title: Part 1: Dual-tuned proton/sodium magnetic resonance imaging of the lumbar spine in a rabbit model.
abstract: METHODS
  Development of a dual-tuned proton/sodium radiofrequency (RF) coil for magnetic resonance imaging (MRI) of the rabbit spine and quantification of sodium concentration in intervertebral discs.
  
  
  OBJECTIVE
  To develop the dual-tuned proton/sodium MRI of rabbit lumbar spine to investigate proteoglycan matrix content and intervertebral disc degeneration (IDD).
  
  
  BACKGROUND
  IDD is a common chronic condition that may lead to back pain, limited activity, and disability. Early-stage IDD involves the loss of proteoglycan matrix and water content in the disc. Sodium MRI is a promising noninvasive technique for quantitative measurement of proteoglycan changes associated with IDD. The combined structural (proton) and biochemical (sodium) MRI facilitates the investigation of morphological and molecular changes associated with degeneration of discs.
  
  
  METHODS
  Multichannel dual-tuned proton/sodium transceiver RF coil of the rabbit spine was developed and optimized at 3T human scanner-8 channels allocated for the sodium coil and 4 channels for the proton coil. High-resolution anatomy proton images of the discs were acquired using turbo spin echo and dual echo steady state sequence. Sodium concentration of the discs was quantified from sodium magnetic resonance (MR) images that were calibrated for signal attenuation because of RF field inhomogeneity, sodium MR relaxation times, and disc thickness. Twelve rabbits (~1-yr old, female, 5.2 ± 0.4 kg) were used for measuring disc sodium concentration.
  
  
  RESULTS
  High-resolution in vivo proton and sodium MR images of rabbit discs (≤2-mm thickness) were successfully obtained using an in-house dual-tuned proton/sodium RF coil at 3T. The total acquisition time for each set of images was approximately 40 minutes. Sodium concentration of normal rabbit lumbar discs was measured at 269.7 ± 6.3 mM, and this measurement was highly reproducible, with 5.3% of coefficient of variation.
  
  
  CONCLUSIONS
  Sodium concentrations of rabbit lumbar discs were reliably measured using our newly developed dual-tuned multichannel proton/sodium RF coil at 3T.
authors.affiliation: Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
authors.forename: Chan Hong
authors.initials: CH
authors.lastname: Moon
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Lloydine
authors.initials: L
authors.lastname: Jacobs
authors.forename: Tiejun
authors.initials: T
authors.lastname: Zhao
authors.forename: Gwendolyn
authors.initials: G
authors.lastname: Sowa
authors.forename: Nam
authors.initials: N
authors.lastname: Vo
authors.forename: James
authors.initials: J
authors.lastname: Kang
authors.forename: Kyongtae Ty
authors.initials: KT
authors.lastname: Bae
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007403:Intervertebral Disc / Q000378:metabolism / Q000473:pathology*; D055959:Intervertebral Disc Degeneration / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D011509:Proteoglycans / Q000378:metabolism; D011522:Protons; D011677:Punctures / Q000009:adverse effects; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012964:Sodium
chemical_list: D011509:Proteoglycans; D011522:Protons; D012964:Sodium