Submitted in fulfillment of Masters in Radiography, Durban University of Technology, Durban, 2007. / Aim/research questions The aim of the study was to evaluate CT-based treatment planning versus digitised image planning (standard planning technique) for carcinoma of the breast, using the four-field breast technique, in terms of the depth of supraclavicular and axillary nodes, the variability of the breast tissue and the dose inhomogeneity at the matchline. The variability of the depth of supraclavicular and axillary nodes has not been documented in any local or national studies. When simulating patients for treatment, it is evident that the anatomical variability of patient chest wall thickness, shape and size is a contributing factor towards the final treatment plan and dose distribution achieved. Therefore knowing the correct depth of the nodes and being able to clearly demarcate the breast tissue should result in a favourable dose administration. The following questions were addressed:  What is the dose to the supraclavicular nodes from both plans?  What is the dose to the axillary nodes from both plans?  How do the plans differ in terms of dose coverage to the supraclavicular and axillary nodes?  What is the relationship between the depth of the supraclavicular nodes and the patient separation? ii  What is the relationship between the depth of the axillary nodes and the patient separation?  Does the target volume receive adequate dose coverage from the plans?  How is dose to the heart volume affected by target coverage on both plans?  How is dose to the lung volume affected by target coverage on both plans?  What is the dose variability along the matchline?  Are the plans over dosing?  Are the plans under dosing? / M

We present a novel two-dimensional (2D) MAET scanner, with a rotating object of interest and two fixed pairs of electrodes. Such an acquisition scheme, with our novel reconstruction techniques, recovers the boundaries of the regions of constant conductivity uniformly well, regardless of their orientation. We also present a general image reconstruction algorithm for the 2D MAET in a circular chamber with point-like electrodes immersed into the saline surrounding the object. An alternative linearized reconstruction procedure is developed, suitable for recovering the material interfaces (boundaries) when a non-ideal piezoelectric transducer is used for acoustic excitation. The work of the scanner and the linearized reconstruction algorithm is demonstrated using several phantoms made of high-contrast materials and a biological sample.

Electrical capacitance tomography (ECT) is a technology that images the dielectric permittivity distribution of materials under test. ECT has been used as a tool for process monitoring in particular for two-phase flow measurement. These applications mainly focus on the dielectric samples, whose conductivity is negligibly small. This thesis studies ECT imaging with conductivity considerations. The conductive materials will affect the capacitance measurements and introduce difficulties in the ECT image reconstruction. This thesis presents solutions based on ECT to image material of different values of conductivity in different practical process or monitoring scenarios: the conductivity within materials under test is considered to be higher than 10^6 S/m, or less than 10 S/m. This work consists of the following innovative steps. (i) Through an ECT monitoring, floating (i.e., electrically non-grounded) metallic samples are imaged as dielectric illusions and the analysis of capacitance measurements over the conductors is delivered. (ii) Magnetic induction tomography (MIT) is firstly used for locating grounded metallic samples, thereafter as an assistant method to guide ECT to image the dielectric components. (iii) In low conductivity case MIT, as an indicator of conductive material again, helps ECT to solve multiphase flow problems. (iv) The multi-frequency complex ECT measurement provides a potential method to improve the ECT imaging ability for both conductive and dielectric materials. The first three ideas have been testified by both simulated and experimental results, while the fourth part is simulation-based results only on current stage.

In computed tomography (CT) cross-sectional images of the attenuation distribution within a slice are created by scanning radiographic projections of an object with a rotating X-ray source detector compound and subsequent reconstruction of the images from these projection data on a computer. CT can be made very fast by employing a scanned electron beam instead of a mechanically moving X-ray source. Now this principle was extended towards high-energy electron beam tomography with an electrostatic accelerator. Therefore a dedicated experimental campaign was planned and carried out at the Budker Insitute of Nuclear Physics (BINP), Novosibirsk. There we investigated the capabilities of BINP’s accelerators as an electron beam generating and scanning unit of a potential high-energy electron beam tomography device. The setup based on a 1 MeV ELV-6 (BINP) electron accelerator and a single detector. Besides tomographic measurements with different phantoms, further experiments were carried out concerning the focal spot size and repeat accuracy of the electron beam as well as the detector’s response time and signal to noise ratio.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Eric Sandvol. Vita. Includes bibliographical references.

Thesis (M.Tech.: Radiography)-Dept. of Radiography, Durban University of Technology, 2007 xxiv, 142 leaves, Annexures A-L / The aim of the study was to evaluate CT-based treatment planning versus digitised image planning (standard planning technique) for carcinoma of the breast, using the four-field breast technique, in terms of the depth of supraclavicular and axillary nodes, the variability of the breast tissue and the dose inhomogeneity at the matchline.

No description available.

In X-ray computed tomography, motion of the object (breathing, for example) while X-ray projections are acquired for tomographic reconstruction leads to mo- tion artifacts in the reconstructed image. Object motion (such as that of breathing lungs) during acquisition of a computed tomography scan causes artifacts in the reconstructed image due to the reason that the source and detectors require a finite amount of time to rotate around the object while acquiring measurements even as the object is changing with time. With traditional reconstruction algorithms, the object is assumed to be stationary while data is acquired. However, in the case of dynamic tomography, the projection data that is acquired is not consistent, as it is data measured from an object that is deformed at each view angle of measurement. In this work, we propose a method for estimation of general (non-rigid) small motion for dynamic tomography from motion-corrupted projection data. For a static object, the Helgason-Ludwig consistency conditions impose some structure on the moments of the projections. However in the case of dynamic object (result- ing in motion-corrupted projections) this is violated. In the proposed method, we estimate motion parameters of the general motion model from the moments of the dynamic projections. The dynamic object can be modeled as f (g(x, t)) where g is a time-dependent warping function. The non-linear problem of solving a system involving composition of functions is dealt with in the Fourier transform space where it simplifies into a problem involving multiplicatively separable functions. The system is then linearized to solve for object motion. We assume a general basis function in our model. For numerical simulations, we use polynomial and B-spline basis functions as special cases of the basis functions. Simulation is performed by applying known deformations to the Shepp-Logan phantom, to a head slice of the Visible Human phantom and a thorax slice of the Zubal phantom. Simulations are performed for projections generated by parallel- beam and fan-beam geometry. Simulation for fan-beam geometry are performed by rebinning the motion corrupted fan beam projections to parallel beam projections, followed by the proposed motion estimation method. Simulation for the Visible Human phantom and the thorax slice of the Zubal phantom are performed for fan- beam geometry. Poisson noise is also added to the generated dynamic projections before motion estimation is performed. To solve the ill-posed problem of motion estimation by the proposed method, we use a Tikhonov type regularization that involves minimizing an objective function that is the sum of a data discrepancy term, a term that penalizes temporal variation of motion, and another term to penalize large magnitudes of motion. Using the estimated motion, the original image has been reconstructed from the motion corrupted projection data, with the knowledge of the underlying motion which is estimated by the proposed algorithm, by an algebraic technique similar to the dynamic SART algorithm from the literature. Here, a SART-type coefficient matrix is computed using ray tracing with rays whose paths are warped according to the estimated motion. The dynamic image at t = 0 is then reconstructed with using the computed dynamic SART matrix.

In computed tomography (CT) cross-sectional images of the attenuation distribution within a slice are created by scanning radiographic projections of an object with a rotating X-ray source detector compound and subsequent reconstruction of the images from these projection data on a computer. CT can be made very fast by employing a scanned electron beam instead of a mechanically moving X-ray source. Now this principle was extended towards high-energy electron beam tomography with an electrostatic accelerator. Therefore a dedicated experimental campaign was planned and carried out at the Budker Insitute of Nuclear Physics (BINP), Novosibirsk. There we investigated the capabilities of BINP’s accelerators as an electron beam generating and scanning unit of a potential high-energy electron beam tomography device. The setup based on a 1 MeV ELV-6 (BINP) electron accelerator and a single detector. Besides tomographic measurements with different phantoms, further experiments were carried out concerning the focal spot size and repeat accuracy of the electron beam as well as the detector’s response time and signal to noise ratio.

Dissertation