title: Effect of Post-Reconstruction Gaussian Filtering on Image Quality and Myocardial Blood Flow Measurement with N-13 Ammonia PET.
abstract: OBJECTIVE
  In order to evaluate the effect of post-reconstruction Gaussian filtering on image quality and myocardial blood flow (MBF) measurement by dynamic N-13 ammonia positron emission tomography (PET), we compared various reconstruction and filtering methods with image characteristics.
  
  
  METHODS
  Dynamic PET images of three patients with coronary artery disease (male-female ratio of 2:1; age: 57, 53, and 76 years) were reconstructed, using filtered back projection (FBP) and ordered subset expectation maximization (OSEM) methods. OSEM reconstruction consisted of OSEM_2I, OSEM_4I, and OSEM_6I with 2, 4, and 6 iterations, respectively. The images, reconstructed and filtered by Gaussian filters of 5, 10, and 15 mm, were obtained, as well as non-filtered images. Visual analysis of image quality (IQ) was performed using a 3-grade scoring system by 2 independent readers, blinded to the reconstruction and filtering methods of stress images. Then, signal-to-noise ratio (SNR) was calculated by noise and contrast recovery (CR). Stress and rest MBF and coronary flow reserve (CFR) were obtained for each method. IQ scores, stress and rest MBF, and CFR were compared between the methods, using Chi-square and Kruskal-Wallis tests.
  
  
  RESULTS
  In the visual analysis, IQ was significantly higher by 10 mm Gaussian filtering, compared to other sizes of filter (P<0.001 for both readers). However, no significant difference of IQ was found between FBP and various numbers of iteration in OSEM (P=0.923 and 0.855 for readers 1 and 2, respectively). SNR was significantly higher in 10 mm Gaussian filter. There was a significant difference in stress and rest MBF between several vascular territories. However CFR was not significantly different according to various filtering methods.
  
  
  CONCLUSIONS
  Post-reconstruction Gaussian filtering with a filter size of 10 mm significantly enhances the IQ of N-13 ammonia PET-CT, without changing the results of CFR calculation.
authors.affiliation: Department of Nuclear Medicine, Chonnam National University Hwasun Hospital, Hwasun-Gun, Jeollanamdo, South Korea.
authors.forename: Hyeon Sik
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Department of Nuclear Medicine, Chonnam National University Hospital, Hwasun-Gun, Jeollanamdo, South Korea.
authors.forename: Sang-Geon
authors.initials: SG
authors.lastname: Cho
authors.affiliation: Department of Cardiology, Chonnam National University Hospital, Hwasun-Gun, Jeollanamdo, South Korea.
authors.forename: Ju Han
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Nuclear Medicine, Chonnam National University Hwasun Hospital, Hwasun-Gun, Jeollanamdo, South Korea.
authors.forename: Seong Young
authors.initials: SY
authors.lastname: Kwon
authors.affiliation: Korea Photonics Technology Institute, Gwangju City, South Korea.
authors.forename: Byeong-Il
authors.initials: BI
authors.lastname: Lee
authors.affiliation: Department of Nuclear Medicine, Chonnam National University Hwasun Hospital, Hwasun-Gun, Jeollanamdo, South Korea.
authors.forename: Hee-Seung
authors.initials: HS
authors.lastname: Bom
keywords: Gaussian filtering; Myocardial blood flow; PET image reconstruction