vivo imaging, Tissue optics, Absorption

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PROCEEDINGS ARTICLE | February 13, 2007

Phantom and in-vivo measurements of hemoglobin concentration and oxygen saturation using PCT-S small animal scanner

Proc. SPIE. 6437, Photons Plus Ultrasound: Imaging and Sensing 2007: The Eighth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

KEYWORDS: Veins, Tumors, Calibration, Blood, Scanners, Arteries, Oxygen, Hypoxia, In vivo imaging, Absorption

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PROCEEDINGS ARTICLE | February 13, 2007

Using Monte Carlo simulations to understand the influence of photon propagation on photoacoustic spectroscopic imaging

Proc. SPIE. 6437, Photons Plus Ultrasound: Imaging and Sensing 2007: The Eighth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

KEYWORDS: Near infrared, Tumors, Signal attenuation, Blood, Monte Carlo methods, Photoacoustic spectroscopy, Tissue optics, Acoustics, Photon transport, Absorption

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Purpose: The purpose of this study is to evaluate the influence of photon propagation on the NIR spectral features associated with photoacoustic imaging. Introduction: Photoacoustic CT spectroscopy (PCT-S) has the potential to identify molecular properties of tumors while overcoming the limited depth resolution associated with optical imaging modalities (e.g., OCT and DOT). Photoacoustics is based on the fact that biological tissue generates high-frequency acoustic signals due to volume of expansion when irradiated by pulsed light. The amplitude of the acoustic signal is proportional to the optical absorption properties of tissue, which varies with wavelength depending on the molecular makeup of the tissue. To obtain quantifiable information necessitate modeling and correcting for photon and acoustic propagation in tumors. Material and Methods: A Monte Carlo (MC) algorithm based on MCML (Monte Carlo for Multi-Layered edia) has been developed to simulate photon propagation within objects comprised of a series of complex 3D surfaces (Mcml3D). This code has been used to simulate and correct for the optical attenuation of photons in blood, and for subcutaneous tumors with homogenous and radially heterogeneous vascular distributions. Results: The NIR spectra for oxygenated and deoxygenated blood as determined from Monte Carlo simulated photoacoustic data matched measured data, and improving oxygen saturation calculations. Subcutaneous tumors with a homogeneous and radially heterogeneous distribution of blood revealed large variations in photon absorption as a function of the scanner projection angle. For select voxels near the periphery of the tumor, this angular profile between the two different tumors appeared similar. Conclusions: A Monte Carlo code has been successfully developed and used to correct for photon propagation effects in blood phantoms and restoring the integrity of the NIR spectra associated with oxygenated and deoxygenated blood. This code can be used to simulate the influence of intra-tumor heterogeneity on the molecular identification via NIR spectroscopy.

PROCEEDINGS ARTICLE | March 20, 2006

Evaluating dynamic contrast-enhanced and photoacoustic CT to assess intra-tumor heterogeneity in xenograft mouse models

Proc. SPIE. 6143, Medical Imaging 2006: Physiology, Function, and Structure from Medical Images

KEYWORDS: Breast, Tumors, Calibration, Blood, Error analysis, Oxygen, Photoacoustic spectroscopy, In vivo imaging, Plasma, Vascular physiology

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Purpose: To evaluate photoacoustic CT spectroscopy (PCT-S) and dynamic contrast-enhanced CT (DCE-CT) ability to measure parameters - oxygen saturation and vascular physiology - associated with the intra-tumor oxygenation status. Material and Methods: Breast (VEGF165 enhance MCF-7) and ovarian (SKOV3x) cancer cells were implanted into the fat pads and flanks of immune deficient mice and allowed to grow to a diameter of 8-15 mm. CT was used to determine physiological parameters by acquiring a sequence of scans over a 10 minute period after an i.v. injection of a radio-opaque contrast agent (Isovue). These time-dependent contrast-enhanced curves were fit to a two-compartmental model determining tumor perfusion, fractional plasma volume, permeability-surface area produce, and fractional interstitial volume on a voxel-by-voxel basis. After which, the tumors were imaged using photoacoustic CT (Optosonics, Inc., Indianapolis, IN 46202). The near infrared spectra (700-910 nm) within the vasculature was fit to linear combination of measured oxy- and deoxy-hemoglobin blood samples to obtain oxygen saturation levels (SaO2). Results: The PCT-S scanner was first calibrated using different samples of oxygenated blood, from which a statistical error ranging from 2.5-6.5% was measured and a plot of the hemoglobin dissociation curve was consistent with empirical formula. In vivo determination of tumor vasculature SaO2 levels were measurably tracked, and spatially correlated to the periphery of the tumor. Tumor depend variations in SaO2 - 0.32 (ovarian) and 0.60 (breast) - and in vascular physiology - perfusion, 1.03 and 0.063 mL/min/mL, and fractional plasma volume, 0.20 and 0.07 - were observed. Conclusion: Combined, PCT-S and CED-CT has the potential to measure intra-tumor levels of tumor oxygen saturation and vascular physiology, key parameters associated with hypoxia.

PROCEEDINGS ARTICLE | March 6, 2006

Assessment of photoacoustic computed tomography to classify tissue in a polycystic-kidney disease mouse model

Proc. SPIE. 6086, Photons Plus Ultrasound: Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

KEYWORDS: Tissues, Image segmentation, Photons, Photography, Photoacoustic tomography, Kidney, Computed tomography, Tissue optics, Mouse models, Absorption

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PROCEEDINGS ARTICLE | March 6, 2006

Photoacoustic spectroscopic imaging of intra-tumor heterogeneity and molecular identification

Proc. SPIE. 6086, Photons Plus Ultrasound: Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics

KEYWORDS: Liver, Tumors, Blood, Spectroscopy, Error analysis, Oxygen, Bladder, Photoacoustic spectroscopy, In vivo imaging, Tissue optics

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Purpose. To evaluate photoacoustic spectroscopy as a potential imaging modality capable of measuring intra-tumor heterogeneity and spectral features associated with hemoglobin and the molecular probe indocyanine green (ICG). Material and Methods. Immune deficient mice were injected with wildtype and VEGF enhanced MCF-7 breast cancer cells or SKOV3x ovarian cancer cells, which were allowed to grow to a size of 6-12 mm in diameter. Two mice were imaged alive and after euthanasia for (oxy/deoxy)-hemoglobin content. A 0.4 mL volume of 1 μg/mL concentration of ICG was injected into the tail veins of two mice prior to imaging using the photoacoustic computed tomography (PCT) spectrometer (Optosonics, Inc., Indianapolis, IN 46202) scanner. Mouse images were acquired for wavelengths spanning 700-920 nm, after which the major organs were excised, and similarly imaged. A histological study was performed by sectioning the organ and optically imaging the fluorescence distribution. Results. Calibration of PCT-spectroscopy with different samples of oxygenated blood reproduced a hemoglobin dissociation curve consistent with empirical formula with an average error of 5.6%. In vivo PCT determination of SaO2 levels within the tumor vascular was measurably tracked, and spatially correlated to the periphery of the tumor. Statistical and systematic errors associated with hypoxia were estimated to be 10 and 13%, respectively. Measured ICG concentrations determined by contrast-differential PCT images in excised organs (tumor, liver) were approximately 0.8 μg/mL, consistent with fluorescent histological results. Also, the difference in the ratio of ICG concentration in the gall bladder-to-vasculature between the mice was consistent with excretion times between the two mice. Conclusion. PCT spectroscopic imaging has shown to be a noninvasive modality capable of imaging intra-tumor heterogeneity of (oxy/deoxy)-hemoglobin and ICG in vivo, with an estimated error in SaO2 at 17% and in ICG at 0.8 μg/mL in excised tissue. Ongoing development of spectroscopic analysis techniques, probe development, and calibration techniques are being developed to improve sensitivity to both exogenous molecular probes and (oxy/deoxy)-hemoglobin fraction.

PROCEEDINGS ARTICLE | July 12, 2004

Thermoacoustic in vivo determination of blood oxygenation

Proc. SPIE. 5320, Photons Plus Ultrasound: Imaging and Sensing

KEYWORDS: Near infrared, Tumors, Tissues, Imaging systems, Blood, Image processing, Infrared radiation, Computed tomography, Tissue optics, Absorption

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PROCEEDINGS ARTICLE | May 3, 2002

Thermoacoustic CT of the breast

Proc. SPIE. 4682, Medical Imaging 2002: Physics of Medical Imaging

KEYWORDS: Breast, Optical spheres, Waveguides, Ultrasonography, Scanners, Data acquisition, Image quality, Transducers, Computed tomography, 3D image processing

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PROCEEDINGS ARTICLE | June 15, 2001

Thermoacoustic CT of the breast: pilot study observations

Proc. SPIE. 4256, Biomedical Optoacoustics II

KEYWORDS: Breast, Cancer, Visualization, Tissues, Ultrasonography, X-rays, Image quality, Mammography, Computed tomography, Absorption

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PROCEEDINGS ARTICLE | May 19, 2000

Thermoacoustic CT: imaging principles

Proc. SPIE. 3916, Biomedical Optoacoustics

KEYWORDS: Breast, Point spread functions, Optical spheres, Tissues, Transducers, Antennas, Computed tomography, Spatial resolution, 3D image processing, Absorption

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PROCEEDINGS ARTICLE | April 12, 2000

Thermoacoustic CT scanner for breast imaging: design considerations

Proc. SPIE. 3982, Medical Imaging 2000: Ultrasonic Imaging and Signal Processing

KEYWORDS: Breast, Point spread functions, Waveguides, Tissues, Scanners, Transducers, Computed tomography, Phased arrays, Spatial resolution, Breast imaging

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PROCEEDINGS ARTICLE | May 28, 1999

Application of thermoacoustic computed tomography to breast imaging

Proc. SPIE. 3659, Medical Imaging 1999: Physics of Medical Imaging

KEYWORDS: Breast, 3D image reconstruction, CT reconstruction, Tissues, Scanners, Transducers, Computed tomography, Spatial resolution, Acoustics, Absorption

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PROCEEDINGS ARTICLE | May 28, 1999

Thermoacoustic computed tomography: limits to spatial resolution

Proc. SPIE. 3659, Medical Imaging 1999: Physics of Medical Imaging

KEYWORDS: Tissues, Imaging systems, Computing systems, Image resolution, Transducers, Photoacoustic spectroscopy, Spatial resolution, Microwave radiation, Acoustics, Absorption

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PROCEEDINGS ARTICLE | April 11, 1996

Microwave applicators for photoacoustic ultrasonagraphy

Proc. SPIE. 2708, Medical Imaging 1996: Physics of Medical Imaging

KEYWORDS: Optical fibers, Waveguides, Polarization, Tissues, Ultrasonography, Transducers, Photoacoustic spectroscopy, Microwave radiation, Temperature metrology, Absorption

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PROCEEDINGS ARTICLE | April 11, 1996

Energy deposition patterns in the breast at 1064 nm for photoacoustic ultrasound

Proc. SPIE. 2708, Medical Imaging 1996: Physics of Medical Imaging

KEYWORDS: Breast, Scattering, Ultrasonography, Light scattering, Ultrasonics, Monte Carlo methods, Photoacoustic spectroscopy, Acoustics, Photon transport, Absorption

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PROCEEDINGS ARTICLE | April 11, 1996

Simulation of photoacoustic signal production in human breast phantoms at 1064 nm

Proc. SPIE. 2708, Medical Imaging 1996: Physics of Medical Imaging

KEYWORDS: Breast, Tumors, Scattering, Transducers, Photoacoustic spectroscopy, Signal generators, Chlorine, Natural surfaces, Liquids, Absorption

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PROCEEDINGS ARTICLE | August 17, 1994

Photoacoustic ultrasound: theory

Proc. SPIE. 2134, Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards

KEYWORDS: Biomedical optics, Tissues, Scattering, Ultrasonography, Light scattering, Ultrasonics, Photoacoustic spectroscopy, Tissue optics, Acoustics, Absorption

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PROCEEDINGS ARTICLE | August 17, 1994

Photoacoustic ultrasound: experimental results

Proc. SPIE. 2134, Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards

KEYWORDS: Biomedical optics, Scattering, Scattering media, Ultrasonography, Laser scattering, Ultrasonics, Transducers, Photoacoustic spectroscopy, Tissue optics, Absorption

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SPIE Journal Paper | August 1, 1994

Semianalytical approach to pulsed light propagation in scattering and absorbing media

Pingyu Liu, Robert Kruger

OE Vol. 33 Issue 08

KEYWORDS: Scattering, Light scattering, Mie scattering, Biomedical optics, Signal attenuation, Photons, Picosecond phenomena, Laser scattering, Sensors, Radiative transfer

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PROCEEDINGS ARTICLE | July 8, 1994

Computerized tomographic angiography image segmentation for 3D-volume reconstruction

Proc. SPIE. 2299, Mathematical Methods in Medical Imaging III

KEYWORDS: X-ray computed tomography, 3D image reconstruction, Tissues, Image segmentation, Image processing, Arteries, Bone, Angiography, Computed tomography, 3D image processing

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PROCEEDINGS ARTICLE | May 19, 1994

Time-resolved optical diffusion tomography

Proc. SPIE. 2135, Advances in Laser and Light Spectroscopy to Diagnose Cancer and Other Diseases

KEYWORDS: Tissues, Scattering, Photons, Diffusion, Light scattering, Laser scattering, Tomography, Reconstruction algorithms, Algorithm development, Absorption

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PROCEEDINGS ARTICLE | May 19, 1994

Simulation of photon paths through isotropically scattering media

Proc. SPIE. 2135, Advances in Laser and Light Spectroscopy to Diagnose Cancer and Other Diseases

KEYWORDS: Tissues, Scattering, Scattering media, Particles, Diffusion, Light scattering, Monte Carlo methods, Tissue optics, Photon transport, Absorption

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PROCEEDINGS ARTICLE | May 19, 1994

New approach to the "forward problem" of optical diffusion tomography of turbid media

Proc. SPIE. 2135, Advances in Laser and Light Spectroscopy to Diagnose Cancer and Other Diseases

KEYWORDS: Biomedical optics, Scattering, Diffusion, Computer simulations, Tomography, Monte Carlo methods, Optical tomography, Inverse optics, Radiative transfer, Maxwell's equations

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PROCEEDINGS ARTICLE | February 1, 1994

Solution to the time-dependent photon transport equation

Proc. SPIE. 2077, Laser Interaction with Hard and Soft Tissue

KEYWORDS: Biomedical optics, Scattering, Diffusion, Image restoration, Tomography, Monte Carlo methods, Picosecond phenomena, Optical tomography, Geometrical optics, Photon transport

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PROCEEDINGS ARTICLE | July 1, 1991

Tomographic imaging using picosecond pulses of light

Proc. SPIE. 1443, Medical Imaging V: Image Physics

KEYWORDS: Scattering, Signal attenuation, Photons, Light scattering, Diagnostics, Medical imaging, Tomography, Streak cameras, Picosecond phenomena, Tissue optics

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PROCEEDINGS ARTICLE | July 1, 1991

Clinical image-intensifier-based volume CT imager for angiography

Proc. SPIE. 1443, Medical Imaging V: Image Physics

KEYWORDS: X-ray computed tomography, 3D image reconstruction, Imaging systems, Distortion, Medical imaging, Image quality, Angiography, Reconstruction algorithms, Image intensifiers, 3D image processing

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PROCEEDINGS ARTICLE | May 1, 1991

Time-of-flight breast imaging system: spatial resolution performance

Proc. SPIE. 1431, Time-Resolved Spectroscopy and Imaging of Tissues

KEYWORDS: Tissues, Imaging systems, Photons, Diagnostics, Imaging spectroscopy, Streak cameras, Picosecond phenomena, Modulation transfer functions, Spatial resolution, Tissue optics

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PROCEEDINGS ARTICLE | August 1, 1990

Simulating the performance of a time-of-flight transillumination imaging system

Proc. SPIE. 1205, Bioimaging and Two-Dimensional Spectroscopy

KEYWORDS: Breast, Tissues, Imaging systems, Scattering, Signal attenuation, Photons, Picosecond phenomena, Spatial resolution, Tissue optics, Absorption

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PROCEEDINGS ARTICLE | July 1, 1990

Acoustically modulated electrical impedance tomography

Proc. SPIE. 1231, Medical Imaging IV: Image Formation

KEYWORDS: Signal to noise ratio, Breast, Modulation, Tissues, Electrodes, Resistance, Diagnostics, Image acquisition, Amplifiers, Acoustics

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PROCEEDINGS ARTICLE | July 1, 1990

Image-intensifier-based volume CT imager: angiographic application

Proc. SPIE. 1233, Medical Imaging IV: Image Processing

KEYWORDS: Signal to noise ratio, X-ray computed tomography, 3D image reconstruction, Imaging systems, CCD cameras, Angiography, Reconstruction algorithms, Image intensifiers, Prototyping, 3D image processing

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