Srirang Manohar - Academia.edu (original) (raw)
Papers by Srirang Manohar
Tissue engineering. Part C, Methods, Jan 8, 2016
The non-invasive and longitudinal imaging of cells or cell aggregates in large optically scatteri... more The non-invasive and longitudinal imaging of cells or cell aggregates in large optically scattering scaffolds is still a largely unresolved problem in tissue engineering. In this work, we investigated the potential of near-infrared (NIR) photoacoustic tomography imaging to address this issue. We used clinically relevant sizes of highly light scattering polyethersulfone (PESM) multibore hollow fiber scaffolds seeded with cells. Since cells have little optical absorption at NIR wavelengths, we studied labelling of cells with absorbers. Four NIR labels were examined for their suitability based on absorption characteristics, resistance to bleaching, and influence on cell viability. On the basis of these criteria, carbon nanoparticles proved most suitable in a variety of cells. For photoacoustic imaging, we used a research setup, based on a computed tomography geometry. As proof of principle, using this imager we monitored the distribution and clustering of labelled rat insulinoma beta (...
Applied Physics Letters, Sep 24, 2007
We present a method to generate quantitative cross-sectional maps of acoustic propagation speed i... more We present a method to generate quantitative cross-sectional maps of acoustic propagation speed in tissue using the photoacoustic principle. The method is based on the interaction of laser-induced ultrasound from an extraneous absorber with the object under photoacoustic investigation. The propagation times of the ultrasound transients through the object at angles around 360° are measured using a multielement ultrasound detector. The geometry lends itself to fan-beam reconstruction allowing speed-of-sound tomograms to be generated. Simultaneously, conventional photoacoustic computed tomography can be performed as well. We demonstrate the concept showing results on phantoms carrying speed-of-sound distributions.
Biomedical Spectroscopy and Imaging, 2016
Annals Surg Oncology, 2009
Rod shaped gold nanoparticles are synthesized using cetyltriammonium bromide (CTAB) as a major co... more Rod shaped gold nanoparticles are synthesized using cetyltriammonium bromide (CTAB) as a major component of growth solutions. This surfactant is toxic to cells, but is at the moment unavoidable when monodisperse and high yield nanorods are to be synthesized. CTAB is found coating side walls of the nanoparticles and plays a role in maintaining colloidal stability. It may be displaced using thiolated PEG which is non-toxic to cells. Here we report on systematic studies of cell viability of such PEGylated nanorods on an SKBR3 cell-line using the MTS assay. These PEGylated particles are characterized using electron microscopy, optical spectroscopy and zeta potential measurements. It is expected that such treatment will be crucial in making nanorods compatible for in vivo biomedical applications.
Proceedings of Spie the International Society For Optical Engineering, 2008
Photoacoustic imaging is an upcoming medical imaging modality with the potential of imaging both ... more Photoacoustic imaging is an upcoming medical imaging modality with the potential of imaging both optical and acoustic properties of objects. We present a measurement system and outline reconstruction methods to image both speed of sound and acoustic attenuation distributions of an object using only pulsed light excitation. These acoustic properties can be used in a subsequent step to improve the image quality of the optical absorption distribution. A passive element, which is a high absorbing material with a small cross-section such as a carbon fiber, is introduced between the light beam and the object. This passive element acts as a photoacoustic source and measurements are obtained by allowing the generated acoustic signal to propagate through the object. From these measurements we can extract measures of line integrals over the acoustic property distribution for both the speed of sound and the acoustic attenuation. Reconstruction of the acoustic property distributions then comes down to the inversion of a linear system relating the obtained projection measurements to the acoustic property distributions. We show the results of applying our approach on phantom objects. Satisfactory results are obtained for both the reconstruction of speed of sound and the acoustic attenuation.
Ultrasonic Imaging
Photoacoustic imaging of interphalangeal peripheral joints is of interest in the context of using... more Photoacoustic imaging of interphalangeal peripheral joints is of interest in the context of using the synovial membrane as a surrogate marker of rheumatoid arthritis. Previous work has shown that ultrasound produced by absorption of light at the epidermis reflects on the bone surfaces within the finger. When the reflected signals are backprojected in the region of interest, artifacts are produced, confounding interpretation of the images. In this work, we present an approach where the photoacoustic signals known to originate from the epidermis, are treated as virtual ultrasound transmitters, and a separate reconstruction is performed as in ultrasound reflection imaging. This allows us to identify the bone surfaces. Further, the identification of the joint space is important as this provides a landmark to localize a region-of-interest in seeking the inflamed synovial membrane. The ability to delineate bone surfaces allows us not only to identify the artifacts, but also to identify the interphalangeal joint space without recourse to new US hardware or a new measurement. We test the approach on phantoms and on a healthy human finger.
We present a fast, computed tomography (CT) photoacoustic imager for mouse imaging. The system fe... more We present a fast, computed tomography (CT) photoacoustic imager for mouse imaging. The system features a 32 element curvilinear detector and an illumination system coupled to a rotary mechanism to enable a slice to be imaged in less than 1 minute. Image reconstruction is performed using a modified acoustic backprojection algorithm. We describe the system overview and imaging results on sacrificed mouse.
Photons Plus Ultrasound: Imaging and Sensing 2012, 2012
ABSTRACT Current imaging modalities are often not able to detect early stages of breast cancer wi... more ABSTRACT Current imaging modalities are often not able to detect early stages of breast cancer with high imaging contrast. Visualizing malignancy-associated increased hemoglobin concentrations might improve breast cancer diagnosis. Photoacoustic imaging can visualize hemoglobin in tissue with optical contrast and ultrasound resolution, which makes it potentially ideal for breast imaging. The Twente Photoacoustic Mammoscope (PAM) has been designed specifically for this purpose. Based on a successful pilot study in 2007, a large clinical study using PAM has been started in December 2010. PAM uses a pulsed Q-switched Nd:YAG laser at 1064 nm to illuminate a region of interest on the breast. Photoacoustic signals are detected with a 1MHz, unfocused ultrasound detector array. Three dimensional data are reconstructed using an acoustic backprojection algorithm. Those reconstructed images are compared with conventional imaging and histopathology. In the first phase of the study, the goal was to optimize the visualization of malignancies. We performed sixteen technically acceptable measurements on confined breast malignancies. In the reconstructed volumes of all malignancies, a confined high contrast region could be identified at the expected lesion depth. After ten successful measurements, the illumination area was increased and the fluence was substantially decreased. This caused a further significant increase in PAM lesion contrast.
Novel Optical Instrumentation for Biomedical Applications IV, 2009
... J.Jithin@tnw.utwente.nl, phone +31 534893112, fax +31 53 4891105 Novel Optical Instrumentatio... more ... J.Jithin@tnw.utwente.nl, phone +31 534893112, fax +31 53 4891105 Novel Optical Instrumentation for Biomedical Applications IV, edited by Christian D. Depeursinge, I. Alex Vitkin, Proc. of SPIE-OSA Biomedical Optics, SPIE Vol. ...
Photons Plus Ultrasound: Imaging and Sensing 2011, 2011
Accurate lymph node analysis is essential to determine the prognosis and treatment of patients su... more Accurate lymph node analysis is essential to determine the prognosis and treatment of patients suffering from melanoma. The initial results of a tomographic photoacoustic modality to detect melanoma metastases in resected lymph nodes are presented based on phantom models and a human lymph node. The results show melanoma metastases detection is feasible and the setup is capable of distinguishing absorbing
Photons Plus Ultrasound: Imaging and Sensing 2007: The Eighth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, 2007
The effects of an inappropriately chosen speed-of-sound in photoacoustic imaging reconstructions ... more The effects of an inappropriately chosen speed-of-sound in photoacoustic imaging reconstructions are to cause blurring of images and impairment of contrast. Here we outline a new methodology to measure the speed-of-sound in a photoacoustic imager with little or no additional cost and without the need to perform extra measurements. The method uses a strong absorber of light which is placed
Diffuse Optical Imaging of Tissue, 2007
Breast cancer dominates cancers in females. This burden on society and the room for improvements ... more Breast cancer dominates cancers in females. This burden on society and the room for improvements in the current practice of mammography have been stimuli for developing new modalities like photoacoustic mammography. At the University of Twente (UT), an instrument had been developed aimed at performing limited area scans on the human breast. This instrument is called the Twente Photoacoustic Mammoscope
Photons Plus Ultrasound: Imaging and Sensing 2011, 2011
In the reconstruction process of photo acoustic experiments, it was observed that adding a passiv... more In the reconstruction process of photo acoustic experiments, it was observed that adding a passive element to the experimental setup, improves the quality of the reconstruction of the object. This contribution analyzes this effect in some detail. We consider a cylindrical configuration. We start from an artificial and theoretically constructed optical absorption distribution that radiates sound waves when interrogated by the optical pulse. We analyze in the experimental setup the addition of the passive element to this example. The reported investigation is a part of a larger study on the existence, uniqueness and stability of photo acoustic inverse source reconstructions.
Solid State Communications, 2005
Thermal diffusivities (a) and molar volumes (V m ) of bulk Al 20 As x Te 80Kx alloy glasses in th... more Thermal diffusivities (a) and molar volumes (V m ) of bulk Al 20 As x Te 80Kx alloy glasses in the composition range 0%x%35 are examined. The results reveal a broad maximum in alpha and a broad minimum in V m in the 15!x!25 range. Earlier temperature modulated differential scanning calorimetric measurements on these glasses have revealed the non-reversing heat flow to show a global minimum (reversibility window) in the same composition range. Taken together these results suggest that present glasses in the 15!x!25 range are self-organized. The thermal diffusivity maximum observed near xZ20 is consistent with a minimal scattering of thermal waves in the homogeneous and stress-free glass composition residing in the center of the self-organized phase.
Breast Cancer Management, 2014
Molecular Imaging, 2007
Gold nanoparticles exhibit intense and narrow optical extinction bands due to the phenomenon of p... more Gold nanoparticles exhibit intense and narrow optical extinction bands due to the phenomenon of plasmon resonance making them useful as contrast agents for light-based imaging techniques. Localized heating results from the absorbed light energy, which shows potential for these particles in photothermal therapy as well. The bioconjugation of gold nanoparticles to appropriate antibodies targeted to tumors in vivo, could make
Opto-Acoustic Methods and Applications, 2013
ABSTRACT
Photons Plus Ultrasound: Imaging and Sensing 2012, 2012
Tissue engineering. Part C, Methods, Jan 8, 2016
The non-invasive and longitudinal imaging of cells or cell aggregates in large optically scatteri... more The non-invasive and longitudinal imaging of cells or cell aggregates in large optically scattering scaffolds is still a largely unresolved problem in tissue engineering. In this work, we investigated the potential of near-infrared (NIR) photoacoustic tomography imaging to address this issue. We used clinically relevant sizes of highly light scattering polyethersulfone (PESM) multibore hollow fiber scaffolds seeded with cells. Since cells have little optical absorption at NIR wavelengths, we studied labelling of cells with absorbers. Four NIR labels were examined for their suitability based on absorption characteristics, resistance to bleaching, and influence on cell viability. On the basis of these criteria, carbon nanoparticles proved most suitable in a variety of cells. For photoacoustic imaging, we used a research setup, based on a computed tomography geometry. As proof of principle, using this imager we monitored the distribution and clustering of labelled rat insulinoma beta (...
Applied Physics Letters, Sep 24, 2007
We present a method to generate quantitative cross-sectional maps of acoustic propagation speed i... more We present a method to generate quantitative cross-sectional maps of acoustic propagation speed in tissue using the photoacoustic principle. The method is based on the interaction of laser-induced ultrasound from an extraneous absorber with the object under photoacoustic investigation. The propagation times of the ultrasound transients through the object at angles around 360° are measured using a multielement ultrasound detector. The geometry lends itself to fan-beam reconstruction allowing speed-of-sound tomograms to be generated. Simultaneously, conventional photoacoustic computed tomography can be performed as well. We demonstrate the concept showing results on phantoms carrying speed-of-sound distributions.
Biomedical Spectroscopy and Imaging, 2016
Annals Surg Oncology, 2009
Rod shaped gold nanoparticles are synthesized using cetyltriammonium bromide (CTAB) as a major co... more Rod shaped gold nanoparticles are synthesized using cetyltriammonium bromide (CTAB) as a major component of growth solutions. This surfactant is toxic to cells, but is at the moment unavoidable when monodisperse and high yield nanorods are to be synthesized. CTAB is found coating side walls of the nanoparticles and plays a role in maintaining colloidal stability. It may be displaced using thiolated PEG which is non-toxic to cells. Here we report on systematic studies of cell viability of such PEGylated nanorods on an SKBR3 cell-line using the MTS assay. These PEGylated particles are characterized using electron microscopy, optical spectroscopy and zeta potential measurements. It is expected that such treatment will be crucial in making nanorods compatible for in vivo biomedical applications.
Proceedings of Spie the International Society For Optical Engineering, 2008
Photoacoustic imaging is an upcoming medical imaging modality with the potential of imaging both ... more Photoacoustic imaging is an upcoming medical imaging modality with the potential of imaging both optical and acoustic properties of objects. We present a measurement system and outline reconstruction methods to image both speed of sound and acoustic attenuation distributions of an object using only pulsed light excitation. These acoustic properties can be used in a subsequent step to improve the image quality of the optical absorption distribution. A passive element, which is a high absorbing material with a small cross-section such as a carbon fiber, is introduced between the light beam and the object. This passive element acts as a photoacoustic source and measurements are obtained by allowing the generated acoustic signal to propagate through the object. From these measurements we can extract measures of line integrals over the acoustic property distribution for both the speed of sound and the acoustic attenuation. Reconstruction of the acoustic property distributions then comes down to the inversion of a linear system relating the obtained projection measurements to the acoustic property distributions. We show the results of applying our approach on phantom objects. Satisfactory results are obtained for both the reconstruction of speed of sound and the acoustic attenuation.
Ultrasonic Imaging
Photoacoustic imaging of interphalangeal peripheral joints is of interest in the context of using... more Photoacoustic imaging of interphalangeal peripheral joints is of interest in the context of using the synovial membrane as a surrogate marker of rheumatoid arthritis. Previous work has shown that ultrasound produced by absorption of light at the epidermis reflects on the bone surfaces within the finger. When the reflected signals are backprojected in the region of interest, artifacts are produced, confounding interpretation of the images. In this work, we present an approach where the photoacoustic signals known to originate from the epidermis, are treated as virtual ultrasound transmitters, and a separate reconstruction is performed as in ultrasound reflection imaging. This allows us to identify the bone surfaces. Further, the identification of the joint space is important as this provides a landmark to localize a region-of-interest in seeking the inflamed synovial membrane. The ability to delineate bone surfaces allows us not only to identify the artifacts, but also to identify the interphalangeal joint space without recourse to new US hardware or a new measurement. We test the approach on phantoms and on a healthy human finger.
We present a fast, computed tomography (CT) photoacoustic imager for mouse imaging. The system fe... more We present a fast, computed tomography (CT) photoacoustic imager for mouse imaging. The system features a 32 element curvilinear detector and an illumination system coupled to a rotary mechanism to enable a slice to be imaged in less than 1 minute. Image reconstruction is performed using a modified acoustic backprojection algorithm. We describe the system overview and imaging results on sacrificed mouse.
Photons Plus Ultrasound: Imaging and Sensing 2012, 2012
ABSTRACT Current imaging modalities are often not able to detect early stages of breast cancer wi... more ABSTRACT Current imaging modalities are often not able to detect early stages of breast cancer with high imaging contrast. Visualizing malignancy-associated increased hemoglobin concentrations might improve breast cancer diagnosis. Photoacoustic imaging can visualize hemoglobin in tissue with optical contrast and ultrasound resolution, which makes it potentially ideal for breast imaging. The Twente Photoacoustic Mammoscope (PAM) has been designed specifically for this purpose. Based on a successful pilot study in 2007, a large clinical study using PAM has been started in December 2010. PAM uses a pulsed Q-switched Nd:YAG laser at 1064 nm to illuminate a region of interest on the breast. Photoacoustic signals are detected with a 1MHz, unfocused ultrasound detector array. Three dimensional data are reconstructed using an acoustic backprojection algorithm. Those reconstructed images are compared with conventional imaging and histopathology. In the first phase of the study, the goal was to optimize the visualization of malignancies. We performed sixteen technically acceptable measurements on confined breast malignancies. In the reconstructed volumes of all malignancies, a confined high contrast region could be identified at the expected lesion depth. After ten successful measurements, the illumination area was increased and the fluence was substantially decreased. This caused a further significant increase in PAM lesion contrast.
Novel Optical Instrumentation for Biomedical Applications IV, 2009
... J.Jithin@tnw.utwente.nl, phone +31 534893112, fax +31 53 4891105 Novel Optical Instrumentatio... more ... J.Jithin@tnw.utwente.nl, phone +31 534893112, fax +31 53 4891105 Novel Optical Instrumentation for Biomedical Applications IV, edited by Christian D. Depeursinge, I. Alex Vitkin, Proc. of SPIE-OSA Biomedical Optics, SPIE Vol. ...
Photons Plus Ultrasound: Imaging and Sensing 2011, 2011
Accurate lymph node analysis is essential to determine the prognosis and treatment of patients su... more Accurate lymph node analysis is essential to determine the prognosis and treatment of patients suffering from melanoma. The initial results of a tomographic photoacoustic modality to detect melanoma metastases in resected lymph nodes are presented based on phantom models and a human lymph node. The results show melanoma metastases detection is feasible and the setup is capable of distinguishing absorbing
Photons Plus Ultrasound: Imaging and Sensing 2007: The Eighth Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, 2007
The effects of an inappropriately chosen speed-of-sound in photoacoustic imaging reconstructions ... more The effects of an inappropriately chosen speed-of-sound in photoacoustic imaging reconstructions are to cause blurring of images and impairment of contrast. Here we outline a new methodology to measure the speed-of-sound in a photoacoustic imager with little or no additional cost and without the need to perform extra measurements. The method uses a strong absorber of light which is placed
Diffuse Optical Imaging of Tissue, 2007
Breast cancer dominates cancers in females. This burden on society and the room for improvements ... more Breast cancer dominates cancers in females. This burden on society and the room for improvements in the current practice of mammography have been stimuli for developing new modalities like photoacoustic mammography. At the University of Twente (UT), an instrument had been developed aimed at performing limited area scans on the human breast. This instrument is called the Twente Photoacoustic Mammoscope
Photons Plus Ultrasound: Imaging and Sensing 2011, 2011
In the reconstruction process of photo acoustic experiments, it was observed that adding a passiv... more In the reconstruction process of photo acoustic experiments, it was observed that adding a passive element to the experimental setup, improves the quality of the reconstruction of the object. This contribution analyzes this effect in some detail. We consider a cylindrical configuration. We start from an artificial and theoretically constructed optical absorption distribution that radiates sound waves when interrogated by the optical pulse. We analyze in the experimental setup the addition of the passive element to this example. The reported investigation is a part of a larger study on the existence, uniqueness and stability of photo acoustic inverse source reconstructions.
Solid State Communications, 2005
Thermal diffusivities (a) and molar volumes (V m ) of bulk Al 20 As x Te 80Kx alloy glasses in th... more Thermal diffusivities (a) and molar volumes (V m ) of bulk Al 20 As x Te 80Kx alloy glasses in the composition range 0%x%35 are examined. The results reveal a broad maximum in alpha and a broad minimum in V m in the 15!x!25 range. Earlier temperature modulated differential scanning calorimetric measurements on these glasses have revealed the non-reversing heat flow to show a global minimum (reversibility window) in the same composition range. Taken together these results suggest that present glasses in the 15!x!25 range are self-organized. The thermal diffusivity maximum observed near xZ20 is consistent with a minimal scattering of thermal waves in the homogeneous and stress-free glass composition residing in the center of the self-organized phase.
Breast Cancer Management, 2014
Molecular Imaging, 2007
Gold nanoparticles exhibit intense and narrow optical extinction bands due to the phenomenon of p... more Gold nanoparticles exhibit intense and narrow optical extinction bands due to the phenomenon of plasmon resonance making them useful as contrast agents for light-based imaging techniques. Localized heating results from the absorbed light energy, which shows potential for these particles in photothermal therapy as well. The bioconjugation of gold nanoparticles to appropriate antibodies targeted to tumors in vivo, could make
Opto-Acoustic Methods and Applications, 2013
ABSTRACT
Photons Plus Ultrasound: Imaging and Sensing 2012, 2012