title: Usefulness of noise adaptive non-linear gaussian filter in FDG-PET study.
abstract: OBJECTIVE
  In positron emission tomography (PET) studies, shortening transmission (TR) scan time can improve patient comfort and increase scanner throughput. However, PET images from short TR scans may be degraded due to the statistical noise included in the TR image. The purpose of this study was to apply non-linear Gaussian (NLG) and noise adaptive NLG (ANLG) filters to TR images, and to evaluate the extent of noise reduction by the ANLG filter in comparison with that by the NLG filter using phantom and clinical studies.
  
  
  METHODS
  In phantom studies, pool phantoms of various diameters and injected doses of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) were used and the coefficients of variation (CVs) of the counts in the TR images processed with the NLG and ANLG filters were compared. In clinical studies, two normal volunteers and 13 patients with tumors were studied. In volunteer studies, the CV values in the liver were compared. In patient studies, the standardized uptake values (SUVs) of tumors in the emission images were obtained after processing the TR images using the NLG and ANLG filters.
  
  
  RESULTS
  In phantom studies, the CV values in the TR images processed with the ANLG filter were smaller than those in the images processed with the NLG filter. When using the ANLG filter, their dependency on the phantom size, injected dose of FDG and TR scan time was smaller than when using the NLG filter. In volunteer studies, the CV values in the images processed with the ANLG filter were smaller than those in the images processed with the NLG filter, and were almost constant regardless of the TR scan time. In patient studies, there was an excellent correlation between the SUVs obtained from the images with a TR scan time of 7 min processed with the NLG filter (x) and those obtained from the images with a TR scan time of 4 min processed with the ANLG filter (y) (r = 0.995, y = 1.034x - 0.075).
  
  
  CONCLUSIONS
  Our results suggest that the ANLG filter is effective and useful for noise reduction in TR images and shortening TR scan time while maintaining the quantitative accuracy of FDG-PET studies.
authors.affiliation: Department of Medical Physics and Engineering, Graduate School of Medicine, Osaka University, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Nagayoshi
authors.forename: Kenya
authors.initials: K
authors.lastname: Murase
authors.forename: Kouichi
authors.initials: K
authors.lastname: Fujino
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Uenishi
authors.forename: Minoru
authors.initials: M
authors.lastname: Kawamata
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Keishi
authors.initials: K
authors.lastname: Kitamura
authors.forename: Ichiro
authors.initials: I
authors.lastname: Higuchi
authors.forename: Naohiko
authors.initials: N
authors.lastname: Oku
authors.forename: Jun
authors.initials: J
authors.lastname: Hatazawa
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D003198:Computer Simulation; D005260:Female; D005374:Filtration / Q000379:methods; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015233:Models, Statistical; D009369:Neoplasms / Q000000981:diagnostic imaging*; D016011:Normal Distribution; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013269:Stochastic Processes
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18