title: B1homogeneity of breast MRI using RF shimming with individual specific values in volunteers simulating patients after mastectomy.
abstract: Background Magnetic resonance imaging (MRI) using a 3-T MRI scanner is now widely used for clinical examinations. However, B1inhomogeneity becomes larger with MRI scanners using 3-T and higher. It especially becomes a problem in the breast. To improve B1homogeneity, a RF shimming technique has been developed. Purpose To evaluate the B1homogeneity of breast MRI using RF shimming with individual specific values for subjects after mastectomy. Material and Methods The subjects are healthy female volunteers who underwent normal breast imaging, followed by imaging of one breast while the other breast was bound tightly to the chest by bleached cotton cloths (simulating volunteers after mastectomy). B1mappings were performed with RF shimming using two techniques: (i) optimized fixed value; and (ii) individual specific values using a 3-T MRI scanner. The means and standard deviations of the B1maps for all slices in the breast were measured and compared between the fixed value and the individual specific value cases. Results For normal volunteers, the breast B1variation was not statistically significantly different between the RF shimming techniques. For volunteers after simulated surgery, the breast B1variation was (1.02 ± 0.29) with the fixed value and (0.98 ± 0.22) with the individual specific value ( P < 0.01). With the individual specific optimization, B1variation for all slices in the breast was improved for volunteers after simulated surgery. Conclusion RF shimming with individual specific values has the potential to improve the B1homogeneity of breast MRI in patients after mastectomy.
authors.affiliation: National Institute of Radiological Sciences, Inage, Chiba, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Abe
mesh_terms: D000328:Adult; D016477:Artifacts; D001940:Breast / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000601:surgery*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008408:Mastectomy; D008875:Middle Aged; D016544:Patient Simulation; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D055815:Young Adult
keywords: B1 homogeneity; RF shimming; breast; individual specific; magnetic resonance imaging (MRI); parallel transmission