摘要：

Michael EbertDevelopment of a large-scale polarizer and compressor forpolarized 3-He for medical MR ImagingBy direct Optical Pumping of metastable3-He*-atoms at a pressure of about 1 mb and spintransfer to the ground state atoms via metastability exchangescattering, we reach a 3-He polarization of 53 % ata flux of 58 bar*l/day. At f = 122 bar*l/day a polarization of 30 % 3-He isachieved. By increasing the laser power from the present 12 Watt system to desirable 20 to 30 Watt it should be possible to reach a nuclear polarization of about 70 % at the same flux.An all metal titanium piston compressor was designed and built. Ina two step procedure we are able to compress the polarized 3-Hefirst into a buffer cell to a pressure of 200 to800 mb, depending on the experimental conditions. Thenthe polarized 3-He is extracted out of the buffer cell andcompressed into a disconnectable storage cell at 1 to6 bar. Due to the large compression volume of15,4 liter it is possible to transport alarge quantity of gas per compression cycle. Together with thelarge compression stroke of 100 cm compared with thesmall diameter of 14 cm and the large compressionfactor of K = 10000 these constructions are responsable forpreserving the polarization during compression.These large quantities of hyperpolarized 3-He lead to the firstclinical studies with patients and volunteers using MRI for lungfunction tests. This includes an assessment of regional oxygenconcentrations, the ventilation and the diffusion coefficientinside the lung.

展开