title: Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children.
abstract: We adopted a combination of pieces of permanent magnets and a single-channel (SC) shim coil to shim the magnetic field in a magnetic resonance imaging system dedicated for skeletal age assessment of children. The target magnet was a 0.3-T open and compact permanent magnet tailored to the hand imaging of young children. The homogeneity of the magnetic field was first improved by shimming using pieces of permanent magnets. The residual local inhomogeneity was then compensated for by shimming using the SC shim coil. The effectiveness of the shimming was measured by imaging the left hands of human subjects and evaluating the image quality. The magnetic resonance images for the child subject clearly visualized anatomical structures of all bones necessary for skeletal age assessment, demonstrating the usefulness of combined shimming.
authors.affiliation: Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan. terada@bk.tsukuba.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Terada
authors.forename: S
authors.initials: S
authors.lastname: Kono
authors.forename: K
authors.initials: K
authors.lastname: Ishizawa
authors.forename: S
authors.initials: S
authors.lastname: Inamura
authors.forename: T
authors.initials: T
authors.lastname: Uchiumi
authors.forename: D
authors.initials: D
authors.lastname: Tamada
authors.forename: K
authors.initials: K
authors.lastname: Kose
mesh_terms: D000293:Adolescent; D000328:Adult; D000365:Age Determination by Skeleton / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D050276:Hand Bones / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D007223:Infant; D007231:Infant, Newborn; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation; D059346:Magnets; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D055815:Young Adult