title: An analytic study of the effects of attenuation on tumor detection in whole-body PET oncology imaging.
abstract: There has been considerable debate about the desirability of attenuation correction in whole-body PET oncology imaging. The advantages of attenuation correction are quantitative accuracy, whereas the perceived disadvantages are loss of contrast, noise amplification, and increased scanning time. In this work, we explain contrast changes between images reconstructed with and without attenuation correction.
  
  
  METHODS
  To analytically explain both well-known and surprising phenomena in images reconstructed without attenuation correction, we performed a series of simulation studies, a phantom experiment, and a patient experiment.
  
  
  RESULTS
  We showed that it is possible to calculate a priori the appearance of images reconstructed without attenuation correction. Compared with attenuation-corrected images, images without attenuation correction may have locally enhanced contrast in the abdomen or other regions of uniform attenuation, although the amount of enhancement varies with position in a complex manner. In regions of nonuniform attenuation, such as the thorax, it is possible that foci of increased tracer uptake disappear in images reconstructed without attenuation correction. The critical tracer concentration for this zero-contrast effect depends on the size, location, and density of the foci. Above the critical value, foci are visible in images with and without attenuation correction, whereas below the critical value, foci are visible in attenuation-corrected images but appear as photopenic regions in images without attenuation correction.
  
  
  CONCLUSIONS
  Even though images without attenuation correction may be desired, these results suggest that all studies should at least be reconstructed with attenuation correction to avoid missing regions of elevated tracer uptake.
authors: Philips Medical Systems, ADAC Laboratories, Milpitas, California, USA.
authors: Chuanyong
authors: C
authors: Bai
authors: Paul E
authors: PE
authors: Kinahan
authors: David
authors: D
authors: Brasse
authors: Claude
authors: C
authors: Comtat
authors: David W
authors: DW
authors: Townsend
authors: Carolyn C
authors: CC
authors: Meltzer
authors: Victor
authors: V
authors: Villemagne
authors: Martin
authors: M
authors: Charron
authors: Michel
authors: M
authors: Defrise
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009369:Neoplasms / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D014055:Tomography, Emission-Computed
chemical_list: D019788:Fluorodeoxyglucose F18