title: Enhanced accuracy of defect detection by myocardial single-photon emission computed tomography with attenuation correction with gadolinium 153 line sources: evaluation with a cardiac phantom.
abstract: BACKGROUND
  Photon attenuation is a major cause of artifacts on single-photon emission tomographic imaging.
  
  
  RESULTS
  To study a new method to perform photon attenuation correction (AC), we used a cardiac phantom filled with (99m)Tc and imaged it (1) without extrinsic attenuation or defects, (2) with extrinsic attenuation but without defects, (3) without extrinsic attenuation but with defects involving 10% of the myocardial volume and activity ranging from 0% to 75% of maximum, and (4) with both extrinsic attenuation and defects. Transmission and emission images acquired with a dual-head single-photon emission computed tomographic system with 153Gd line sources were processed by iterative maximum-likelihood-expectation-maximization and were evaluated both qualitatively and quantitatively. The small defects were readily identified both before and after AC. Mean count activity (percent of maximal activity) of the segments with overlying extrinsic attenuation but without defects was only 56% +/- 4% without AC but increased to 86% +/- 4% with AC (p < 0.0001). Without AC, the count activities in the defects with overlying extrinsic attenuation were lower than the actual defect activities, but AC resulted in better approximation of actual defect activities in all but the most severe (0% tracer activity) defects.
  
  
  CONCLUSIONS
  This new AC method provided an improved estimation of actual myocardial count activity. Even small defects with mild reduction in tracer activity were still identifiable after AC.
authors.affiliation: Section of Cardiology, Baylor College of Medicine and the Methodist Hospital, Houston, Texas 77030, USA.
authors.forename: Z X
authors.initials: ZX
authors.lastname: He
authors.forename: M D
authors.initials: MD
authors.lastname: Scarlett
authors.forename: J J
authors.initials: JJ
authors.lastname: Mahmarian
authors.forename: M S
authors.initials: MS
authors.lastname: Verani
mesh_terms: D016477:Artifacts; D005682:Gadolinium; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D019047:Phantoms, Imaging; D011868:Radioisotopes; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D011868:Radioisotopes; D005682:Gadolinium