title: Multicenter cross-calibration of I-123 metaiodobenzylguanidine heart-to-mediastinum ratios to overcome camera-collimator variations.
abstract: BACKGROUND
  The heart-to-mediastinum ratio (HMR) of (123)I-metaiodobenzylguanidine (MIBG) showed variations among institutions and needs to be standardized among various scinticamera-collimator combinations.
  
  
  METHODS
  A total of 225 phantom experiments were performed in 84 institutions to calculate cross-calibration coefficients of HMR. Based on phantom studies, a conversion coefficient for each camera-collimator system was created, including low-energy (LE, n = 125) and a medium-energy (ME, n = 100) collimators. An average conversion coefficient from the most common ME group was used to calculate the standard HMR. In clinical MIBG studies (n = 52) from three institutions, HMRs were standardized from both LE- and ME-type collimators and classified into risk groups of <1.60, 1.60-2.19, and ≥2.20.
  
  
  RESULTS
  The average conversion coefficients from the individual camera-collimator condition to the mathematically calculated reference HMR ranged from 0.55 to 0.75 for LE groups and from 0.83 to 0.95 for ME groups. The conversion coefficient of 0.88 was used to unify HMRs from all acquisition conditions. Using the standardized HMR, clinical studies (n = 52) showed good agreement between LE and ME types regarding three risk groups (κ = 0.83, P < .0001, complete agreement in 90%, 42% of the patients reclassified into the same risk group).
  
  
  CONCLUSIONS
  By using the reference HMR and conversion coefficients for the system, HMRs with various conditions can be converted to the standard HMRs in a range of normal to low HMRs.
authors.affiliation: Department of Nuclear Medicine, Kanazawa University Hospital, 13-1 Takara-machi, Kanazawa, 920-8641, Japan, nakajima@med.kanazawa-u.ac.jp.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Nakajima
authors.forename: Koichi
authors.initials: K
authors.lastname: Okuda
authors.forename: Mana
authors.initials: M
authors.lastname: Yoshimura
authors.forename: Shinro
authors.initials: S
authors.lastname: Matsuo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Wakabayashi
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Imanishi
authors.forename: Seigo
authors.initials: S
authors.lastname: Kinuya
mesh_terms: D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics* / Q000592:standards*; D016477:Artifacts; D002138:Calibration / Q000592:standards; D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000592:standards; D015902:Gamma Cameras / Q000592:standards*; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D007564:Japan; D008482:Mediastinum / Q000000981:diagnostic imaging / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D019047:Phantoms, Imaging; D011785:Quality Assurance, Health Care / Q000592:standards*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics / Q000592:standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine