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Articles 1  13 of 13
FullText Articles in Biomedical Engineering and Bioengineering
RadiotherapyInduced Cherenkov Luminescence Imaging In A Human Body Phantom, Syed Rakin Ahmed, Mengyu Jia, Petr Bruza, Sergei A. Vinogradov, Shudong Jiang, David J. Gladstone, Lesley A. Jarvis, Brian W. Pogue
RadiotherapyInduced Cherenkov Luminescence Imaging In A Human Body Phantom, Syed Rakin Ahmed, Mengyu Jia, Petr Bruza, Sergei A. Vinogradov, Shudong Jiang, David J. Gladstone, Lesley A. Jarvis, Brian W. Pogue
Open Dartmouth: Faculty Open Access Scholarship
Radiation therapy produces Cherenkov optical emission in tissue, and this light can be utilized to activate molecular probes. The feasibility of sensing luminescence from a tissue molecular oxygen sensor from within a human body phantom was examined using the geometry of the axillary lymph node region. Detection of regions down to 30mm deep was feasible with submillimeter spatial resolution with the total quantity of the phosphorescent sensor PtG4 near 1 nanomole. Radiation sheet scanning in an epiillumination geometry provided optimal coverage, and maximum intensity projection images provided illustration of the concept. This work provides the preliminary information needed to attempt ...
Quantifying CrossScatter Contamination In Biplane Fluoroscopy Motion Analysis Systems, Janelle A. Cross, Ben Mchenry, Taly GilatSchmidt
Quantifying CrossScatter Contamination In Biplane Fluoroscopy Motion Analysis Systems, Janelle A. Cross, Ben Mchenry, Taly GilatSchmidt
Biomedical Engineering Faculty Research and Publications
Biplane fluoroscopy is used for dynamic in vivo threedimensional motion analysis of various joints of the body. Crossscatter between the two fluoroscopy systems may limit tracking accuracy. This study measured the magnitude and effects of crossscatter in biplane fluoroscopic images. Four cylindrical phantoms of 4, 6, 8, and 10in. diameter were imaged at varying kVp levels to determine the crossscatter fraction and contrasttonoise ratio (CNR). Monte Carlo simulations quantified the effect of the gantry angle on the crossscatter fraction. A cadaver foot with implanted beads was also imaged. The effect of crossscatter on markerbased tracking accuracy was investigated. Results demonstrated ...
The Effects Of Extending The Spectral Information Acquired By A PhotonCounting Detector For Spectral Ct, Taly Gilat Schmidt, Kevin C. Zimmerman, Emil Y. Sidky
The Effects Of Extending The Spectral Information Acquired By A PhotonCounting Detector For Spectral Ct, Taly Gilat Schmidt, Kevin C. Zimmerman, Emil Y. Sidky
Biomedical Engineering Faculty Research and Publications
Photoncounting xray detectors with pulseheight analysis provide spectral information that may improve material decomposition and contrasttonoise ratio (CNR) in CT images. The number of energy measurements that can be acquired simultaneously on a detector pixel is equal to the number of comparator channels. Some spectral CT designs have a limited number of comparator channels, due to the complexity of readout electronics. The spectral information could be extended by changing the comparator threshold levels over time, sub pixels, or view angle. However, acquiring more energy measurements than comparator channels increases the noise and/or dose, due to differences in noise correlations ...
Sparse Signal Reconstruction From Polychromatic XRay Ct Measurements Via Mass Attenuation Discretization, Renliang Gu, Aleksandar Dogandžić
Sparse Signal Reconstruction From Polychromatic XRay Ct Measurements Via Mass Attenuation Discretization, Renliang Gu, Aleksandar Dogandžić
Electrical and Computer Engineering Publications
We propose a method for reconstructing sparse images from polychromatic xray computed tomography (ct) measurements via mass attenuation coefficient discretization. The material of the inspected object and the incident spectrum are assumed to be unknown. We rewrite the LambertBeer’s law in terms of integral expressions of mass attenuation and discretize the resulting integrals. We then present a penalized constrained leastsquares optimization approach forreconstructing the underlying object from logdomain measurements, where an active set approach is employed to estimate incident energy density parameters and the nonnegativity and sparsity of the image density map are imposed using negativeenergy and smooth ℓ ...
Sparse XRay Ct Image Reconstruction And Blind Beam Hardening Correction Via Mass Attenuation Discretization, Renliang Gu, Aleksandar Dogandžić
Sparse XRay Ct Image Reconstruction And Blind Beam Hardening Correction Via Mass Attenuation Discretization, Renliang Gu, Aleksandar Dogandžić
Electrical and Computer Engineering Conference Papers, Posters and Presentations
We develop a nonlinear sparse Xray computed tomography (CT) image reconstruction method that accounts for beam hardening effects due to polychromatic Xray sources. We adopt the blind scenario where the material of the inspected object and the incident polychromatic source spectrum are unknown and apply mass attenuation discretization of the underlying integral expressions that model the noiseless measurements. Our reconstruction algorithm employs constrained minimization of a penalized leastsquares cost function, where nonnegativity and maximumenergy constraints are imposed on incident spectrum parameters and negativeenergy and smooth ℓ1norm penalty terms are introduced to ensure the nonnegativity and sparsity of the density map ...
Reducing Radiation Dose To The Female Breast During Ct Coronary Angiography: A Simulation Study Comparing Breast Shielding, Angular Tube Current Modulation, Reduced Kv, And Partial Angle Protocols Using An UnknownLocation SignalDetectability Metric, Franco Rupcich, Andreu Badal, Lucretiu M. Popescu, Iacovos Kyprianou, Taly Gilat Schmidt
Reducing Radiation Dose To The Female Breast During Ct Coronary Angiography: A Simulation Study Comparing Breast Shielding, Angular Tube Current Modulation, Reduced Kv, And Partial Angle Protocols Using An UnknownLocation SignalDetectability Metric, Franco Rupcich, Andreu Badal, Lucretiu M. Popescu, Iacovos Kyprianou, Taly Gilat Schmidt
Biomedical Engineering Faculty Research and Publications
Purpose:
The authors compared the performance of five protocols intended to reduce dose to the breast during computed tomography (CT) coronary angiography scans using a model observer unknownlocation signaldetectability metric.
Methods:
The authors simulated CT images of an anthropomorphic female thorax phantom for a 120 kV reference protocol and five “dose reduction” protocols intended to reduce dose to the breast: 120 kV partial angle (posteriorly centered), 120 kV tubecurrent modulated (TCM), 120 kV with shielded breasts, 80 kV, and 80 kV partial angle (posteriorly centered). Two image quality tasks were investigated: the detection and localization of 4mm, 3.25 mg ...
Beam Hardening Correction Via Mass Attenuation Discretization, Renliang Gu, Aleksandar Dogandžić
Beam Hardening Correction Via Mass Attenuation Discretization, Renliang Gu, Aleksandar Dogandžić
Electrical and Computer Engineering Conference Papers, Posters and Presentations
We develop a beamhardening correction method for polychromatic xray computed tomography (ct) reconstruction based on mass attenuation coefficient discretization. We assume that the inspected object consists of an unknown single material and that the incident xray spectrum is unknown. In this case, the standard photonenergy discretization of the Beer’s law measurement equation leads to an excessive number of unknown parameters and scaling ambiguity. To obtain a parsimonious measurement model parametrization, we first rewrite the measurement equation in terms of integral expressions of the mass attenuation rather than photon energy. The resulting integrals can be discretized easily thanks to the ...
Propagation Of Ultrasound Through Freshly Excised Human Calvarium, Armando Garcia Noguera
Propagation Of Ultrasound Through Freshly Excised Human Calvarium, Armando Garcia Noguera
Engineering Mechanics Dissertations & Theses
The propagation of ultrasound through complex biological media, such as the human calvarium, poses a great challenge for modern medicine. Several ultrasonic techniques commonly used for treatment and diagnosis in most of the human body are still difficult to apply to the human brain, in part, because of the properties of the skull. Moreover, an understanding of the biomechanics of transcranial ultrasound may provide needed insight into the problem of blast wave induced traumatic brain injury (TBI). In the present study, the spatial variability of ultrasonic properties was evaluated for relevant frequencies of 0.5, 1, and 2.25 MHz ...
Energy Deposition In The Breast During Ct Scanning: Quantification And Implications For Dose Reduction, Franco Rupcich, Iacovos Kyprianou, Andreu Badal, Taly Gilat Schmidt
Energy Deposition In The Breast During Ct Scanning: Quantification And Implications For Dose Reduction, Franco Rupcich, Iacovos Kyprianou, Andreu Badal, Taly Gilat Schmidt
Biomedical Engineering Faculty Research and Publications
Studies suggest that dose to the breast leads to a higher lifetime attributable cancer incidence risk from a chest CT scan for women compared to men. Numerous methods have been proposed for reducing dose to the breast during CT scanning, including bismuth shielding, tube current modulation, partialangular scanning, and reduced kVp. These methods differ in how they alter the spectrum and fluence across projection angle. This study used Monte Carlo CT simulations of a voxelized female phantom to investigate the energy (dose) deposition in the breast as a function of both photon energy and projection angle. The resulting dose deposition ...
Sparse XRay Ct Image Reconstruction Using Ecme Hard Thresholding Methods, Kun Qiu, Aleksandar Dogandžić
Sparse XRay Ct Image Reconstruction Using Ecme Hard Thresholding Methods, Kun Qiu, Aleksandar Dogandžić
Electrical and Computer Engineering Publications
We apply expectation‐conditional maximization either (ECME) hard thresholding algorithms to X‐ray computed tomography (CT) reconstruction, where we implement the sampling operator using the nonuniform fast Fourier transform (NUFFT). The measurements follow an underdetermined linear model, where the regression‐coefficient vector is a sum of an unknown deterministic sparse signal component and a zero‐mean white Gaussian component with an unknown variance. Our ECME schemes aim at maximizing this model’s likelihood function with respect to the sparse signal and variance of the random signal component. These schemes exploit signal sparsity in the discrete wavelet transform (DWT) domain and ...
Statistical Hypothesis Testing For Postreconstructed And Postregistered Medical Images, Eugene Demidenko
Statistical Hypothesis Testing For Postreconstructed And Postregistered Medical Images, Eugene Demidenko
Open Dartmouth: Faculty Open Access Scholarship
Postreconstructed and postregistered medical images are typically treated as the raw data, implicitly assuming that those operations are error free. We question this assumption and explore how the precision of reconstruction and affine registration can be assessed by the image covariance matrix and confidence interval, called the confidence eigenimage, using a statistical modelbased approach. Various hypotheses may be tested after image reconstruction and registration using classical statistical hypothesis testing vehicles: Is there a statistically significant difference between images? Does the intensity at a specific location or area of interest belong to the “normal” range? Is there a tumor? Does the ...
QuasiExact Helical Cone Beam Reconstruction For Micro Ct, Jicun Hu, Robert C. Molthen, Roger Johnson, Steven Haworth, Christopher Dawson
QuasiExact Helical Cone Beam Reconstruction For Micro Ct, Jicun Hu, Robert C. Molthen, Roger Johnson, Steven Haworth, Christopher Dawson
Biomedical Engineering Faculty Research and Publications
A cone beam microCT system is set up to collect truncated helical cone beam data. This system includes a microfocal Xray source, a precision computercontrolled XYZtheta stage, and an imageintensifier coupled to a large format CCD detector. The helical scanning mode is implemented by rotating and translating the stage while keeping Xray source and detector stationary. A chunk of bone and a mouse leg are scanned and quasiexact reconstruction is performed using the approach proposed in J. Hu et al. (2001). This approach introduced the original idea of accessory paths with upper and lower virtual detectors having infinite axial extent ...
Pulmonary Arterial Remodeling Revealed By Microfocal XRay Tomography, Kelly L. Karau, Robert C. Molthen, Anita H. Dhyani, Steven Thomas Haworth, Christopher A. Dawson
Pulmonary Arterial Remodeling Revealed By Microfocal XRay Tomography, Kelly L. Karau, Robert C. Molthen, Anita H. Dhyani, Steven Thomas Haworth, Christopher A. Dawson
Biomedical Engineering Faculty Research and Publications
Animal models and microCT imaging are useful for understanding the functional consequences of, and identifying the genes involved in, the remodeling of vascular structures that accompanies pulmonary vascular disease. Using a microCT scanner to image contrastenhanced arteries in excised lungs from fawn hooded rats (a strain genetically susceptible to hypoxia induced pulmonary hypertension), we found that portions of the pulmonary arterial tree downstream from a given diameter were morphometrically indistinguishable. This 'selfconsistency' property provided a means for summarizing the pulmonary arterial tree architecture and mechanical properties using a parameter vector obtained from measurements of the contiguous set of vessel segments ...