title: Comparison of the image-derived radioactivity and blood-sample radioactivity for estimating the clinical indicators of the efficacy of boron neutron capture therapy (BNCT): 4-borono-2-18F-fluoro-phenylalanine (FBPA) PET study.
abstract: BACKGROUND
  In boron neutron capture therapy (BNCT), positron emission tomography (PET) with 4-borono-2-18F-fluoro-phenylalanine (FBPA) is the only method to estimate an accumulation of10B to target tumor and surrounding normal tissue after administering10B carrier of L-paraboronophenylalanine and to search the indication of BNCT for individual patient. Absolute concentration of10B in tumor has been estimated by multiplying10B concentration in blood during BNCT by tumor to blood radioactivity (T/B) ratio derived from FBPA PET. However, the method to measure blood radioactivity either by blood sampling or image data has not been standardized. We compared image-derived blood radioactivity of FBPA with blood sampling data and studied appropriate timing and location for measuring image-derived blood counts.
  
  
  METHODS
  We obtained 7 repeated whole-body PET scans in five healthy subjects. Arterialized venous blood samples were obtained from the antecubital vein, heated in a heating blanket. Time-activity curves (TACs) of image-derived blood radioactivity were obtained using volumes of interest (VOIs) over ascending aorta, aortic arch, pulmonary artery, left and right ventricles, inferior vena cava, and abdominal aorta. Image-derived blood radioactivity was compared with those measured by blood sampling data in each location.
  
  
  RESULTS
  Both the TACs of blood sampling radioactivity in each subject, and the TACs of image-derived blood radioactivity showed a peak within 5 min after the tracer injection, and promptly decreased soon thereafter. Linear relationship was found between blood sampling radioactivity and image-derived blood radioactivity in all the VOIs at any timing of data sampling (p < 0.001). Image-derived radioactivity measured in the left and right ventricles 30 min after injection showed high correlation with blood radioactivity. Image-derived blood radioactivity was lower than blood sampling radioactivity data by 20 %. Reduction of blood radioactivity of FBPA in left ventricle after 30 min of FBPA injection was minimal.
  
  
  CONCLUSIONS
  We conclude that the image-derived T/B ratio can be reliably used by setting the VOI on the left ventricle at 30 min after FBPA administration and correcting for underestimation due to partial volume effect and reduction of FBPA blood radioactivity.
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan. isohashi-k@tracer.med.osaka-u.ac.jp.
authors.forename: Kayako
authors.identifier: http://orcid.org/0000-0002-2081-3020
authors.initials: K
authors.lastname: Isohashi
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.|Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Suita City, Osaka, Japan.
authors.forename: Eku
authors.initials: E
authors.lastname: Shimosegawa
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.
authors.forename: Sadahiro
authors.initials: S
authors.lastname: Naka
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.|Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Suita City, Osaka, Japan.
authors.forename: Yasukazu
authors.initials: Y
authors.lastname: Kanai
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.
authors.forename: Genki
authors.initials: G
authors.lastname: Horitsugi
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Mochida
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.|Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Suita City, Osaka, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Matsunaga
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Watabe
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kato
authors.affiliation: Department of Radiology, Osaka University Graduate School of Medicine, Suita City, Osaka, Japan.
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Tatsumi
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka, 565-0871, Japan.|Department of Immunology Frontier Research Center, Osaka University, Suita City, Osaka, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Hatazawa
keywords: BNCT; FBPA; PET; T/B ratio