Abstract
High-field (>3 T) cardiac MRI is challenged by inhomogeneities of both the static magnetic field (B0) and the transmit radiofrequency field (B1+). The inhomogeneous B fields not only demand improved shimming methods but also impede the correct determination of the zero-order terms, i.e., the local resonance frequency f0 and the radiofrequency power to generate the intended local B1+ field. In this work, dual echo time B0-map and dual flip angle B1+-map acquisition methods are combined to acquire multislice B0- and B1+-maps simultaneously covering the entire heart in a single breath hold of 18 heartbeats. A previously proposed excitation pulse shape dependent slice profile correction is tested and applied to reduce systematic errors of the multislice B1+-map. Localized higher-order shim correction values including the zeroorder terms for frequency f0 and radiofrequency power can be determined based on the acquired B0- and B1+-maps. This method has been tested in 7 healthy adult human subjects at 3 T and improved the B0 field homogeneity (standard deviation) from 60 Hz to 35 Hz and the average B1+ field from 77% to 100% of the desired B1+ field when compared to more commonly used preparation methods.
Original language | English (US) |
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Pages (from-to) | 419-426 |
Number of pages | 8 |
Journal | Magnetic resonance in medicine |
Volume | 63 |
Issue number | 2 |
DOIs | |
State | Published - Feb 2010 |
Keywords
- 3 tesla
- Cardiac MR
- Localized power preparation
- Localized shimming
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging