Quadrature transmit coil for breast imaging at 7 tesla using forced current excitation for improved homogeneity.
OBJECTIVE
To demonstrate the use of forced current excitation (FCE) to create homogeneous excitation of the breast at 7 tesla, insensitive to the effects of asymmetries in the electrical environment.


METHODS
FCE was implemented on two breast coils: one for quadrature (1) H imaging and one for proton-decoupled (13) C spectroscopy. Both were a Helmholtz-saddle combination, with the saddle tuned to 298 MHz for imaging and 75 MHz for spectroscopy. Bench measurements were acquired to demonstrate the ability to force equal currents on elements in the presence of asymmetric loading to improve homogeneity. Modeling and temperature measurements were conducted per safety protocol. B1 mapping, imaging, and proton-decoupled (13) C spectroscopy were demonstrated in vivo.


RESULTS
Using FCE to ensure balanced currents on elements enabled straightforward tuning and maintaining of isolation between quadrature elements of the coil. Modeling and bench measurements confirmed homogeneity of the field, which resulted in images with excellent fat suppression and in broadband proton-decoupled carbon-13 spectra.


CONCLUSIONS
FCE is a straightforward approach to ensure equal currents on multiple coil elements and a homogeneous excitation field, insensitive to the effects of asymmetries in the electrical environment. This enabled effective breast imaging and proton-decoupled carbon-13 spectroscopy at 7T.
Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA; Department of Electrical Engineering, Texas A&M University, College Station, Texas, USA.
Mary Preston
MP
McDougall
Sergey
S
Cheshkov
Joseph
J
Rispoli
Craig
C
Malloy
Ivan
I
Dimitrov
Steven M
SM
Wright
D016477:Artifacts; D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000175:diagnosis*; D004574:Electromagnetic Fields; D004867:Equipment Design; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D019047:Phantoms, Imaging; D012016:Reference Values; D012984:Software
7T; breast MRI; transmit coil