Phased array RF coils for high-resolution MRI of the inner ear and brain stem.
OBJECTIVE
The spatial resolution in MRI is predominantly limited by the available signal-to-noise ratio (S/N). To increase the S/N, a four coil phased array consisting of bilateral pairs of semioval coils was constructed for high resolution imaging of the temporal bone and brainstem.


METHODS
Coil sizes of 10 x 6 and 6 x 4.5 cm were tested. The S/N values were measured in vivo and with homogeneous phantoms and compared to commercial 3 in receive and quadrature head coils.


RESULTS
At a depth of 4-5 cm, phantom studies yielded S/N improvements of a factor of 1.26-1.37 with the large array compared to the 3 in coil and 2.33-1.74 compared to the head coil. Similar improvements (1.16 and 2.37) were obtained in inner ear images. No further improvement was achieved at this depth with the small array. At a depth of 8 cm, phantom studies yielded similar S/N for the quadrature head coil and two bilaterally placed large array coils, while a factor of 1.27 was obtained in brainstem images.


CONCLUSIONS
The use of phased array coils yields significantly increased S/N and is thus valuable for high resolution MRI.
Schmalbrock
P
P
Department of Radiology, Ohio State University, Columbus 43210.
Pruski
J
J
Sun
L
L
Rao
A
A
Monroe
J W
JW
D001933:Brain Stem / Q000033:anatomy & histology*; D007758:Ear, Inner / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008961:Models, Structural