Prashant R. Bhadri

University of Southern California, Los Angeles, California, United States

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Publications (23)7.41 Total impact

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    ABSTRACT: A cerebral aneurysm is defined as a weakened portion of an artery in the brain. Rupture of a cerebral aneurysm leads to subarachnoid hemorrhage (SAH). A significant number of patients with SAH are initially misdiagnosed and subjected to the risks associated with aneurysm re-rupture. Traditional detection methods recommended by physicians include computed tomography (CT) scan, lumbar puncture and angiography. Unfortunately, the CT scan is ineffective after 12 h, and angiography is best suited for those cases of finding the aneurysm before surgery. Physicians may therefore rely on lumbar puncture to develop a quick and objective evaluation by assessing xanthochromia. Bilirubin in the cerebrospinal fluid, resulting from the chemical decomposition of whole blood, is an indicator of hemorrhage. This metabolite can be detected after lumbar puncture, by differentiating its optical signature in the spinal fluid. In cases of traumatic spinal tap, bilirubin needs to be distinguished from whole blood. We introduce a diagnostic system based on visible spectroscopy to quickly and objectively assess low blood-volume SAH. The system integrates innovative hardware and a powerful software interface. We explore an algorithm that accounts for the noise and distortion from blood in the cerebrospinal fluid. We introduce a portable, user-friendly hardware platform composed of specific components designed for their sensitivity and specificity.
    Analog Integrated Circuits and Signal Processing 08/2008; 56(1-2):127-134. · 0.55 Impact Factor
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    ABSTRACT: Annually, approximately 30,000 people suffer from aneurysmal subarachnoid hemorrhage (SAH) in the United States. In an estimated 5% of these patients, the hemorrhage is difficult to diagnose using conventional methods. Clinicians must rely upon a combination of clinical history, Computerized Tomography (CT) scan evidence and lumbar puncture results to diagnose and differentiate SAH from a traumatic spinal tap (blood in the spinal fluid due to the procedure). Here we describe an algorithm based development of an analytic methodology using visible spectroscopy to reliably quantify bilirubin in hemorrhagic spinal fluid. The analysis, which may be useful for diagnoses concerning hemorrhagic stroke, is based on the detection of bilirubin, and concomitant blood products produced within the Cerebral Spinal Fluid (CSF) following SAH. The algorithm quantifies bilirubin (0.3 to 10 mg/dL) from the resultant absorption spectrum. A model is developed from standard visible spectroscopic absorption curves of bilirubin and hemoglobin by applying traditional Beer's Law principles. The model is coupled to a modified partial least square analysis and control theory concept where the bilirubin is the "signal" and is masked by hemoglobin "noise." This paper describes the computational methods, sensitivity and utility of a system to quantify bilirubin in CSF like solutions containing hemoglobin and bilirubin over 0.5 g/dL-10 g/dL of hemoglobin concentrations.
    Medicinal Chemistry 02/2007; 3(1):21-7. · 1.37 Impact Factor
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    ABSTRACT: The need to monitor the conditions prevailing in the external environment in order to control environmental pollution is one of the prime necessities of the modern age. This paper introduces a robust, self-contained, inexpensive integrated potentiometric sensor that can be used for in situ environmental monitoring. The primary focus is to design, implement and integrate a potentiometric CMOS circuit with the sensor device to measure the potential developed across a working probe (microelectrode sensor) and the reference probe. The magnitude of the output voltage signal is dependent on the characteristics (pH) of the solution being evaluated by the system. A Printed Circuit Board has been built to integrate the microelectrode sensor device and the sensor chip with the aim of producing a fully integrated system. The microelectrode sensor device may be replaced by a NEMS based sensor device in areas that require further miniaturization like biomedical applications.
    Nanotechnology, 2006. IEEE-NANO 2006. Sixth IEEE Conference on; 07/2006
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    ABSTRACT: In the modern era, some of the most serious causes for public health problems can be attributed to environmental pollution. Proper monitoring of environmental conditions helps us to control the pollution in an effective manner. This paper introduces a robust, self-contained, inexpensive integrated amperiometric microelectrode sensor that can be used for in situ environmental monitoring. The work primarily focuses on the design, implementation and integration of an amperiometric CMOS sensor chip with a microelectrode sensor device in order to measure the current flowing through the working probe (microelectrode sensor) and the reference probe, when they are immersed in the test solution. The magnitude of the current signal, of the order of nanoamperes, is shown to be dependent on the characteristics (oxygen content) of the solution being evaluated by the system. The integration of the microelectrode sensor with the sensor chip is done with the help of a Printed Circuit Board. The microelectrode sensor device may be replaced by a NEMS based sensor device for applications requiring further miniaturization, like that in the biomedical field where the solution under test may be a biofilm.
    Nanotechnology, 2006. IEEE-NANO 2006. Sixth IEEE Conference on; 07/2006
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    ABSTRACT: There is a clear need for in situ monitoring of oxidation–reduction potential (ORP) in many environmental applications, particularly those involving water quality monitoring and wastewater treatment. This paper describes fabrication of microelectrode sensor arrays for measurements of ORP in situ in the environment, such as at Superfund sites. The four-probe microelectrode arrays were fabricated from glass using a two-step, HF-based meniscus etching process. The tip size of individual microelectrodes was approximately 200 nm. The electrochemical performance of these ORP electrodes was fully characterized by measuring redox potentials of standard and reference solutions. When compared with commercial milli-electrodes, the microelectrode arrays exhibited very fast response time (from a few milliseconds to 30 s) and proved to be extraordinarily stable (variability on the order of 2 mV over a 4-day test period). This successful development of microelectrode arrays for ORP measurements will enable in situ measurement of redox potentials in the environment, such as contaminated soils, biofilm or sediments at Superfund sites.
    Sensors and Actuators B: Chemical. 01/2006;
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    ABSTRACT: Microelectrodes have been developed over the last few years with tip diameters of 1-10 μm, but they are fragile and susceptible to electrical interference. In addition, they are difficult to manufacture and operate, and are often unsuitable for measurement in small volumes of liquid or in soils. This limits their use to specialized laboratories under highly controlled conditions. The paper introduces a robust, self-contained, inexpensive MEMS based microelectrode sensor that can be used in situ environments. It deals with the design, analysis and performance of circuitry for a microelectrode sensor. The primary focus is to design, implement and integrate a CMOS circuit with the MEMS device to process, amplify and transmit the signal from the microelectrode to a measuring instrument. A current sensing circuit is developed for amperometric measurement with the microelectrode array. The magnitude of the output signal is dependent on the characteristics of the liquid being evaluated by the system. A printed circuit board (PCB) has been built to integrate the microelectrode sensor array along with the sensor chip with the aim of producing a fully integrated system.
    Circuits and Systems, 2005. 48th Midwest Symposium on; 09/2005
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    ABSTRACT: The need for accurate, robust in situ microscale monitoring of oxidation-reduction potentials (ORP) is required for continuous soil pore water quality monitoring. We are developing a suite of self-contained microelectrodes that can be used in the environment, such as at Superfund sites, to monitor ORP in contaminated soils and sediments. This paper presents details on our development of microelectrode sensor arrays for ORP measurements. The electrochemical performance of these ORP electrodes was fully characterized by measuring redox potentials in standard solutions. It found that the newly developed integrated ORP microelectrodes produced a very stable voltage response (the corresponding rate of the integrated microelectrode potential change was in the range of 0.6-1.1 mV/min), even when the measurement was carried out outside of a Faraday cage where signals from most conventional microelectrodes are usually inhibited by external electrical nose. These new microelectrodes were easier to fabricate and were more robust than conventional microelectrodes. The tip size of the integrated ORP microelectrode was approximately 200 nm square, with a taper angle of approximately 20 degrees and a length of 57 microm. The integrated ORP microelectrode exhibited better signal stability and substantially shorter response times (from less than a few milliseconds to 30 s, depending on the standard solution used) than the commercial millielectrode (a few minutes). Compared with the slope of the commercial millelectrode, the slope of the integrated microelectrode (61.5 mV/pH) was closerto the ideal slope against quinhydrone calibration solutions. Therefore, it is to be expected that the newly developed ORP microelectrode may have wider applications in contaminated soils, biofilms, and sediments.
    Environmental Science and Technology 09/2005; 39(16):6191-7. · 5.48 Impact Factor
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    ABSTRACT: This paper describes a microelectrode array (MEA) sensor system for measurements of oxidation-reduction potentials (ORP) in situ in the environment. The four-probe MEAs were fabricated from glass using a two-step, HF-based meniscus etching process. A CMOS ASIC chip was developed for signal acquisition and processing and packaged with the microelectrode sensors to reduce noise. The electrochemical performance of these ORP MEAs was fully characterized by measuring redox potentials of standard and reference solutions. The MEAs exhibited a substantially faster response time, proved to be extraordinarily stable, and were independent of the microelectrode position within the array.
    Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05. The 13th International Conference on; 07/2005
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    ABSTRACT: In North America, approximately 30,000 people annually suffer an aneurismal subarachnoid hemorrhage (SAH). Using computerized tomography (CT), the blood is generally not visible after 12 hours. Currently lumbar puncture (LP) results are equivocal for diagnosing SAH largely because of technical limitations in performing a quick and objective evaluation. Having ruptured once, an aneurysm is statistically more likely to rupture again. Therefore, for those individuals with a sentinel (or warning) hemorrhage, detection within the first 12 hours is paramount. We present a diagnostic technology based on visible spectroscopy to quickly and objectively assess low-blood volume SAH from a diagnostic spinal tap. This technology provides clinicians, with the resources necessary for assessing patients with suspected aneurismal SAH beyond the current 12-hour limitation imposed by CT scans. This aids in the improvement of patient care and results in rapid and appropriate treatment of the patient. To perform this diagnosis, we quantify bilirubin and hemoglobin in human CSF over a range of concentrations. Because the bilirubin and hemoglobin spectra overlap quantification is problematic. To solve this problem, two algorithmic approaches are presented: a statistical or a random stochastic component known as Partial Least Square (PLS) and a control theory based mathematical model. These algorithms account for the noise and distortion from blood in CSF leading to the quantification of bilirubin and methemoglobin spectroscopically. The configurations for a hardware platform is introduced, that is portable and user-friendly composed of specific components designed to have the sensitivity and specificity required. This aids in measuring bilirubin in CSF, hemorrhagic-CSF and CSF-like solutions. The prototype uses purpose built algorithms contained within the platform, such that physicians can use it in the hospital and lab as a point of care diagnostic test.
    Proc SPIE 04/2005;
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    ABSTRACT: This work presents the mixed mode integrated circuit design. The development of SOC technology, CAD and simulation resources are providing system and chip designers with design tools necessary for successfully completing fully integrated CMOS hardware. The design methodology and new CAD/simulation tools allow the design engineer to focus on the mixed mode integrated circuit design without losing chip functionality or system level performance specifications. Integrated circuits-are designed, prototypes are fabricated, layout implemented and tested with varying degrees of automation. Very large scale integration (VLSI) systems have digital and analog components on the same chip. This shift from purely digital to mixed-signal (MS) systems is due to the high values of operating frequencies in communication circuits and shrinking feature sizes. Hardware description languages and simulators and automatic design software programs (called synthesizers) describe the functionality of each module as a "simulatable" model (also called a virtual prototype) and redesign or modification of the requirements is necessary if model need to meet the functional requirements of the module.
    IEEE Potentials 03/2005;
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    ABSTRACT: Cerebral aneurysm is defined as a weakened portion of an artery in the brain. Its rupture leads to a specific case of bleeding known as a subarachnoid hemorrhage (SAH). Literature indicates that a significant portion of patients suffering from SAH are initially misdiagnosed and subjected to the risks associated with aneurysm re-rupture. Traditional methods of detection that are recommended by the physicians include computer tomography (CT) scan, lumbar puncture (LP) and angiogram. Unfortunately, CT scan is ineffective after 12 hours, and angiogram only applicable in cases of finding the aneurysm before surgery. This paper discusses the invasive technique of lumbar puncture because of the technical limitations in performing a quick and objective evaluation. Bilirubin, resulting from the chemical decomposition of whole blood is a clear indicator a hemorrhage. This metabolite can be detected after a spinal tap, by differentiating its optical signature from that of fresh whole blood. We introduce the development of a diagnostic system that is based on visible spectroscopy to quickly and objectively assess low-blood volume SAH. The system integrates innovative hardware and a powerful software interface. The paper explores algorithms that accounts for the noise and distortion from blood in CSF. Furthermore, a hardware platform is introduced, that is portable and user-friendly composed of specific components designed to have the sensitivity and specificity.
    Circuits and Systems, 2005. 48th Midwest Symposium on; 01/2005
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    ABSTRACT: Neonatal jaundice is a condition in new born babies, where a high level of bilirubin is present in the blood. This condition is known as hyperbilirubinemia. Bilirubin, which results from the breakdown of hemoglobin, is processed in the liver. In a significant number of cases, due to the slow development of the liver organ, a condition of excess bilirubin production occurs in the neonates. Therefore, careful attention to bilirubin levels in neonates is required to prevent serious complications. It is estimated, that about 50% of newborns have an episode of jaundice in the first few days. Approximately, 6% of them may develop hyperbilirubinemia, which can potentially cause bilirubin encephalopathy or kernicterus, a severe neonatal disease. Bilirubin is yellow in color and therefore stains the skin and other tissues if its concentration is high. Invasive procedures expose the neonates to trauma and risk of infection. Therefore, a non-invasive quantification of bilirubin in neonates has been sought by the pediatric community. Furthermore, these performing invasive tests are not always done accurately or unreliably. This paper puts forth the non-invasive approach of quantifying the bilirubin.
    Circuits and Systems, 2005. 48th Midwest Symposium on; 01/2005
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    ABSTRACT: A new breed of microelectrode sensor arrays for oxidation-reduction potential (ORP) measurements in situ at environmental sites has been successfully developed. The microelectrodes were fabricated from glass using a two-step, HF-based meniscus etching process, and demonstrated electrochemical performance nearly identical to that of the commercial millielectrode, with significantly faster response times.
    Sensors, 2004. Proceedings of IEEE; 11/2004
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    ABSTRACT: A weakened portion of an artery in the brain leads to a medical condition known as a cerebral aneurysm. A subarachnoid hemorrhage (SAH) occurs when an aneurysm ruptures. For those individuals suspected of having a SAH, a computerized tomography (CT) scan of the brain usually demonstrates evidence of the bleeding. However, in a considerable portion of people, the CT scan is unable to detect the blood that has escaped from the blood vessel. Recent studies have indicated nearly 30% of patients with a SAH are initially misdiagnosed. For circumstances when a SAH is suspected despite a normal CT scan, physicians make the diagnosis of SAH by performing a spinal tap. A spinal tap uses a needle to sample the cerebrospinal fluid (CSF) collected from the patient"s lumbar spine. However, it is also possible for blood to be introduced into the CSF as a result of the spinal tap procedure. Therefore, an effective solution is required to help medical personnel differentiate between the blood that results from a tap and that from a ruptured aneurysm. In this paper, the development of a prototype is described which is sensitive and specific for measuring bilirubin in CSF, hemorrhagic-CSF and CSF-like solutions. To develop this instrument a combination of spectrophotometric analysis, custom data analysis software and other hardware interfaces are assembled that lay the foundation for the development of portable and user-friendly equipment suitable for assisting trained medical personnel with the diagnosis of a ruptured cerebral aneurysm.
    Proc SPIE 11/2004;
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    ABSTRACT: Over the years, Field Programmable Gate Arrays (FPGAs) have made a profound impact on the electronics industry with rapidly improving semiconductor-manufacturing technology ranging from sub-micron to deep sub-micron processes and equally innovative CAD tools. Though FPGA has revolutionized programmable/reconfigurable digital logic technology, one limitation of current FPGA"s is that the user is limited to strictly electronic designs. Thus, they are not suitable for applications that are not purely electronic, such as optical communications, photonic information processing systems and other multi-technology applications (ex. analog devices, MEMS devices and microwave components). Over recent years, the growing trend has been towards the incorporation of non-traditional device technologies into traditional CMOS VLSI systems. The integration of these technologies requires a new kind of FPGA that can merge conventional FPGA technology with photonic and other multi-technology devices. The proposed new class of field programmable device will extend the flexibility, rapid prototyping and reusability benefits associated with conventional electronic into photonic and multi-technology domain and give rise to the development of a wider class of programmable and embedded integrated systems. This new technology will create a tremendous opportunity for applying the conventional programmable/reconfigurable hardware concepts in other disciplines like photonic information processing. To substantiate this novel architectural concept, we have fabricated proof-of-the-concept CMOS VLSI Multi-technology FPGA (MT-FPGA) chips that include both digital field programmable logic blocks and threshold programmable photoreceivers which are suitable for sensing optical signals. Results from these chips strongly support the feasibility of this new optoelectronic device concept.
    01/2004;
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    ABSTRACT: Recent advances in the integrated electronic circuit industry have spurred efforts to develop technologies that efficiently integrate optics and electronics on a single Complementary Metal Oxide Semiconductor (CMOS) chip. Such CMOS technologies can significantly increase circuit functionality and performance at low fabrication and system cost, thereby accelerating the trend of significant growth in this area. The new functionality could include optical based sensors, image processing, and intelligent optical read heads for faster and more efficient data sorting and searching. The reliability of such monolithic CMOS based functions would be drastically improved relative to their bulk optic counterparts. In the optical telecommunications industry, short haul fiber links would benefit from low cost, silicon CMOS based photoreceivers. One of the primary challenges facing the designers in implementing CMOS based optoelectronic circuits is opto-electrical conversion efficiency. The poor optical responsivity of silicon leads to a bottleneck in the optical to electrical conversion for CMOS based photodetectors. This can be compensated in part through more efficient receiver electronics. Efforts have been made to provide mixed signal circuit design to analyze CMOS based high performance, low noise, integrated receiver circuits. This paper evaluates the performance analysis of five types of photoreceiver configurations that were designed for specific applications.
    01/2004;
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    ABSTRACT: An accurate quantification of bilirubin in cerebrospinal fluid (CSF) will provide a simple, sensitive and rapid mechanism for detecting subarachnoid hemorrhage (SAH) and for its differentiation from a traumatic spinal tap. Derivative analysis of the spectrophotometric data provides a model for determining bilirubin in CSF where the primary contaminant is Methemoglobin. Bilirubin values are determined in the range 0-9mg/dl within a methemoglobin concentration of 4.6g/dl using the derivative analysis method. The algorithm is also implemented on test samples in which the bilirubin value is constant (4.6mg/dl) and the methemoglobin varies between 0-9g/dl. The performance of the derivative analysis method is compared to the modified minimum distance method developed in reference one. We suggest a combination of these methods for accurate bilirubin estimation in CSF/hemoglobin. This will provide the foundation for the development of a portable user friendly device for diagnosis of SAH.
    Proc SPIE 01/2004;
  • Prosenjit Mal, Prashant R. Bhadri, Fred R. Beyette Jr
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    ABSTRACT: In the past decade, Field Programmable Gate Arrays (FPGA) has significantly influenced the landscape of the electronic industry. In particular, in the areas of semiconductor manufacturing, CAD tool designs and a wide range of digital logic applications. Primarily, research efforts in the FPGA community have concentrated on improving the reconfigurability or programmability of present day architecture for digital applications. However, the digital nature of FPGA technologies limits their applicability to a wide range of applications that depend on analog circuitry, photonic and RF based technologies. As with any ASIC design, the turn-around time between design iterations may be several months which is prohibitively long for multi-technology test-bed systems where the system designer depends on a rapid prototyping/experimentation environment that allows for optimization of processing algorithms and system architecture. Therefore, we developed innovative FPGA architecture that merges conventional FPGA technology with mixed signal and other multi-technology device. In this paper we discuss the Multi-Technology-FPGA (MT-FPGA) architecture that allows the user to have flexible rapid prototyping environment and provides him or her with the benefits of a conventional FPGA in a mixed signal domain. We substantiate this concept by implementing this architecture in TSMC 0.35 mum process and discussing the results of a variable threshold optical receiver circuit suitable for photonic information processing.
    01/2004;
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    ABSTRACT: A cerebral aneurysm is a weakened portion of an artery in the brain. When a cerebral aneurysm ruptures, a specific type of bleeding known as a subarachnoid hemorrhage (SAH) occurs. No test exists currently to screen people for the presence of an aneurysm. The diagnosis of a SAH is made after an aneurysm ruptures, and the literature indicates that nearly one-third of patients with a SAH are initially misdiagnosed and subjected to the risks associated with aneurysm re-rupture. For those individuals with a suspected SAH, a computerized tomography (CT) scan of the brain usually demonstrates evidence of the bleeding. However, in a considerable portion of people, the CT scan is unable to detect the blood that has escaped from the blood vessel. For circumstances when a SAH is suspected despite a normal CT scan, physicians make the diagnosis of SAH by performing a spinal tap. A spinal tap uses a needle to sample the cerebrospinal fluid (CSF) collected from the patient"s back; CSF is tainted with blood after the aneurysm ruptures. To distinguish between a common headache and a SAH, a fast and an effective solution is required. We describe the development of an effective detection system integrating hardware and a powerful software interface solution. Briefly, CSF from the patient is aspirated and excited with an appropriate wavelength of light. The software employs spectrophotometric analysis of the output spectra and lays the foundation for the development of portable and user-friendly equipment for detection of a ruptured cerebral aneurysm.
    Proc SPIE 11/2003;
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    ABSTRACT: We present in this paper several different photodetector structures implemented with a conventional CMOS fabrication process that can be incorporated into optical data links and information processing systems. We investigate several detector structures using the 2-D materials simulation package MEDICI. The detector structure is evaluated by fabrication using an AMI 1.5 μm CMOS process available through the MOSIS foundry service. When geometric and other structural differences are accounted for, the results indicate that the simulation adequately predicts photodetector operation under normal operating conditions.
    Lasers and Electro-Optics Society, 2002. LEOS 2002. The 15th Annual Meeting of the IEEE; 12/2002

Publication Stats

55 Citations
7.41 Total Impact Points

Institutions

  • 2008
    • University of Southern California
      • Doheny Eye Institute
      Los Angeles, California, United States
  • 2007
    • Doheny Eye Institute
      Los Angeles, California, United States
  • 2001–2005
    • University of Cincinnati
      • Department of Electrical and Computer Engineering and Computer Science
      Cincinnati, OH, United States