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Multimodality imaging systems combining optical techniques with MRI/CT provide high-resolution functional characterization of tissue by imaging molecular and vascular biomarkers. To optimize these hybrid systems for clinical use, faster and automatable algorithms are required for 3-D imaging. Towards this end, a boundary element model was used to incorporate tissue boundaries from MRI/CT into image...
X-ray fluoroscopy is widely used for intra-operative dosimetry in prostate brachytherapy. Three-dimensional locations of the implanted radioactive seeds can be calculated from multiple X-ray images upon resolving the correspondence of seeds. This is usually modeled as an assignment problem that is NP-hard. We propose an algorithm that allows us to derive an equivalent problem of reduced dimensionality...
Reliable feature tracking is important for accurate tissue deformation recovery, 3D anatomical registration and navigation in computer assisted minimally invasive surgical procedures. Despite a wide range of feature detectors developed in the computer vision community, direct application of these approaches to surgical navigation has shown significant difficulties due to the paucity of reliable feature...
Accurate physically based biomechanical modelling of tissue deformation is important to surgical simulation and image guided intervention. Achieving real-time performance whilst maintaining relatively accurate simulation result has been a challenging problem to resolve. The purpose of this paper is to describe a novel yet practical image constrained finite element modelling framework for real-time...
Regulatory actions through 2007-2008 demonstrate FDA's response to multiple reports of sudden death and severe cardiopulmonary reactions temporally related to the administration of Ultrasound Contrast Agents (UCA). Certain animal data showed similar adverse effects at a clinically relevant dose. The products labels were changed to include the boxed warning encouraging healthcare providers to assess...
The helical arrangement of cardiac myofibers is responsible for equalizing myofiber strain and maximizing the ejection fraction in a normal heart. In one form of chronic heart failure (CHF) known as dilated cardiomyopathy (DCM), the heart dilates, wall stress is increased, and ventricular pump function is reduced. We investigated whether myofiber orientation is altered in DCM by quantifying fiber...
Recently various mathematical models have been proposed to model the signal attenuation obtained from Diffusion Weighted Magnetic Resonance Imaging (DW-MRI). Though effective to various extents, almost all of the existing methods involve model parameters which are abstract mathematical quantities without any tangible connection to physical quantities (e.g. the b-value, gradient pulse duration, pulse...
We investigate the use of anatomical priors in a Bayesian framework for diffusion tractography. We compare priors that utilize different types of information on the white-matter pathways to be reconstructed. This information includes manually labeled paths from a set of training subjects and anatomical segmentation labels obtained from T1-weighted MR images of the same subjects. Our results indicate...
MRI techniques for tissue motion and strain quantifications have limited resolution because of interference from the conjugate echo or spectral peak in Fourier space. Methods have been proposed to remove this interference in order to improve resolution; however, these methods are clinically impractical due to long image acquisition time. In this paper, we propose TruHARP, an MRI motion and strain...
Dynamic cardiac metrics, including myocardial strains and displacements, provide a quantitative approach to evaluate cardiac function. However, in current clinical diagnosis, largely 2D strain measures are used despite that cardiac motions are complex 3D volumes over time. Recent advances in 4D ultrasound enable the capability to capture such complex motion in a single image data set. In our previous...
Sliding effects often occur along tissue/organ boundaries. For instance, it is widely observed that the lung and diaphragm slide against the rib cage and the atria during breathing. Conventional homogeneous smooth registration methods fail to address this issue. Some recent studies preserve motion discontinuities by either using joint registration/segmentation or utilizing robust regularization energy...
Positron emission tomography (PET) is a molecular imaging technique which is now widely established as a powerful tool for diagnosing a variety of cancers. However, PET images are substantially degraded by respiratory motion to the extent that this may adversely impact upon subsequent diagnosis and patient management. A spatio-temporal image registration algorithm is proposed to align the moving images...
We propose a new EEG source localization method that simultaneously performs source and forward model reconstruction (SOFOMORE) in a hierarchical Bayesian framework. Reconstruction of the forward model is motivated by the many uncertainties involved in the forward model, including the representation of the cortical surface, conductivity distribution, and electrode positions. We demonstrate in both...
Recently, we generalized the Delta-Eddington phase function and applied it to the radiative transfer equation for modeling the photon propagation in biological tissue. The resultant phase approximation model was shown to be highly accurate with a wide range of optical properties, including the strongly absorbing and weakly scattering media. In this paper, we propose phase-approximation-based method...
In this work, a nonconvex Compressive Sensing model targeted at true 3D reconstructions of highly undersampled MR angiograms acquired with parallel imaging is proposed. When combined with the Max-CAPR acquisition sequence, it is demonstrated that high quality, non-view-shared, 3D images of the contrast-filled neurovasculature can be acquired (at acceleration factors exceeding the number of coils)...
Although iterative reconstruction techniques (IRTs) have been shown to produce images of superior quality over conventional filtered back projection (FBP) based algorithms, the use of IRT in a clinical setting has been hampered by the significant computational demands of these algorithms. In this paper we present results of our efforts to overcome this hurdle by exploiting the combined computational...
Echo planar imaging (EPI) is a widely used rapid MRI technique to image dynamic neurological functionally, but can suffer from Nyquist ghosts and distortions due to magnetic field inhomogeneity. Distortion effects can be reduced by parallel MR imaging (pMRI), via a reduced echo train length, and/or methods that measure and estimate magnetic field distortions using multiple TEs. Recent Nyquist ghost...
Here, we used both the neuromagnetic (MEG) and the hemodynamic (fMRI) measures to visualize the spatiotemporal brain dynamics during 3-D structure perception from 2D motion (3D-SFM). The coherence of the random-dot motion stimuli was parametrically controlled to infer the changes of the brain dynamics corresponding to different 3-D percepts. The results of the fMRI analysis were used to impose plausible...
The potential of ultrasound elasticity imaging (USEI) have been shown in numerous medical applications especially in detection and diagnosis of cancer. However, the widespread use of this imaging technique in clinical setups is limited by its dependency to the user expertise. Insufficient skill in freehand palpation of the tissue easily translates into poor quality of the images. In this paper, the...
We propose a novel cerebellum segmentation method for MRI, based on a combination of statistical models of the structure's expected location in the brain and its local appearance. The appearance model is obtained from a k-nearest-neighbor classifier, which uses a set of multi-scale local image descriptors as features. The spatial model is constructed by registering multiple manually annotated datasets...
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