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Numerical Comparison Between TEM Head Coil and Birdcage Head Coil at 7T
| Content Provider | Semantic Scholar |
|---|---|
| Author | Demeester, Gordon D. Zhai, Zhiyong Morich, Michael A. Leussler, Christoph Guenther Findeklee, Christian |
| Copyright Year | 2004 |
| Abstract | ++ -field strength over the central slice - the transverse slice at the isocenter of two head coils. Results In Fig. 2(a), we plot the normalized |B1 + |-field with respect to the field at the isocenter along the z-axis for the unloaded TEM and birdcage head coils. It shows that, the TEM coil curve has a higher B1 + -field near the end cap that monotonically decreases toward the front of the coil. The birdcage coil B1 + -field curve is relatively flat near the end cap and decreases similarly to the TEM curve toward the front of the coil. In this comparison, the birdcage has better B1 + -field homogeneity along the zaxis than that of the TEM coil. With the loading of a human head model, we found, that the B1 + -field inside the head is dramatically deviated from the unloaded field by the dielectric head tissues and eddy current effects. In Fig. 2(b), we plot the normalized average B1 + -field per slice with respect to the central slice vs. z-axis. In this case, the two curves show a similar trend but with slightly better B1 + -field uniformity in the brain for the birdcage coil. In Fig. 2 (c), we also plot the corresponding B1 + field standard deviation per slice vs. z-axis. It shows that, B1 + -field homogeneity within a slice generally improves as one moves from the neck to the brain. In the brain slices, B1 + -field standard deviation is below 11% for both head coils. In Table 1, we listed the calculated head SAR and maximum local SAR for the two head coil configurations. For purposes of comparison, the RF duty cycle is fixed at 2.4% and the average B1 + -field field strength is 10µT over the central slice. It shows, that the IEC’s local SAR limit (≤10W/kg) is reached first in the head for the TEM |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://cds.ismrm.org/ismrm-2004/Files/000035.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
