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We have built a four-layer detector to obtain the depth of interaction (DOI) information in which all four layers have a relative offset of a half crystal pitch with each other. The main characteristics of the detector, especially the energy and spatial resolutions, strongly depend on the crystal surface treatments. As a part of the work for the development of an animal PET, we have investigated the...
In this paper, the resolution of the Siemens high resolution research tomograph (HRRT) was centrally (r < 60 mm) homogenous with a FWHM of 1.4 mm for 18F-FDG in air. This was where the main part of the brain is located if the patient has been positioned correctly. The 1.4 mm resolution was obtained using the newly develop 3D-OSEM PSF reconstruction algorithm, which was a significant improvement...
In list-mode acquisition, data is collected as a list of events with different attributes recorded for each event. List-mode reconstruction methods are used in this case. In this paper, we have contributed towards an assessment of resolution properties of list-mode image reconstruction methods, through an investigation of impulse responses, obtained using Local Impulse Response (LIR) function in Penalized-Likelihood...
Positron Emission Tomography (PET) techniques have gained an important role in the diagnosis of human diseases as well as for pharmaceutical and biomedical research. In order to best optimize their capabilities, evaluation of their performance has to be achieved through standardized methodology from specific standards. The aim of this work was to assess the performance evaluation of the microPET R4...
Position Emission Tomography (PET) allows the in-vivo monitoring of functional processes in the body. However its limited spatial resolution induces Partial Volume Effect (PVE), which leads to a loss of signal in tissues of size similar to the Point Spread Function (PSF) of the imaging device and induces activity spillover between adjacent structures with different amounts of activity. The aim of...
Iterative reconstruction (IR) has recently been proposed to improve multiple aspects of image quality over conventional filtered backprojection (FBP) in X-ray computed tomography (CT). FBP reconstruction and its corresponding reconstruction kernels have been optimized for decades to provide the best possible image quality. IR does not have the notion of reconstruction kernels but uses other mechanisms...
A point source was used to sample the point spread function (PSF) at over 6000 locations within the field of view (FOV) of a General Electric Discovery ST PET scanner (DST) in 2D high sensitivity acquisition mode. These measurements were used to optimize the derivation of a system matrix for the DST. We found for 2D acquisition mode that a system matrix using a PSF with radial, depth, axial, and azimuthal...
For circular cone-beam CT often one scan covers not the complete z-range of interest. If this is the case two or more circle scans are made. These sequence scans are typically reconstructed by separately reconstructing each circle scan followed by combining the resulting partial volumes. This image-based concatenation method uses only those data that are needed for each partial volume, the contribution...
We have evaluated the coincidence imaging performance of a monolithic detector block design for a human brain PET scanner by implementing a demonstrator based on two detector blocks. Each detector is composed of a monolithic LYSO:Ce scintillator coupled to a pair of Hamamatsu S8550-02 APD arrays with custom ASIC readout electronics. Results show that this design is suitable for our application and...
Cross-sectional imaging of an electrical conductivity distribution inside the human body has been an active research topic in the field of impedance imaging. This paper describes the recent progress in magnetic resonance electrical impedance tomography (MREIT) where conductivity imaging with a spatial resolution of a few mm is pursued. After the early studies on its theory and image reconstruction...
A relatively new neuroimaging modality is simultaneous EEG and fMRI. Though such a multi-modal acquisition is attractive given that it can exploit the temporal resolution of EEG and spatial resolution of fMRI, it comes with unique signal processing and pattern classification challenges. In this paper I will review some our work at developing signal processing and pattern recognition for analysis of...
Computational fluid dynamic (CFD) based on patient-specific medical imaging data has found widespread use for visualizing and quantifying hemodynamics in cerebrovascular disease such as cerebral aneurysms or stenotic vessels. This paper focuses on optimizing mesh parameters for CFD simulation of cerebral aneurysms. Valid blood flow simulations strongly depend on the mesh quality. Meshes with a coarse...
Cardiac MRI performed while the patient is breathing is typically achieved using non-real-time techniques such as ECG triggering with respiratory gating; however, modern dynamic imaging techniques are beginning to enable this type of imaging in real-time. One of these dynamic imaging techniques is based on forming a partially separable function (PSF) model of the data, but the model fitting process...
A number of revolutionary techniques have been developed for cardiac electrophysiology research to better study the various arrhythmia mechanisms that can enhance ablating strategies for cardiac arrhythmias. Once the three-dimensional high resolution cardiac optical imaging data is acquired, it is time consuming to manually go through them and try to identify the patterns associated with various arrhythmia...
Traditional imaging techniques for studying the spatial distribution of biological molecules such as proteins, metabolites, and lipids, require the a priori selection of a handful of target molecules. Imaging mass spectrometry provides a means to analyze thousands of molecules at a time within a tissue sample, adding spatial detail to proteomic, metabolomic, and lipidomic studies. Compared to traditional...
The analysis of electromagnetic forward and inverse problems is very important in the process of image reconstruction for magnetoacoustic tomography with magnetic induction (MAT-MI). A new analysis method was introduced in this paper. It breaks through some illogical supposes that the existing methods applied and can improve the spatial resolution of the image availably. Besides it can avoid rotating...
Conventional B-mode imaging in ultrasound consists of displaying the log-compressed envelope of the backscattered signal. While clinical ultrasonic B-mode images have good spatial resolution, i.e., better than a millimeter, the contrast resolution of ultrasonic B-mode images is typically low. However, additional information is contained in the ultrasonic backscattered signal, which can be used to...
Proton magnetic resonance spectroscopic imaging (MRSI) provides spatial information about tissue metabolite concentrations used in differentiating diseased from normal tissue. Obtaining metabolic maps with high spatial resolution requires long acquisition time where the patient has to lie still inside the magnet bore (scanner) especially if classical Chemical Shift Imaging (CSI) is used. To reduce...
Optimal noise control is important for improving image quality and reducing radiation dose in computed tomography. Here we investigated two image space based nonlinear filters for noise reduction: the bilateral filter (BF) and the nonlocal means (NLM) algorithm. Images from both methods were compared against those from a commercially available weighted filtered backprojection (WFBP) method. A standard...
Magnetoacoustic tomography with magnetic induction (MAT-MI) is a recently introduced method for imaging electrical conductivity properties of biological tissue with high spatial resolution close to sonography. In MAT-MI the sample resides in a static magnetic field and a time-varying magnetic stimulation is applied to the sample volume. Through the action of the Lorentz force, the magnetically induced...
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