title: Correction of collimator-dependent differences in the heart-to-mediastinum ratio in123I-metaiodobenzylguanidine cardiac sympathetic imaging: Determination of conversion equations using point-source imaging.
abstract: Septal penetration causes collimator-dependent differences in the heart-to-mediastinum (H/M) ratio in123I-metaiodobenzylguanidine (MIBG) cardiac imaging. We investigated generally applicable methods to correct such differences.
  
  
  
  Four hours after123I-MIBG injection, 40 patients underwent anterior chest imaging successively with medium-energy (ME) and various non-ME collimators. The H/M ratios obtained with the non-ME collimators before and after123I-dual-window penetration correction were compared with the ME-derived standard values to determine patient-based conversion equations for empiric and combined corrections, respectively. A123I point source was imaged with various collimators, and the central ratio, the ratio of count in a small central region of interest to count in a large one, was calculated. The method of predicting the conversion equations from the central ratios was determined. Correction using the patient-based conversion equations removed systematic underestimation of the H/M ratios obtained with the non-ME collimators, and combined correction depressed residual random errors to some degree. Point-source-based equations yielded results comparable to the patient-based equations.
  
  
  
  Empiric and combined corrections effectively reduce collimator-dependent differences in the H/M ratio. The conversion equations can be predicted from simple point-source imaging, which would allow to apply these corrections to data obtained with various collimators.
authors.affiliation: Department of Diagnostic Radiology, Kitasato University School of Medicine, 1-15-1 Kitasato Minami-ku, Sagamihara, Kanagawa, 252-0374, Japan. inoueys34@gmail.com.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: Department of Radiology, Kitasato University Hospital, Sagamihara, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Abe
authors.affiliation: Department of Radiology, Kitasato University Hospital, Sagamihara, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Kikuchi
authors.affiliation: Department of Diagnostic Radiology, Kitasato University School of Medicine, 1-15-1 Kitasato Minami-ku, Sagamihara, Kanagawa, 252-0374, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Matsunaga
authors.affiliation: Department of Neurology, Kitasato University School of Medicine, Sagamihara, Japan.
authors.forename: Ray
authors.initials: R
authors.lastname: Masuda
authors.affiliation: Department of Neurology, Kitasato University School of Medicine, Sagamihara, Japan.
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Nishiyama
mesh_terms: D019797:3-Iodobenzylguanidine; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D057791:Cardiac Imaging Techniques; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007457:Iodine Radioisotopes / Q000737:chemistry*; D008297:Male; D008482:Mediastinum / Q000000981:diagnostic imaging*; D008875:Middle Aged; D009206:Myocardium; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine
keywords: 123I-metaiodobenzylguanidine (MIBG); collimator; heart-to-mediastinum (H/M) ratio; septal penetration