title: MRI and (31)P magnetic resonance spectroscopy hardware for axillary lymph node investigation at 7T.
abstract: OBJECTIVE
  Neoadjuvant treatment response in lymph nodes predicts patient outcome, but existing methods do not track response during therapy accurately. In this study, specialized hardware was used to adapt high-field (7T) (31) P magnetic resonance spectroscopy (MRS), which has been shown to track treatment response in small breast tumors, to monitor axillary lymph nodes.
  
  
  METHODS
  A dual-tuned quadrature coil that is a (31) P (120 MHz) transceiver and a (1) H (300 MHz) receiver was designed using a novel detune circuit. The transceiver/receiver coil in the axilla is used with a fractionated dipole antenna on the back of the subject and the conventional breast coil for transmit.
  
  
  RESULTS
  The novel circuit detuned the (1) H resonance without disturbing the (31) P resonance. In vivo demonstrations included: >80% homogeneous B1 (+) for (1) H over the axilla, identification of a small (3-mm diameter) lymph node, and (31) P MR spectra from a single healthy lymph node. The setup can detect <2 millimolar concentrations of metabolites from a 2-mL voxel.
  
  
  CONCLUSIONS
  The first (31) P MR spectrum from an in vivo lymph node indicates that the presented design may be sufficiently sensitive to detect metabolic response to neoadjuvant therapy. Multinuclei MRS of the lymph nodes at 7T is possible through combining lightweight antenna elements with dual-tuned transceiver/receive-only coils.
authors.affiliation: Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
authors.forename: Debra S
authors.initials: DS
authors.lastname: Rivera
authors.forename: Jannie P
authors.initials: JP
authors.lastname: Wijnen
authors.forename: Wybe J M
authors.initials: WJ
authors.lastname: van der Kemp
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Raaijmakers
authors.forename: Peter R
authors.initials: PR
authors.lastname: Luijten
authors.forename: Dennis W J
authors.initials: DW
authors.lastname: Klomp
mesh_terms: D000328:Adult; D001365:Axilla; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D004867:Equipment Design; D004869:Equipment Safety; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008207:Lymphatic Metastasis / Q000175:diagnosis* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D020360:Neoadjuvant Therapy; D019047:Phantoms, Imaging; D011379:Prognosis; D066244:Proton Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D012016:Reference Values; D012680:Sensitivity and Specificity
keywords: 31P-spectroscopy; RF coils; cancer; high-field MR techniques