Magnetic resonance imaging (MRI) is a non-invasive technique used to produce high-quality images of the interior of the human body. Compared to other imaging modalities, however, MRI requires a relatively long data acquisition time to form an image. Patients often have difficulty staying still during this period. This is problematic as motion produces artifacts in the image. This thesis explores the methods of imaging a moving object using MRI. Testing is performed using simulations, a moving phantom, and human subjects. Several strategies developed to avoid motion artifact problems are presented. Emphasis is placed on techniques that provide motion correction without penalty in terms of acquisition time. The most significant contribution presented is the development and assessment of the 'TRELLIS' pulse sequence and reconstruction algorithm. TRELLIS is a unique approach to motion correction in MRI. Orthogonal overlapping strips fill k-space and phase-encode and frequency-encode directions are alternated such that the frequency-encode direction always runs lengthwise along each strip. The overlap between pairs of orthogonal strips is used for signal averaging and to produce a system of equations that, when solved, quantifies the rotational and translational motion of the object. Acquired data is then corrected using this motion estimation. The advantage of TRELLIS over existing techniques is that k-space is sampled uniformly and all collected data is used for both motion detection and image reconstruction. This thesis presents a number of other contributions: a proposed means of motion correction using parallel imaging; an extension to the phase-correlation method for determining displacement between two objects; a metric to quantify the level of motion artifacts; a moving phantom; a physical version of the ubiquitous Shepp-Logan head phantom; a motion resistant data acquisition technique; and a means of correcting for T2 blurring artifacts.

In this study, three different MR pulse sequences, IR-FSE, MP2RAGE, and firstly proposed MP3RAGE, were applied to obtain high-resolution 3D T1 mapping of whole brain at 1.5 Tesla. Among these three sequences, MP2RAGE uses fast gradient echo as readout module. Signals of two different inversion times are acquired at once and can be used to calculate T1 relaxation time according to Bloch equation. However, the magnetization was also influenced by the excitation efficiency of inversion adiabatic pulse, which was usually estimated by numerical simulation and taken as a constant over the field of view in the literature. However, this might not be true in practice. Therefore, a newly modified pulse sequence, MP3RAGE, was proposed to acquire data of three distinct inversion times without increasing scanning time. As a result, the spatial distribution of T1 and inversion efficiency can be assessed by solving nonlinear least square problem. In addition, the IR-FSE sequence with six inversion times was also applied in every experiment to provide T1 value for reference. Results showed that the T1 estimation obtained by MP2RAGE is close to, but slightly lower than that by IR-FSE, which is in agreement with those reported in literatures. In addition, the 3D high-resolution maps of T1 and efficiency were successfully estimated with the use of MP3RAGE. Spatial smoothing on inversion efficiency helps reducing the sensitivity to noise in the nonlinear approach, leading to T1 values closer to those by IR-FSE.

This thesis deals with comparison of rapid and conventional methods used in MRI (Magnetic Resonance Imaging). There is a description of imaging methods such as EPI (Echo Planar Imaging), Ultra-fast GRE, FSE (Fast spin echo) as well as a snapshot-FLASH and FISP (Fast Imaging with Steady Precession). Experimental part of this thesis deals with the rapid FSE (Fast Spin Echo) method. Especially is explained and assembled an algorithm for proper compilation of data from the FSE method. This algorithm allows us to evaluate the images from the FSE method. This method is examined in detail (in terms of impact parameters) and compared with traditional conventional methods. Finally, the individual images are evaluated, and the best parameters for FSE method are identified.

BACKGROUND: The abnormal signal intensity in cardiac T₂-weighted images is associated with various pathologies including myocardial edema. However, the assessment of pathologies based on signal intensity is affected by the acquisition parameters and the sensitivities of the receiver coils. T₂ mapping has been proposed to overcome limitations of T₂-weighted imaging, but most methods are limited in spatial and/or temporal resolution. Here we present and evaluate a double inversion recovery radial fast spin-echo (DIR-RADFSE) technique that yields data with high spatiotemporal resolution for cardiac T₂ mapping. METHODS: DIR-RADFSE data were collected at 1.5 T on phantoms and subjects with echo train length (ETL) = 16, receiver bandwidth (BW) = +/-32 kHz, TR = 1RR, matrix size = 256 x 256. Since only 16 views per echo time (TE) are collected, two algorithms designed to reconstruct highly undersampled radial data were used to generate images for 16 time points: the Echo-Sharing (ES) and the CUrve Reconstruction via pca-based Linearization with Indirect Echo compensation (CURLIE) algorithm. T₂ maps were generated via least-squares fitting or the Slice-resolved Extended Phase Graph (SEPG) model fitting. The CURLIE-SEPG algorithm accounts for the effect of indirect echoes. The algorithms were compared based on reproducibility, using Bland-Altman analysis on data from 7 healthy volunteers, and T₂ accuracy (against a single-echo spin-echo technique) using phantoms. RESULTS: Both reconstruction algorithms generated in vivo images with high spatiotemporal resolution and showed good reproducibility. Mean T₂ difference between repeated measures and the coefficient of repeatability were 0.58 ms and 2.97 for ES and 0.09 ms and 4.85 for CURLIE-SEPG. In vivo T₂ estimates from ES were higher than those from CURLIE-SEPG. In phantoms, CURLIE-SEPG yielded more accurate T₂s compared to reference values (error was 7.5-13.9% for ES and 0.6-2.1% for CURLIE-SEPG), consistent with the fact that CURLIE-SEPG compensates for the effects of indirect echoes. The potential of T₂ mapping with CURLIE-SEPG is demonstrated in two subjects with known heart disease. Elevated T₂ values were observed in areas of suspected pathology. CONCLUSIONS: DIR-RADFSE yielded TE images with high spatiotemporal resolution. Two algorithms for generating T₂ maps from highly undersampled data were evaluated in terms of accuracy and reproducibility. Results showed that CURLIE-SEPG yields T₂ estimates that are reproducible and more accurate than ES.

The signal resulting from the IR-FSE sequence has been thoroughly analyzed in order to improve the accuracy of quantitative T1 mapping of the human brain. Several optimized post-processing algorithms have been studied and compared in terms of their T1 mapping accuracy. The modified multipoint two-parameter fitting method was found to produce less underestimation compared to the traditional multipoint three-parameter fitting method, and therefore, to result in a smaller T1 estimation error. Two correction methods were proposed to reduce the underestimation problem which is commonly seen in IR-FSE sequences used for measuring T1, especially when a large turbo factor is used. The intra-scan linear regression method corrects the systematic error effectively but the RMSE may still increase due to the increase of uncertainty in sequences with large turbo factors. The weighted fitting model corrects not only the systematic error but also the random error and therefore the aggregate RMSE for T1 mapping can be effectively reduced. A new fitting model that uses only three different TI measurements for T1 estimation was proposed. The performance for the three-point fitting method is as good as that of the multipoint fitting method with correction in the phantom simulation. In addition, a new ordering scheme that implements the three-point fitting method is proposed; it is theoretically able to reduce the total scan time by 1/3 compared to the TESO-IRFSE sequence. The performance of the three-point fitting method on the real human brain is also evaluated, and the T1 mapping results are consistent to with the conventional IR-FSE sequence. More samples of true anatomy are needed to thoroughly evaluate the performance of the proposed techniques when applied to T1 mapping of the human brain.

The goal of the diploma thesis: "Fundamental analysis of RWE AG title" is to determine an intrinsic value of the RWE AG share using detail analysis. The first -- theoretical -- part deals with financial environment where the title is being traded and quoted. This part characterised german indices, mainly index DAX 30, because its component is also RWE AG share. The electronic system Xetra is described here as well. Fundamental analysis itself - including global, sector and enterprise analysis - is the subject of the second section. At the end of this work, the intrinsic value is evaluated and subsequently the forecast is outlined.

The main contribution of my thesis is the analysis of substantial empirical material that I have collected from Community trade union actors. My analysis focuses on the institutional strategies of the sectoral European trade union federations and their implications for the Europeanisation of wages policy. I have demonstrated that the development of European coordination processes of national collective bargaining, particularly at sectoral level, has contributed to reviving the concept of collective bargaining and professional relations in the European Area, which until then had been covered in the literature by the social dialogue. I have identified three obstacles to collective negociations at a European level: the “depoliticised” wage in the economic partnership, employers identified as the “lobby partner” in the sectoral social dialogue, and the difficulties encountered in the Europeanisation of trade unions. L’apport majeur de notre thèse est l’analyse d’un matériel empirique conséquent que nous avons collecté auprès des acteurs syndicaux communautaires. Notre analyse se concentre sur les stratégies institutionnelles des fédérations syndicales sectorielles européennes et sur leurs implications en matière d’européanisation de la politique salariale. Nous avons démontré que le développement des processus de coordination européenne des négociations collectives nationales, en particulier au niveau sectoriel, peut contribuer à renouveler la conception de la négociation collective et des relations professionnelles dans l’espace européen jusqu’alors appréhendée dans la littérature par le dialogue social. Nous avons identifié trois obstacles à la négociation collective européenne : le salaire « dépolitisé » dans le partenariat économique, le patronat devenu « partenaire-lobby » dans le dialogue social sectoriel, et la difficile européanisation syndicale.

The main contribution of my thesis is the analysis of substantial empirical material that I have collected from Community trade union actors. My analysis focuses on the institutional strategies of the sectoral European trade union federations and their implications for the Europeanisation of wages policy. I have demonstrated that the development of European coordination processes of national collective bargaining, particularly at sectoral level, has contributed to reviving the concept of collective bargaining and professional relations in the European Area, which until then had been covered in the literature by the social dialogue. I have identified three obstacles to collective negociations at a European level: the “depoliticised” wage in the economic partnership, employers identified as the “lobby partner” in the sectoral social dialogue, and the difficulties encountered in the Europeanisation of trade unions.<p><p>L’apport majeur de notre thèse est l’analyse d’un matériel empirique conséquent que nous avons collecté auprès des acteurs syndicaux communautaires. Notre analyse se concentre sur les stratégies institutionnelles des fédérations syndicales sectorielles européennes et sur leurs implications en matière d’européanisation de la politique salariale. Nous avons démontré que le développement des processus de coordination européenne des négociations collectives nationales, en particulier au niveau sectoriel, peut contribuer à renouveler la conception de la négociation collective et des relations professionnelles dans l’espace européen jusqu’alors appréhendée dans la littérature par le dialogue social. Nous avons identifié trois obstacles à la négociation collective européenne :le salaire « dépolitisé » dans le partenariat économique, le patronat devenu « partenaire-lobby » dans le dialogue social sectoriel, et la difficile européanisation syndicale.<p><p><p> / Doctorat en sciences sociales, Orientation sociologie / info:eu-repo/semantics/nonPublished