title: A novel adaptive discrete cosine transform-domain filter for gap-inpainting of high resolution PET scanners.
abstract: OBJECTIVE
  Several positron emission tomography (PET) scanners with special detector block arrangements have been developed in recent years to improve the resolution of PET images. However, the discontinuous detector blocks cause gaps in the sinogram. This study proposes an adaptive discrete cosine transform-based (aDCT) filter for gap-inpainting.
  
  
  METHODS
  The gap-corrupted sinogram was morphologically closed and subsequently converted to the DCT domain. A certain number of the largest coefficients in the DCT spectrum were identified to determine the low-frequency preservation region. The weighting factors for the remaining coefficients were determined by an exponential weighting function. The aDCT filter was constructed and applied to two digital phantoms and a simulated phantom introduced with various levels of noise.
  
  
  RESULTS
  For the Shepp-Logan head phantom, the aDCT filter filled the gaps effectively. For the Jaszczak phantom, no secondary artifacts were induced after aDCT filtering. The percent mean square error and mean structure similarity of the aDCT filter were superior to those of the DCT2 filter at all noise levels. For the simulated striatal dopamine innervation study, the aDCT filter recovered the shape of the striatum and restored the striatum to reference activity ratios to the ideal value.
  
  
  CONCLUSIONS
  The proposed aDCT filter can recover the missing gap data in the sinogram and improve the image quality and quantitative accuracy of PET images.
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Cheng-Ting
authors.initials: CT
authors.lastname: Shih
authors.affiliation: Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung 40402, Taiwan, Republic of China.
authors.forename: Jay
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Hsin-Hon
authors.initials: HH
authors.lastname: Lin
authors.affiliation: Health Physics Division, Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan 32546, Taiwan, Republic of China.
authors.forename: Shu-Jun
authors.initials: SJ
authors.lastname: Chang
authors.affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Keh-Shih
authors.initials: KS
authors.lastname: Chuang
mesh_terms: D003198:Computer Simulation; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives; D004298:Dopamine / Q000378:metabolism; D006257:Head; D006801:Humans; D008954:Models, Biological; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000379:methods*; D019275:Radiopharmaceuticals; D012815:Signal Processing, Computer-Assisted
chemical_list: D019275:Radiopharmaceuticals; C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine; D004298:Dopamine