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28th Annual International Conference of the IEEE engineering in Medicine and Biology Society, EMBS'06

作者： Gehalot, Piyush Zhang, Rong Mathew, Aby Behbehani, Khosrow Joint Biomedical Engineering Program Southwestern Medical Centre University of Texas at Arlington Dallas TX United States Institute for Exercise and Environmental Medicine University of Texas Southwestern Medical Center Dallas

ISBN: (纸本)1424400325

The three-element Windkessel model is widely used and accepted for analyzing blood flow and pressure in arterial system and cerebral circulation. In most studies, changes in mean arterial blood pressure data is used as input to estimate the model parameters. However, estimation of linear model parameters, using input-output data, requires that the input be persistently exciting. This study examined the efficacy of using mean arterial blood pressure (MABP) sequence as an input stimulus for estimating the parameters of the three-element Windkessel model. Additionally, the study explored the use of a shorter MABP data segment of 1.5 min as compared to the commonly used 6 min data. MABP data was obtained from 11 healthy subjects. One thousand three-element Windkessel models, with parameter values randomly selected to be within physiological range, were subjected to seven different input sequences. For each input sequence and model, the values of the model (target-parameters) were estimated. The seven input sequence were: 1) six minutes of MABP measured from subjects;2-5) four 1.5 min of measured MABP obtained by dividing the measured six minutes of MABP into non-overlapping contiguous segments;6) a six-minutes of pseudo random binary sequence (PRBS) with amplitudes comparable to the MABP sequence;and 7) a 1.5 min of PRBS sequence with amplitudes comparable to the MABP sequence. The MABP data used was randomly selected from the 11 subjects for each estimation run. The model parameter estimation method had two phases of optimization. In the first phase, the parameters were estimated and optimized using the frequency transform of the input and output. In the second phase, the values of the estimated parameters were used as initial estimates and time-domain optimization was carried out to further refine the estimates. Results from the study, comparing the estimated-parameters with the target-parameters, show that for the MABP data, there was no significant difference betwee

关键词： Blood pressure

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Tumour oxygen dynamics measured simultaneously by near-infrared spectroscopy and 19F magnetic resonance imaging in rats

Tumour oxygen dynamics measured simultaneously by near-infra...

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作者： Xia, Mengna Kodibagkar, Vikram Liu, Hanli Mason, Ralph P. Joint Biomedical Engineering Graduate Program University of Texas at Arlington University of Texas Southwestern Medical Center Dallas TX 76019 United States Cancer Imaging Program Department of Radiology University of Texas Southwestern Medical Center Dallas TX 75390 United States

Simultaneous near-infrared spectroscopy (NIRS) and magnetic resonance imaging (MRI) were used to investigate the correlation between tumour vascular oxygenation and tissue oxygen tension dynamics in rat breast 13762NF tumours with respect to hyperoxic gas breathing. NIRS directly detected global variations in the oxygenated haemoglobin concentration (Δ[HbO 2]) within tumours and oxygen tension (pO2) maps were achieved using 19F MRI of the reporter molecule hexafluorobenzene. Multiple correlations were examined between rates and magnitudes of vascular (Δ[HbO2]) and tissue (pO2) responses. Significant correlations were found between response to oxygen and carbogen breathing using either modality. Comparison of results for the two methods showed a correlation between the vascular perfusion rate ratio and the mean pO2 values (R2 > 0.7). The initial rates of increase of Δ[HbO 2] and the slope of dynamic pO2 response, d(pO 2)/dt, of well-oxygenated voxels in response to hyperoxic challenge were also correlated. These results demonstrate the feasibility of simultaneous measurements using NIRS and MRI. As expected, the rate of pO2 response to oxygen is primarily dependent upon the well perfused rather than poorly perfused vasculature. © 2006 IOP Publishing Ltd.

关键词： Tumors

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Acute effects of combreatastatin A4 phosphate on breast tumor hemodynamics monitored by near infrared spectroscopy

Acute effects of combreatastatin A4 phosphate on breast tumo...

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biomedical Topical Meeting, BIO 2006

作者： Kim, Jae G. Liu, Hanli Zhao, Dawen Mason, Ralph P. Joint Program in Biomedical Engineering University of Texas Southwestern Medical Center at Dallas University of Texas at Arlington Arlington TX 76019 United States Advanced Radiological Science Program Department of Radiology University of Texas Southwestern Medical Center at Dallas Dallas TX 75390 United States

ISBN: (纸本)1557528071

关键词： Infrared devices

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Application of near infrared spectroscopy to study hot flashes in women

Application of near infrared spectroscopy to study hot flash...

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biomedical Topical Meeting, BIO 2006

作者： Sharma, Vikrant Raman, Pradheep Liu, Hanli Ratka, Anna Joint Program in Biomedical Engineering University of Texas Southwestern Medical Center Dallas and University of Texas at Arlington Arlington TX 76019 United States Department of Pharmacology and Neuroscience University of North Texas Health Science Center Fort Worth TX 76107 United States

We introduce a novel application of near infrared spectroscopy (NIRS) to study hot flashes, the most reported symptom of menopausal transition. A three-wavelength, continuous wave NIRS system was developed for this ap... 详细信息

ISBN: (纸本)1557528071

关键词： Near infrared spectroscopy

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Resolution of optical microscope redefined

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Biophotonics International 2006年第7期13卷 42-45页

作者： Ram, Sripad Ward, E. Sally Ober, Raimund J. Joint Biomedical Engineering Graduate Program University of Texas Arlington University of Texas Southwestern Medical Center Dallas Center for Immunology Southwestern Medical Center Department of Electrical Engineering University of Texas Dallas Center for Immunology

A resolution measure that overcomes the limitations of Rayleigh's criterion was proposed that predicted the resolution of an optical microscope was not limited and that it can be improved by increasing the number of detected photons. An interdisciplinary approach was used to obtain the new resolution measure in which tools of advanced statistical image processing address a classical problem in optical microscopy. Single-molecule imaging experiments have verified that distances between single molecules that are well below Rayleigh's criterion can be measured with an accuracy in accordance with that prediction. An analytical expression for the fundamental resolution measure (FREM) was obtained by assuming imaging conditions analogous to those of Rayleigh's criterion. The proposed resolution measure shows that certain single-molecule experiments can be performed that were once unfeasible with optical microscope.

关键词： Optical microscopy

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Efficacy of Using Mean Arterial Blood Pressure Sequence for Three-Element Windkessel Model Estimation

Efficacy of Using Mean Arterial Blood Pressure Sequence for ...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： Piyush Gehalot Rong Zhang Aby Mathew Khosrow Behbehani Joint Biomedical Engineering Program University of Texas Southwestern Medical Center Dallas TX USA Institute for Exercise and Environmental Medicine University of Texas Southwestern Medical Center Dallas USA

The three-element Windkessel model is widely used and accepted for analyzing blood flow and pressure in arterial system and cerebral circulation. In most studies, changes in mean arterial blood pressure data is used as input to estimate the model parameters. However, estimation of linear model parameters, using input-output data, requires that the input be persistently exciting. This study examined the efficacy of using mean arterial blood pressure (MABP) sequence as an input stimulus for estimating the parameters of the three-element Windkessel model. Additionally, the study explored the use of a shorter MABP data segment of 1.5 mm as compared to the commonly used 6 mm data. MABP data was obtained from 11 healthy subjects. One thousand three-element Windkessel models, with parameter values randomly selected to be within physiological range, were subjected to seven different input sequences. For each input sequence and model, the values of the model (target-parameters) were estimated. The seven input sequence were: 1) six minutes of MABP measured from subjects; 2-5) four 1.5 mm of measured MABP obtained by dividing the measured six minutes of MABP into non- overlapping contiguous segments; 6) a six-minutes of pseudo random binary sequence (PRBS) with amplitudes comparable to the MABP sequence; and 7) a 1.5 mm of PRBS sequence with amplitudes comparable to the MABP sequence. The MABP data used was randomly selected from the 11 subjects for each estimation run. The model parameter estimation method had two phases of optimization. In the first phase, the parameters were estimated and optimized using the frequency transform of the input and output. In the second phase, the values of the estimated parameters were used as initial estimates and time-domain optimization was carried out to further refine the estimates. Results from the study, comparing the estimated-parameters with the target-parameters, show that for the MABP data, there was no significant difference betwee

关键词： Arterial blood pressure Parameter estimation Frequency estimation Phase estimation biomedical measurements Time domain analysis USA Councils Blood flow Circuits Frequency measurement

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Classification of Cheyne Stokes Breathing and Obstructive Sleep Apnea Using ECG

Classification of Cheyne Stokes Breathing and Obstructive Sl...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： Sanjee R. Suhas Sridhar Vijendra John R. Burk Edgar A. Lucas Khosrow Behbehani University of Texas Southwestern Medical Center Dallas USA Joint Biomedical Engineering Program University of Texas Arlington USA Sleep Consultants Inc. Fort Worth Texas.

High cost of diagnostic studies to detect sleep disordered breathing and lack of availability of certified sleep laboratories in all inhabited areas make investigation of alternative methods of detecting sleep disordered breathing attractive. This study aimed to explore the possibility of discerning obstructive sleep apnea (OSA) from Cheyne-Stokes respiration (CSR) using overnight electrocardiography (ECG). Polysomnographic and ECG signals were acquired from the 13 OSA and 7 CSR volunteer subjects. Two signals: R-Wave Attenuation (RWA) and Heart Rate Variability (HRV) series were derived from the ECG. Using frequency domain analysis, various frequency bands in the power spectrum of RWA and HRV signals were identified that showed sensitivity to OSA and CSR events. A three-stage algorithm was developed to detect and differentiate OSA events from CSR events using RWA and HRV analysis. To test the algorithm, the ECG data was divided into fifteen minute epochs for analysis. Seventy two epochs containing OSA and 72 with CSR events were selected. 48 OSA clips and 48 CSR clips were randomly selected to form the training set. The remaining 24 clips in each category formed the test set. This method produced an average sensitivity of 95.83% and specificity of 79.16% in the training set and sensitivity of 87.5% and a specificity of 75% in the test set

关键词： Sleep apnea Electrocardiography Heart rate variability Testing Frequency domain analysis Algorithm design and analysis Costs Availability Laboratories Attenuation

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A stochastic analysis of performance limits for optical microscopes

A stochastic analysis of performance limits for optical micr...

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作者： Ram, Sripad Ward, E. Sally Center for Immunology NB9.106 University of Texas Southwestern Medical Center at Dallas 6000 Harry Hines Boulevard Dallas TX 75390-8576 United States Joint Biomedical Engineering Graduate Program University of Texas at Arlington University of Texas Southwestern Medical Center Dallas IEEE SPIE Biophysical Society Department of Microbiology Cancer Immunobiology Center University of Texas Southwestern Medical Center Dallas

The optical microscope is a powerful instrument for observing cellular events. Recently, the increased use of microscopy in quantitative biological research, including single molecule microscopy, has generated significant interest in determining the performance limits of an optical microscope. Here, we formulate this problem in the context of a parameter estimation approach in which the acquired imaging data is modeled as a spatio-temporal stochastic process. We derive formulations of the Fisher information matrix for models that allow both stationary and moving objects. The effects of background signal, detector size, pixelation and noise sources are also considered. Further, formulations are given that allow the study of defocused objects. Applications are discussed for the special case of the estimation of the location of objects, especially single molecules. Specific emphasis is placed on the derivation of conditions that guarantee block diagonal or diagonal Fisher information matrices.

关键词： Optical microscopy

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Cytotoxic T cell recognition of allelic variants of HLA B35 bound to an Epstein-Barr virus epitope: influence of peptide conformation and TCR-peptide interaction

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European Journal of Immunology 2006年第5期29卷

作者： Rajiv Khanna Sharon L. Silins Zhiping Weng David Gatchell Scott R. Burrows Leanne Cooper Tumour Immunology Laboratory EBV Unit Queensland Institute of Medical Research and Joint Oncology Program University of Queensland Brisbane Australia Department of Biomedical Engineering Boston University College of Engineering Boston USA

Fine specificity analysis of HLA B35-restricted Epstein-Barr virus (EBV)-specific cytotoxic T lymphocyte (CTL) clones revealed a unique heterogeneity whereby one group of these clones cross-recognized an EBV epitope (YPLHEQHGM) on virus-infected cells expressing either HLA B*3501 or HLA B*3503, while another group cross-recognized this epitope in association with either HLA B*3502 or HLA B*3503. Peptide binding and titration studies ruled out the possibility that these differences were due to variation in the efficiency of peptide presentation by the HLA B35 alleles. Sequence analysis of the TCR genetic elements showed that these clonotypes either expressed BV12/AV3 or BV14/ADV17S1 heterodimers. Interestingly, CTL analysis with monosubstituted alanine mutants of the YPLHEQHGM epitope indicated that the BV12/AV3 + clones preferentially recognized residues towards the C terminus of the peptide, while the BV14/ADV17S1 + clones interacted with residues towards N terminus of the peptide. Molecular modelling of the MHC-peptide complexes suggests that the differences in two floor positions (114 and 116) of the HLA B35 alleles dictate different conformations of the peptide residues L3 and/or H7 and directly contribute in the discerning allele-specific immune recognition by the CTL clonotypes. These results provide evidence for a critical role for the selective interaction of the TCR with specific residues within the peptide epitope in the fine specificity of CTL recognition of allelic variants of an HLA molecule.

关键词： Virus Cytotoxic T lymphocyte HLA allele Peptide TCR

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Triphasic force dependence of dissociation kinetics of E-selectin/ligand interaction

Triphasic force dependence of dissociation kinetics of E-sel...

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2005 Summer Bioengineering Conference

作者： Wayman, Annica M. McEver, Rodger P. Zhu, Cheng Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta GA 30332-0363 United States Joint Emory/Georgia Tech Coulter School of Biomedical Engineering Georgia Institute of Technology Atlanta GA 30332-0363 United States Cardiovascular Biology Research Program Oklahoma Medical Research Foundation University of Oklahoma Health Sciences Center Oklahoma City OK 73104 United States

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