title: Extrinsic Versus Intrinsic Uniformity Correction for γ-cameras.
abstract: SPECT produces nuclear medicine images using a 3-dimensional diagnostic tool that eliminates the superimposition of adjacent structures, thus providing improved disease localization. Another method of uniformity correction-to use the complete capabilities of this tool-is discussed and evaluated in this article. The conventional method of intrinsic uniformity correction accounts only for nonuniformities within the γ-camera, excluding the collimator. If SPECT image quality is related to overall camera performance, then using an extrinsic uniformity correction method rather than an intrinsic method will improve image quality.
  
  
  METHODS
  SPECT uniformity images were obtained using a SPECT phantom with application of intrinsic and extrinsic uniformity correction tables with 2 different γ-imaging systems. The image results were qualitatively assessed.
  
  
  RESULTS
  Even with acceptable nonuniformity analyses, significant ring artifacts within the intrinsic uniformity-corrected images are observed, whereas the artifacts are considerably less significant with the extrinsic uniformity correction and disappear completely in some of these images.
  
  
  CONCLUSIONS
  Extrinsic uniformity correction may significantly improve the overall image quality by taking into account nonuniformities that arise from the collimator. This method will result in fewer image artifacts and improved image quality, thereby improving patient care.
authors.affiliation: Department of Medical Imaging and Radiation Sciences, College of Allied Health, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, USA.
authors.forename: Randy
authors.initials: R
authors.lastname: Bolstad
authors.forename: Jody
authors.initials: J
authors.lastname: Brown
authors.forename: Vesper
authors.initials: V
authors.lastname: Grantham
mesh_terms: D000465:Algorithms; D016477:Artifacts; D015902:Gamma Cameras; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*