Karaktärisering av 8-kanals transmitsystem
Sammanfattning: Ultra high magnetic field (UHF) MR-systemsis an interesting research area, the systems offer images with higher spatial resolution than its lower field counterpart. One of the disadvantages with UHF MR is that they lead to a worsened B1-field homogenity, a homogentity essential for the creation of MR-images. In the project an 8 independent channel transmit system is charachterised. The transmit system offers the oppurtunity for B1-shimming for increased B1-homogenity. B1-mapping is the process of gathering information regarding the B1-field and in this project the fast DREAM-method is used. This mapping is essential for the four B1 shimmingtools (RPN, volextAP, adaptextAP, preset) being tested to be able to improve the homogenity. The project’s data is gathered from 10 individuals on a 7T Philips MR-system, both with the classic coil acting as a reference and with the new 8 channel transmit coil (mtx8). The preprocessing have included the process of aligning the data to MNI-space, a standarised brain, to simplify the data comparison. The results show a 50 % higher SNR for the classic coil which has a marginally smaller CNR than mtx8. Two of the B1-shimmingtools, adaptextAP and RPN, offered a subpar performance unlike volextAP and preset which gave interesting results that has to be analysed further. It is to early to draw any conclusions if mtx8 can replace the classic coil or not, but regarding the applications surrounding B1-shimming mtx8 is very interesting.
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