Hyperpolarized (hp) gases such 129Xe and 83Kr (spin I = 1/2 and I = 9/2 respectively) can allow for significantly enhanced signal in a number of magnetic resonance applications. As a result there has been a growing interest in recent years to advance hp noble gas technology to non-invasively image the airspace of lungs, with the goal of developing a helpful probe for lung pathologies. 83Kr longitudinal relaxation (T1) has been shown to be sensitive to various surface properties, and may prove to be an interesting for identifying certain diseases including those that change surface chemistry (such as cystic fibrosis) or the surface-to-volume ratio in the lung (like in emphysema). This thesis contains several studies furthering 83Kr lung imaging, while also exploring methods for 129Xe imaging. A major focus has been on increasing spin polarization of the noble gases, as an increased polarization yields a greater MR signal strength. A novel low-pressure spin-exchange optical pumping technique has been utilized in this work allowing for 83Kr polarizations exceeding 17.5 %; as opposed to 4.4 % previously reported in literature. Gas produced in this fashion must be pressurized to above ambient before it is possible for it to be delivered to a lung. Two methodologies for pressurizing the noble gas via compression are explored and optimized for hp gas delivery to excised lungs with 83Kr polarizations as high as 13.8 % achievable after compression. This ultimately allowed for the first ever coronal 83Kr lung images in an ex vivo lung model. Further work repeated with isotopically enriched 83Kr achieved a surface-sensitive T1 relaxation map in this system. Finally gas handling techniques where created to allow for efficient and thorough mixing of the hp noble gases and O2 while minimizing relaxation effects. This is vital for any future in vivo studies.

No description available.

The Pseudo Random Arterial Modulation (PRAM) is a non-invasive MRI based method to measure blood flow. It does not require any contrast agent but rather uses water protons in the body as the contrast. PRAM is based on a pseudo random sequence of inversions and non-inversions of the arterial blood using radio frequency (RF) pulses at a labeling plane inferior to the imaging plane. A series of images are taken at the imaging plane and flow reconstructed from the transit time measurements. PRAM does not require separate control and label acquisition as is common in Arterial Spin Labeling (ASL) but rather measures the distribution of transit times to a voxel within one integrated scan. Adiabatic inversion or non-inversion pre-pulses (PRAM pulses) are performed prior to a gradient echo imaging. The PRAM method has been tested on a flow phantom and the results were in confirmation with the theoretical flow and velocity measurements. Subsequently the PRAM method was tested on a human leg and the results were comparable with the Ultrasound measurements. The final testing phase was performed on a human brain and the results were compared with the phased contrast MRA. We have demonstrated here that that the PRAM technique can measure the velocity profile and the transit time accurately and efficiently on any organ such as human brain.

Abstract This research is to explore the high school student potential misconceptions on evolution, based on the two-tier diagnostic test and diagnostic interview. Through a proper teaching design, the researcher has developed an untraditional teaching method. The effects of the untraditional teaching method and the traditional teaching method were compared. With the retest of two-tier diagnostic test, a survey was conducted to evaluate the students¡¦ achievement resulting from the teaching strategy designed by the researcher. The survey can also be consulted and used in the improvement of future teaching activities. This research adopted a Quasi-experimental research method. Data included the analysis of quantity and the description of quality. The research tool is a two-tier diagnostic questionable. The sample groups consist of two classes in the grade-10 and two classes in the grade-12 with 35 students in each class, taught by the researcher. The results of this research indicate that (1) in general , the students are in lack of the structural knowledge of evolution in their prior learning especially¡§the relationship between organism and organism¡¨and the concept of human selection; (2) the comparison of learning results brought about between the untraditional teaching method and traditional teaching method, apparently shows that the experimental group students are far better than the control group students in understanding the connection of evolutional concepts and the abundance of conceptive maps; (3) the difference of student learning process of the two teaching methods , compared by the quiz results on each unit, are not significantly different between the two groups of students; and (4) as far as the teaching of the concept of evolution is concerned, the improved teaching method design is appreciated by the experiment group students and is highly expected by the control group students.

Thèse d'exercice : Médecine. Médecine générale : Université de Nantes : 2003. / Bibliogr. f. 134-135 [34 réf.].

Thèse de doctorat : Génie biologique et médical : Paris 12 : 2003. / Titre provenant de l'écran-titre.

Reproduction de : Thèse d'université : Génie biologique et médical : Grenoble 1 : 1994. / Titre provenant de l'écran-titre.

Reproduction de : Mémoire de Sage-femme : Médecine : Nantes : 2008. / Bibliogr.

Reproduction de : Thèse d'exercice : Chirurgie dentaire : Nantes : 2008. / Bibliogr.

Reproduction de : Thèse d'exercice : Médecine vétérinaire : Toulouse 3 : 2007. / Titre provenant de l'écran titre. Bibliogr. p. 127-135.