tytuł: | Metastability exchange optical pumping (MEOP) of ^{3}He in situ |
wariant tytułu: |
Pompowanie optyczne z wymianą metastabilności (MEOP) helu-3 in situ |
autor: | Collier Guilhem |
recenzent: | Figiel Henryk, Gawlik Wojciech |
promotor: | Dohnalik Tomasz |
instytucja sprawcza: | Jagiellonian University. Institute of Physics. Department of Atomic Optics |
miejsce powstania: |
Kraków |
data obrony : | 2011-11-04 |
strony: | [4], X, 114 |
sygnatura : |
Dokt. 2011/216 |
adres URL: |
http://www.fais.uj.edu.pl/documents/41628/1bc3c70a-d796-4766-9a02-cea7ca02a30b |
data dostępu: |
2018-03-22 |
uwagi: | Bibliogr. s. 108-114 |
język: | angielski |
abstrakt w j. angielskim: | Polarized helium-3 is used as a contrast agent for lungs magnetic resonance imaging that has recently reached the pre-clinical applications. The main method to hyperpolarize 3He is the metastability exchange optical pumping (MEOP). Optical pumping is performed in standard conditions at low pressure (≈ 1 mbar) and low magnetic field (≈ 1 Gauss). In this work, the complete update of a low field polarizer dedicated to small animal lungs imaging is presented. The implementation of a new 10 W laser, new peristaltic compressor and others components resulted in a production of 3-4 scc/min for a polarization between 30 to 40%. Images of rat lungs made with better resolution and a new dynamic radial sequence are presented as a validation of the system. Since few years, MEOP has also been studied at higher pressures and higher magnetic fields in small sealed cells. It showed that, thanks to hyperfine decoupling effect induced by high magnetic field, it was also possible to efficiently polarize at higher pressure (67 mbar). Experiments done at 4.7 and 1.5 T are reported in this work. The first ones show a benefic (higher polarization values) and a negative effect (lower production rates) of the magnetic field. The seconds highlight the advantage of using an annular beam shape of the laser that matches the distribution of 23S state atoms at higher pressure. Nuclear polarization values of 66.4% at 32 mbar and 31% at 267 mbar were obtained in 20 mL sealed cells and a 10 times increase in the production rate compare to best standard conditions. These promising results were the first motivation for building a high-field polarizer working inside MRI scanner in hospital. The design and construction of such a polarizer is described in detail in the last part of the dissertation. The polarizer produces hyperpolarize 3He at 30-40% with a 4 times higher flow than the low field polarizer (10-15 scc/min). The first good quality human lungs images made in Poland with healthy volunteers are the main result of this work. |
słowa kluczowe w j. polskim: | hel-3, MEOP, polaryzator, MRI, obrazowanie płuc |
słowa kluczowe w j. angielskim: | helium-3, MEOP, polarizer, MRI, lungs imaging, metastability exchange, hyperpolarized gas, optical pumping, nuclear polarization, 1083 nm, hyperfine decoupling |
wydział: instytut / zakład / katedra: | Wydział Fizyki, Astronomii i Informatyki Stosowanej : Instytut Fizyki im. Mariana Smoluchowskiego |
typ: | rozprawa doktorska |