Trevor Andrews PhD, Presenter: Employee, Koninklijke Philips Electronics NV

Alisa Kathleen Johnson MD, Abstract Co-Author: Nothing to Disclose

Sally D. Herschorn MD, Abstract Co-Author: Nothing to Disclose

Jay Gonyea, Abstract Co-Author: Nothing to Disclose

Christopher G. Filippi MD, Abstract Co-Author: Nothing to Disclose

B1 shimming with multitransmit MR at 3.0T greatly reduced right/left signal inhomogeneity for every subject and each sequence and improved image quality, which may increase the conspicuity of breast pathology.

Breast MRI at 3.0T often suffers from signal inhomogeneity typically between the right and left breast. This complicates interpretation, since the opposite breast is often used as an internal control and signal inhomogeneity can mask pathology. This non-uniformity of signal is due to inhomogeneity in the RF transmit (or B1) field. This study evaluates image quality improvement in breast MR at 3.0T using a new dual-transmitter system (multitransmit MR) that uses patient-adaptive RF transmit homogeneity calibration (B1 shimming).  

Nine volunteers were scanned using T1-weighted turbo spin echo (T1W-TSE) and fat suppressed pre-contrast dynamic e-THRIVE sequence. Images were acquired on a 3.0T Philips Achieva Multitransmit Scanner (Best, Netherlands). Patient-adaptive image-based B0 shimming was used for all scans. Sequence parameters: T1W-TSE: TR 400ms, TE 10ms, Acq. Matrix 424x335, FOV 340x340mm, Slice 3mm, Flip Angle 90deg, Scan Duration 3min38sec; e-THRIVE: TR 4.66ms, TE 2.3ms, Acq. Matrix 340x340, FOV 340x340, Slice 2mm, Flip Angle 10deg, Scan Duration 61sec. Each sequence was performed with and without patient-adaptive B1 shimming. ROIs were drawn on matching tissues with the largest difference in signal magnitude on each breast for a single slice on the images without B1 shimming. An identical ROI was drawn on the same image performed with B1 shimming. Image quality was evaluated by a breast radiologist using a 3-point scale.

For e-THRIVE signal between right and left breast varied from 38% to 118% without B1 shimming, but with B1 shimming the difference was markedly reduced and ranged from 0% to 19%. For the T1W-TSE signal difference between right and left breast ranged from 14% to 102% without B1 shimming. With B1 shimming, this difference was markedly reduced and ranged from 1% to 16%. Using Friedman rank test, eThrive and T1W TSE sequences without B1 shimming had significantly lower scores compared to B1 shimming (eThrive p=0.014, T1W TSE p=0.005).

Andrews, T, Johnson, A, Herschorn, S, Gonyea, J, Filippi, C, Breast MR Image Quality Improvement Using a 3.0 T Clinical Parallel Transmit System.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9010943.html