title: Development of a 7 T RF coil system for breast imaging.
abstract: In ultrahigh-field MRI, such as 7 T, the signal-to-noise ratio (SNR) increases while transmit (Tx) field (B1+) can be degraded due to inhomogeneity and elevated specific absorption rate (SAR). By applying new array coil concepts to both Tx and receive (Rx) coils, the B1+homogeneity and SNR can be improved. In this study, we developed and tested in vivo a new RF coil system for 7 T breast MRI. An RF coil system composed of an eight-channel Tx-only array based on a tic-tac-toe design (can be combined to operate in single-Tx mode) in conjunction with an eight-channel Rx-only insert was developed. Characterizations of the B1+field and associated SAR generated by the developed RF coil system were numerically calculated and empirically measured using an anatomically detailed breast model, phantom and human breasts. In vivo comparisons between 3 T (using standard commercial solutions) and 7 T (using the newly developed coil system) breast imaging were made. At 7 T, about 20% B1+inhomogeneity (standard deviation over the mean) was measured within the breast tissue for both the RF simulations and 7 T experiments. The addition of the Rx-only array enhances the SNR by a factor of about three. High-quality MR images of human breast were acquired in vivo at 7 T. For the in vivo comparisons between 3 T and 7 T, an approximately fourfold increase of SNR was measured with 7 T imaging. The B1+field distributions in the breast model, phantom and in vivo were in reasonable agreement. High-quality 7 T in vivo breast MRI was successfully acquired at 0.6 mm isotropic resolution using the newly developed RF coil system.
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Junghwan
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Tales
authors.initials: T
authors.lastname: Santini
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.|Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Kyongtae Ty
authors.initials: KT
authors.lastname: Bae
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Narayan
authors.initials: N
authors.lastname: Krishnamurthy
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Yujuan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: MR Research Support, Siemens Healthcare, Pittsburgh, PA, USA.
authors.forename: Tiejun
authors.initials: T
authors.lastname: Zhao
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.|Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Tamer S
authors.initials: TS
authors.lastname: Ibrahim
mesh_terms: D000328:Adult; D001940:Breast / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers
keywords: 7 T; Rx-only array; SNR; Tx-only array; breast