title: Assessment of clinical impact in the application of Chang attenuation correction to lung ventilation/perfusion SPECT.
abstract: The presence of a highly nonuniform distribution of attenuating tissues in the thorax may lead to attenuation artifacts and inaccuracies in reconstructed lung ventilation/perfusion SPECT images. The Chang algorithm is an easily applicable and accessible method of attenuation correction. The advantages inherent in the technique prompted us to evaluate the effect of using Chang attenuation correction on the quality of lung SPECT images and the clinical impact on interpretation.
  
  
  METHODS
  Lung scintigraphy started with planar and SPECT ventilation scans using (81m)Kr. A few minutes after the ventilation scintigraphy, planar and SPECT perfusion studies using (99m)Tc-macroaggregated albumin were performed. The Chang algorithm was applied for attenuation correction. Afterward, standard SPECT processing was performed on the images, leading to images in the horizontal, coronal, and sagittal planes. The same studies were also processed to the same planes without application of attenuation correction. Finally, all scintigraphic images were reviewed by 2 nuclear medicine academic clinicians, and a final diagnosis was reached by consensus, categorizing the studies into 3 groups-normal, low/intermediate, and high probability-for pulmonary embolism.
  
  
  RESULTS
  The study included 45 patients (16 men and 29 women) with a mean age of 50.0 y. Between the 2 noncorrected and attenuation-corrected readings, 16 diagnoses remained the same. However, after attenuation correction, 13 patients were moved to lower categories (i.e., from high probability to normal or low/intermediate probability or from low/intermediate probability to normal) and 16 patients were moved to higher categories (i.e., from low/intermediate probability to high probability or from normal to low/intermediate or high probability). The difference between noncorrected and attenuation-corrected readings was statistically significant (P < 0.01).
  
  
  CONCLUSIONS
  After attenuation correction, subjective image quality and sharpness improved, leading in some cases to increased confidence on the part of the readers. The Chang attenuation correction method may have the potential to be considered as an alternative approach toward attenuation correction in those situations in which the additional radiation burden of CT is not acceptable.
authors.affiliation: Department of Nuclear Medicine, Imam Khomeini Complex Hospital, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Sina
authors.initials: S
authors.lastname: Izadyar
authors.forename: Sassan
authors.initials: S
authors.lastname: Saber
authors.forename: Ali
authors.initials: A
authors.lastname: Gholamrezanezhad
mesh_terms: D000465:Algorithms; D016477:Artifacts; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008168:Lung / Q000000981:diagnostic imaging*; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014692:Ventilation-Perfusion Ratio