title: Ytterbium-based PARACEST agent: feasibility of CEST imaging on a clinical MR scanner.
abstract: OBJECTIVE
  We investigated the feasibility of performing chemical exchange saturation transfer (CEST) imaging using ytterbium-based paramagnetic CEST (PARACEST) agents on a clinical magnetic resonance (MR) scanner.
  
  
  METHODS
  We prepared solutions of 3 different ytterbium-based PARACEST agents at concentrations of 5, 10, 20, and 50 mM at a pH of 7.4 and at a concentration of 50 mM at pHs of 3.0, 5.0, 7.4, and 9.5. We acquired images with a turbo spin echo technique using a quadrature head coil and a clinical 3.0-tesla MR system in accordance with the safety limits of the specific absorption rate (SAR). We acquired CEST images with presaturation offset frequencies from -5,000 Hz (-39.1 ppm) to 5,000 Hz (39.1 ppm) with an interval of 500 Hz (3.9 ppm) for each condition. We repeated each scan 3 times and then calculated the mean and standard deviations of the magnitude of the CEST effect at different concentrations and pH values for each agent. We used one-way analysis of variance and Tukey's honestly significant difference post hoc test to compare mean values of the magnitude of the CEST effect obtained at different concentrations and pH values. P < 0.05 was considered significant.
  
  
  RESULTS
  PARACEST agents showed a strong CEST effect at their specific presaturation offset frequencies. For each agent, the CEST effect showed significant concentration dependency (P < 0.05), increasing with agent concentration, and significant pH dependency (P < 0.05), with strong effect near physiological pH.
  
  
  CONCLUSIONS
  CEST imaging using ytterbium-based PARACEST agents might be feasible on a clinical MR scanner with further modifications, such as adjustments of the presaturation radiofrequency pulse and imaging protocols.
authors.affiliation: Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. ytaka@radiol.med.kyushu-u.ac.jp
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Takayama
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshiura
authors.forename: Akihiro
authors.initials: A
authors.lastname: Nishie
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nakayama
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Hatakenaka
authors.forename: Naoki
authors.initials: N
authors.lastname: Kato
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yoshise
authors.forename: Jochen
authors.initials: J
authors.lastname: Keupp
authors.forename: Dirk
authors.initials: D
authors.lastname: Burdinski
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Honda
mesh_terms: D005240:Feasibility Studies; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015018:Ytterbium / Q000172:deficiency*
chemical_list: D015018:Ytterbium