Comparison of three commercially available radio frequency coils for human brain imaging at 3 Tesla.
OBJECTIVE
To evaluate a transverse electromagnetic (TEM), a circularly polarized (CP) (birdcage), and a 12-channel phased array head coil at the clinical field strength of B0 = 3T in terms of signal-to-noise ratio (SNR), signal homogeneity, and maps of the effective flip angle alpha.


METHODS
SNR measurements were performed on low flip angle gradient echo images. In addition, flip angle maps were generated for alpha(nominal) = 30 degrees using the double angle method. These evaluation steps were performed on phantom and human brain data acquired with each coil. Moreover, the signal intensity variation was computed for phantom data using five different regions of interest.


RESULTS
In terms of SNR, the TEM coil performs slightly better than the CP coil, but is second to the smaller 12-channel coil for human data. As expected, both the TEM and the CP coils show superior image intensity homogeneity than the 12-channel coil, and achieve larger mean effective flip angles than the combination of body and 12-channel coil with reduced radio frequency power deposition.


CONCLUSIONS
At 3T the benefits of TEM coil design over conventional lumped element(s) coil design start to emerge, though the phased array coil retains an advantage with respect to SNR performance.
Mekle
Ralf
R
Centre d'Imagerie BioMedicale, Ecole Polytechnique Federale de Lausanne, EPFL SB IPMC LIFMET, CH F0 572 (Batiment CH), Station 6, 1015 Lausanne, Switzerland. ralf.mekle@epfl.ch
van der Zwaag
Wietske
W
Joosten
Andreas
A
Gruetter
Rolf
R
D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods*; D003952:Diagnostic Imaging / Q000295:instrumentation / Q000379:methods; D055590:Electromagnetic Phenomena; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D011827:Radiation; D011846:Radio Waves; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D012984:Software