Kambiz Pourrezaei

Drexel University, Philadelphia, Pennsylvania, United States

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Publications (75)56.9 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Modeling behavior of broadband (30-1000 MHz) frequency modulated near infrared photons through a multilayer phantom is of interest to optical bio-imaging research. Photon dynamics in phantom are predicted using three-dimension (3D) finite element numerical simulation and are related to the measured insertion loss and phase for a given human head geometry in this paper based on three layers of phantom each with distinct optical parameter properties. Simulation and experimental results are achieved for single, two, and three layers solid phantoms using COMSOL (COMSOL AB, Tegnérgatan 23, SE-111 40, Stockholm, Sweden) (for FEM) simulation and custom-designed broadband free space optical transmitter (Tx) and receiver (Rx) modules that are developed for photon migration at wavelengths of 680, 795, and 850 nm. Standard error is used to compute error between two-dimension and 3D FE modeling along with experimental results by fitting experimental data to the functional form of afrequency+b. Error results are shown at narrowband and broadband frequency modulation. Confidence in numerical modeling of the photonic behavior using 3D FEM for human head has been established here by comparing the reflection mode's experimental results with the predictions made by COMSOL for known commercial solid brain phantoms. Copyright © 2013 John Wiley & Sons, Ltd.
    International journal for numerical methods in biomedical engineering. 11/2013;
  • Zeinab Barati, Issa Zakeri, Kambiz Pourrezaei
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    ABSTRACT: Functional near infrared spectroscopy (fNIRS) is a powerful tool for the study of oxygenation and hemodynamics of living tissues. Despite the continuous nature of the processes generating the data, analysis of fNIRS data has been limited to discrete-time methods. We propose a technique, namely functional data analysis (fDA), that converts discrete samples to continuous curves. We used fNIRS data collected on forehead during a cold pressor test (CPT) from 20 healthy subjects. Using functional principal component analysis, oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) curves were decomposed into several components based on variability across the subjects. Each component corresponded to an experimental condition and provided qualitative and quantitative information of the shape and weight of that component. Furthermore, we applied functional canonical correlation analysis to investigate the interaction between Hb and HbO2 curves. We showed that the variation of Hb and HbO2 was positively correlated during the CPT, with a "far" channel on right forehead showing a smaller and faster HbO2 variation than Hb. This research suggests the fDA platform for the analysis of fNIRS data, which solves problem of high dimensionality, enables study of response dynamics, enhances characterization of the evoked response, and may improve design of future fNIRS experiments.
    Journal of Biomedical Optics 11/2013; 18(11):117007. · 2.88 Impact Factor
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    ABSTRACT: Modeling behavior of broadband (30 to 1000 MHz) frequency modulated near-infrared (NIR) photons through a phantom is the basis for accurate extraction of optical absorption and scattering parameters of biological turbid media. Photon dynamics in a phantom are predicted using both analytical and numerical simulation and are related to the measured insertion loss (IL) and insertion phase (IP) for a given geometry based on phantom optical parameters. Accuracy of the extracted optical parameters using finite element method (FEM) simulation is compared to baseline analytical calculations from the diffusion equation (DE) for homogenous brain phantoms. NIR spectroscopy is performed using custom-designed, broadband, free-space optical transmitter (Tx) and receiver (Rx) modules that are developed for photon migration at wavelengths of 680, 780, and 820 nm. Differential detection between two optical Rx locations separated by 0.3 cm is employed to eliminate systemic artifacts associated with interfaces of the optical Tx and Rx with the phantoms. Optical parameter extraction is achieved for four solid phantom samples using the least-square-error method in MATLAB (for DE) and COMSOL (for FEM) simulation by fitting data to measured results over broadband and narrowband frequency modulation. Confidence in numerical modeling of the photonic behavior using FEM has been established here by comparing the transmission mode's experimental results with the predictions made by DE and FEM for known commercial solid brain phantoms.
    Journal of Biomedical Optics 01/2013; 18(1):17008. · 2.88 Impact Factor
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    ABSTRACT: The objective of this research was to assess the utility of a simple near infrared spectroscopy (NIRS) technology for objective assessment of the hemodynamic response to acute pain. For this exploration, we used functional near infrared spectroscopy (fNIRS) to measure the hemodynamic response on the forehead during three trials of a cold pressor test (CPT) in 20 adults. To measure hemodynamic changes at the superficial tissues as well as the intracranial tissues, two configurations of 'far' and 'near' source-detector separations were used. We identified two features that were found to be fairly consistent across all subjects. The first feature was the change of total hemoglobin (THb) concentration in a given condition divided by the duration of that condition [Formula: see text]. Statistical analyses revealed that during the first CPT trial [Formula: see text] significantly changed from its baseline value in all channels. Also, adaptation to repeated CPTs was observed in both [Formula: see text] parameter and the reported post-stimulus pain rating scores. The second feature was the difference between the maximum and the minimum of the evoked changes in the THb concentration (ΔTHb). A significant correlation was observed between the post-stimulus pain rating score and ΔTHb at all channels. An asymmetrical activity was observed only at the 'far' channels. These results suggest that fNIRS can potentially be used as a reliable technique for the assessment of the hemodynamic response to tonic pain induced by the CPT.
    Annals of Biomedical Engineering 09/2012; · 3.23 Impact Factor
  • Manuel Figueroa, Kambiz Pourrezaei, Somdev Tyagi
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    ABSTRACT: In order to analyze a sample using SERS, the analyte has to be brought in intimate contact with the substrate. This can be problematic when, let's say, the molecules of interest in trace amounts are located in large volumes. For example a biotoxin aerosol in a large room or a trace amount of bio-hazardous substances mixed in large volumes of water or other liquids. In principle it is possible to filter out the molecules of interest and then deposit them on the SERS substrate for further analyses. In practice this is very cumbersome and therefore is rarely used. Here we discuss flexible and porous SERS substrates that have been fabricated by depositing silver nano-particle inks on woven or spun fabrics made of glass fiber or cellulose followed by thermal annealing at 170-200°C for 10-15 minutes. Use of microwave absorption at about 10 GHz in the polymer-nanoparticle matrix to monitor the sintering process and to optimize the SERS amplification is also discussed. By varying the annealing time, different levels of nanoparticle clustering and the consequent SERS amplification can be achieved. Sampling of large volumes using the SERS filter substrates to detect airborne molecules is also discussed.
    07/2012;
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    ABSTRACT: This study used functional near-infrared spectroscopy (fNIRs) to test the hypothesis that non-treatment seeking alcohol-dependent participants (NTSA) would show greater response in dorsolateral prefrontal cortex (DLPFC) to alcohol cues than recovering alcoholics (RA; sober 90-180 days) or social drinkers. Opposite predictions were made for responses to natural reward cues. NTSA (n=4), RA (n=6), and social drinkers (n=4) were exposed to alcohol and natural reward cues while being monitored with fNIRs. Results confirmed enhanced responses to alcohol cues among NTSA vs. RA in right middle frontal gyrus. The opposite effect (RA>NTSA) was found in response to natural reward cues. Neural responses to alcohol and natural reward cues were negatively correlated in right DLPFC. Real-time craving ratings were positively correlated with greater neural response to alcohol cues. Differential responses to drug and natural reward cues suggest that a psychological mechanism related to treatment status may modulate drug cue responses in DLPFC.
    07/2012: pages 183-191; , ISBN: 978-3-642-31560-2
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    ABSTRACT: Metallic nanoparticle inks - colloidal suspensions of silver or gold nanoparticles in water or other organic solvents - can be sintered at relatively low temperatures (70 - 200°C). With appropriate thermal treatment the sintering can be controlled to fabricate nanoparticle substrates with a distribution of clusters sizes and interparticle distances. Such substrates exhibit relatively high (108 - 109) surface enhanced Raman scattering (SERS) amplification factors (AFs). The high AFs in such substrates arise from several mechanisms. The 'dimers' - two nanoparticles separated by a nanometersize gap - are known to produce amplification of the local electric field orders of magnitude larger than at the surface of an isolated single nanoparticle due to surface plasmon resonance. Furthermore, the lack of translational symmetry in the clusters leads to localizations of electromagnetic excitations to very small regions that can create SERS hot spots. Here we report that microwave absorption (~ 10 GHz) as a function of thermal annealing in dry-drop substrates can be used to monitor the sintering process in metallic nanoparticle inks. The predominant contribution to microwave absorption comes from electrically resistive weak links that are formed between nanoparticles as a result of the thermal treatment. Just before the creation of these weak links, such nanoparticle pairs are also the ones that make a major contribution to the SERS AFs. This leads to a correlation between the observed microwave absorption and the SERS signal intensities. We also present a simple model that describes the microwave absorption as a function of the isothermal annealing treatment.
    Proc SPIE 02/2012;
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    01/2012: pages 183-191; , ISBN: 9783642315602
  • Manuel Figueroa, Kambiz Pourrezaei, Somdev Tyagi
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    ABSTRACT: One of the most widely used methods for surface‐enhanced Raman scattering (SERS) employs silver or gold nanoparticles either in colloidal suspension or in the dry‐drop form. In such substrates the SERS amplification factors depend critically on the interparticle distances. Here, we report that microwave absorption as a function of temperature in dry‐drop substrates can be used as a probe to demarcate temperature regions for thermal annealing to produce SERS substrates with very high amplification factors. Copyright © 2011 John Wiley & Sons, Ltd.
    Journal of Raman Spectroscopy 10/2011; 43(4):588 - 591. · 2.68 Impact Factor
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    ABSTRACT: Broadband (30-1000MHz) frequency modulated spectroscopic measurements of brain tissue using near IR wavelengths are used for accurate extraction of absorption and scattering coefficients of cortex, CSF, and skull. Design of a helmet mounted untethered functional near IR system is presented in this paper that provides wireless communication between the monitoring and helmet mounted fNIR imaging sensors using high speed wireless ISM band Transmitter and UWB communication standards. Design specifications and predicted performance requirements are presented of the custom designed low power consuming optical transceivers and wireless communication subsystems using IBM 90nm CMOS foundry parameters.
    Microwave Symposium Digest (MTT), 2011 IEEE MTT-S International; 07/2011
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    ABSTRACT: Rapid and sensitive detection of serum tumor biomarkers are needed to monitor cancer patients for disease progression. Highly sensitive piezoelectric microcantilever sensors (PEMS) offer an attractive tool for biomarker detection; however, their utility in the complex environment encountered in serum has yet to be determined. As a proof of concept, we have functionalized PEMS with antibodies that specifically bind to HER2, a biomarker (antigen) that is commonly overexpressed in the blood of breast cancer patients. The function and sensitivity of these anti-HER2 PEMS biosensors was initially assessed using recombinant HER2 spiked into human serum. Their ability to detect native HER2 present in the serum of breast cancer patients was then determined. We have found that the anti-HER2 PEMS were able to accurately detect both recombinant and naturally occurring HER2 at clinically relevant levels (>2 ng/mL). This indicates that PEMS-based biosensors provide a potentially effective tool for biomarker detection.
    Analytical Chemistry 03/2011; 83(9):3392-7. · 5.70 Impact Factor
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    ABSTRACT: Functional spectroscopic measurements of brain matter using near IR wavelengths are characterized by absorption coefficient μ<sub>a</sub> and scattering coefficient μ<sub>s</sub>. To increase the accuracy of parameter extraction, a broadband frequency modulated system is proposed and design and implementation challenges of a completely untethered and field deployable unit and a high speed wireless communication system is considered to complement a free space optical communication system.
    Radio and Wireless Symposium (RWS), 2011 IEEE; 02/2011
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    ABSTRACT: Fiber based functional near infra-red (fNIR) spectroscopy has been considered as a cost effective imaging modality. To achieve a better spatial resolution and greater accuracy in extraction of the optical parameters (i.e., mua and mu's), broadband frequency modulated systems covering multi-octave frequencies of 10-1000MHz is considered. A helmet mounted broadband free space fNIR system is considered as significant improvement over bulky commercial fiber fNIR realizations that are inherently uncomfortable and dispersive for broadband operation. Accurate measurements of amplitude and phase of the frequency modulated NIR signals (670nm, 795nm, and 850nm) is reported here using free space optical transmitters and receivers realized in a small size and low cost modules. The tri-wavelength optical transmitter is based on vertical cavity semiconductor lasers (VCSEL), whereas the sensitive optical receiver is based on either PIN or APD photodiodes combined with transimpedance amplifiers. This paper also has considered brain phantoms to perform optical parameter extraction experiments using broadband modulated light for separations of up to 5cm. Analytical models for predicting forward (transmittance) and backward (reflectance) scattering of modulated photons in diffused media has been modeled using Diffusion Equation (DE). The robustness of the DE modeling and parameter extraction algorithm was studied by experimental verification of multi-layer diffused media phantoms. In particular, comparison between analytical and experimental models for narrow band and broadband has been performed to analyze the advantages of our broadband fNIR system.
    Proc SPIE 02/2011;
  • K. Pourrezaei, Z. Barati
    Journal of Pain - J PAIN. 01/2011; 12(4).
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    ABSTRACT: In the late 1980s and early 1990s, Dr. Britton Chance and his colleagues, using picosecond-long laser pulses, spearheaded the development of time-resolved spectroscopy techniques in an e®ort to obtain quantitative information about the optical characteristics of the tissue. These e®orts by Chance and colleagues expedited the translation of near-infrared spectroscopy (NIRS)-based techniques into a neuroimaging modality for various cognitive studies. Beginning in the early 2000s, Dr. Britton Chance guided and steered the collaboration with the Optical Brain Imaging team at Drexel University toward the development and application of a ̄eld deployable con- tinuous wave functional near-infrared spectroscopy (fNIR) system as a means to monitor cog- nitive functions, particularly during attention and working memory tasks as well as for complex tasks such as war games and air tra±c control scenarios performed by healthy volunteers under operational conditions. Further, these collaborative e®orts led to various clinical applications, including traumatic brain injury, depth of anesthesia monitoring, pediatric pain assessment, and brain␣computer interface in neurology. In this paper, we introduce how these collaborative studies have made fNIR an excellent candidate for speci ̄ed clinical and research applications, including repeated cortical neuroimaging, bedside or home monitoring, the elicitation of a posi- tive e®ect, and protocols requiring ecological validity. This paper represents a token of our gratitude to Dr. Britton Chance for his in°uence and leadership. Through this manuscript we show our appreciation by contributing to his commemoration and through our work we will strive to advance the ̄eld of optical brain imaging and promote his legacy.
    Journal of Innovative Optical Health Sciences 01/2011; 4(3):239-250. · 0.63 Impact Factor
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    ABSTRACT: An accurate measure of mental workload would help improve operational safety and efficacy in many environments that involve multitasking or sustained vigilance. The current study utilized functional near-infrared spectroscopy (fNIRs) to examine the relationship of the hemodynamic response in dorsolateral prefrontal cortex (DLPFC) as it related to mental workload, level of expertise, and task performance. DLPFC responses were monitored with fNIRs while 8 participants (4 with high practice, 4 novices) completed a quasirealistic computerized Warship Commander Task with various levels of difficulty. The results show that greater expertise was associated with relatively lower oxygenation (less neural activity) at low to moderate levels of taskload, but higher oxygenation and better performance at high levels of taskload. For novices, oxygenation was higher at moderate levels of taskload, but dropped precipitously at higher levels of taskload, along with performance, consistent with disengaging from the task. Results are interpreted within a “scaffoldingstorage” framework.
    Foundations of Augmented Cognition. Directing the Future of Adaptive Systems - 6th International Conference, FAC 2011, Held as Part of HCI International 2011, Orlando, FL, USA, July 9-14, 2011. Proceedings; 01/2011
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    ABSTRACT: Broadband (30–1000MHz) frequency modulated spectroscopic measurements of brain tissue using near infra red wavelengths is used to get an accurate extraction of absorption and scattering coefficients of various regions of brain. The design and realization challenges of developing this system are discussed in this paper. The challenges lie in developing small size, low power consuming, efficient custom designed modules on a helmet for broadband NIR spectroscopy and high speed wireless or minimally wired communications to a remote processing unit. The design requirements and expected performance of the custom designed modules is conducted using IBM 90nm CMOS technology. Finally, a comparison between the system level performance of untethered and a minimally tethered systems is shown in terms power consumption and implementation.
    01/2011;
  • M. Figueroa, Kambiz Pourrezaei, S. Tyagi
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    ABSTRACT: Hyaluronic acid (HA) is a high molecular weight glycosaminoglycan found in the extracellular matrix and joints in the body. Elevated levels in the serum are associated with liver disease so detection at concentrations in the microgram per liter range is useful for monitoring cirrhosis progression. Conventional methods can measure HA in this range but they take several days and require multiple preparation steps. Surface-enhanced Raman scattering (SERS) could be an alternative as it yields specific signatures stemming from molecular vibrations and has been shown to provide large enhancement factors. However, due to its intrinsic negative charge HA does not readily adsorb on metallic surfaces. To overcome this, a functionalized SERS substrate was developed to immobilize HA. A cysteamine self-assembling monolayer in the trans conformation allows the HA carboxyl group to attach to the ligand's amine group. The SERS signal can be used to monitor the concentration of cysteamine trans conformers in order to optimize HA attachment. In addition, SERS analysis shows an increase in HA Raman band intensity when immobilized to the substrate as compared to free HA on the substrate. Correlations between HA concentration and Raman band intensity are also discussed.
    Bioengineering Conference (NEBEC), 2011 IEEE 37th Annual Northeast; 01/2011
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    ABSTRACT: Functional Near-Infrared (fNIR) spectroscopy is an emerging optical brain imaging technology that enables assessment of brain activity through the intact skull in human subjects. fNIR systems developed during the last decade allow for a rapid, non-invasive method of measuring the brain activity of a subject while conducting tasks in realistic environments. This paper introduces underlying principles and various fNIR designs currently applied to real-time settings, such as monitoring Unmanned Aerial Vehicle (UAV) operator’s expertise development and cognitive workload during simulated missions.
    Foundations of Augmented Cognition. Directing the Future of Adaptive Systems - 6th International Conference, FAC 2011, Held as Part of HCI International 2011, Orlando, FL, USA, July 9-14, 2011. Proceedings; 01/2011
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    ABSTRACT: Piezoelectric microcantilever sensors (PEMS) can be sensitive tools for the detection of proteins and cells in biological fluids. However, currently available PEMS can only be used a single time or must be completely stripped and refunctionalized prior to subsequent uses. Here we report the successful use of an alternative regeneration protocol employing high salt concentrations to remove the target, leaving the functional probe immobilized on the microcantilever surface. Our model system employed the extracellular domain (ECD) of recombinant human Epidermal Growth Factor Receptor (EGFR) as the probe and anti-human EGFR polyclonal antibodies as the target. We report that high concentrations of MgCl2 dissociated polyclonal antibodies specifically bound to EGFR ECD immobilized on the sensor surface without affecting its bioactivity. This simple regeneration protocol both minimized the time required to re-conjugate the probe and preserved the density of probe immobilized on PEMS surface, yielding identical biosensor sensitivity over a series of assays.
    Sensors 01/2011; 11(5):5520-8. · 2.05 Impact Factor

Publication Stats

356 Citations
56.90 Total Impact Points

Institutions

  • 2002–2012
    • Drexel University
      • School of Biomedical Engineering, Science and Health Systems
      Philadelphia, Pennsylvania, United States
  • 2006–2010
    • Drexel University College of Medicine
      • Department of Surgery
      Philadelphia, Pennsylvania, United States
  • 2001
    • University of Pennsylvania
      Philadelphia, Pennsylvania, United States