OF DOCTORAL DISSERTATION AALTO UNIVERSITY SCHOOL OF SCIENCE AND TECHNOLOGY P.O. BOX 11000, FI-00076 AALTO http://www.aalto.fi Author Ville Renvall Name of the dissertation Studying functional magnetic resonance imaging with artificial imaging objects Manuscript submitted 19.1.2010 Manuscript revised 9.3.2010 Date of the defence 24.3.2010 Monograph Article dissertation (summary + original articl...

introduction: in diagnostic and therapeutic procedures, dosimetric studies are performed on the dosimetric systems in order to comply the radiation safety standards. monte carlo methods are used due to the high complexity and cost of patient-specific phantom construction. the high complexity of the digitized phantoms greatly increases the time and computational task of the monte carlo calculati...

GENERALIZED SCALE: THEORY, ALGORITHMS, AND APPLICATIONS IN IMAGE ANALYSIS Anant Madabhushi Supervisor: Jayaram K. Udupa Magnetic Resonance (MR) Imaging (MRI) is a non-invasive method for imaging the human body and has revolutionized medical imaging. MR image processing, particularly segmentation, and analysis are used extensively in medical and clinical research for advancing our understanding ...

The ability of the analytic anisotropic algorithm (AAA), a superposition- convolution algorithm implemented in the Eclipse (Varian Medical Systems, Palo Alto, CA) treatment planning system (TPS), to accurately account for the presence of inhomogeneities in simple geometries is examined. The goal of 2% accuracy, as set out by the American Association of Physicists in Medicine Task Group 65, serv...

Signals from intermolecular double-quantum coherences (iDQCs) have been shown to be insensitive to macroscopic field inhomogeneities and thus enable acquisition of high- resolution MR spectroscopy in the presence of large inhomogeneous fields. In this paper, localized iDQC (1)H spectroscopy on a whole-body 3-T MR scanner is reported. Experiments with a brain metabolite phantom were performed to...

background: in treating patients with radiation, the degree of accuracy for the delivery of tumor dose is recommended to be within ± 5% by icru in report 24. the experimental studies have shown that the presence of low-density inhomogeneity in areas such as the lung can lead to a greater than 30% change in the water dose data. therefore, inhomogeneity corrections should be used in treatment pla...

The discrete Fourier transform (FT) is a conventional method for spatial reconstruction of chemical shifting imaging (CSI) data. Due to point spread function (PSF) effects, FT reconstruction leads to intervoxel signal leakage (Gibbs ringing). Spectral localization by imaging (SLIM) reconstruction was previously proposed to overcome this intervoxel signal contamination. However, the existence of...

Off-resonance effects can cause image blurring in spiral scanning and various forms of image degradation in other MRI methods. Off-resonance effects can be caused by both B0 inhomogeneity and concomitant gradient fields. Previously developed off-resonance correction methods focus on the correction of a single source of off-resonance. This work introduces a computationally efficient method of co...

The effect of geometrical parameters involved in vortex extrusion (VE) die design, on AA1050 aluminium alloy processed by VE were investigated using finite element analysis (FEA) and response surface methodology (RSM). For this, VE die length (L), reduction in area (RA), twist angle , and position of control points in Beziers' formulation (C1) were considered as input parameters and strain inho...

INTRODUCTION The field inhomogeneity mapped using MRI offers the opportunity to characterize tissue magnetic susceptibility. The field measured in a voxel is a dipole kernel convolution of all tissue susceptibility sources surrounding the voxel [1]. The zero cone surfaces of the dipole kernel in Fourier domain undersamples the measured field, causing illposedness for the inverse problem of deri...