VTechWorks Repository :: Browsing by Author "Wang, Ge"

Browsing by Author "Wang, Ge"

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Advanced Projection Ultrasound Imaging with CMOS-based Sensor Array: Development, Characterization, and Potential Medical Applications
Liu, Chu Chuan (Virginia Tech, 2009-12-17)
Since early 1960s, ultrasound has become one of the most widely used medical imaging device as a diagnostic tool or an image guider for surgical intervention because of its high portability, non-ionization, non-invasiveness and low cost. Although continuous improvements in commercial equipments have been underway for many years, almost all systems are developed with pulse-echo geometry. In this research, a newly invented ultrasound sensor array was incorporated into the developments of a projection imaging system. Three C-scan prototypes, which included prototypes #1, #2 and an ultrasound mammography system, were constructed. Systematic and Evaluative studies included ultrasound CT, 3-D ultrasound, and multi-modality investigations were also performed. Furthermore, a new analytical method to model ultrasound forward scattering distribution (FSD) was developed by employing a specific annular apparatus. After applying this method, the scattering-corrected C-scan images revealed more detail structures as compared to unprocessed images. This new analytical modelling approach is believed to be effective for most imaging systems operating in projection geometry. In summary, while awaiting additional clinical validation, the C-scan ultrasound prototypes with the state-of-the-art PE-CMOS sensor arrays can provide veritable value and holds real and imminent promise in medical diagnostic imaging. Potential future uses of C-scan ultrasound include but not limit to computerized tomography, biopsy guidance, therapeutic device placing, foreign object detection, pediatric imaging, breast imaging, prostate imaging, human extremities imaging and live animal imaging. With continuous research and development, we believe that C-scan ultrasound has the potential to make a significant impact in the field of medical ultrasound imaging.
Axiomatic Imaging Theory - Formulate with Fairness & Fun
Wang, Ge (2008-06-17)
There are many imaging systems. Their performance characterization is important for all applications. Various definitions are introduced for quantification of image resolution, which is the ability of an imaging system to separate two localized signals. In the nonnegative space, we postulated a set of axioms that a good image resolution measure should satisfy, obtained such an image resolution measure, applied our finding in comparing medical CT scanners, and won a 2004 Herbert M. Stauffer Award. We believe that imaging theory can be unified using the axiomatic approach.
Bioluminescence Imaging Strategies for Tissue Engineering Applications
Lapp, Sarah Julia (Virginia Tech, 2010-04-26)
In vitro differentiation of stem cells in biocompatible scaffolds in a bioreactor is a promising method for creating functional engineered tissue replacements suitable for implantation. Basic studies have shown that mechanical, chemical, and pharmaceutical stimuli enhance biological functionality of the replacement as often defined by parameters such as cell viability, gene expression, and protein accumulation. Most of the assays to evaluate these parameters require damage or destruction of the cell-scaffold construct. Therefore, these methods are not suitable for monitoring the development of a functional tissue replacement in a spatial and temporal manner prior to implantation. Bioluminescence imaging is a technique that has been utilized to monitor cell viability and gene expression in various in vivo applications. However, it has never been applied in an in vitro setting for the specific purpose of evaluating a cell-scaffold construct. This research describes the design of flow perfusion bioreactor system suitable for bioluminescence imaging. In the first experimental chapter, the system was tested using MC3T3-E1 cells transfected with a constitutive bioluminescent reporter. It was found that bioluminescence imaging was possible with this system. In the second experimental chapter, MC3T3-E1 cells transfected with BMP-2 linked bioluminescence reporter were cultured by flow perfusion for a period of 11 days. Bioluminescence was detectable from the cells starting at day 4, while peaking in intensity between days 7 and 9. Further, it was also found that bioluminescence occurred in distinct regions within the scaffold. These results indicate that these strategies may yield information not available with current assays.
Bioluminescence Tomography - Inner-light, Insight from Infrared
Wang, Ge (2008-06-12)
Bioluminescence tomography (BLT) is a molecular imaging modality, which derives a bioluminescent source distribution inside a small animal from external bioluminescent signals. We published the first paper on BLT in 2004 using the modality fusion approach. The introduction of BLT can be compared to the development of x-ray CT based on radiography. Without BLT, bioluminescent imaging is basically qualitative. With BLT, quantitative and 3D analyses become feasible inside a living mouse, which reveal important molecular and cellular information for numerous preclinical applications. *Complimentary film demonstrates 3D analysis of a living mouse with bioluminescent source
Bolus-chasing CT Angiography - Catch the Contrast via Control
Wang, Ge (2008-06-16)
Intravenous injection of contrast media is required to enhance conspicuity of the vasculature, organs and tumors in CT angiography (CTA) for diagnosis of cardiovascular structures, peripheral vessels and solid organs. The overall goal of this project is to develop boluschasing CTA for a wide class of diagnostic applications. This will be achieved by instantaneously reconstructing CT images, dynamically predicting bolus propagation, and adaptively varying scanning pitch from the aortic arch to the feet to allow real-time correction of any significant deviation from the prediction. *Complimentary film demonstrates the solution to resonating the bolus peak and imaging aperture of the CTA angiography function, that is, via real-time peak bolus identification and prediction as well as adaptively moving the patient table.
Cardiac computed tomography methods and systems using fast exact/quasi-exact filtered back projection algorithms
(United States Patent and Trademark Office, 2013-07-09)
The present invention provides systems, methods, and devices for improved computed tomography (CT). More specifically, the present invention includes methods for improved cone-beam computed tomography (CBCT) resolution using improved filtered back projection (FBP) algorithms, which can be used for cardiac tomography and across other tomographic modalities. Embodiments provide methods, systems, and devices for reconstructing an image from projection data provided by a computed tomography scanner using the algorithms disclosed herein to generate an image with improved temporal resolution.
Collimator width Optimization in X-ray Luminescent Computed Tomography
Mishra, Sourav (Virginia Tech, 2013-06-17)
X-ray Luminescent Computed Tomography (XLCT) is a new imaging modality which is under extensive trials at present. The modality works by selective excitation of X-ray sensitive nanophosphors and detecting the optical signal thus generated. This system can be used towards recreating high quality tomographic slices even with low X-ray dose. There have been many studies which have reported successful validation of the underlying philosophy. However, there is still lack of information about optimal settings or combination of imaging parameters, which could yield best outputs. Research groups participating in this area have reported results on basis of dose, signal to noise ratio or resolution only. In this thesis, the candidate has evaluated XLCT taking into consideration noise and resolution in terms of composite indices. Simulations have been performed for various beam widths and noise & resolution metrics deduced. This information has been used in evaluating quality of images on basis of CT Figure of Merit & a modified Wang-Bovik Image Quality index. Simulations indicate the presence of an optimal setting which can be set prior to extensive scans. The conducted study, although focusing on a particular implementation, hopes to establish a paradigm in finding best settings for any XLCT system. Scanning with an optimal setting preconfigured can help in vastly reducing the cost and risks involved with this imaging modality.
Compressed Sensing based Micro-CT Methods and Applications
Sen Sharma, Kriti (Virginia Tech, 2013-06-12)
High-resolution micro computed tomography (micro-CT) offers 3D image resolution of 1 um for non-destructive evaluation of various samples. However, the micro-CT performance is limited by several factors. Primarily, scan time is extremely long, and sample dimension is restricted by the x-ray beam and the detector size. The latter is the cause for the well-known interior problem. Recent advancement in image reconstruction, spurred by the advent of compressed sensing (CS) theory in 2006 and interior tomography theory since 2007, offers great reduction in the number of views and an increment in the volume of samples, while maintaining reconstruction accuracy. Yet, for a number of reasons, traditional filtered back-projection based reconstruction methods remain the de facto standard on all manufactured scanners. This work demonstrates that CS based global and interior reconstruction methods can enhance the imaging capability of micro-CT scanners. First, CS based few-view reconstruction methods have been developed for use with data from a real micro-CT scanner. By achieving high quality few-view reconstruction, the new approach is able to reduce micro-CT scan time to up to 1/8th of the time required by the conventional protocol. Next, two new reconstruction techniques have been developed that allow accurate interior reconstruction using just a limited number of global scout views as additional information. The techniques represent a significant progress relative to the previous methods that assume a fully sampled global scan. Of the two methods, the second method uses CS techniques and does not place any restrictions on scanning geometry. Finally, analytic and iterative reconstruction methods have been developed for enlargement of the field of view for the interior scan with a small detector. The idea is that truncated projections are acquired in an offset detector geometry, and the reconstruction procedure is performed through the use of a weighting function / weighted iteration updates, and projection completion. The CS based reconstruction yields the highest image quality in the numerical simulation. Yet, some limitations of the CS based techniques are observed in case of real data with various imperfect properties. In all the studies, physical micro-CT phantoms have been designed and utilized for performance analysis. Also, important guidelines are suggested for future improvements.
Compressed Sensing Inspired Image Reconstruction from Overlapped Projections
Yang, Lin; Lu, Yang; Wang, Ge (Hindawi, 2010-06-22)
The key idea discussed in this paper is to reconstruct an image from overlapped projections so that the data acquisition process can be shortened while the image quality remains essentially uncompromised. To perform image reconstruction from overlapped projections, the conventional reconstruction approach (e.g., filtered backprojection (FBP) algorithms) cannot be directly used because of two problems. First, overlapped projections represent an imaging system in terms of summed exponentials, which cannot be transformed into a linear form. Second, the overlapped measurement carries less information than the traditional line integrals. To meet these challenges, we propose a compressive sensing-(CS-) based iterative algorithm for reconstruction from overlapped data. This algorithm starts with a good initial guess, relies on adaptive linearization, and minimizes the total variation (TV). Then, we demonstrated the feasibility of this algorithm in numerical tests.
Cone-Beam Composite-Circling Scan and Exact Image Reconstruction for a Quasi-Short Object
Yu, Hengyong; Wang, Ge (Hindawi, 2008-02-03)
Here we propose a cone-beam composite-circling mode to solve the quasi-short object problem, which is to reconstruct a short portion of a long object from longitudinally truncated cone-beam data involving the short object. In contrast to the saddle curve cone-beam scanning, the proposed scanning mode requires that the X-ray focal spot undergoes a circular motion in a plane facing the short object, while the X-ray source is rotated in the gantry main plane. Because of the symmetry of the proposed mechanical rotations and the compatibility with the physiological conditions, this new mode has significant advantages over the saddle curve from perspectives of both engineering implementation and clinical applications. As a feasibility study, a backprojection filtration (BPF) algorithm is developed to reconstruct images from data collected along a composite-circling trajectory. The initial simulation results demonstrate the correctness of the proposed exact reconstruction method and the merits of the proposed mode.
Design and nondestructive imaging of a bioengineered vascular graft endothelium
Whited, Bryce Matthew (Virginia Tech, 2013-02-01)
Cardiovascular disease is currently the leading cause of death in the U.S. that frequently requires bypass surgery using vascular grafts for treatment. Current limitations with fully synthetic grafts have led researchers to bioengineered alternatives that consist of a combination of vascular scaffolds and cells. A major challenge in creating a functional bioengineered vascular graft is development of a confluent endothelium on the lumen that is able to resist detachment under physiologic fluid flow. In addition, methodologies used to assess the growth and maturation of the endothelium in a noninvasive and dynamic manner are severely lacking. Therefore, the overall goal of this research is to advance the field of vascular tissue engineering by 1) creating methodologies to enhance EC adherence to a vascular graft and 2) development of a noninvasive and real-time imaging system capable of assessing the graft endothelium. To achieve these objectives, three separate studies were performed. In the first study, electrospun scaffold fiber diameter and alignment were systematically varied to determine their effect on endothelial cell (EC) morphology and adherence under fluid flow. ECs on uniaxially aligned nanofibers displayed elongated and aligned morphologies leading to higher adherence to the scaffolds under physiologic levels of fluid flow as compared to those on randomly oriented scaffolds. In the second study, a fiber optic based (FOB) imaging system was developed to image fluorescent ECs through a thick electrospun scaffold. Results demonstrated that the FOB imaging system was able to accurately visualize fluorescent ECs in a noninvasive manner through the thick and highly opaque scaffold. In the final study, the FOB imaging system was used to noninvasively quantify vascular graft endothelialization, EC detachment, and apoptosis through the vessel wall with greater imaging penetration depth than two-photon microscopy. Additionally, the FOB method was capable of continuously tracking EC migration and endothelialization of a bioengineered graft in a bioreactor. Overall, these results demonstrate that aligned scaffold topographies enhance EC adherence under fluid flow and the FOB imaging system is a promising tool to monitor endothelium development and response to fluid flow in a manner that has not previously been afforded using conventional imaging methods.
Development and Applications of Interior Tomography - Multi-source Interior Tomography for Ultrafast Performance
Wang, Ge; Ritman, Erik; Ye, Yangbo; Katsevich, Alexander; Yu, Hengyong; Cao, Guohua; Zhou, Otto (2010-04-05)
Conventional tomography allows excellent reconstruction of an object from non-truncated projections. The long-standing interior problem is to reconstruct an interior ROI accurately only from local projection segments. Interior tomography solves the interior problem with practical knowledge such as a known sub-region or a sparsity model using compressive sensing. Advantages of interior tomography include radiation dose reduction (no x-rays go outside an ROI), scattering artifact suppression (no cross-talk from radiation outside the ROI), image quality improvement (with the novel reconstruction approach), large object handling (measurement can be truncated in any direction), and ultrafast imaging performance (with multiple source detector chains tightly integrated targeting the ROI).
Development of Mechanical Optical Clearing Devices for Improved Light Delivery in Optical Diagnostics
Vogt, William C. (Virginia Tech, 2013-09-12)
Biomedical optics is a rapidly expanding field of research focusing on the development of methods to detect, diagnose, and treat disease using light. While there are a myriad of optical systems that have been developed for biological tissue imaging, optical diagnostics, and optical therapeutics, all of these methods suffer severely limited penetration depths due to attenuation of light by tissue constituent chromophores, including cells, water, blood, and protein structures. Tissue optical clearing is a recent area of study within biomedical optics and photonics, where chemical agents have been used to alter tissue optical properties, reducing optical absorption and scattering and enabling light delivery to and collection from deeper tissue regions. However, there are concerns as to the safety and efficacy of these chemical clearing agents in vivo, especially in the skin, where the projective barrier function of the stratum corneum must be removed. Mechanical optical clearing is a recently developed technology which utilizes mechanical loading to reversibly modify light transport through soft tissues, and much of the work published on this technique has focused on applications in skin tissue. This clearing technique enables deeper light delivery into soft tissues but does not require use of exogenous chemicals, nor does it compromise the skin barrier function. While this clearing effect is thought to be resultant from interstitial water and blood transport, the underlying mechanism has not been concretely identified nor characterized. The hypothesis of this body of work was that interstitial transport of tissue chromophores (e.g. water and blood) causes intrinsic optical property changes, reduces tissue optical absorption and scattering, and improves light delivery in diagnostic applications. To test this hypothesis, we first developed a mathematical framework to simulate mechanical optical clearing, using both mechanical finite element models and optical Monte Carlo simulations. By directly simulating interstitial water transport in response to loading, data from mechanical simulations was combined with optical Monte Carlo simulations, which enabled prediction of light transmission measurements made during mechanical indentation experiments. We also investigated changes in optical properties during mechanical indentation using diffuse reflectance spectroscopy. These studies used controlled flat indentation by a fiberoptic probe to dynamically measure intrinsic optical properties as they changed over time. Finally, we apply mechanical optical clearing principles to functional near-infrared spectroscopy for neuroimaging. By building a prototypical mechanical optical clearing device for measuring cerebral hemodynamics, we demonstrated that mechanical optical clearing devices modify measured cerebral hemodynamic signals in human subjects, improving signal quality.
Digital Eversion of a Hollow Structure: An Application in Virtual Colonography
Zhao, Jun; Cao, Liji; Zhuang, Tiange; Wang, Ge (Hindawi, 2008-07-22)
A new methodology is presented for digital eversion of a hollow structure. The digital eversion is advantageous for better visualization of a larger portion of the inner surface with preservation of geometric relationship and without time-consuming navigation. Together with other techniques, digital eversion may help improve screening, diagnosis, surgical planning, and medical education. Two eversion algorithms are proposed and evaluated in numerical simulation to demonstrate the feasibility of the approach.
Digital Spectral Separation Methods And Systems For Bioluminescence Imaging
Wang, Ge; Shen, Haiou; Liu, Y.; Cong, A.; Cong, W. X.; Wang, Y.; Dubey, P. (Optical Society of America, 2008-01-01)
We propose a digital spectral separation (DSS) system and methods to extract spectral information optimally from a weak multispectral signal such as in the bioluminescent imaging (BLI) studies. This system utilizes our newly invented spatially-translated spectral-image mixer (SSM), which consists of dichroic beam splitters, a mirror, and a DSS algorithm. The DSS approach overcomes the shortcomings of the data acquisition scheme used for the current BLI systems. Primarily, using our DSS scheme, spectral information will not be filtered out. Accordingly, truly parallel multi-spectral multi-view acquisition is enabled for the first time to minimize experimental time and optimize data quality. This approach also permits recovery of the bioluminescent signal time course, which is useful to study the kinetics of multiple bioluminescent probes using multi-spectral bioluminescence tomography (MSBT).
Dynamic Non-Destructive Monitoring of Bioengineered Blood Vessel Development within a Bioreactor using Multi-Modality Imaging
Gurjarpadhye, Abhijit Achyut (Virginia Tech, 2013-08-20)
Regenerative medicine involves formation of tissue or organ for replacement of a wounded or dysfunctional tissue. Healthy cells extracted from the patient are expanded and are seeded on a three-dimensional biodegradable scaffold. The structure is then placed in a bioreactor and is provided with nutrients for the cells, which proliferate and migrate throughout the scaffold to eventually form a desired to tissue that can be transplanted into the patient's body. Inability to monitor this complex process of regeneration in real-time makes control and optimization of this process extremely difficult. Histology, the gold standard used for tissue structural assessment, is a static technique that only provides "snapshots" of the progress and requires the specimen to be sacrificed. This inefficiency severely limits our understanding of the biological processes associated with tissue growth during the in vitro pre-conditioning phase. Optical Coherence Tomography (OCT) enables imaging of cross sectional structure in biological tissues by measuring the echo time delay of backreflected light. OCT has recently emerged as an important method to assess the structures of physiological, pathological as well as tissue engineered blood vessels. The goal of the present study is to develop an imaging system for non-destructive monitoring of blood vessels maturing within a bioreactor. Non-destructive structural imaging of tissue-engineered blood vessels cultured in a novel bioreactor was performed using free-space and catheter-based OCT imaging, while monitoring of the endothelium development was performed using a fluorescence imaging system that utilizes a commercial OCT catheter. The project included execution of three specific aims. Firstly, we developed OCT instrumentation to determine geometrical and optical properties of porcine and human skin in real-time. The purpose of the second aim was to assess structural development of tissue-engineered blood vessels maturing in a bioreactor. We constructed a novel quartz-based bioreactor that will permit free space and catheter-based OCT imaging of vascular grafts. The grafts were made of biodegradable PCL-collagen and seeded with multipotent mesenchymal cells. We imaged the maturing grafts over 30 days to assess changes in graft wall thickness. We also monitored change in optical properties of the grafts based on free-space OCT scanning. Finally, in order to visualize the proliferation of endothelial cells and development of the endothelium, we developed an imaging system that utilizes a commercial OCT catheter for single-cell-level imaging of the growing endothelium of a tissue-engineered blood vessel. We have developed two modules of an imaging system for non-destructive monitoring of maturing bioengineered vascular grafts. The first module provides the ability to non-destructively examine the structure of the grafts while the second module can track the progress of endothelialization. As both modules use the same endoscope for imaging, when operated in sequence, they will produce high-resolution, three-dimensional, structural details of the graft and two-dimensional spatial distribution of ECs on the lumen. This non-destructive, multi-modality imaging can be potentially used to monitor and assess the development of luminal bioengineered constructs such as colon or trachea.
Dynamic, Nondestructive Imaging of a Bioengineered Vascular Graft Endothelium
Whited, Bryce M.; Hofmann, Matthias C.; Lu, Peng; Xu, Yong; Rylander, Christopher G.; Wang, Ge; Sapoznik, Etai; Criswell, Tracy; Lee, Sang Jin; Soker, Shay; Rylander, M. Nichole (PLOS, 2013-04-09)
Bioengineering of vascular grafts holds great potential to address the shortcomings associated with autologous and conventional synthetic vascular grafts used for small diameter grafting procedures. Lumen endothelialization of bioengineered vascular grafts is essential to provide an antithrombogenic graft surface to ensure long-term patency after implantation. Conventional methods used to assess endothelialization in vitro typically involve periodic harvesting of the graft for histological sectioning and staining of the lumen. Endpoint testing methods such as these are effective but do not provide real-time information of endothelial cells in their intact microenvironment, rather only a single time point measurement of endothelium development. Therefore, nondestructive methods are needed to provide dynamic information of graft endothelialization and endothelium maturation in vitro. To address this need, we have developed a nondestructive fiber optic based (FOB) imaging method that is capable of dynamic assessment of graft endothelialization without disturbing the graft housed in a bioreactor. In this study we demonstrate the capability of the FOB imaging method to quantify electrospun vascular graft endothelialization, EC detachment, and apoptosis in a nondestructive manner. The electrospun scaffold fiber diameter of the graft lumen was systematically varied and the FOB imaging system was used to noninvasively quantify the affect of topography on graft endothelialization over a 7-day period. Additionally, results demonstrated that the FOB imaging method had a greater imaging penetration depth than that of two-photon microscopy. This imaging method is a powerful tool to optimize vascular grafts and bioreactor conditions in vitro, and can be further adapted to monitor endothelium maturation and response to fluid flow bioreactor preconditioning.
Exact Interior Reconstruction from Truncated Limited-Angle Projection Data
Ye, Yangbo; Yu, Hengyong; Wang, Ge (Hindawi, 2008-05-06)
Using filtered backprojection (FBP) and an analytic continuation approach, we prove that exact interior reconstruction is possible and unique from truncated limited-angle projection data, if we assume a prior knowledge on a subregion or subvolume within an object to be reconstructed. Our results show that (i) the interior region-of-interest (ROI) problem and interior volume-of-interest (VOI) problem can be exactly reconstructed from a limited-angle scan of the ROI/VOI and a 180 degree PI-scan of the subregion or subvolume and (ii) the whole object function can be exactly reconstructed from nontruncated projections from a limited-angle scan. These results improve the classical theory of Hamaker et al. (1980).
Exact Interior Reconstruction with Cone-Beam CT
Ye, Yangbo; Yu, Hengyong; Wang, Ge (Hindawi, 2008-01-23)
Using the backprojection filtration (BPF) and filtered backprojection (FBP) approaches, respectively, we prove that with cone-beam CT the interior problem can be exactly solved by analytic continuation. The prior knowledge we assume is that a volume of interest (VOI) in an object to be reconstructed is known in a subregion of the VOI. Our derivations are based on the so-called generalized PI-segment (chord). The available projection onto convex set (POCS) algorithm and singular value decomposition (SVD) method can be applied to perform the exact interior reconstruction. These results have many implications in the CT field and can be extended to other tomographic modalities, such as SPECT/PET, MRI.
Exact local computed tomography based on compressive sampling
(United States Patent and Trademark Office, 2014-08-19)
A system and method for tomographic image reconstruction using truncated projection data that allows exact interior reconstruction (interior tomography) of a region of interest (ROI) based on the known sparsity models of the ROI, thereby improving image quality while reducing radiation dosage. In addition, the method includes parallel interior tomography using multiple sources beamed at multiple angles through an ROI and that enables higher temporal resolution.

Browsing by Author "Wang, Ge"

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