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A Complementary Images Shimming Method to Mitigate B1 Inhomogeneity for High Field MRI
| Content Provider | Semantic Scholar |
|---|---|
| Author | Ferrand, Guillaume Luong, Michel Cloos, Martijn A. Amadon, Alexis |
| Copyright Year | 2010 |
| Abstract | , where + j B , 1 corresponds to complex-valued maps measured with the AFI sequence (3) for each channel, and s ij ' α the static shimming complex weighting coefficients to be optimized in the CIS approach. According to Roemer's work (2), the optimum final combined image in term of S/N could be obtained if we choose to minimize the criterion: , t I is a constant image intensity assuming a uniform distribution of proton density, T1 and T2. As an example, we used an 8-channel RF coil and 2 image acquisitions (m = 2, n = 8). If m = 1, then the CIS approach would be nothing else but the classical static shimming. For the experimental demonstration, we used a round bottom flask of 16 cm diameter, filled with a CuSO4-doped saline solution providing a spherical homogeneous phantom with a T1 of 330 ms. The experimental reception sensitivity pattern was not measured, but considered uniform and then assigned a unit value in the optimization criterion equation. Under this condition, we superposed the flip angle image at the end of the process instead of the intensity image itself to check the quality of the CIS technique. A simulation test has also been carried out with an inhomogeneous phantom composed of 8 human tissues in Finite Elements Method based simulations (Aarkid head model with Ansoft HFSS code). In this case, the simulated ) (r Rc r was considered: ∑ = − = n j j c r B |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://cds.ismrm.org/protected/10MProceedings/files/1474_4657.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
