title: Attenuation correction for myocardial perfusion imaging. A comparison between SPECT and PET imaging by polar map analysis.
abstract: OBJECTIVE
  We investigated the impact of photon attenuation in myocardial perfusion imaging with SPECT and PET in patients with coronary artery disease. In fact, the regional tracer distribution can be quantitatively assessed by polar map analysis if the effects of photon attenuation are accounted for. PET imaging permits accurate measurement of and correction for photon attenuation, whereas results of attenuation correction in SPECT imaging have been inconsistent.
  
  
  METHODS
  We compared photon attenuation in resting perfusion imaging studies with SPECT ((99m)Tc-sestamibi) and PET ((13)N-ammonia) from 21 patients. Transaxial images were reconstructed with and without attenuation correction and reoriented into short axis images. Polar map analysis was utilized to generate regional tracer uptake in six anatomical segments.
  
  
  RESULTS
  Average segmental photon attenuation calculated as the ratio of counts in corrected and uncorrected images was 7.2 +/- 1.4 in SPECT and 14.0 +/- 3.1 in PET imaging (p < 0.01). This attenuation factor was significantly related to body mass index for both methods (p < 0.001). While attenuation correction for SPECT imaging did compensate for attenuation effects in the inferior wall (from -15% to +6% vs. PET), relative tracer uptake in the anterior wall in SPECT images was significantly reduced after attenuation correction (from -2% to -18% vs. PET, p < 0.01).
  
  
  CONCLUSIONS
  Differential effects of attenuation correction for myocardial SPECT perfusion imaging need to be considered when algorithms designed to compensate effects of photon attenuation in SPECT imaging are employed in clinical practice.
authors.affiliation: Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria. senta.graf@meduniwien.ac.at
authors.forename: S
authors.initials: S
authors.lastname: Graf
authors.forename: A
authors.initials: A
authors.lastname: Khorsand
authors.forename: G
authors.initials: G
authors.lastname: Stix
authors.forename: S
authors.initials: S
authors.lastname: Nekolla
authors.forename: A
authors.initials: A
authors.lastname: Becherer
authors.forename: K
authors.initials: K
authors.lastname: Kletter
authors.forename: R
authors.initials: R
authors.lastname: Dudczak
authors.forename: H
authors.initials: H
authors.lastname: Sochor
authors.forename: G
authors.initials: G
authors.lastname: Maurer
authors.forename: G
authors.initials: G
authors.lastname: Porenta
mesh_terms: D000368:Aged; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi