Simultaneous T(1) and B(1) (+) mapping using reference region variable flip angle imaging.
OBJECTIVE
To present a new method that can simultaneously and efficiently measure T1 and B1 (+) maps using reference region variable flip angle (RR-VFA) imaging.


METHODS
Assuming T1 relaxation time in a reference region such as fat is well characterized, and the reference region sufficiently covers smoothly varying B1 (+) field inhomogeneity, B1 (+) maps can be measured from VFA images, conventionally used for T1 measurements. Fat-only images from two-point Dixon acquisitions were used to compute B1 (+) maps, and the B1 (+) maps were compared with ones using the double-angle method (DAM) in 22 breast MRI patients at 3T. Additionally, high spatial resolution VFA images were acquired to show T1 measurements with and without the RR-VFA B1 (+) correction in six patients.


RESULTS
RR-VFA is able to generate reliable B1 (+) maps, similar to those using the conventional DAM. This simultaneous T1 and B1 (+) mapping can also be used to reduce T1 estimation errors, where T1 maps have more uniform fibroglandular tissue T1 and better depiction of heterogeneous T1 of breast masses.


CONCLUSIONS
A new method that can measure both T1 and B1 (+) maps based on Dixon VFA images is described, offering improved T1 quantification with no scan time penalty.
Department of Radiological Sciences, UCLA, Los Angeles, California, USA.
Kyunghyun
K
Sung
Manojkumar
M
Saranathan
Bruce L
BL
Daniel
Brian A
BA
Hargreaves
D000328:Adult; D000368:Aged; D000465:Algorithms; D059925:Anatomic Landmarks / Q000473:pathology*; D001943:Breast Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
B1 field inhomogeneity; T1 mapping; breast imaging; high‐field MRI; quantitative DCE‐MRI