Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 16 of 16 for “"Fan Beam"”.
-
Area Based Fan Beam Projection Model for Computed Tomography
… approach is used instead. In addition emitter beam shapes affect the reconstruction effectiveness and data collection efficiency, with the two main types of beam choice for 2-D scanning being fan beam and parallel beam. Fan beam scanning offers some advantages over parallel beam, such as faster …
-
Development of X-ray Fan Beam Coded Aperture Diffraction Imaging for Improving Breast Cancer Diagnostics
… transfer (q) resolution of 0.02 Å-1. An X-ray fan beam was used to collect a 15 cm line of XRD measurements in a single snapshot, while a coded aperture is placed between imaged objects and detector, enabling XRD spectra for individual pixels along the fan beam extent to be recovered from the …
-
Comparison of Cone-Beam Computed Tomography (CBCT), Fan-Beam Computed Tomography (FBCT), and Low-Field Magnetic Resonance Imaging (MRI) for Detection of Equine Fetlock Lesions
… presented in this thesis was to compare cone-beam CT (CBCT), 64-slice fan-beam CT (FBCT), and low-field (0.27 Tesla) MRI for detection of equine fetlock lesions. The first part of the work compared imaging diagnosis and measurement of third metacarpal/metatarsal parasagittal groove and …
-
A Methodology for the Design of Spaceborne Pencil-Beam Scatterometer Systems
… two decades. These previous systems have been "fan-beam" scatterometers, where multiple antennas placed in fixed positions are used. The fan-beam scatterometer approach, however, has disadvantages which limit its utility for future missions. An alternate approach, the conically-scanning …
-
Development of Spect and Ct Tomographic Image Reconstruction
… voxel-based system matrix in parallel-beam, fan-beam, and cone-beam collimator geometries while modeling the process of attenuation, system resolution and sensitivity. This is achieved by casting rays through a volume of voxels and using ray-voxel intersection lengths to determine …
-
Algorithms for Tomographic Reconstruction: Fast Back Projection and Cardiac Computed Tomography
… of a movie of the moving heart from fan-beam tomographic projections. We consider the problem within a state-space framework and present a reconstruction algorithm based on the ensemble Kalman filter. The algorithm reconstructs a movie of the moving heart that is free of the motion …
-
Standards in clinical dual energy x-ray absorptiometry
… The original technology was based on a pencil beam x-ray source but later systems use a fan beam. Additional functionality includes measurement of hand BMD and vertebral fracture assessment (VFA). Smaller devices have also been developed to measure BMD at peripheral sites in the body. As the …
-
Synthetic aperture sonar for sub bottom imaging
… of synthetic apertures realises a narrow fan beam. By directing this beam out sideways, a more rapid survey rate is possible than that achieved by the normal echo-sounding mode used in sub-bottom profiling. The synthetic aperture technique appears to offer significant advantages over that …
-
Distortion Correction in LODOX StatScan X-Ray Images
… based correction method. It takes multiple fan beam x-ray projections and uses them to create a single virtual parallel beam x-ray image suitable for making accurate measurements with.
-
Geometry of cone-beam reconstruction
… we use to unify all existing analytical cone-beam reconstruction methods. These reconstructions are based on formulae derived by Tuy [Tuy, 1983], Smith [Smith, 1985] and Grangeat [Grangeat, 1991] which explicitly link the cone-beam data to some intermediate functions in the Radon transform …
-
Design and performance of a compact high-energy computed tomography system for the study of metal solidification
… photons were emitted from a 2-mm spot in a 320 fan-beam configuration. A 128-channel detector system, placed on an arc 84.5 cm away from the source, performed x-ray attenuation measurements. Channels consisted of 1.8 mm wide cadmium tungstate scintillation crystals coupled to photodiodes. …
-
A Field-Wise Retrieval Algorithm for SeaWinds
… in that it employs a rotating pencil-beam antenna as opposed to fixed fan-beam antennas. The scanning beam provides greater coverage but causes the wind retrieval accuracy to vary across the swath. This thesis develops a filed-wise wind retrieval algorithm to improve the overall wind …
-
Algebraic Reconstruction Methods for Complex Geometry Components
… of acquisition and reconstruction of Cone Beam CT (CBCT) data utilising reconstruction algorithms such as the FDK, which are mathematically based on traditional FBP. While these algorithms are computationally efficient, limitations in the acquisition make inspection of large complex …
-
An experimental and theoretical approach to correct for the scattered radiation in an X-ray computer tomography system for industrial applications
The main problem connected to cone beam computed tomography (CT) systems for industrial applications employing 450 kV X-ray tubes is the high amount of scattered radiation which is added to the primary radiation (signal). This stray radiation leads to a significant degradation of the image quality. …
-
Applications of cone beam computed tomography in radiotherapy treatment planning.
… of 2D planar imaging, fluoroscopy and 3D Cone Beam Computed Tomography (CBCT) imaging. With CBCT imaging, the treatment plan can be modified based on patient’s anatomy just before the treatment session. This method of Adaptive Radiotherapy (ART) helps in managing a patient’s treatment by …