title: Septal penetration in iodine-123 metaiodobenzylguanidine cardiac sympathetic imaging using a medium-energy collimator.
abstract: BACKGROUND
  Septal penetration of high-energy photons affects the estimation of the heart-to-mediastinum (H/M) ratio in cardiac (123)I-metaiodobenzylguanidine (MIBG) imaging, and the use of a medium-energy (ME) collimator has been shown to improve quantitative accuracy. We investigated the effect of septal penetration on the estimation of H/M ratios using an ME collimator.
  
  
  RESULTS
  Point sources of (99m)Tc and (123)I were imaged using various collimators, which indicated that the effect of high-energy photons with the ME collimator was relatively small but larger than that with the high-energy (HE) collimator. Four hours after (123)I-MIBG injection, 20 patients underwent planar anterior chest imaging by different methods in succession. The ME collimator gave lower H/M ratios (mean 2.52) than the HE collimator (2.57), indicating influence of septal penetration in the ME collimator; however, the difference was limited. Although narrowing the energy window from 20% (2.51) to 15% (2.54) increased the H/M ratios in imaging with the ME collimator, the difference was quite limited.
  
  
  CONCLUSIONS
  Septal penetration affects the estimation of the H/M ratios using an ME collimator; however, this influence is small and would not have clinical significance.
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.forename: Yutaka
authors.initials: Y
authors.lastname: Abe
authors.forename: Yuji
authors.initials: Y
authors.lastname: Asano
authors.forename: Kei
authors.initials: K
authors.lastname: Kikuchi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Iizuka
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Nishiyama
mesh_terms: D019797:3-Iodobenzylguanidine; D000368:Aged; D057791:Cardiac Imaging Techniques; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007457:Iodine Radioisotopes; D008297:Male; D008482:Mediastinum / Q000000981:diagnostic imaging*; D008875:Middle Aged; D017785:Photons; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D013667:Technetium / Q000737:chemistry
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine; D013667:Technetium