title: Evaluation of delineation of image details in semiconductor PET utilizing the normalized mutual information technique.
abstract: OBJECTIVE
  PET using semiconductor detectors provides high-quality images of the human brain because of its high spatial resolution. To quantitatively evaluate the delineation of image details in clinical PET images, we used normalized mutual information (NMI) to quantify the similarity with images obtained through MRI. NMI is used to evaluate image quality by determining similarity with a reference image. The aim of this study was to evaluate quantitatively the delineation of image details provided by semiconductor PET.
  
  
  METHODS
  To quantitatively evaluate anatomical delineation in clinical PET images, MRI scans of patients were used as T1-weighted images. [(18)F]-fluorodeoxyglucose ((18)F-FDG) PET brain images were obtained from six patients using (a) a Hitachi semiconductor PET scanner and (b) a ECAT HR+ scintillator PET scanner. The NMI calculated from the semiconductor PET and MRI was denoted by NMIsemic, whereas the NMI calculated from conventional scintillator PET and MRI was denoted by NMIconve. The higher the value of NMI, the greater the similarity to MRI.
  
  
  RESULTS
  NMIsemic ranged from 1.22 to 1.29, whereas NMIconve ranged from 1.13 to 1.18 (P<0.05). Furthermore, all the NMI values of the semiconductor PET were higher than those of the conventional scintillator PET.
  
  
  CONCLUSIONS
  Utilizing NMI, we quantitatively evaluated the delineation of image details in clinical PET images. The results reveal that semiconductor PET has superior anatomical delineation and physical performance compared with conventional scintillator PET. This improved delineation of image details makes semiconductor PET promising for clinical applications.
authors.affiliation: aCentral Institute of Isotope Science bDepartment of Nuclear Medicine, Hokkaido University, Sapporo cCentral Research Laboratory, Hitachi Ltd, Tokyo, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Kubo
authors.forename: Kenji
authors.initials: K
authors.lastname: Hirata
authors.forename: Kazuki
authors.initials: K
authors.lastname: Matsuzaki
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Morimoto
authors.forename: Wataru
authors.initials: W
authors.lastname: Takeuchi
authors.forename: Naoya
authors.initials: N
authors.lastname: Hattori
authors.forename: Tohru
authors.initials: T
authors.lastname: Shiga
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kuge
authors.forename: Nagara
authors.initials: N
authors.lastname: Tamaki
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging; D002675:Child, Preschool; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation*; D012666:Semiconductors
chemical_list: D019788:Fluorodeoxyglucose F18